Skip to main content

Full text of "Live wired : a guide to networking Macs"

See other formats

A Guide to Networking Macs 


James K. Anders 

A ^ Easy-to-Use 
Mac Symbol Library 
for Simplified 
Network Design 

Foreword By Guy Kawasaki 

Live Wired 

A Guide to Networking Macs 

y ^ '*L 

James K. Anders 



n 11/97 


$ 2.00 



Live Wired: A Guide to Networking Macs 

Copyright © 1993 James K. Anders 

All rights reserved. Printed in the United States of America. No part of this 
book may be used or reproduced in any form or by any means, or stored in 
a database or retrieval system, without prior written permission of the 
publisher except in the case of brief quotations embodied in critical 
articles and reviews. Making copies of any part of this book for any 
purpose other than your own personal use is a violation of United States 
copyright laws. For information, address Hayden, 1 171 1 N. College Ave„ 
Carmel, IN 46032. 

Librar>^ of Congress Catalog No.: 93-77320 
ISBN: 1-56830-015-8 

This book is sold as is, without warranty of any kind, either express or 
implied. While every precaution has been taken in the preparation of this 
book, the publisher and authors assume no responsibility for errors or 
omissions. Neither is any liability assumed for damages resulting from the 
use of the information or instructions contained herein. It is further stated 
that the publisher and authors are not responsible for any damage or loss 
to your data or your equipment that results directly or indirectly from your 
use of this book. 

95 94 93 4 3 2 

Interpretation of the printing code: the rightmost double-digit number is 
the year of the book’s printing; the rightmost single- digit number the 
number of tlie book’s printing. For example, a printing code of 93-1 shows 
that the first printing of the book occurred in 1993. 

Trademark Acknowledgments: All products mentioned in this book are either 

uademarks of the companies referenced in diis book, registered trademarks of the 
companies referenced in this book, or neither. We strongly advise that you inves- 
tigate a particular product’s name thoroughly before you use the name as your own. 



To Ada 

Time passes... 
but memories remain. 


Development Editor 

Karen Whitehouse 

Production Editor 

David Ciskowski 

Technical Reviewer 

Richard Leach 

Cover Designer 

Kathy Hanley 


Scott Cook 


Jeanne Clark 

Production Team 

Diana Bigham, Tim Cox, Mark Enochs, Tom Loveman, 
Michael J. Nolan, Joe Ramon, Carrie Roth, 

Mary Beth Wakefield, Barbara Webster 

Composed in Utopia 


About the Author 

James K. Anders 

Jim Anders is a Senior Consulting Engineer with Computer Meth- 
ods Corporation, where, for the last five years, he specialized in 
desktop systems integration, focusing on Macintosh/VAX integra- 
tion and CAD/CAM technologies. Through Computer Methods, 
Mr. Anders teaches the seminar “Integrating Apple’s Macintosh 
into VAX System Networks,” for Digital Equipment Corporation. 

He has provided consulting services for companies such as Apple 
Computer, Inc., Boeing Aerospace, Colgate Palmolive, Digital 
Equipment Corporation, Du Pont, Mobil Oil, and Union Carbide 

Jim Anders writes and lectures on Macintosh networking, systems 
integration, and CAD/CAM topics in a variety of forums, such as 
the Mactivity networking conference and the Macintosh Summit 
Conference. He is also the author of Technical Drawing with Claris 
CAD and The Macintosh CAD/CAM Book. He also writes reviews 
and articles for MacUser magazine. 

His background includes over fifteen years experience with the 
implementation and administration of networked, integrated 
CAD/CAM systems. He was an engineering staff member of 
RCA Missile and Surface Radar, where in 1986 he spearheaded a 
successful effort to integrate Apple’s Macintosh with their 
multivendor network. Previously, Mr. Anders worked for RCA 
Laboratories in Princeton, New Jersey, and for various companies 
in the medical and semiconductor manufacturing industries. 

We Want to Hear 
from You 

What our readers think of Hayden is crucial to our sense of well- 
being. If you have any comments, no matter how great or how 
small, we’d appreciate your taking the time to send us a note. 

We can be reached at the foUowing address: 


11711 N. College Ave. 

Carmel, IN (yes, Indiana — not California. . .) 46032 
(317) 573-6880 voice 
(317) 571-3484 fax 

If this book has changed your life, please write and describe the 
euphoria you’ve experienced. Do you have a cool book idea? Please 
contact us at the above address with any proposals. 



Books are collaborative efforts. Even though there’s one name on 
the cover, there are many people who deserve credit. 

Guy Kawasaki deserves a special note of thanks. It was his contin- 
ued insistence and cajoling that prompted me to expand and 
formalize a set of lecture notes that were used to help explain 
networking concepts to attendees of the Macintosh Summit 
Conference, held at the University of California at Santa Barbara. 

Joe Dallatore provided valuable assistance with the Management 
and Troubleshooting chapter and with the technical aspects of the 

Sunny Anders spent countless hours reading and re-reading every 
page of this book — making sure that everything made sense. 

Gloria Anders created the wonderful cartoons used throughout the 

Thanks to Bill Sturdevant, and Silk City Software, for their timely 
and professional development of the PICTviewer application 
included on the disk that comes with this book. 

I also would like to acknowledge the efforts of Garry Hornbuckle of 
Apple Computer, and the many representatives from the various 
Macintosh and AppleTalk networking companies. 

Thanks also to Stephen and Maria Hull. 

A special thanks to Karen Whitehouse and David Ciskowski of 
Hayden Books for their tireless efforts providing the necessary 
direction and editing to take this project from a big Microsoft Word 
file and a bunch of MacDraw Pro documents into the finished 
product that you see before you. 

Finally, thanks to A1 Cini (of Computer Methods Corporation), who 
nurtured and encouraged many of the ideas and concepts outlined 
in this book. I would like to offer my undying gratitude for those 
individuals — Frank Monzo, Anthony Caraffa, Ruth Logue and 
Vickie Briggs — at CMC who make my job so much easier. 

Jim Anders 
Feasterville, Pennsylvania 
March, 1993 


For a computer that was supposed to be for “the rest of us,” 
Macintosh has progressed (I use the term loosely) until it's now a 
computer for “the best of us.” 1 often reminisce about the days 
when LocalTalk was AppleTalk, and AppleTalk was nothing more 
than a long printer cable to reduce the cost of a LaserWriter: “You 
see, if we buy a $7,000 printer, seven people can share it on an 
AppleTalk network, so it really only costs $1,000.” 

That was then — and this is now. IBM and Apple are allies. There's a 
twelve month warranty for Macs in the United States. The Berlin 
Wall is gone. “Macintosh Portable” isn't an oxymoron anymore. 
And Macs are connected on networks in organizations ail around 
the world — even on half breed, mulatto, hapa-haole networks of 
Macintoshes, IBMs, DECs, HPs, and other superfluous mini- and 
mainframe computers. 

In this confusing world, all 1 can say is, “Thank God for Jim 
Anders.” I’ve sat through many a presentation about networking 
and communications and Jim is the only person I can understand. 
He's so good at it that I usually beg him to explain networking and 
communications to a Macintosh conference I run for desktop 
publishing weenies. 

Indeed, part of the reason this book exists is because I pounded on 
Jim to write a book that would explain networking and communi- 
cations to the rest of us. I don’t know how he positions Live Wired, 
but in my mind, it’s the The Mac is Not a Typewriter (by Robin 
Williams) of networking and communications books. If you know 
that book, you’ll know how good Live Wired is. If you don't, 
trust me. 

Guy Kawasaki 
Macintosh Curmudgeon 


Table of Contents 
at a Glance 

Foreword ix 

Introduction 1 

I Networking Fundamentals 

1 How Does Communication Take Place? 9 

2 How Does Networking Take Place? 17 

3 Network Diagramming with NetPICTs 31 

4 Networking Concepts 47 

5 Common Network Components 65 

II Macintosh Networking 

6 Macintosh Services 99 

7 Macintosh Formats 115 

8 Macintosh Transport: AppleTalk 127 

9 Macintosh Media/Cabling 179 

III Multivendor Networks 

10 Living in an Intel /DOS World 211 

11 UNIX Connectivity 231 

12 DEC VAX Connectivity 251 

13 IBM Connectivity 269 

IV Network Design, Implementation, 
and Management 

14 Design and Implementation 283 

15 Management and Troubleshooting 313 

16 The Future of Macintosh Networking 337 

Glossary of Networking Terminology 341 

Appendix A: NetPICT Encyclopedia 369 

Appendix B: Listing of Macintosh 

Networking Companies 383 

Index 395 

How to Use the Disk 433 

Table of Contents 

Acknowledgments vii 

Foreword ix 

Introduction 1 

I Networking Fundamentals 

1 How Does Communication Take Place? 9 

Idea 10 

Expression 10 

Transport 11 

Medium 11 

Matching Layers 13 

Conclusion 16 

2 How Does Networking Take Place? 17 

Idea > Services and Programs 18 

Expression > Formats 19 

Transport > Protocols 22 

Medium > Cabling 25 

Conclusion 30 

3 Network Diagramming with NetPICTs 31 

Introducing the NetPlCT symbol 31 

Swapping Layers 36 

Matching Layers 37 

Clients and Servers 39 

The OSl Reference Model and NetPICTs 40 

A Seven Layer OSI Example 44 

Conclusion 45 


Live Wired 

4 Networking Concepts 47 

Types of Networks 47 

Network Frames 56 

Network Signaling 57 

Conclusion 63 

5 Common Network Components 65 

LANs & WANs 65 

Repeaters 66 

Bridges 69 

Routers & Brouters 73 

Gateways 86 

Miscellaneous: Hubs, Concentrators, and So Forth 90 

Network Topologies 91 

Conclusion 96 

II Macintosh Networking 

6 Macintosh Services 99 

AppleShare (AFP) 99 

System 7 File Sharing 101 

Other AFP Clients and Servers 102 

Print Services (PAP) 103 

Apple Open Collaboration Environment (AOCE) 105 

Terminal Services 106 

Data Access Language (DAL) 

and Other Database Services 108 

Mail Services 110 

Conclusion 113 

7 Macintosh Formats 115 

ASCII Text and Word Processors 116 

MacPaint and PICT Formats 118 

PostScript 119 

TIFF and GIF 120 

Binary 121 

Document Interchange 122 

Conversions 124 

Conclusion 126 

Live Wired 

8 Macintosh Transport: AppleTalk 1 27 

The AppleTalk Protocol Family: An Overview 127 

How Does AppleTalk Work? 137 

AppleTalk Phase 1 and 2 148 

How Does the Chooser Work? 155 

AppleTalk Routing 166 

Conclusion 178 

9 Macintosh Media/Cabling 1 79 

LocalTalk/Phone-Type Connectors 179 

Ethernet/EtherTalk 187 

Other Cabling Systems 196 

WAN Media 203 

Conclusion 207 

III Multivendor Networks 

10 Living in an Intel/DOS World 211 

Services: Application -Based 211 

Formats; ASCII, EPS, Binary Compatible 213 

Transports: AppleTalk (PhoneNET PC), 

MacIPX, DECnet, TCP/IP 218 

Cabling Options 227 

Conclusion 230 

11 UNIX Connectivity 231 

Services: FTP, NFS, AFP, X- Windows, TELNET 231 

Formats 242 

Transports: AppleTalk, TCP/IP 244 

Cabling: Ethernet, LocalTalk, Token Ring 248 

Conclusion 249 

12 DEC VAX Connectivity 251 

Services: PATHWORKS for Macintosh 251 

Formats 257 

Transports: AppleTalk for VMS, DECnet, LAT 260 

Cabling: LocalTalk and Ethernet 266 

Conclusion 268 

Live Wired 

13 IBM Connectivity 269 

Services; Mainframe and AS/400 269 

Formats: Mainframe and AS/400 273 

Transports: Mainframe and AS/400 273 

Media: Mainframe and AS/400 275 

Conclusion 279 

IV Network Design, Implementation, 
and Management 

14 Design and Implementation 283 

Top-Down Design Techniques 283 

Using NetPICTs to Help 

with Systems Integration 285 

Wiring Strategies 288 

Conclusion 312 

1 5 Management and Troubleshooting 31 3 

Configuration Management 313 

Network Management 315 

Troubleshooting 318 

Performance 330 

Security 335 

Conclusion 336 

16 The Future of Macintosh Networking 337 

Glossary of Networking Terminology 341 

A NetPICT Encyclopedia 369 

B Listing of Macintosh Networking Companies 383 




r. Richard Feynman (see figure 1) was one of 
America's leading nuclear physicists. He 
achieved this acclaim by demonstrating his 
genius at M.I.T. and Princeton University, and 
later by playing a key role in the Manhattan 
Project, which produced the first atomic bomb at 
Los Alamos, New Mexico. 

Figure 1 

R.P. feynman. 

After World War II, Feynman became a professor at Cornell Uni- 
versity, where he tackled the complexities of the newly emerging 
science of quantum mechanics. At the time, quantum physics was 
awash in competing theories, none of which effectively explained 

Live Wired 

the intricacies of the sub-atomic world or satisfied the members of 
the physics community. 

In the late 1940s, Feynman published a sequence of papers that 
completely redefined physics. While Feynman’s writings were 
revolutionary, they were also full of simple examples and meta- 
phors that made the complex subject accessible to a new genera- 
tion of particle physicists. 

One of the metaphors employed by Fejmman was a simple dia- 
gram that depicted particle interactions (see figure 2). In fact, these 
“Feynman diagrams” were just a part of an entire language in- 
vented by Feynman — a language that has a complete and consis- 
tent grammar, with corresponding syntactical rules. 

Feynman Diagram 

During the remainder of his years, Feynman continued his 
achievements: winning the Nobel Prize for Physics in 1965, and 
serving on the commission to investigate the Space Shuttle Chal- 
lenger disaster. 

Richard Feynman died in 1987 after a long batde with cancer, but 
his diagrams lived on and are now the lingua franca of the particle 
physics community. The symbols gave physicists the power to 
express complex phenomena in an elegant, graphical form. 

The power of symbolic representation has been repeatedly demon- 
strated throughout history. From our numbers and alphabet to the 

Figure 2 

Feynman Diaoram. 



iconic Macintosh user-interface, s>Tnbolic representation gives us 
the power to master complex concepts. 

When we master complex concepts through using symbolic 
representation, we use a higher level of abstraction to deal with 
objects and events. For the programmer, it’s the difference be- 
tween writing a computer program in the computer's native 
language of assembler or in a higher level s^mibolic language such 
as Pascal or HyperTalk. 

Just as the Macintosh made computing accessible to the general 
public, it also has made computer networking commonplace. 

Tasks that once were left to engineers and “authorized” network- 
ing professionals are becoming the responsibility of desktop 
publishers, architects, and other Macintosh end users. 

At the simplest level — networking a Macintosh to a LaserWriter, for 
example — Macintosh networking is a plug-and-play operation 
that’s as easy as connecting stereo components. But networks are 
not always this simple, and for many Macintosh users networking 
seems as complex as nuclear physics. 

To extend beyond the simple LocalTalk network requires an 
understanding of basic networking principles and concepts. When 
the average Macintosh user tries to learn and understand these 
networking concepts, he or she is often confronted vAth confusing 
and ambiguous terms. 

This book demystifies Macintosh networking and makes it under- 
standable for everyone. Macintosh users, network administrators, 
and systems integrators will find the material presented in this 
book as clear and understandable as the Macintosh itself. It will 
bring an order and a symbolic representation to Macintosh net- 
working by introducing a graphical language and diagramming 
technique that unifies and simplifies Macintosh network design 


Live Wired 

and systems integration. This language is used throughout the 
book to introduce and define complex network protocols and 

A disk containing a complete library of this symbolic networking 
language is included with this book. The disk contains hundreds of 
PICT-based networking symbols, called NetPICTs, that define all 
major networking components, computers, and software environ- 
ments. These symbols also will be offered by Macintosh network- 
ing vendors and will be posted on online services such as 
CompuServe, AppleLink, and America Online. 

Every hardware or software element that has some relevance to 
networking will be explained and diagrammed so that you can 
understand its function and role in tlie larger picture. You'll be able 
to use your favorite Macintosh drawing program to open these 
PICT symbols, so you easily can combine them to solve problems 
or diagram your Macintosh network. 

The language breaks down Macintosh networking into four basic 
categories, or layers. Thoughout the book, obscure networking 
concepts like bridging, routing, and tunneling are clearly posi- 
tioned and explained. Is Ethernet a networking protocol or cable? 

Is AppleTalk hardware or software? Is it necessary to use the same 
networking protocols and cabling on each netw'orked computer? 
These are the kind of questions that this book readily answers. 
You’ll learn from the diagrams that AppleTalk, Apple’s networking 
software, not only runs on Macs and LaserWriters, but also on PCs, 
Unix workstations, and many other computers. 

This book also provides a practical guide to designing, implement- 
ing and troubleshooting AppleTalk and multivendor networks. 
Numerous real-world examples are used, so it’s likely that the 
“blueprint” of your present (or planned) network exists between 
these covers. 



Unlike other computer books that focus solely on products and 
have a limited lifetime, this book will focus on making the basic 
Apple networking concepts clear and understandable. This book 
will be as relevant five years from now as it is today. 

Years ago, Feynman’s diagrams profoundly changed the world of 
physics by introducing a new graphical language that made 
difficult and obscure concepts understandable. For me, the goal of 
this book is much more pedestrian than Feynman’s achievements: 
to pro\ade a graphical user interface for Macintosh networking, 
and to make Mac networking understandable and accessible for 
the rest of us. 

Jim Anders 
March, 1993 


srstandable to everyone 


Part I covers the fundamentals oi 
networking, using concepts and 

Part I covers the fundamentals of networking, 

metaphors that are understandal 

using concepts and metaphors that are 

everyone. It establishes the founc 

understandable to everyone. It establishes the 

that will be used throughout the I 

foundation that will be used throughout the book 

describe Macintosh networking. 

to describe Macintosh networking. 


v/ie.s the loundmion that will 
hroughout the book to 
Macintosh networking. 


How Does 
Take Place? 

Ithough computer networking appears to be a 
_ confusing world of terminology and buzzwords, 

the basic concepts can be reduced to four basic, 
|H interrelated layers. These layers apply to com- 
puter networking, spoken English, written 
German, sign language, smoke signals — any 
language you choose. This chapter describes each 
of these four layers, common to all communication, by starting at 
the top with the first layer (the Idea layer) and then proceeding 
down through the remaining three layers. 

To make the position of the layers easy to remember, the number 
of lines in the ends of the layer diagram indicate the number of the 
layer. The Idea Layer (layer 1) has one line on its ends; the Expres- 
sion Layer (layer 2) has two lines; the Transport Layer (layer 3) has 
three; and the Medium Layer (layer 4) has four (see figure 1.1). 
These end treatments will gain additional significance and will be 
used in other ways later in the book. 

Part One Networking FundamentaJs 

Figure 1.1 

layers of coimnunicaiion. 






The Idea is the reason behind the communication. It’s the thought 
or essence behind the message. It’s an abstract concept that, when 
expressed, transforms the idea into a specific form and causes the 
process to move down into the next layer. Expression. 

For example, if you have an idea that you would like to express, 
it first starts as an abstract concept in your mind. Fortunately, 
developing and fostering these concepts is what our minds do best. 
Within your mind you can entertain such abstractions as the fall of 
communism, the smell of morning coffee, your expectations of 
future Macintosh computers, and the sound of your favorite piece 
of music. All communications start at this abstract layer of the 


Until ESP becomes a proven and reliable way to communicate, the 
external expression of ideas is necessary in order to prepare the 
ideas for conveyance. To express the idea of the fall of commu- 
nism, you could use English, Braille, or a sequence of pictures. 
Each format of expression has inherent advantages and disadvan- 
tages that make one format better than others for a particular 

Chapter One How Does Communication Take Place? 


Once the abstract idea has been expressed in an external form, the 
message then can be transported from the origin to the destina- 
tion. This is the function of the Transport layer. Each method of 
transport has certain rules, or protocols, that must be adhered to in 
order to ensure error-free delivery of the message. 

Just as there are many different forms of expression, there also are 
many different transport mechanisms. If 1 decide to tell you about 
the fall of communism by speaking to you direcdy, 1 am using a 
specific, mutually agreeable protocol known as conversation. 
Usually, a conversation is a two-way process. One person speaks; 
another person listens and acknowledges the message. The order 
then reverses and the process repeats itself. 

I could also convey my English-based message about the fall of 
communism using a written transport protocol. The rules for 
conveying written English are much different than those for 
spoken English. To convey ideas about the fall of communism 
using the written transport protocols of English, I write on a piece 
of paper, starting at the top, writing from left to right. I then convey 
the message by handing you the piece of paper. 

Of course, the idea and the expression (the language) remain the 
same using either transport mechanism. The only thing that has 
changed is the method of transport. 


The last step in the process is the communications Medium — the 
mechanism used by the Transport layer to deliver the message. 


Part One Networking Fundamentals 

Figure 1.2 

Spoken tomniunicaiion 
uses compiessed air. 

When you deliver a message by speaking, the delivery mechanism 
is compressed air. Your lungs force compressed air over your vocal 
cords, which vibrate and in turn vibrate the air and create modu- 
lated waves of compressed air (see figure 1.2). These sound waves 
hit the listener’s ear drum, which vibrates, causing electrical 
impulses to be sent to the brain where they’re finally "heard.” 

NOTE: So, just in case you were wondering; if a tree falls in the forest and 
there is no one there, it doesn’t make a noise, it just compresses the air. 

If I want to deliver my hand-written document on the fall of 
communism, I can choose from numerous delivery media — hand 
delivery, mail, fax, or Federal Express. Each method has distinct 
benefits and disadvantages, but they all do the same thing: they 
transmit my hand-written document. 


Chapter One How Does Communication Take Place? 

Matching Layers 

By using separate four-layer diagrams for the sender and the 
recipient of the message, we can better illustrate the degree of 
interaction between the two parties (see figure 1.3). 



Figure 1 .3 


In order for communications to be successful, each corresponding 
layer of the sender and the recipient must match. To illustrate this 
point, let’s analyze a communications transaction from the bottom 

The sender’s and the recipient’s chosen communications medium 
(layer 4) is compressed air. For this example, we’ll assume that 
they’re within speaking distance of each other in normal atmo- 
spheric conditions, and therefore would have no problem commu- 
nicating over this medium. If either of the participants were deaf, 
then a better choice for the communication medium might be 
visual in nature. 

Both parties are familiar with the protocol of spoken language, so 
the next layer up the stack, the Transport layer (layer 3), matches as 
well. If one of the participants only understood the protocol of 
spoken language and the other only understood the reading of lips, 
the layers would not match and communication would be unlikely. 


Part One Networking Fundamentals 

Moving up to the Expression layer (layer 2), both parties under- 
stand the English format. Here, as with the other layers, if there 
was a mismatch where one person understood English and the 
other only French, the communication process would not occur. 

Finally, even at the uppermost Idea layer (layer 1), there must be a 
match between the sender and the receiver. If the recipient of the 
message has no idea what communism is, or was, the purpose of 
the message will be lost. The beauty of this diagramming tech- 
nique is that all forms and instances of communications can be 
diagrammed and analyzed. 

What if the sender and recipient are too far away for the medium of 
compressed air to work effectively? Let's say they were 100 yards 
apart. In this case, the medium would have to be altered in order to 
support the greater distance (see figure 1.4). 

Figure 1.4 

II ihe medium of 
losuilicient perhaps 
radio waves will work. 

A walkie-talkie is such a device. It converts the compressed air 
waves into electrical signals. These signals are transmitted as radio 
waves to another walkie-talkie, which reverses the process and 


Chapter One How Does Communication Take Place? 

converts tlie radio waves back into electrical signals. These electri- 
cal signals vibrate the internal speaker, which in turn compresses 
the air so the listener can hear the message (see figure 1.5). 


Figure 1.5 

Diaofaniining a complex 
commonicaiion using 

Notice how each side of the diagram matches the other. The 
compressed air medium of the sender’s mouth matches the 
medium of the microphone; the compressed air medium of the 
walkie-talkie’s speaker matches the medium of the receiver’s ear. 

This conversion process only happens at the Medium layer (layer 
4) since it’s strictly a medium conversion. Walkie-talkies are 
ignorant of the protocols of spoken communication and therefore 
the process is limited to the medium layer. You’re totally free to be 
rude, incoherent, and ignore all the established protocols of 
spoken communication. Since the walkie-talkie only operates at 
the lowest layer, it will not attempt to police the conversation. 


Part One Networking Fundamentals 


Each layer of the communication process serves a specific func- 
tion, but provides us with unlimited choice. We can tailor the 
method of expression, transport, and medium to best convey our 
ideas. Each layer is connected to its neighbor, but each layer can 
also stand independently and can be analyzed and judged on its 
own merits. If English doesn’t properly convey a certain idea, then 
perhaps haiku can do a better job. If the U.S. Postal Service is too 
slow, then perhaps Federal Express is a better choice. 

A key tenet of this idea is that when two or more parties are in- 
volved, communication can only occur when their corresponding 
layers match identically. 

How Does 
Networking Take 

his chapter introduces computer networking by 
defining network concepts in terms of the four 
basic concepts of communication (Idea, Expres- 
sion, Transport, and Medium) as defined in the 
first chapter. 

As with any communication, computer network- 
ing can be broken down into four layers (see figure 
2.1). We’ll use slightly different nomenclature (nomenclature that’s 
specific to networking) to describe these layers. 





Figure 2.1 

layers Dimpuiei 

Part One Networking Fundamentals 

Figure 2.2 

Clieni/Servei Willi Mac 

Idea > Services and Programs 

In Chapter 1, the first layer represented the idea — the reason 
behind the communication. In general, layer one embodies the 
purpose behind the communication. With computer networking, 
the purpose or reason behind the communication is to deliver 
services to the participants. 

In a simple network consisting of a Macintosh and a LaserWriter, 
the LaserWriter provides a print service to the Macintosh user (see 
figure 2.2). Software on the Macintosh communicates with soft- 
ware on the LaserWriter and establishes what is known as a client/ 
server relationship. 

Macintosh Client LaserWriter Server 

The client/server model has been used throughout all aspects of 
Macintosh networking to provide access to file, database, and mail 
servers. Today, the concept continues to expand to include 
workgroup applications such as calendar and time management 
programs, document librarian systems, and System 7’s Publish and 
Subscribe capabilities. 


Chapter Two How Does Networking Take Place? 

Expression > Formats 

Humans rely on standard languages to provide effective communi- 
cations. We have numerous expressive formats to satisfy different 
situations and cultures. The same is true for computers. Informa- 
tion can be represented in thousands of computer formats. Some 
of these formats are widely adopted standards, while most of them 
are unique to a specific computer application. 

To start with, all computer formats have at least one thing in 
common — they’re all comprised of binary data. That means that 
all computer file formats consist of a sequence of ones and zeros. 
Each one and zero is called a btf of information. For convenience, 
these ones and zeros are often put into eight-bit groups, com- 
monly called bytes (see figure 2.3). 



T- CO f- 00 tr CM T- — 

a] 010100 ( 0 ]— 



00001101 — 

Each column of a binary 
number Is a successive 
power of 2 ... 

Each one and zero Is 
a bit of Information... 

Each group of eight 
Is a called a byte or 

This byte represents the 
decimal value 13 (8+4+1) 
and In the ASCII code, 
represents a Carriage 

Figure 2.3 

Oils anil bytes. 


Bytes are often referred to as octets, particularly in the networking community. 


Part One Networking Fundamentals 

Early in the history of computing, it became obvious that digital 
information would need to be standardized. For example, ASCII 
(American Standard Code for Information Interchange) has been a 
widely used and popular standard for some time. It uses seven bits 
of information to represent most of the characters on an English 
typewriter keyboard. 

Within a byte of information, there are 256 possible characters, 
ranging from 00000000 to 11111111. Of these, ASCII uses the first 
128 characters to represent common alphanumeric characters and 
special characters unique to data processing. The first 32 charac- 
ters of the ASCII code are special control characters that cannot be 
printed: these control characters are used to represent characters 
such as carriage returns (which have an ASCII decimal value of 13 
and a binary value of 00001101), line feeds, and tabs. The remain- 
ing 128 values are used for special characters or symbols. The 
Greek letter “pi,” for example, has an ASCII decimal value of 185 an 
a binary valueoflOlllOOl. 

The problem with ASCII is that it doesn’t have enough values to 
encode all the symbols used throughout the world. To accommo- 
date other alphabets and symbols, a more expansive standard was 

To solve this problem, industry groups put forth the Unicode 
standard, which uses 16 bits, for 65,536 possible characters. This 
standard can accommodate every symbolic character used in the 
world today and is destined to eclipse the ASCII standard. Apple 
uses double-byte characters (but not yet the Unicode standard) in 
System 7.1 to accommodate these additional characters. 

Today, many computer applications, particularly word processing 
applications, can read and write the ASCII standard. But since 
ASCII only encodes information about the characters and basic 
formatting, it is not used as a native word processing format. 

Chapter TwoHovv Does Networking Take Place? 

Therefore, every word processor developer must devise another 
special binary format to handle all the other attributes common to 
modern word processors. With an application such as Microsoft 
Word for the Macintosh, these attributes can include color, fonts, 
graphics (of varying formats), and even sound. Of course, when 
you save a document that has tliese elements as an ASCII File, all 
that remains is the plaintext. The other elements are lost. 

There are many other standard formats, such as PostScript, 
QuickDraw, PICT, TIFF, GIF, EBCDIC, QuickTime, DXF, and IGES. 
For the most part, these formats are independent of the computer 
on which they were created. A QuickTime file, composed of a 
specific sequence of ones and zeros, can be played on a Macintosh, 
a PC, or a Silicon Graphics workstation. All that is needed is an 
application that understands the QuickTime format. 

Some formats use other formats as a starting point. For example, 
PostScript, DXF, and IGES Files are composed of strings of ASCII 
text. The ASCII text is actually a series of commands or statements 
in the higher language. (The English format is based upon the 
Roman alphabet text format, as is the French format and the 
Italian format.) 

When it comes to the native format used by most applications, 
nearly every one has its own unique (and often proprietary) file 
format. In other words, if you create identical documents in 
MacWrite and Microsoft Word, each application would use differ- 
ent patterns of ones and zeros to describe the same data. Both 
applications can import and export each other’s format, but that’s 
because the respective applicadons can translate the competitor’s 

More than any other layer, the Format layer is responsible for 
successful communications. A transcontinental telephone conver- 
sation is an apt analogy. It’s easy to dial the phone number of 


Part One Networking Fundamentals 

someone who lives in France. The call gets routed and placed widi 
all kinds of sophisticated technology, but the ultimate measure of 
successful communications is whether or not I can understand 
French, or if my counterpart understands English (see figure 2.4). 

Figure 2.4 

foimai) of ilie message is 
crucial lor uodersianding. 

Yo! What’s 
for breakfast? 

Du Fromage! 


Establishing a common format for communications is by far the 
most difficult challenge in computer networking. It’s the task that 
requires the most thought and effort to solve. 

Transport > Protocols 

Until this point, all we’ve done is establish a service and agree on a 
common descriptive format. No information has moved across the 
network. The rules for moving formatted information across the 
network are the function of the third level; protocols. 

Chapter Two How Does NeuvorkingTake Place? 

Networking software must solve many problems: the rules that 
describe the solutions are the networking protocols. First, the 
sender and recipient must be uniquely identified on the network. 
(This is analogous to assigning phone numbers to identify 
phones — you need to know the number of the phone you want to 
call.) Next, there must be a means to route data over complex 
pathways without the loss of data. This is just a sample of the 
functions of the Protocol layer. 

Apple developed a protocol known as AppleTalk that very elegantly 
solved the problem of identifying the sender and the recipient. 
AppleTalk provides reliable, error-free transmissions, and chooses 
appropriate routes on the netu'ork. AppleTalk, like other network- 
ing protocols (such as TCP/IP, Novell, and DECnet), exists only in 
software. All Macintosh computers and most of Apple’s networked 
printers come equipped with AppleTalk software. 

Although AppleTalk is part of the Macintosh System software, it is 
by no means limited to the Macintosh. The AppleTalk protocols 
are available for many other computers and networking devices 
(see figure 2.5). DOS-equipped PCs can use Farallon’s PhoneNet 
Talk PC software to gain the AppleTalk protocols. PCs running 
OS/2 2.0 come with AppleTalk protocols. (This was one of the goals 
of the Apple/IBM alliance.) AppleTalk protocols are available for 
other computer platforms, including NeXT workstations running 
NextStep 2.0 and Digital’s VAX family. 

Computers — the Macintosh included — are not limited to running a 
single networking protocol. Just as humans can deal with multiple 
transport methods, so can computers. 

Your Macintosh can have several transport protocols loaded at one 
time (see figure 2.6). In addition to the standard AppleTalk proto- 
col, you could install MacTCP from Apple and DECnet for 
Macintosh from Digital. These protocols would enable your 

Part OneNetworking Fundamentals 

Figure 2.5 

Applelalk protocols on 
other platforms. 

Figure 2.6 

A Macintosh roiinlnp 
multiple protocols. 

Macintosh to communicate using the native transport protocol of 
other computers. 

Intel/DOS Machine 






AFP Server & | 

PAP Spooler 

NeXT Workstation 

AppleTalk / 

AFP & PostScript 

AFP Client 

^ LocalTalk or [ 
Ethernet 1 

AppleTalk / 


Ethernet [ 








MacTCP equips the Macintosh with the TCP/IP protocol used by 
most UNIX computers. Ruiming DECnet for Macintosh turns your 
Mac into a DECnet node and enables it to communicate with 
DECnet-equipped computers such as PCs and VAXes. 

Figure 2.7 shows another diagram depicting the concept of mul- 
tiple protocols. Here, the protocols are shown as geometric shapes. 
Those computers that are able to send and receive these protocols 
have corresponding notches designed to handle the protocols. 


Chapter Two How Does Networking Take Place? 

Computer A Computer B Computer C Computer D 

Different Networking Protocols 
(I.e. AppleTalk, DECnet, TCP/IP) 

O □ A 

Figure 2.7 

Multiple piolocols. 

While it’s possible for a Macintosh to run multiple transport 
protocols, it’s important to note that these transports don’t always 
support every Macintosh service. For example, the Chooser only 
works with AppleTalk transport protocol. The file service of NFS is 
only accessible with the TCP/IP transport. 

There are only a few Macintosh services that work with multiple 
transport protocols. The best example of such a service is MacX, 
which works over several transports, such as AppleTalk, TCP/IP, 
and DECnet. In this case, the choice of a transport depends largely 
on the transport protocol of other network participants. 

Medium > Cabling 

At some point, the networking software, or protocols, must deal 
with the physical world to send the message. When we speak, it's 
the air that carries our words. When computers speak, they rely on 
electromagnetic signals to carr>' the sequences of ones and zeros. 
These encode the networking protocols that contain the formatted 
information which ultimately delivers the service to the user. There 
are several ways computers can transrnit electromagnetic signals, 
but the most common way is through a cable. 


Part One Networking Fundamentals 

Every Macintosh has two serial ports. They are most commonly 
known as the printer port and the modem port. Both ports can be 
used for serial communications, but only the printer port can be 
used to connect to Apple’s low-cost netw'orking cabling medium 
known as LocalTalk. 

Since LocalTalk hardware is included on every Macintosh and on 
most Apple printers, it is a simple task to create a basic network. 
Just acquire the LocalTalk connectors and connect them using the 
appropriate cabling. 

Apple’s LocalTalk was designed in the mid 1980s, when Ethernet 
hardware cost $750 to $1000 per node. Apple needed an inexpen- 
sive way to send AppleTalk protocols over a simple network. At $50 
per node, LocalTalk networks rapidly took hold. To get the price 
down, Apple made some reasonable tradeoffs. 

First, LocalTalk networks have a limited bandwidth, of 230,400 bits 
per second (230.4 Kbps). This limits the maximum number of 
connected nodes to 32. This was much less than Etliernet or other 
cabling systems, but it was reasonable for Apple’s small workgroup 
strategy of 1985. While LocalTalk put serious limitations on large 
and complex networks, Apple took the necessary steps to expand 
the AppleTalk protocols to other popular cabling systems. 

First came support for Ethernet. Apple and third-party vendors 
began to develop Ethernet cards for the Macintosh. Included with 
the cards was special driver software that enabled the AppleTalk 
netw’orking software to communicate over the Ethernet card, 
instead of the standard LocalTalk port. 

Apple decided to trademark the software that sends AppleTalk 
protocols over Ethernet, and called it EtherTalk. But don’t be 
confused. It’s not a new kind of cable or a different protocol. Just 
think of EtherTalk as AppleTalk protocols over Ethernet cabling, 
and it will make more sense. 

Chapter Two How Does Networking Take Place? 

Ethernet has a much higher bandwidth than LocalTalk. It’s capable 
of carrying information at a rate of 10 million bits per second (10 
Mbps). This is roughly 40 times the bandwidth of LocalTalk. There 
are three different implementations of Ethernet: all have the same 
bandwidth, but the cable type, connectors, and maximum segment 
lengths differ. 

After Ethernet, Apple provided support for Token Ring networks. 
Token Ring is common in the IBM mainframe and minicomputer 
world. There are two implementations: a 4 Mbps version, and a 16 
Mbps version. As with Ethernet, Apple included driver software to 
connect the higher-level AppleTalk protocols to the Token Ring 
hardware. The Apple trademark for this is TokenTalk. Again, just 
think of it as AppleTalk protocols running over Token Ring cabling. 

Usually, the decision to use Token Ring as a cabling medium has 
more to do with IBM connectivity than it has to do with the relative 
merits of the cabling system. Token Ring cards are significantly 
more expensive than Ethernet cards, but as vve’U see later on. 

Token Ring cabling operates in a fundamentally different way than 
Ethernet does, and it might make sense to consider Token Ring 
even if you don’t have an IBM mainframe. 

More recently, Apple introduced AppleTalk support for another 
kind of cabling. With AppleTalk Remote Access Protocol, or ARAP, 
AppleTalk protocols are sent over serial connections, such as RS- 
232 cabling used by modems. As with the other cabling choices, 
only the low-level drivers are affected. The higher-level AppleTalk 
protocols remain the same. 

ARAP makes it possible for a remote Macintosh client to connect to 
a Macintosh or another server by calling in through a modem. The 
computer that receives the call acts as the ARAP server. Once the 
connection is made, the remote Macintosh client becomes a ptu-t 
of the network and is able to access the serxdces as if the remote 


Part One Networking Fundamentals 

Figure 2.8 

Remote access diBoiam. 

Mac were directly connected to the network. Of course, since the 
dial-up modem connection is significantly slower than either 
LocalTalk or Ethernet, the trade-off is performance. 

Apple’s Remote Access software provides both tlie client and 
server applications for the Mac (see figure 2.8). However, third- 
party vendors are offering ARA servers that run on dedicated server 
boxes, such as Shiva’s LanRover products and Computer Methods 
Corporation’s AsyncServeR (which enables a DEC VAX to become 
an enterprise-wide AppleTalk Remote Access server). 

Remote Macintosh 

Apple has already released the specification for the next generation 
of high-speed cabling systems. Fiber Distributed Data Intercon- 
nect (or FDDI) has a bandwidth that is an order of magnitude 
more than Etliernet (see figure 2.9). At 100 Mbps, FDDI interfaces 
should provide the necessary bandwidth for the demanding 
applications where voice data and real-time video are sent over the 

Chapter Two How Does Networking Take Place? 

network. Several vendors are already starting to offer FDDl NuBus 
cards for the Macintosh, and Apple has no doubt trademarked the 
FDDITalk name. Prices are still high, but just as Ethernet prices 
have plummeted during the last few years, you can expect the 
same to happen with FDDI technology as well. 

Electromagnetic communication is not limited to copper wiring or 
fiber optics. In fact, it seems likely that the next generation of small 
hand-held computers, as exemplified by Apple’s Newton, will not 
use any cabling. 

Instead, different portions of the electromagnetic spectrum v\all be 
used in place of physical cabling. Your TV or VCR remote control 
uses infrared waves to communicate. Your pager, remote auto 
alarm, and cellular phone use radio waves to communicate. All 
these methods will be common communications and networking 
mediums in the near future. 

Figure 2.9 


Part One Networking Fundamentals 


Networking may appear to be a a complex subject, but it easily can 
be broken down into four layers. Services are the applications, 
which use a variety of formats or data structures. These formats are 
delivered with networking transport protocols, over some kind of 
delivery medium, such as cabling. This is true of all computers and 
network systems. Once this concept is understood, all that remains 
is to determine which buzzwords belong to which layer. 

with NetPICTs 

n this chapter, the symbolic language based 
on the NetPICT symbols and the associated 
diagramming technique is introduced and 
explained, using several basic Macintosh 
network scenarios. Using the four-layer 
NetPICT symbol as a starting point, the 
seven-layer OSI reference model is finally 
explained in an easily understandable fashion. 

Introducing the NetPICT symbol 

To this point, the NetPICT symbols have been used to describe 
fairly simple networking scenarios. Combined with a few simple 
rules, we will use the symbols to depict common Macintosh 
networking scenarios, and to solve some simple problems. 

Part One Networking Fundamentals 

Let’s start with a typical Macintosh. Out of the box, the Macintosh, 
combined with its System softwcU'e, fulfills each of the four layers. 

Starting at the top, the most familiar Macintosh service is the 
Chooser desk accessory. Found under the Apple menu, the 
Chooser application is a service that delivers other services to the 
user (see figure 3.1). With the Chooser, a Macintosh user can select 
services from the network, including file, print, mail, and other 

Figure 3.1 

Service layei. 

Macintosh Client 

Once a service (a LaserWriter, for example) has been selected, 
other Macintosh applications, such as MacDraw Pro, can utilize 
that service and print documents. So, in addition to the Chooser, 
we’ve also placed MacDraw Pro as a typical application that 
appears at the Service layer. 

Working our way down, the next layer is the Format layer (see 
figure 3.2). Here, we see that the MacDraw Pro application sup- 
ports several different formats. 

First, there is the native binary MacDraw Pro format that is unique 
to MacDraw Pro. This is the format that writes to your disk when 
you save a MacDraw Pro document. 

Another format used by MacDraw Pro is QuickDraw, which is used 
as an imaging format to draw entities on the Macintosh screen. 

Chapter Three Netw^ork Diagramming with NetPICTs 

It also can be used for printing, when combined with a QuickDraw 
printer such as Apple’s StyleWriter. If you’re using a PostScript 
printer instead, the MacDraw Pro application generates yet an- 
other format, known as PostScript. 

Macintosh Client 

Figure 3.2 

llie standard Mac 
Format layer. 

As mentioned before, every Macintosh comes equipped with 
AppleTalk protocols as part of its System software. Thus, we’ve 
placed AppleTalk in the third Protocol layer (see figure 3.3). The 
PostScript generated in the second layer is now passed down to the 
third level for subsequent delivery. 

Macintosh Client 

MacDraw Pro 

MacDraw Binary 


Figure 3.3 

Pioiocol layer. 

And finally at the fourth layer, the LocalTalk cabling, which pro- 
vides the physical cabling connection to the outside world, is used 
to actually transmit the PostScript data, along with network and 
printer control data, to the printer (see figure 3.4). 

Part One Networking Fundamentals 

Figure 3.4 

Ihe Standard Mac 
Cabling layer. 

Macintosh Client 

MacDraw Pro 

MacDraw Binary 



Figure 3.5 

Ihe standard PC 
Service layer. 

To further illustrate the function of each layer, let's look at a few 
examples of other systems. With an IBM (or compatible) PC, the 
layers perform the same function. 

At the Semce layer, the PC user chooses services in different ways, 
often depending on the application (see figure 3.5). Printers are 
usually assigned code names such as LPTl or LPT2. With DOS, the 
printer selection is usually typed in as part of the command line. 
With Windows-equipped PCs, the printers often have iconic 

PC Client 

As witli the Macintosh example, applications also belong at the 
service layer. So Lotus 1-2-3 (and any other application) would be 
placed here as well. 

Lotus 1-2-3 supports a number of formats, in addition to its own 
native file format. Some of these formats are used for printing. 


Chapter Three Network Diagramming with NetPICTs 

These include Hewlett-Packard’s PCL, used by LaserJet printers, 
and the industry' standard PostScript, which is understood by 
many laser printers. 

PC Client 

At the transport layer, the PC user is confronted with many confus- 
ing choices (see figure 3.7). Unlike the Macintosh, the PC was 
never designed with a networking protocol built-in, so third-party 
companies proceeded to fill the void. Novell NetWare, Banyan 
Vines, and Microsoft LAN Manager are all examples of popular 
transport protocols available for the PC. 

PC Client 

Figure 3.6 

loimai layer. 


Proiocol layer. 

There's a similar problem at the lowest Cabling/Media layer as well 
(see figure 3.8). The only communications port that comes stan- 
dard on a PC is a serial communications port. Serial ports are not 
normally thought of as networking ports, since they only support a 
single connection at one time. To provide a PC with a true network 
connection, a networking card must be purchased. 

Part One Networking Fundamentals 

Figure 3.8 

Ilie standard PC 
Cabling layer. 

PC Client 

Lotus Native Format 

Novell Netware 
Banyan Vines 
MS LAN Manager 

Token Ring 

There are several networking cards that are popular for PCs. Today, 
most PC networking cards are either Token Ring, Ethernet, and 
Arcnet. In its day, Arcnet was the LocalTalk of PCs. It was inexpen- 
sive and used standard twisted pair wiring. But as the price of 
Ethernet and Token Ring cards dropped over the years, these cards 
have come to dominate the PC market. 

Swapping Layers 

Let’s return to the Macintosh example used earlier. Here we have a 
Macintosh that “speaks” AppleTalk over a LocalTalk interface. If 
we wanted to trade-up to an Ethernet connection, we would 
simply install a networking card and install the appropriate 
EtherTalk driver software (figure 3.9). 

Figure 3.9 

Swapping locallalk lor 

Macintosh Client 

Macintosh Client 

MacDraw Pro 

MacDraw Pro 

MacDraw Binary 

\ / MacDraw Binary 

) ( QuickDraw 

/ \ PostScript 


1 1 AppleTalk 

> LocalTalk 

c > Ethernet - 

Chapter Three Network Diagramming with NetPICTs 

As far as the diagram is concerned, the only change we would need 
to make is to replace the current Cabling layer of LocalTalk with 
one of Ethernet. All the other layers remain the same. With the PC, 
we might want to get a bit more ambitious. Here, we might want to 
get rid of the Novell networking protocols and replace them with 
the AppleTalk protocols (see figure 3.10). This can be done with 
Farallon’s PhoneNet PC. PhoneNet PC works with most PC 
Ethernet cards, or with PC LocalTalk cards that are offered by 
Farallon and other third-party vendors. 

PC Client 

PC Client 


Lotus 1-2-3 


Lotus 1-2-3 

Lotus Native Format \ / 

HP PCL ) ( 

PostScript / \ 

Lotus Native Format 

AppleTalk J [ 


LocalTalk < > 

Ethernet - 

Figure 3.10 

PC ninoApplelalk Willi 

As evidenced from the prior example, the process of network 
design or systems integration often involves the swapping and 
substitution of various layers, in order to achieve the desired 

IMPORTANT NOTE: The most important rule to remember is: Two 
computers can only fully communicate when each of their respective four 
layers match exactly, or have counterparts that can work together. 

Matching Layers 

Let's look at the NetPICTs of a Macintosh and LaserWriter and see 
why they're able to communicate. As shown in figure 3.1 1, the 
Macintosh and the LaserWriter match all four layers. 


Part One Networking Fundamentals 

Figure 3.1 1 

matcliiag layers. 

Macintosh Client LaserWriter Server 

The LaserWriter icon in the Chooser represents the client portion 
that is responsible for printing. It matches and connects with the 
server application that runs on the LaserWriter. 

At the Format layer, the PostScript generated by MacDraw Pro 
can be readily processed by the PostScript interpreter on the 

Both machines can speak and understand AppleTalk, which is 
being used to convey the printing instructions at the Protocol 

Since both machines have LocalTalk interfaces at the Cabling 
layer, they can use a common mechanism for carrying the 
AppleTalk protocols. 

If any one or more of these layers didn't match, the printing 
process wouldn’t be possible. For example, Hewlett-Packard offers 
a LocalTalk card for certain models of their LaserJet printers. They 
also provide AppleTalk protocol and PostScript support as well. If I 
were to just install the LocalTalk card into a LaserJet, without also 
installing the AppleTalk and PostScript software, I would be unable 
to print (see figure 3.12). The same situation would also exist if I 
installed the AppleTalk protocols without the PostScript, or vice 

Again, all four layers must match exacdy for communications to 

Chapter Three Network Diagramming with NetPICTs 

Macintosh Client HP LaserJet 

Figure 3.12 



Clients and Servers 

Client/server computing is not a product or a specific application. 
It’s a way of designing computer programs. It’s a design philoso- 
phy. In the client/server model, computers and programs interact 
in a way that’s ideal for a networked environment. 

The general idea is simple. A client program submits a request to a 
server program, which acts on the request along with die requests 
of other clients. The obvious example is a file server that handles 
the requests of clients that desire file ser\'ices. Database servers, 
such as Apple’s Data Access Language (DAL), performs a similar 
function for clients desiring database services. 

The client/server model even applies to the design of computer 
programs. The popular symbolic math program, Mathematica, was 
written using a client/server model. When Mathematica is running 
on a single computer, such as the Mac, the client and server 
portions of the program are running on the same machine. In a 
networked environment, a different sei^ver could be used. By 
having the option to choose different Mathematica servers, the 
user has the option of selecting a ser\'er that runs on a super 
minicomputer, while still using the client interface on the Mac. 

Throughout this book, the concept of client/server computing will 
appear quite often. It will be used to describe the way applica- 
tions work together, or how one network layer interacts with its 

Part One Networking Fundamentals 

Hgure 3.13 

OSIReiefence Model with 
seven layers. 

The OSI Reference Model 
and NetPICTs 

The four layers used in the NetPICT diagrams are essentially a 
condensed version of an industry standard known as the OSI 
Reference Model. The model, developed by the International 
Standards Organization (ISO), is used to describe the ISO’s stan- 
dard networking protocols and also to act as a road map for other 
networking protocols as the fundamental layers can be applied 

The OSI Reference Model uses seven layers, as opposed to the four 
used by the NetPICT diagrams (see figure 3.13). As we discussed 
earlier, the end treatments of the different NetPICT layers serve 
different functions. 





Data Link 


First, the number of lines in the ends of the NetPICT layers indicate 
their respective position on the stack. Secondly, many of the end 
treatment lines correspond to key layers of the OSI Reference 
Model (see figure 3.14). 


Chapter Three Network Diagramming with NetPICTs 

The three lines in the Protocol layer symbolize the three layers in 
the OSl Reference Model that focus on the neu\'orking transport 
protocol. Another similarity can be found in the fourth Cabling 
layer. Here the four line end treatment can be readily divided in 
half, where the upper half represents the Data Link OSl layer and 
the lower half represents the Physical layer. 

The only de\aation from the strict interpretation of the OSl model 
is the two lines of the Format layer. Here, the entire Format layer is 
represented by the Presentation layer of the OSl model. 

For the purposes of this book, however, later we’ll use the two lines 
of the Format layer to separate different kinds of formats. 

NetPICT OSl Reference Model 

Figure 3.14 


So, by starting with our simplified four-layer approach, you already 
have a basic understanding of the OSl Model. Table 3.1 describes 
the specific relationships between the NetPICT model and the OSl 
model. As the function of each layer is described, keep in mind that 
each layer dovetails with its neighbor in a client/server relation- 


Part One Networking Fundamentals 

Table 3.1 OSI Reference Model Layers 

OSI Layer 

NetPICT layer 




The place where network 
services and applications 
reside; utilizes the formats 
established in the next layer 
of the stack. 



These include file formats, 
such as PostScript, ASCII 
and Microsoft Word; and 
file access formats such as 
the Apple Filing Protocol. 


upper third 
of Protocol 

Addresses the problem of 
establishing and maintain- 
ing a connection between 
computers; also maintains 
a logical sequence to the 


middle third 
of Protocol 

Ensures reliable delivery of 
tlie message. 


bottom third 
of Protocol 

Essentially addresses the 
message for delivery. 

Data Link 

upper half of 

Concerns the specific kind 
of cabling or communica- 
tions medium employed. 


bottom half 
of Cabling 

The level where the physical 
cable or delivery medium 

A few of these descriptions are new and require a brief explana- 
tion. The Transport layer ensures that the message is correctly 

Chapter Three Network Diagramming with NetPICTs 

transmitted. If one portion of the communication transmission is 
lost or garbled, it’s the job of the Transport layer to re-transmit the 
necessary portion. 

The Network layer functions as an envelope containing the mes- 
sage. The envelope has the address of the message recipient and 
the return address of the sender. These addresses are logical 
addresses that are specific to a particular networking protocol. This 
logically addressed envelope is known as a datagram. This concept 
is very important and will be covered in detail in the next chapter. 

The function of the Data Link layer is to place the datagram, 
created at the Network layer, inside a network delivery vehicle, 
known as a frame. Network delivery frames are specific to the 
particular kind of cable being used. An Ethernet frame can hold the 
same AppleTalk datagram as a Token Ring frame, but the respec- 
tive network frames are different. Another way for Macintosh users 
to think of the Data Link layer is by looking at the Mac’s Network 
Control Panel. When a Macintosh user chooses a different network 
driver with the Network Control Panel, a different Data Link layer 
is being selected. 

The Physical layer is the level at which the actual delivery medium 
is realized. The three different kinds of Ethernet and two different 
kinds of Token Ring cable are defined in this layer. The Physical 
layer often has its own form of addressing in addition to the 
protocol-specific logical addressing. For example, each Ethernet 
node, or device, has a unique 48-bit hardware address that remains 
constant. LocalTalk, on the other hand, doesn’t use physical 
hardware addresses and relies on the logical AppleTalk address 
instead. Physical hardware addresses and their relationship to the 
protocol logical addresses will be covered in the next chapter. 

With that quick overview of the OSI Reference Model, let’s take 
another look at how a Macintosh prints to a LaserWriter, but this 
time, we’ll use the full seven layers of the OSI Model. 


Part One Networking Fundamentals 

Figure 3.1 5 

Priming describeilwilh 
lire OSIRelerence Model. 

A Seven Layer OSI Example 

As before, starting at the top, the most familiar Macintosh Applica- 
tion is the Chooser desk accessory. Found under the Apple menu, 
the Chooser application delivers other services to the user (see 
figure 3.15). With the Chooser, a Macintosh user can select file, 
print, mail and otlier services from the network. 

Macintosh Client 

HP LaserJet 

Once a service, such as a LaserWriter print server, has been chosen, 
other Macintosh applications, such as MacDraw Pro, can utilize 
that service and print documents. So, in addition to the Chooser, 
we've also placed MacDraw Pro as an application that appears at 
the OSI Application layer. 

Working our way down, the next layer is the Presentation layer. 
Here, as before, we see that the MacDraw Pro application supports 
several different formats. First, there is the native binary MacDraw 
Pro format that is unique to MacDraw Pro. This is the format that is 
written to your disk when you save a MacDraw Pro document. 

Another format used by MacDraw Pro is QuickDraw, which is used 
as an imaging format to draw entities on the Macintosh screen. It 
also can be used for printing when connected to a QuickDraw 
printer such as Apple’s StyleWriter. If you’re printing to a Post- 
Script printer instead, the MacDraw Pro application generates yet 
another Presentation layer format, known as PostScript. 

Chapter ThreeNetwork Diagramming with NetPlCTs 

The Presentation layer of PostScript gets sent to the Session layer. 
The Session layer is the first layer where the AppleTalk networking 
protocols really come into play. At the AppleTalk Session layer, 
there’s an Apple protocol known as the Printer Access Protocol 
(PAP), pap’s job is to add printer control information to the 
PostScript data. 

Once the AppleTalk PAP Session layer has done its job, it passes 
the data down the stack to the Transport layer. At the Transport 
layer, the AppleTalk Transaction Protocol, or ATP, adds transac- 
tion-oriented commands to manage the give-and-take nature of 
the transmission. 

With the transaction data added to the message, it’s placed inside 
an AppleTalk datagram at the Network layer. Here, the Datagram 
Delivery Protocol (DDP) has the task of creating the datagram and 
logically addressing it for delivery. 

The addressed datagram is then sent to the Data Link layer where 
the selected network driver — either the LocalTalk Link Access 
Protocol (LLAP), EtherTalk Link Access Protocol (ELAP), TokenTalk 
Link Access Protocol (TLAP), or another AppleTalk network 
driver — places the datagram into the appropriate network frame. 

Finally, the Data Link layer passes the frame onto the Physical 
cabling layer and the message is sent to the recipient. 


The seven layer OSI Reference Model provides a complete — but 
often complex — view of Macintosh networking. To address this 
problem of complexity, a simplified four-layer symbology has 
been introduced which essentially collapses some of the detail. 
The collapsed layers of the OSI Model have importance and 

Part One Networking Fundamentals 

significance, and will be discussed, where appropriate, throughout 
this book. But, for most basic Macintosh networking activities, the 
four layer NetPlCT approach will enhance the reader’s under- 
standing and comprehension of a complicated world. 





xtending and adding to the NetPICT concept, 
this chapter explores concepts such as network 
addressing (botli logical and physical) and how 
digital signals are conveyed over a network. 

Types of Networks 

Basically, there are two kinds of computer networks: circuit- 
switched and packet-switched. Circuit-switched networks ermpXoy 
point-to-point links between the participating nodes of the net- 
work (see figure 4.1). The link is dedicated between the partici- 
pants of the connection. This is similar to most telephone systems, 
where the phone company uses elaborate switching mechanisms 
to connect the callers. 

Packet-switched netivorks uiWize a common connection which is 
shared simultaneously among all nodes of the network. Members 
of a packet-switched network communicate by sending discrete 
packets of information that are identified with the network address 
of the sender and recipient. To better describe the differences 
between circuit and packet switching, let’s imagine a classroom 
full of students. 

Part OneNetworking Fundamentals 

Figure 4.1 


The students aren’t allowed to talk out loud, so one of them 
fashions a circuit-switched network with two tin cans and some 
string. Each time it’s used, the cormection is dedicated between 
the two participants. The switching occurs when other students 
need access to the network. Then, the tin cans get passed along to 
another pair of students. Of course, waiting for the tin cans be- 
comes tiring, and when a number of students need to communi- 
cate, the circuit-switched network becomes inefficient. 

So, in place of the tin cans, another solution was devised. The 
students began to pass notes to each other. To identify who 
receives emd who sends the note, each note has the names of the 
sender and the recipient on the outside of the note. This network- 
ing technique is known as packet-switching. 

If the sending and receiving students are sitting next to each other, 
they simply can pass messages between themselves. If the sender 
and the recipient are sitting at opposite ends of the classroom, the 

Chapter Four Networking Concepts 

note has to be passed from student to student. Each student who 
handles the note looks at the names of the sender and recipient to 
determine how best to route the message. This is similar to the task 
that network routers perform when they route network packets 
from the source to their destination (see Figure 4.2). 

Figure 4.2 

Packet swiicliino. 

One advantage of the note-passing packet-switching scheme is 
that multiple notes or packets can be handled at any given instant. 
This is in direct contrast to the circuit-switching technique, where 
each connection remains dedicated for the duration of the transac- 

Most LANs, such as LocalTalk, Ethernet, and Token Ring, rely on 
packet-switching technology. Obviously, one of the important 
aspects of a packet-switched network involves the identification of 
the sender and the recipient. This general problem is referred to as 
network addressing. 

Part One Networking Fundamentals 

Network addressing, like the street address of where you live or the 
name of a note-passing student, simply means to uniquely identify 
the network participant. There are two different kinds of network 
addressing: logical and physical. 

Logical addressingis software-based. It’s how a specific networking 
protocol, such as AppleTalk, identifies the senders, recipients, and 
other devices on the network. Physical addressing is hardware- 
based. It’s tied to a specific cabling system. Let’s compare these 
two different addressing schemes. 

Logical Addressing 

Every networking protocol, such as AppleTalk, DECnet, and 
TCP/IP, has a scheme to identify members of its respective net- 
work. Essentially, this means every network member, or node, has 
a unique identification number. 

With AppleTalk, this identifying number, or node number, is based 
on an eight-bit number. With eight bits of information, the maxi- 
mum number of nodes is 2^ or 256 (see figure 4.3). For small 
networks, having a limit of 256 nodes is not a problem. In fact, 
Apple’s LocalTalk cabling system permits no more than 32 nodes. 
(With LocalTalk, the restriction is a physical or electrical limit, not 
a logical limit of node addresses.) 

Figure 4.3 

Applelalk node numbers. 

22 32 


73 63 


But many networks require more than 256 AppleTalk nodes, and 
another mechanism was needed to support these larger networks. 
So, Apple developed a concept that permitted groups of nodes, 
called “networks,” to be established: each AppleTalk network 
would have its own range of 256 potential node IDs. 

Chapter Four Networking Concepts 

To create the boundaries between these different AppleTalk 
networks, Apple developed the specifications for a device knovvTi as 
an AppleTalk router. AppleTalk routers are the glue that connects 
separate AppleTalk networks into a larger whole known as an 
internetu>ork. AppleTalk routers separate and define the bound- 
aries between AppleTalk networks. 

Each AppleTalk network has a unique ID number that is stored 
inside each router connected to that network. In the simplest case 
of two AppleTalk networks connected by a single router, the router 
maintains the AppleTalk network numbers for each of the two 
networks. Routers will be discussed in depth later in the book. 

The current AppleTalk specifications provide a 16-bit network 
number. With 16 bits there can be 2 or 65,536 unique AppleTalk 
networks (see figure 4.4). And since each network can potentially 
support 256 nodes, AppleTalk can support a theoretical maximum 
of 16,777,216 devices! 

Figure 4.4 

Applelalk network 

The 16-bit network and 8-bit node number make up only part of a 
complete AppleTalk logical address. An additional 8 bits is used to 
define something known as an AppleTalk socket number. 


Part One Networking Fundamentals 

Your Macintosh can handle a number of network chores at one 
time. At any given instant, a Macintosh could be accessing a file 
server, printing to a LaserWriter print server, and receiving an 
E-mail message. To keep these diverse transactions separate and 
distinct, AppleTalk assigns a unique socket number for every 
logical connection. With socket numbers consisting of 8-bit values, 
there are 256 possible socket numbers that can be used (see figure 
4.5). Socket numbers start at 0 and end at 255. Both 0 and 255 are 
undefined. Half of the remaining socket numbers, from 1 to 127, 
are reserved for special system use by Apple. The other half, from 
128 to 254, are pooled resources available for general use by 

Figure 4.5 

Applelalk socket 

Network #1 


Socket 132 is being used... 








Network #2 


.to communicate with 
Socket 143. 










When you print a document, a socket number for that transaction 
is automatically assigned from the pool. When the job is com- 
pleted, the number is returned to the pool for subsequent use. 

Collectively, these three numbers — network, node, and socket — 
make up a unique AppleTalk logical address. When a Macintosh 
and LaserWriter engage in printing transactions, they identify the 


Chapter Four Networking Concepts 

participants using netw'ork, node and socket numbers — for in- 
stance, Macintosh node number 22, located in network 100, is 
communicating over socket 129 to LaserWriter node 32, in network 
101, with socket 130. 

The choice of three numbers — the 16-bit network number and the 
8-bit node and socket number — is specific to AppleTalk. Other 
networking protocols, such as DECnet and TCP/IP, use similar but 
different numbering schemes to logically identify their nodes. The 
important thing to remember about these logical network ad- 
dresses is that they are tied to a specific networking protocol, and 
they only exist in software. 

Because Macintosh and other computers can often run multiple 
networking protocols concurrendy, it’s often common to have 
multiple logical addresses on a single computer. For example, a 
Macintosh that’s running AppleTalk, DECnet, and TCP/IP concur- 
rently would have three different logical addresses (see figure 4.6). 
Its AppleTalk address might be 12.22 (network.node), its DECnet 
address might be 5.2 (area.node), and its TCP/IP address might be 

12.22 AppleTalk 
5.2 DECnet TCP/IP 





Figure 4.6 

Oifleieni logical 
addresses on one Mac. 

Every time this Macintosh sends or receives AppleTalk communi- 
cations, its logical network AppleTalk address is 12.22; when 
DECnet is sent or received, the logical DECnet address of the 
Macintosh is 5.2. 

Part One Networking Fundamentals 

Figure 4.7 

Elhemet physical 

Physical Addressing 

Another kind of addressing is used often to facilitate the transmis- 
sion of data over a physical cabling medium. For example, 
Ethernet uses a unique number to identify each Ethernet device 
(see figure 4.7). The best example of an Ethernet device is an 
Ethernet card. Ethernet relies on a unique 48-bit number, where 
the first 24 bits identify the vendor of the device and the last 24 bits 
identify the specific device — kind of like a serial number. These 
numbers are stored permanently inside the Ethernet device. If you 
swap Ethernet cards with another Macintosh, the physical 
Ethernet address remains with the card rather than with the 

This Mac has an Ethernet 
hardware address of 
08 - 22 - 12 - 32 - 37-14 

¥ ^ 




This Mac has an Ethernet 
hardware address of 
08 - 22 - 12 - 32 - 12-12 

With Ethernet, access to the cable and communications over that 
cable are controlled by the physical Ethernet addresses. Each 
networking protocol is responsible for equating its protocol- 
specific logical address to the Ethernet physical address that is 

So, going back to our example of a Macintosh running three 
different protocols (AppleTalk, DECnet, and TCP/IP), each 

Chapter Four Networking Concepts 

protocol has a different logical identification number — but all 
must convert their respective logical addresses to the same 
Ethernet physical address (see figure 4.8). 



100 . 22 . 128.132 




This Mac has an Ethernet 
hardware address of 
08 - 22 - 12 - 32 - 12-12 

TCP/IP uses a special protocol called ARP, which stands for 
Address Resolution Protocol. It resolves the different logical and 
physical addresses. AppleTalk uses a similar protocol called the 
AppleTalk Address Resolution Protocol, or AARP. AARP equates 
logical AppleTalk addresses with physical Ethernet addresses. 

A table containing the AppleTalk addresses, along with their 
respective Ethernet addresses, is maintained on each Ethernet- 
equipped Macintosh. This table is known as the Address Mapping 
Table, or AMT. When a Macintosh needs to send a message to a 
specific AppleTalk address, the corresponding Ethernet address is 
determined from the AMT. Then, when the message is sent to the 
Cabling layer, Ethernet addressing is used to deliver the goods. 

Figure 4.8 

lllieinet physical 
addressing and muliiple 
logical addresses. 

Part One Networking Fundamentals 

Figure 4.9 


Figure 4.10 

Eihernei flame itiagtain. 

Network Frames 

Each cabling system (or transmission medium) in a packet- 
switched network has its own method of conveying or framing 
information. These network frames act as “delivery trucks” de- 
signed for a specific kind of network highway (see figure 4.9). 



W« Sflif Configure 



So You Don’t Have To^ 





t— 1 

Fbnytaile U» 

Z_ s 






Sinco 1976 



Someone Had.. 
To Po It 

With Ethernet, a network frame is composed of a number of 
different components, each with its own function. The first two 
components are the source and destination of the Ethernet frame 
(see figure 4.10). These are identified with the unique 48-bit 
Ethernet hardware addresses. They’re similar to the “From” and 
“To” logical addresses of an AppleTalk DDP datagram. 

Source Destination Type Data CRC 

Chapter Four Networking Concepts 

The next component is known as the type code. The type code 
uniquely identifies the networking protocol contained within the 
next component of the frame. Every Ethernet networking protocol 
has a unique type code. AppleTalk has several type codes, one for 
plain AppleTalk (809B) and one for AARP (80F3). A DECnet packet 
has a type code of 6003. Think of the type code as the sign on the 
side of the truck that identifies the contents held within. 

The actual payload is placed within the data section of the Ethernet 
frame. The data are usually protocol specific. In the case of 
AppleTalk, the data section is the place where the DDP datagrams 
are stored. The data section can vary from anywhere between 5 
and 1500 bytes in length. 

The last component is used for error checking. A special algorithm 
known as a cyclic redundancy check is used to ensure that no 
transmission errors have corrupted the data. 

NOTE: Because most networking frames can support multiple protocols, it’s 
important to remember that networks, such as Ethernet and Token Ring, were 
designed to support multiple protocols. Therefore, it’s not mandatory to 
restrict your network to a single protocol. 

Network Signaling 

When binary signals are finally sent to the Cabling layer for trans- 
mission, the software that generates the binary communications 
data must now interact with the “real,” physical world. While a 
complete explanation of the physical laws and the electronics 
involved with these network communications is beyond the scope 
of this book, an introduction to the basic concepts will help you 
understand the capabilities and limitations of the network. 


Part One Networking Fundamentals 

A good starting point is the concept of network speed. Ethernet is 
not “faster” than LocalTalk. All electrical signals travel at speeds 
close to the speed of light (approximately 80% of it). In order to 
transmit digital, or any kind of data, with electromagnetic signals, 
there are a limited number of choices available. 

One way is to vary the amplitude, or strength, of the signal as time 
progresses. By changing (modulating) the amplitude, the ones and 
zeros of the binary data can be represented by different voltage 
levels (see figure 4.1 1). Actually, amplitude modulation was the 
basis for the very first radio signals; AM radio still works this way 
today. With AM radio, though, the source of the transmission is not 
digital, but tmalog. 

Figure 4.11 

Willi aiiipliiuile 
modulation, itie 
ilie signal varies Willi 
remains cnnsiant 







Another technique is to vary tlie frequency of the signal with time. 
Instead of changing the amplitude or voltage, ones and zeros are 
represented by shifts in frequency (see figure 4.12). This technique, 
known as Frequency Modulation, is a much more efficient and 
reliable way to transmit data. Just compare the broadcast quality of 
AM and FM radio stations and you’ll begin to get the idea. 

In fact, radio and television stations are a good way to describe the 
signaling behind computer networking. The network cable, be it 
LocalTalk, Ethernet, or Token Ring, has many similarities to a radio 
or TV broadcast. 

Chapter Four Networking Concepts 

Figure 4.12 

olllie signal mains 
(ilie distance beiweenihe 
peaks and valleys) vaiies 
will) lime to encndeilie 

With radio and television, each station broadcasts over a specific 
frequency. All these different frequencies are being used simulta- 
neously to carry the hundreds of programs that you can watch or 
hear. All that’s required is to tune in to the appropriate frequency 
with the appropriate receiver. 

In computer networking, this kind of multi-channel access is often 
referred to as broadband networking. Broadband networks are 
common in campus environments and large corporate environ- 
ments where multiple communication channels are required (see 
figure 4.13). 

Channel A 
Channel B 
Channel C 
Channel D 

Figure 4.13 

piuliiple channels pnope 
signalling medinm. 

Most computer networks, particularly local-area networks, use a 
single channel technique known as baseband networking (.see 
figure 4.14). To compare it to radio and television broadcasting, it’s 
as if each station were communicating over the same frequency or 

Part One Networking Fundamentals 




Figure 4.14 

Of course, unless there were strict controls on when each radio and 
TV station were permitted to transmit, the single shared channel 
would be a garbled mess of colliding and interfering transmissions. 

Such is the problem confronted by the designers of modern 
network cabling systems — how best to share the common carrier 
and maximize throughput. Ethernet and Token Ring exemplify two 
of tlie more popular approaches to solve this problem. 

With Ethernet, the solution is to play a statistical game of listen and 
wait. Wlien an Ethernet node has to send a message, it first “lis- 
tens” to the network. If another station is transmitting a message, it 
waits until another check indicates that the channel is clear. If the 
channel is clear, tlie Ethernet station begins to transmit. The major 
problem with this technique is one of timing. Station A can start to 
transmit, but its signal might not reach Station B before Station B 
begins to transmit. Even though the signal travels at close to the 
speed of light, the delay is often enough to fool a station into 
transmitting when anotlier message has already started to make its 
way onto the network (see figure 4.15). 

When this happens on an Ethernet network, it’s called a collision. 
Fortunately, the Ethernet hardware can handle and recover from 
these collisions. When they occur, the messages are retransmitted 
after a short waiting period. 

One of the side effects of this collision detection technique is that 
the actual throughput of heavily loaded Ethernet networks will 
begin to degrade as the number of collisions and retransmits 
begins to increase. 

Chapter Four Networking Concepts 

Figure 4.1 5 

Eihernei collisions. 

To compare Ethernet networking to our radio and TV example, 
imagine that all the radio and TV stations share a common fre- 
quency or channel. Before transmitting, each station turns on a 
radio or TV to check if anyone else is transmitting. If the channel is 
unused, the station begins to transmit for a specific period of time. 

Occasionally, two stations might start to transmit at roughly the 
same time, and the airw^aves become garbled. But shortly after you 
hear a burst of static or the TV screen goes fuzzy, special circuitry 
kicks in, transmits the first signal, and stores the second signal for 
subsequent playback (see figure 4.16). Of course, as more and 
more stations are added, the static bursts and interruptions 
become more frequent, until it reaches a point where there's 
simply too much traffic — the listeners are getting more static than 

With Token Ring, the technique is a bit different. Each station can 
transmit for a specific period of time. The time period is deter- 
mined by a token that gets sent around to each of the stations. 


Part One Networking Fundamentals 

When a station possesses the token, then — and only then — is it 
allowed to transmit. It’s kind of like the hall pass in Junior High 
School that establishes shared use of the rest rooms. 

Figure 4.16 

As ilie level olirallic 
network, a point is 
teaclteil where actoal 
Eventoally, as activity 
increases. throughput 

Unlike Ethernet, it’s not necessary to "listen” to the network before 
transmitting. A welcome side benefit is that the network perfor- 
mance doesn’t degrade when it’s pushed to the limit. With Token 
Ring, as more and more stations are added to the network, a point 
of equilibrium is reached where the network will continue to 
deliver its maximum throughput although each station may have 
to wait a correspondingly longer period of time before transmit- 

With our radio and TV analogy. Token Ring networking is made 
very simple. Each station is allowed to transmit only at specific 
times and only for so long. Every station transmits in turn and 
every station is assured of access to airwaves (see figure 4.17). As 
new stations are added, the time between a given station’s trans- 
mission sessions may increase, but at least the listeners won’t be 
bothered with interruptions and static. 

LocalTalk uses a “wait and listen" approach similar to that of 
Ethernet. With Ethernet, this access metliod is called CSMA/ CD. It 
stands for Carrier Sense (check for carrier before transmission) 

Chapter Four Networking Concepts 

Multiple Access (a number of nodes can use the cable at one time) 
Collision Detection (there’s special circuitry built into the Ethernet 
controller that detects and recovers from collisions). 

Figure 4.17 

As the level oliiallic 
ihroughpui leaches a 
siahle point and lemains 
cnnstani. Unlike liheinei 

In order to get the cost down, Apple omitted the extra components 
required to detect and recover from collisions. Instead, LocalTalk 
tries its best to avoid collisions by waiting random periods of time. 
If any garbling occurs, the signal is retransmitted by the higher- 
level AppleTalk protocols. This technique is called CSMA/CA, 
where the CA stands for Collision Avoidance. 


The fundamentals of networking can be described by the four 
basic layers, but certain aspects of networking require additional 
explanation. These technical aspects can also be easUy explained 
using convenient and common metaphors. 

The basis for most computer networking is the technique of packet 
switching. Discrete packets of data are sent over the networking 
medium from the sender to the recipient. These devices must be 
identified, and that is the reason for a network addressing scheme. 

Part One Networking Fundamentals 

Depending on the physics of the cabling system, different elec- 
tronic access methods must be used. Ethernet is an example of a 
delivery mechanism that detects for the presence of a signal, 
listens for traffic, and then begins to transmit. Other cabling 
systems, such as Token Ring, parse the available bandwidth by 
specifying a specific period for transmission. 





he networking industry is full of terms and 
buzzw'ords that are confusing and often mislead- 
ing. Using NetPlCTs, this chapter unambigu- 
ously defines and depicts common Macintosh 
networking components such as bridges, repeat- 
ers, and gateways. Once these basic components 
are defined, they will be placed in the context of 
various netw'orking topologies. These various topologies 
and networking implementations, such as Local Area Networks 
and Wide Area Netw'orks, will be discussed in Chapter 5. 

LANs & WANs 

LAN and WAN are acronyms, respectively standing for Local Area 
Network and Wide Area Network. Distance is the major difference 
between the two. LANs are usually confined to a single building or 
a group of buildings in the same general vicinity. When multiple 
buildings are involved, it’s common to have a LAN network seg- 

Part One Networking Fundamentals 

ment in each building. These segments are often connected with 
other segments. Underground fiber optic cable is frequently used 
to connect the segments. 

WANs are interconnected networks that span wide geographic 
areas. Basically, this means distances greater than what can be 
supported by a LAN. While there are no definite rules, WAN 
distances are generally measured in miles and LAN distances are 
usually measured in feet. 

Tj'pically, W'AN connections have a limited bandwidth when 
compared to IAN connections. This limitation might be one or two 
orders of magnitude. For example, an Ethernet network has a 
maximum capacity of 10 million bits per second, or 10 Mbps. Tl, a 
popular WAN carrier, has a bandwidth of 1.544 Mbps. In this case, 
the Ethernet network has roughly 6 1 12 times the bandwidth of the 
Tl link. 

WAN links, such as Tl, can be very expensive. These connections 
are usually leased by phone companies or other service providers 
and may cost several thousand dollars per month to maintain. 
Clearly, optimization and rational use of these WAN resources is 
important. Later on, we'll discuss the specific issues and problems 
with AppleTalk protocols on wide-area networks. 

Repeaters are the simplest of networking devices. They exist at the 
very bottom of the stack, functioning at the Cabling layer — the 
Physical layer of the OSl Reference Model (see figure 5.1). At this 
layer, the repeater is entirely ignorant of the higher-level protocols, 
such as AppleTalk. Repeaters only deal with the electrical signals 
that exist at the Cabling layer. As such, repeaters are often referred 
to as being protocol transparent . 

Chapter Five Common Network Components 

LocalTalk Repeater 

Figure 5.1 



Repeaters are essentially signal boosters that amplify weakened 
incoming signals, thus extending the effective range of a cable. 
Since repeaters are "dumb” devices, they also will amplify noise or 
any unwanted signals that might find their way onto your network. 

LocalTalk Repeaters 

There are a number of LocalTalk repeaters on the market. Some of 
them, such as Farallon’s PhoneNET Repeater, simply extend single 
segments of PhoneNET/LocalTalk. Other repeaters (for example, 
Farallon’s StarController) have multiple ports and permit different 
wiring topologies. 

The simplest kind of LocalTalk network is when all the participat- 
ing devices are connected in a daisy-chain fashion. However, 
daisy-chaining can create problems for all but the smallest 
LocalTalk networks. 

With daisy-chained networks, the wiring runs from node to node, 
creating the real possibility of occasional disconnects and disrup- 
tions to the network. By using a star or radial topology with a 
multiport LocalTalk repeater, each branch of the star is indepen- 
dent from the others (see figure 5.2). 


Part One Networking Fundamentals 

Figure 5.2 

Radial repealer topology. 

Punch-Down Blocl< 



Think of repeaters as wiring conveniences. They do not filter or 
limit nem'ork traffic in any way. The same signal and network 
traffic is seen on all ports of the device. 

It is possible to construct very large LocalTalk networks by inter- 
connecting repeaters, but problems often occur as the available 
bandwidth is still being shared across all wiring segments. At some 
point, the limited bandwidth of LocalTalk simply cannot support 
the traffic that’s routinely generated by an AppleTalk network. So, 
it’s best to limit the use of LocalTalk repeaters to extending that 
extra long run for the people in the shipping department, and to 
break away from the nasty habit of daisy-chaining. 

Ethernet Repeaters 

Like their LocalTalk cousins, Ethernet repeaters are protocol- 
transparent wiring conveniences. Like the multiport LocalTalk 
repeater (such as Farallon's StarController and Focus’s TurboStar), 
Ethernet repeaters let you avoid the daisy-chain network. There 
are Ethernet repeaters for all flavors of Ethernet cabling: thick, 
thin, and twisted-pair (see figure 5.3). 

In fact, with twisted-pair Ethernet (othei*wise known as lOBase-T) 
repeaters or hubs are mandatory. All lOBase-T connections are 
made through a hub. 

Chapter Five Common Network Components 

Figure 5.3 



Bridges function at the upper Cabling layer, or the Data Link layer 
of the OSI Model. They are one step higher tlian repeaters on the 
network evolutionary scale. 

Bridges use the layer that connects a specific networking protocol 
to a specific cabling system. Because they function one layer 
higher than repeaters, and thus know about physical hardware 
addresses or cable-specific addressing, bridges are often able to 
use these addresses to optimize traffic (see figure 5.4). 

LocalTalk Bridge 

Figure 5.4 

Bridge NelPICI. 

Bridges can examine the source and destination of netv\^ork frames 
and maintain a listing of which nodes are on which port. Then, the 


Part One Networking Fundamentals 

bridge can minimize traffic by only passing those frames that are 
destined for nodes on the other side (see figure 5.5). 

Hgure 5.5 


08 - 12 - 32 - 19-32 08 - 12 - 32 - 19-33 08 - 12 - 32 - 19-36 

Figure 5.6 


Like repeaters, bridges are often used to extend a particular type of 
network. Unlike repeaters, some bridges also can use the cabling- 
specific information to filter packets based on their protocol type. 

Certain Ethernet bridges are capable of examining the Ethernet 
Type Code of a frame. These bridges also can be programmed to 
pass or block a network frame based on the Type Code. These 
bridges are often referred to as filtering bridges (see figure 5.6). 

08 - 12 - 32 - 19-32 08 - 12 - 32 - 19-33 08 - 12 - 32 - 19-36 


Chapter Five Common Network Components 

Remember, bridges are cable-specific and, like repeaters, are 
essentially protocol-transparent. Bridges don’t inspect the 
datagram to see the logical address data. They can only infer, as in 
the case of Ethernet Type Codes, the networking protocol con- 
tained within. 

LocalTalk Bridges 

At this time, there is only one LocalTalk-specific bridge. Tribe's 
LocalSwitch uses the LocalTalk-specific node number to keep track 
of node locations. It then uses these numbers to limit traffic to only 
those segments containing the valid nodes. 

For example, if segment A of the Tribe bridge has LocalTalk nodes 
1 and 2, and segment B has nodes 3 and 4, then whenever nodes 
1 and 2 communicate, the resultant traffic will only be seen on 
segment A and not on segment B. 

Ethernet Bridges 

Historically, Ethernet bridges have been used to interconnect large 
corporations and organizations over long distances. By using 
bridges that connect to Ethernet on one side and wide-area 
network services on the other, organizations easily could connect 
two geographically remote Ediernet LANs and make them appear 
as a single connected entity (see figure 5.7). 

Unless some form of packet or frame filtering is employed, these 
devices logically connect the segments. Certain types of traffic seen 
on one segment will eventually be seen on the other segment. Of 
course, if the traffic represents frames destined for the other side, 
this makes sense. All too often, however, the traffic seen on one 
side of the bridge is local and is not destined for the other side. This 
unwanted passage of traffic particularly creates problems when the 
interconnection between the two networks is at a restricted 
bandwidth. This often creates a bottleneck between the higher 
bandwidth of the LANs. 


Part One Networking Fundamentals 

Rgure 5.7 


This network 
is conceptually 
the same... this 

...particularly when it comes to network broadcasts. 

Figure 5.8 


For example, it is a common practice to connect two Ethernet 
LANs with a leased telephone line, with a bandwidth of 56 Kbps. 
Considering that Ethernet has a bandwidth of 10 Mbps, it’s like 
having a 179-lane freeway being reduced to a single lane of traffic 
(see figure 5.8). 

Therefore, if you're using wide-area bridges over modest band- 
width connections, it’s very important to keep unwanted or 
unneeded traffic to a minimum. This shortcoming, inherent with 
wide-area network bridges, is one reason why the wide-area router 
is fast replacing the bridge as the wide-area network device of 


Chapter Fine Common Network Components 

Routers & Brouters 

Routers do their work at the Protocol layer, inspecting the source 
and the destination of a specific protocol’s datagram. Routers, like 
the children passing notes in the classroom, make decisions on 
how best to route messages based on the source and destination 
address. This is fundamentally different from bridges, which 
process network frames without regard to the networking protocol 
contained within. 

Because routers operate at the Protocol layer, they are often 
referred to as being protocol-specific. There are AppleTalk routers, 
DECnet routers, TCP/IP routers, and Novell routers. There are 
even routers that can route multiple protocols concurrently. 

Each connection on a router is called a port (see figure 5.9). These 
ports may be the same cabling type, or they may be different. For 
example, there are many AppleTalk routers that have a LxjcalTalk 
port and an Ethernet port. 

Hgure 5.9 


Because of this, it is often assumed that these devices are simply 
used to connect a LocalTalk network to an Ethernet network. In 
addition to providing this basic cable conversion, as shown in 


Part One Networking Fundamentals 

figure 5. 10, routers also possess a special capability. Routers can be 
used to isolate traffic. 

Figure 5.10 

muliiple cable lypes. 

Similar to the filtering bridges mentioned before, routers are able 
to keep local traffic local. For example, if a Macintosh and a 
LaserWriter are connected to a network on port A, the network 
traffic generated between these two devices will be limited to that 
network (see figure 5.1 1). The router will forward a datagram to 
another network only if the destination of the datagram is on that 

So, routers perform two basic functions. They provide a funda- 
mental way to connect one network to another, and they effec- 
tively isolate nenvork traffic. 


Chapter Five Common Network Components 

Figure 5.1 1 

Network itallic isolation 
witi) routers. 

AppleTalk Routers 

What started in 1985 with the Kinetics FastPath has evolved into a 
crowded and competitive market with dozens of AppleTalk rout- 
ers. While these routers support different cabling choices, unique 
configuration software, and value-added options, every AppleTalk 
router works on the same basic principles. All AppleTalk routers 
use AppleTalk network numbers to differentiate their ports. In fact, 
for most AppleTalk networks, the network numbers originate in 
the router. 

Let’s use a simple example of two LocalTalk networks connected 
by a two-port LocalTalk-to-LocalTalk AppleTalk router. In this 
example, we’ve used the configuration software that came with the 
router and established unique network numbers for each of the 
ports. It’s crucial that each network number be unique. This can be 
a challenge for a very large network. With large networks, it’s 
necessary to plan and administer AppleTalk network numbers. If 
an AppleTalk network number is duplicated anywhere on the 
collective network, unpredictable results may occur. 


Part One Networking Fundamentals 

AppleTalk routers can be connected in several different topologies. 
They can be arranged in a serial fashion, where one network is 
simply connected to the other. In Figure 5.12, network number 2 is 
serially connected to 1 and 3. 

Figure 5.12 

AppleTalk neiwoiks. 

Therefore, in order for an AppleTalk datagram to travel from 
network 1 to network 3, it must go through two routers. Each time 
a datagram passes through a router, it is called a hop. A hop is a 
unit of measurement that is used to measure the distance between 
the sender and recipient. AppleTalk has a maximum hop count 
of 15. 

Using serially connected routers to build large AppleTalk networks 
can be problematic because every time a datagram travels through 
a router, it must inspect the network address, which takes a certain 
amount of time. In a large serially-routed network, these delays 
accumulate. Another problem with this topology is that networks 
that are located between the sender and recipient have to deal with 
all the network traffic. 

A better way to build large AppleTalk networks is to use a backbone 
topology (see figure 5.13). Here, a common backbone network acts 
like a common network that connects a number of routers. With 


Chapter Five Common Network Components 

this topology, no network is more than two hops away. Backbone 
topologies are very common in large AppleTalk networks, where 
the backbone is often an Ethernet network and the routers are 
used to connect a number of LocalTalk networks to the backbone. 

Network #1 


q t;i q 


Network #2 

Network #3 

< 5 ^ 

Figure 5.13 

OP a backbone. 

As the cost of Ethernet connections continue to plummet, and 
since Apple now offers computers and printers with built-in 
Ethernet connections, LocalTalk networks and routers are becom- 
ing less popular. Instead, Ethernet-to-Ethernet routers are begin- 
ning to displace the sales of LocalTalk-to-Ethernet routers. These 
routers are not used to connect dissimilar cabling; the goal is 
simply to isolate network traffic. 

For many networks, routers provide a convenient way to isolate 
areas of high network traffic. Let’s use the example of an organiza- 
tion with an Ethernet backbone. Each department within the 
organization has its own Macintosh computers and LaserWriter 
printers connected to the Ethernet. The desktop publishing group 
is continually taxing the network with demanding print jobs and 
the transfer of large image files. The other departments and users 
have started to complain about poor network performance. One 
way to alleviate the problem is to place the DTP group on a sepa- 
rate Ethernet, connected to the primary network with an Ethernet- 
to-Ethernet router (see figure 5.14). With this approach, the 


Part One Networking Fundamentals 

extensive traffic associated with the DTP group will be kept to its 
own network. 

DTP Group 

The network numbers maintained by the routers are the primary 
determinants of an AppleTalk network. As mentioned before, the 
network numbers are used by the AppleTalk software to assist with 
the routing of datagrams. The problem with network numbers is 
that they’re not the best way for users to locate network services. 

To help users find services, Apple devised a way to associate names 
with networks. These names are called zones. AppleTalk zone 
names are stored in the router along with the network numbers. 
Unlike AppleTalk network numbers, which must be unique, 
AppleTalk zone names can be duplicated throughout the network. 
This feature makes it possible to organize network services in 
logical groups. 

As an example, imagine a ten-story building with a backbone 
Ethernet running up through the building. In the wiring closet of 


Chapter Five Common Network Components 

each floor, a LocalTalk-to-Ethernet AppleTalk router is used to 
connect a number of Macs and LaserWriters to the backbone. Each 
LocalTalk network has a unique network number and a zone 
name. The LocalTalk network on the first floor is network number 
1 , and the zone name is “ 1st Floor.” 

The Ethernet backbone also carries AppleTalk traffic, and therefore 
is also considered an AppleTalk network. In this example, the 
backbone is assigned network number 1000 and given the zone 
name of “Backbone.” This is accomplished by configuring the 
routers so that all routers agree that the backbone is defined as 
network 1000 and has the zone name of “Backbone.” 

Most floors only have a dozen or so devices, so the theoretical limit 
of 32 LocalTalk devices per network does not matter. But on the 
tenth floor, there are more than 50 devices that need to be con- 
nected to the network. Since this is too many devices to be placed 
on a single segment of LocalTalk, another LocalTalk segment and 
router will be required. 

Like the other routers, this additional router on the tenth floor 
must have a unique network number. Since it will be convenient 
for the users to refer to this new network with the same zone name 
as the other network, the zone name also will be “10th Floor” (see 
figure 5.15). 

What’s interesting about this process of zone grouping is that the 
AppleTalk protocols will combine all like devices by zone. So, if 
there were five LaserWriters in each of the two networks on the 
tenth floor, the Chooser would combine the devices and display a 
list of ten printers for the “10th Floor” zone. 


Part One Networking Fundamentals 

Rgure 5.15 

Network #100 Zone: "10th Floor 

^ ^ ^ ^ 

Network #10 Zone: "10th Floor' 

® c 

^ o 
^ « 

Network #2 Zone: "2nd Floor" 

■< 5 > 






Network #1 Zone: "1st Floor’ 


Multiprotocol Routers & Brouters 

Certain routers are capable of routing multiple networking proto- 
cols at the same time. These are generally known as multiprotocol 
routers. A good example of such a device is the Shiva FastPath. 

The FastPath is a LocalTalk-to-Ethernet AppleTalk router, but in 
addition to AppleTalk, it can also route DECnet and TCP/IP 
protocols. A multiprotocol router does not convert one protocol 
into another: it simply routes each protocol that comes along 
according to the protocol type. 

When the FastPath encounters DECnet datagrams, it routes them 
in accordance to the DECnet routing rules and configuration data 
maintained in the router’s program and memory. When an 
AppleTalk datagram appears, it’s routed using the AppleTalk rules, 
It’s as if three separate routers — one each for AppleTalk, DECnet 

Chapter Five Common Network Components 

and TCP/IP — were merged together as a single unit, sharing their 
hardware and portions of their configuration software. 

With a multiprotocol router, each protocol must be configured 
separately. So, in order to set up a FastPath to route all three 
protocols, you must configure each protocol independently using 
the FastPath Manager application that comes with the router. 

While AppleTalk, DECnet and TCP/IP are all different protocols, 
they do have something in common. They all can be routed. This is 
because all three protocols utilize the concept that large networks 
can be broken down into smaller pieces. 

With AppleTalk, large networks, called internetworks, are subdi- 
vided into networks by network numbers. The AppleTalk protocols 
support more than 65,000 networks, each potentially supporting 
either 253 or 254 nodes (under Phase 2 or Phase 1 AppleTalk, 

DECnet uses a similar technique where large networks are broken 
down into areas. DECnet supports a maximum of 64 areas; each 
area can potentially support 1024 nodes. TCP/IP, like AppleTalk 
and DECnet, also breaks down large networks into smaller group- 
ings (see figure 5.16). 

Figure 5.16 

Muliiproiocol routers. 

Part One Networking Fundamentals 

Each of these protocols utilize numbers that will be used by their 
respective routers to subdivide large networks. Each subdivision 
enjoys the benefits of traffic isolation, so that unneeded and 
undesirable traffic is kept within each subnetwork. 

Returning to our analog^' of students passing notes in class, imag- 
ine that tlie students form three cliques, and members of each 
clique never talk to the other cliques. To accommodate the note 
passing, the students decide that each clique will use a different 
color of paper for their notes. Also, each clique develops certain 
rules and idiosyncrasies for passing its notes. Those students who 
are allowed to pass all three colors of notes know the rules for each 
clique's notes. For example, the red notes have the last name first 
and have to be passed with the palm held down; the blue notes are 
addressed with just initials and have to be transferred within a 
closed fist. 

The students that know all the rules act as multiprotocol routers. 
Each clique has tlieir own protocol with addressing differences 
that have to be managed by the routing student. He has to be able 
to deal with notes that use different protocols in order to send 
them along to their proper destination. 

Some protocols don't use routing numbers at all. These protocols 
rely on a single monolithic network, with each node having a 
unique identifier. One such protocol is DEC'S Local Area Trans- 
port, or LAT. LAT is primarily used to provide terminal services to 
networked devices, such as ‘"dumb” VT terminals, connected to an 
Ethernet network with a device known as a terminal server. The 
terminal server takes the asynchronous communication from the 
VT terminal and places it onto the Ethernet within a LAT frame. 
The terminal server is a computer that can direct the LAT traffic to 
any available host (usually a DEC VAX) on the Ethernet. PCs and 
Macs equipped with an Ethernet card can also speak LAT directly 
to networked hosts. 

Chapter Five Common Network Components 

Unlike AppleTalk, DECnet, and TCP/IP, however, LAT was de- 
signed to run over a single, logical segment of Ethernet. There is 
nothing equivalent to a LAT network number or area number. 
Therefore, LAT is an example of a non-routable protocol. There is 
no such device as a LAT router — there is no network or area 
number that the router could use to route datagrams. Since LAT 
cannot be routed, it is often difficult to expand LAT terminal 
services beyond the confines of a single Ethernet LAN. 

One way that a LAT network can be expanded to another LAN is 
with a bridge. Since bridges only look at the Cabling layer — and do 
not care about the protocol-specific datagram information — they 
can be used to extend an Ethernet and to bridge LAT ser\dces 
between remote Ethernet segments. As mentioned before, 

Ethernet bridges can be used to essentially create one large 

What if we wanted to design a network providing AppleTalk, 
DECnet, TCP/IP and LAT services to two sites: one in New York 
City and the other in San Francisco (as in figure 5.17)? Each site has 
a backbone Ethernet. 

Figure 5.17 

NY loSFO with bridged 


Part One Networking Fundamentals 

If we simply connect these two networks using Ethernet bridges 
and leased telephone lines, everything would work, but we would 
have essentially created one big Ethernet. All the protocols will 
freely traverse both networks via the phone lines. This might create 
a problem. Every time someone prints a document or sends a mail 
message in New York City, the traffic generated by those activities 
is sent through the phone lines and reproduced on the San Fran- 
cisco network. Filtering bridges would help somewhat, by keeping 
track of what Ethernet devices are on what side of the connection, 
but certain kinds of traffic (known as Ethernet broadcasts or 
multicasts) would still be seen on both sides of the network. 

To really solve the problem, a pair of multiprotocol routers could 
be used to subdivide our AppleTalk, DECnet, and TCP/IP networks 
into logical segments on each side of the connection. This would 
effectively isolate any unwanted traffic, preventing it from travers- 
ing the expensive and restrictive leased phone lines. 

If we simply added the routers in addition to the Ethernet bridges, 
we would have a problem (see figure 5.18). The AppleTalk, DECnet, 
and TCP/IP traffic would still be able to sneak through the bridge 
and get to the other side. We simply can’t do away with the bridge 
because that’s how LAT is getting to the other side. And since LAT 
is a non-routable protocol, it can’t be routed through the multi- 
protocol router. 

One solution would be to configure each bridge to filter out and 
ignore the AppleTalk, DECnet, and TCP/IP traffic (see figure 5.19). 
This would essentially limit the bridge to only carrying LAT traffic, 
and the router would then handle the AppleTalk, DECnet, and 
TCP/IP traffic. 

Chapter Five Common Network Components 


AppleTalk, DECnet, TCP/IP 



. ■ — 

1 in — 

i HMRnti y - ■ ■ ^ 1 eo»wwrt 1 



1 erldg* 1 1 irtdp. | 

AppleTalk, DECnet, TCP/IP 

and LAT 



ngure 5.18 

Tlierouiei is passing 

Figure 5.19 

ICP/IP are filtered at ibe 

Router manufacturers, in an attempt to solve this problem, have 
designed hybrid routers and bridges. These devices, sometimes 
referred to as brouters, route all the routable protocols and bridge 
the non-routable protocols. Most of the high-end routers (such as 
Cisco and Wellfleet) can be set to act as multiprotocol brouters. 

Another approach to solve this problem is to place the non- 
routable protocol inside another protocol that can be routed. This 
general practice is called tunneling, and can be used to solve a 

Part One Networking Fundamentals 

number of different problems in addition to LAT. AppleTalk 
packets can be tunneled inside DECnet and TCP/IP packets for 
several reasons. This practice will be discussed later in the book in 
more detail. 

Figure 5.20 

Gateway Iheofv. 


Gateways are the most complex of network devices, functioning at 
the upper-most layers where the format of the data comes into 
play (see figure 5.20). Simply put, gateways provide translation 
services on the network. They can be used to connect different 
kinds of network cabling, but most important is that gateways 
convert the format in addition to the networking protocol. Gate- 
ways are the language translators of the network. 



A O 

Common or Different Physical Media 

Different Networking Protocols 
(i.e. AppleTalk, DECnet, TCP/IP) 

O □ A 

Since gateways build upon the bottom two layers, it’s common 
that most gatew'ays also function as multiprotocol routers. Some 

Computer A Gateway Computer B 











Chapter Rue Common Network Components 

gateways can even be exclusively set up as routers, thus ignoring 
their higher-level conversion capabilities. 

The main advantage and purpose of gateways is to provide a 
centralized alternative to placing a “foreign" transport and service 
on your client computers. 

AppleTalk Gateways 

Suppose you needed to connect a Macintosh to a UNIX-based 
workstation, perhaps to share files. One approach would be to 
simply equip your Macintosh with the TCP/IP protocol stack, and 
then choose a file service that works in concert with TCP/IP, such 
as NFS (Network Filing System). 

Once equipped, the Macintosh would match the UNDC workstation 
at all layers, and therefore would be able to transfer files. Of course, 
the other solution would be to equip the UNIX machine with 
AppleTalk and its file sharing software, AFP (Apple Filing Protocol). 

But, if we wanted to stick with TCP/IP and NFS on the UNIX 
machine, we would still have another option. With an AFP- 
AppleTalk/NFS-TCP/IP gateway, the Macintosh would use the 
gateway to convert AFP and AppleTalk protocols into correspond- 
ing NFS and TCP/IP protocols. 

To the Macintosh, the AFP-AppleTalk side of the gateway looks like 
any AFP or AppleShare file server. To the UNIX workstation, the 
NFS-TCP/IP side of the gateway looks like an NFS client. The 
gateway handles the complete conversion between the different 
filing systems and network protocols (see figure 5.21). 


Part One Networking Fundamentals 

Figure 5.21 

KeiPICIol NFS gateway 
(Cayman Gaioilioxl. 


UNIX Workstation (NeXT) 

Figure 5.22 

DECnei gateway. 

One appeal of a gateway is that no special software is required on 
either the client or tlie server. The gateway performs all necessary 
functions. This approach may not be as fast as placing the same 
native protocols on each machine, but it can be a simple and cost 
effective way to share dissimilar network services. There are several 
different kinds of gateways for the Macintosh. In addition to the 
AFP/NFS gateways, which are available from several vendors, there 
are AppleTalk gateways that work other protocols as well. 

In dec’s PATHWORKS for Macintosh product, there are two such 
gateways. One gateway is tlie AppleTalk-DECnet gateway. This 
gateway runs on the VAX, in conjunction with AppleTalk for VMS 
and its native DECnet. Macintosh services, such as DEC’s All-In-1 
Mail for Macintosh, can use the AppleTalk protocol to communi- 
cate with the VAX. However, DEC’s mail server doesn’t communi- 
cate over the AppleTalk for VMS protocol stack — it uses DECnet. So 
the gateway converts the protocol and service calls from AppleTalk 
to the corresponding DECnet calls (see figure 5.22). 

Macintosh DEC VAX 

The other PATHWORKS for Mac gateway is the AppleTalk LAT 
Gateway (see figure 5.23). It enables LocalTalk-equipped Macs 

Chapter Five Common Network Components 

(or any non-Ethernet resident Macs, such as dial-in AppleTalk 
Remote Access Macs) to access LAT-based terminal services. This 
gateway runs in the background of an Ethernet-resident Macin- 
tosh. Client Macs use the AppleTalk- LAT tool to connect to the 
gateway; the gateway takes the incoming AppleTalk data, converts 
it to LAT, and sends it out over tlie Ethernet. 


MacTermlnal 3.0 

Apple Macintosh 
AppleTalk / LAT Gateway 

VAX Application 


) / Formats V- 

( Formats ) ( 



1 1 AppleTalk ] I 

f 1 1 


» LocalTalk 

/ S LocalTalk / 

S Ethernet / ^ 

► Ethernet < 

Figure 5.23 

Applelalk/lAI gateway. 

In all these examples, one protocol has been converted and trans- 
formed into another. To help with the basic idea behind gateways, 
let’s return to the analogy of students passing notes in a classroom. 
Before, we discussed how packet-switched networks could be 
likened to students passing notes in a classroom. When a student 
looks at the “To” and “From” on the note and passes the note 
along, she is essentially performing the function of a router. But 
let’s imagine a situation where one of the students, Sonia, can only 
understand Polish and does not understand English. 

For Sonia to communicate with the other students, she can learn 
English, or the other students can learn Polish. Until this happens, 
however, Sonia must rely on a gateway. Her sister, Patrizia, under- 
stands both Polish and English. Notes that are sent to Sonia must 
first be sent to Patrizia, who converts the English to Polish, and 
then passes the note to Sonia. When Sonia sends a note to one of 
the other students, Patrizia reverses the process and converts the 
Polish into English. 

In this brief example, we can see the difference between a router 
and a gateway. Those students who merely passed the notes along 

Part One Networking Fundamentals 

acted as routers. Patrizia, who converted from one format to 
another, acted as a gateway for Sonia. 

Miscellaneous: Hubs, Concentrators, 
and So Forth 

Hubs and concentrators are wiring conveniences that essentially 
perform the same function — they provide a central attachment 
point for network devices. Unless they Incorporate bridges or 
routers, they do not interact with the networking addressing or 
protocols in any way. Most large network installations employ 
some sort of network concentrators in order to implement a radial 
or star wiring topology. The specifics of the various networking 
topologies will be covered in the next section. 

Usually, network hubs and concentrators are installed in a stan- 
dard 19-inch rack. These racks are standardized metal frames that 
hold electronic equipment and permit easy access and mainte- 
nance. Often, other networking components (such as modems, 
bridges, routers, and gateways) are also stored in the rack with the 
concentrator. This makes it easy to interconnect the LAN with the 
desired devices. 

Many hubs and concentrators come wdth diagnostic software that 
assists with the management of network devices and performs 
fault diagnosis. This software should not be confused with the 
protocol-specific configuration software that comes with routers 
and gateways. Instead, this software is often able to turn on and off 
the concentrator's ports, perform line quality checks, and even 
perform rudimentary traffic analysis. 

Chapter Five Common Network Components 

Network Topologies 

One topic that’s covered in all nettvorking books is topology. The 
topology of a netAvork is simply the form and sequence of connec- 
tions. The topology does not depend on the kind of wiring or 
protocols used. There are several different kinds of networking 
topologies, each with their own benefits and disadvantages, and 
these can be combined to create hybrid networks. 

Daisy Chain 

One of the simplest network topologies is the daisy chain. As the 
name implies, a daisy-chain network is created by simply connect- 
ing one node to the next. Perhaps the best example of a daisy- 
chain network is LocalTalk. 

With LocalTalk cabling, the connections are made with segments 
of wire, in a serial fashion — one after the other (see figure 5.24). 
Daisy-chained networks are fine for small workgroups where the 
wires can be conveniently routed. The problem with daisy chaining 
is that the entire network can be easily severed and disrupted if the 
cable is broken or disconnected at any point along its length. 

Figure 5.24 



This often happens when someone disconnects their Mac from the 
LocalTalk segment by disconnecting either of the two network 
segments instead of the single attachment point at the printer port. 
It also happens when a new node is added to the network and 
cannot be added to one of the two free ends of the network. 


Part One Networking FundamentaJs 

Figure 5.25 



Thinwire (or lOBase-2) Ethernet networks can also be set up in a 
daisy-chain topology, but the same problems exist (see figure 5.25). 
The network can be easily severed by a careless disconnection. The 
end points of a thinwire Ethernet network must be terminated with 
resistive end caps. If the network is broken at either of the two 
network connections on the tee, the resistive load is missing and 
the network is disrupted. 

won't disrupt the network... will disrupt the network. 

Apple recently introduced a version of thinwire Ethernet, where 
the resistive loads are automatically maintained in the event of a 
disconnection. (At least this way you’ll still have two functioning 
network segments.) 

For most office and business settings, daisy-chained networks are 
usually avoided because of the problems associated with frequent 
disconnects and maintenance of the wiring. 

Common Bus or Backbone 

A common bus, or backbone, network is simiiar to the daisy-chain 
network except that the cable connecting all the participating 
devices is one entire segment. The nodes connect to the backbone 
with an attachment unit. 

Chapter Five Common Network Components 

The most common example of a backbone network is a thickwire 
or lOBase-5 Ethernet cable. A thickwire Ethernet backbone can be 
as long as 500 meters (1600 feet). Nodes and other network devices 
attach to the thickwire Ethernet with transceiver devices that 
clamp onto the cable. 

These transceiver connections are somewhat expensive (ranging 
anywhere from $100 to $300) and take some time to install. Be- 
cause of this, these transceiver connections are very often used to 
connect hubs or other devices where multiple connections can be 
made at a single location. 

Most large network installations that use Ethernet utilize Ethernet 
backbones that are connected to other devices. These backbones 
often run up through the stories of the building, between the 
wiring closets where the connections are established (see figure 

Wiring Closet 

Wiring Closet 

Thinwire (10Base-2) 

Hgure 5.26 

Backbone or bus 

Radial or Star 

A radial, or star, topology has connections that radiate from a 
single location. Usually there is a single node on each branch of the 

Part One Networking Fundamentals 

Figure 5.27 


star. Some configurations of star networks support the daisy- 
chaining of devices, but this often defeats the principal advantages 
of the star topology. 

One advantage of star networks is ease of wiring. Each node (or 
office) is wired so that all connections converge at a single point — 
usually a concentrator located within a wiring closet. Then, when 
wiring changes are needed, they can take place within tlie closet. 
This avoids the hassle associated with daisy-chaining. Another 
advantage is that connections and disconnections can be easily 
made without disrupting the other members of the network. A 
node could blow up and it still wouldn’t affect the traffic on the 
other segments of the star. 

Star networks are common in the Macintosh world. With LocalTalk 
netvi'orks, there are several repeaters that permit the use of star 
topology (see figure 5.27). Farallon’s StarController and the 
TurboStar from Focus are two well-known examples. These 
devices also come with software which provides some measure 
of network maintenance. 

There are also Ethernet devices that permit the use of a star topol- 
ogy. There are thinwire Ethernet hubs that can be used to get away 
from the problems associated with thinwire daisychaining. The 

Chapter Fiue Common Network Components 

most popular Ethernet hubs today are the lOBase-T (or Uvisted- 
pair) Ethernet hubs. These hubs typically attach to a backbone 
Ethernet and provide several (usually eight) connections for 
twisted-pair Ethernet nodes. 

Twisted-pair Ethernet has a maximum range of 100 meters (320 
feet) and uses inexpensive four-conductor telephone-style wiring. 
Each node must connect to the hub. 


A ring topology (see Figure 5.28) connects all the devices in a 
circular manner. Ring networks are typified by Token Ring and by 
FDDI, which uses dual rings for redundancy and increased 



Figure 5.28 



Most large networks use a combination of topologies (see figure 
5.29). Each topolog>' is used for a specific reason and purpose. 
Performance, maintenance, and cost are all factors that determine 
the choice of a comprehensive networking topology. For example, 
it's common to see star and ring networksthat connected to a 
backbone network, that’s in turn connected to another backbone 
in a serial fashion. 

Part One Networking Fundamentals 

Figure 5.29 

Composite lopology. 




Macintosh Running 
the Appie Internet 
Router between 
Ethernet and Token 
Ring segments 

Ethernet Backbone 

Token Ring 


Part of the difficulty in understanding networking is the plethora of 
networking black boxes that perform unknown or mysterious 
tasks. These components fall into a number of categories, such as 
repeaters, bridges, and routers. Of these, one of the key devices is 
the AppleTalk router. It’s the basis for creating large AppleTalk 
networks and isolates traffic to a specific segment. Many AppleTalk 
routers are also capable of routing other protocols, such as DECnet 
and TCP/IP. These are known as multiprotocol routers. 

These routers, along with other devices (such as bridges, repeaters, 
and gateways), are connected in specific arrangements referred to 
as topologies. These topologies are often dictated by the choice of 
a cabling system. Small networks, such as LocalTalk networks, are 
comprised of a single topology. Most large networks employ 
several topologies, such as a combination of backbone and star 
topologies, to meet specific networking and wiring requirements. 

lats, Transports, and Media. 


Pai t ll introduces Macintosh spet 

networking by breaking the topic 

Part II introduces Macintosh specific 

four basic components: Services, 

networking by breaking the topic into 

Formats, Transports, and Media. 

the four basic components: Services, 

Formats, Transports, and Media. 


ig by breaking the topic into 
asic components: Services, 

Transports, and Media. 



his chapter covers the reason why Macintosh 
and AppleTalk networking is so popular: the 
services. The only reason to network your 
computers is to supply services, such as file and 
I print services, to the users. The common 
Macintosh and AppleTalk-based services will be 

AppleShare (AFP) 

To many Macintosh users, access to an AppleTalk network means 
shared, controlled access to files. To provide such access, Apple 
developed a Service layer (Presentation layer in the OSI model) 
protocol called the Apple Filing Protocol, or AFP. The AFP server at 
the Serv'ice layer represents an implementation of the AFP proto- 
col, which can be described as a Format layer protocol in the 
NetPICT diagram, or as a Presentation layer format in the OSI 
model. Figure 6.1 shows a NetPICT diagram of an AFP Server. In 
this example, the AFP server is running on a Macintosh with an 
Ethernet card. 

Part Two Macintosh Networking 

Figure 6.1 

luaning AppleShare. 

Macintosh Client AppleShare Server 

When Apple introduced AFP, Macintosh users were introduced for 
the first time to such radical concepts as user names, passwords, 
groups, ownership, and protection. AFP provided a mechanism 
whereby Macintosh users could find AFP servers on the network, 
log on these servers, and create, edit, and share files. Apple called 
this product AppleShare. AppleShare was easy to use, because the 
files stored on the server appeared as an extension of the user’s 
local hard disk. All the techniques learned in creating and naming 
folders and files were immediately transferable to the file server 

AppleShare is a textbook example of a client/server connection. A 
user on a client Macintosh identifies and connects to a Macintosh 
that is running the AppleShare server software. This is done by 
clicking on the AppleShare icon in the Chooser. 

AFP Server 

Actually, it would be more correct if the icon were labeled AFP Server, because 
all AFP servers on all platforms will be searched for— not just the Macs 
running AppleShare. 

Once the AppleShare icon is highlighted, as shown in figure 6.2, the 
Macintosh sends out a series of special inquiry packets that look 
for all the AFP servers in the current zone. The AFP servers, hearing 

Chapter Six Macintosh Services 

this request, respond to the sender with their network address and 
name. The names are displayed in the Chooser and the addresses 
are remembered for future communications. 

Chooser ! 

Select a file server: 

Henry’s Hideaway 

Stella’s Trash Can 


® Active 
O Inactive 


Figure 6.2 

Itie Macintosh Chooser, 
showing AppleShare 

The user then selects the desired server and enters a user name 
and password in order to gain entry to the server. Once the user 
has successfully logged onto the sei-ver, a list of volumes — shared 
disks — appears in a dialog box. Multiple volumes can be created to 
address the particular needs of the workgroup. AppleShare comes 
with a management utility that is used to add and delete users and 
perform other necessary administrative tasks. 

System 7 File Sharing 

Starting with System 7, Apple expanded the concept of AFP ser- 
vices so that any Macintosh can be an AFP server and client. This is 
known as Macintosh File Sharing. Assuming your Macintosh is 
running System 7, you can grant or deny access to your Macintosh 
on a user or group (a collection of users) basis. You then designate 

Part Two Macintosh Networking 

Figure 6.3 

With System 7's 
Macintosh File Sharing, 
each Macintosh can be an 
AFP client or seivei. 

folders on your local hard disk that you wish to make available to 
certain users or groups. Figure 6.3 shows several of the Macintosh 
dialog boxes, under System 7, that control or monitor File Sharing. 
With Macintosh File Sharing, there is no dedicated, centralized file 
service. Each participating user acts as a client and as a server. 

Other AFP Clients and Servers 

The AFP standard is not limited to the Macintosh platform. In fact, 
Apple made sure that AFP was an open standard that could be 
implemented on other computers. As shown in figure 6.4, there are 
AFP servers available for most popular platforms, including DEC 
VAX, IBM PC, UNIX, and even dedicated hardware boxes. 

For the most part, AFP services on platforms other than Macintosh 
appear to the user exactly like a Mac running the AppleShare or 
File Share software (although there may be some differences with 
filename limitations, or the number of nested folders). An example 
of this is found in the VAXshare component of PATHWORKS for 

Chapter Six Macintosh Senaces 

Macintosh, from Digital. VAXshare is software that enables a 
VAX/ VMS computer to appear as a AFP server (or servers). The 
AFP volumes, or disks, can correspond to any VMS directory. 
Macintosh folders on these volumes correspond to VMS sub- 

Macintosh Client UNIX AFP Server 

Figure 6.4 

AFP Servers aiefl'llimileil 

One simple problem that often happens with mixed-platform 
environments is filenames. VMS filenames cannot contain spaces, 
so VAXshare must maintain a conversion map that translates 
Macintosh filenames into acceptable VMS filenames. Another 
problem might occur if the VAX is also used to store and share DOS 
files. Wliile the Macintosh and VAX/VMS environments support 
long filenames, DOS filenames are restricted to an eight-character 
limit. Therefore, if you intend to share Macintosh files with DOS 
users over a shared filing system, you may need to restrict your 
Mac filenames to eight characters. 

Print Services (PAP) 

For many Macintosh users, the act of network printing is not 
normally viewed as a client/server activity. In fact, the print 
services provided over AppleTalk netw^orks are an excellent ex- 
ample of client/server computing. Wliile the Macintosh supports 

Part Two Macintosh Networking 

many printers and printing protocols, the most common print 
service is provided by Apple’s Printer Access Protocol (PAP). 

Figure 6.5 

KetPICIol an Apple 

Apple LaserWriter Family 

Perhaps the most popular Macintosh client/server application is 
the printing of documents to an Apple LaserWriter printer. Just as 
in the case of the dedicated AppleShare file server, the Apple 
LaserWriter is an example of a client/sei"ver transaction, where the 
client Macintosh identifies and selects a networked print server, 
then sends the print job to the printer for subsequent queuing and 
printing. Figure 6.5 shows the corresponding NetPICT of a 

Macintosh Client LaserWriter Server 

As was the case with AFP, a special protocol called the Printer 
Access Protocol (PAP) was developed to handle the unique and 
specific requirements of networked laser printing. PAP manages 
the printing specifics, provides the queuing, downloads fonts when 
required, and even informs die user if the printer is out of paper or 
if the paper tray is out of the printer. 

Other PAP-Compliant Printers/Spoolers 

PAP print services aren’t limited to Macintosh. They also can be 
found on UNIX and VAX/VMS hosts as well. There are numerous 
products that allow these computers to accept and spool Macin- 

Chapter Six Macintosh Services 

tosh print jobs. Spooling relieves the Mac of the burden of locally 
spooling print jobs on its hard disk. This practice causes the 
annoying delays seen when the Print Monitor application is used. 
Instead of local spooling and continual polling to check the 
printer’s status, the remote PAP spooler accepts the print job as 
fast as the Mac and network can send it. Figure 6.6 shows a 
NetPICT of the PATHWORKS VAXshare PAP spooler running on a 
DEC VAX. To the Macintosh client, the spooler program appears 
exactly like a LaserWriter. The program queues the print job and 
forw'ards it to the LaserWriter. 

This program, or This program, or 

vlrtuai LaserWriter, virtuai Macintosh, 

appears to the Mac appears to the reai 

user as a reai LaserWriter as a 

LaserWriter. reai, printing, Mac. 

Figure 6.6 

Flint spooling under 

Apple Open Collaboration 
Environment (AOCE) 

AOCE is a new set of Apple services that integrates a wdde variety of 
services necessary for collaborative activities. These services will 
let the Macintosh manage personal communications, workgroup 
collaboration, and enterprise-wide workflow. An important part of 
AOCE is the extensible directory services that will provide personal 
or distributed listings of users, network services, and even phone 

Part Two Macintosh Networking 

Network security is always a concern, and AOCE provides tools 
that ensure private and secure communications. A new AppleTalk 
protocol, the AppleTalk Secure Data Stream Protocol (ASDSP), 
encrypts network traffic to prevent packet snooping. Another 
technique offered by AOCE, digital signatures, will provide a way 
for users to sign electronic documents. These electronic signatures 
will be tamperproof and provide users the assurance that their 
messages and authorizations are secure. 

Starting in 1993, AOCE will lay the foundation for a new generation 
of shared, cooperative applications. Messages such as voice, fax, 
mail, and even video will be managed through a consistent 

Terminal Services 

Although terminal emulation is a throwback to an earlier time, 
there are still a number of application services that require the use 
of terminals. The Macintosh offers a number of terminal emulators 
that work with DEC, UNIX, IBM, Prime, Data General, and many 
other hosts. The types of terminals supported include most of 
Digital’s VT series (that is. the VTIOO, VT220, VT340...), IBM 3270 
and 5250 terminals, Tektronbc graphics terminals, and many 
others. These emulators are able to connect with direct serial 
connections, or through network connections such as LAT, TCP/ 
IP, DECnet or SNA. Figures 6.7 and 6.8 use the NetPICT diagrams 
to illustrate the difference between a terminal emulator (VT220) 
running over a conventional serial connection and a network 
connection using LAT over Ethernet. A more detailed description 
of terminal services can be found in the platform-specific chapters 
later in the book. 

Chapter Six Macintosh Services 

VT Terminal Host Computer 

VT Terminal Emulator VAX Host Computer 

Figure 6.7 

serial coiamanicaiions 
liae is a single-use 
tonneciion only. Unlike a 
cannot be sM. 

Figure 6.8 

lAI network. leiminal 
access through a network 
connection can be shareil 
by many users. 

In the past, most termined services were provided over serial 
transmission lines (RS-232) that used an asynchronous protocol. 
Today, terminal services are often delivered over LAN connections 
and protocols. Figure 6.8 shows terminal access with DEC's LAT 
protocol, which is part of their PATHWORKS for Macintosh 

Alternatives to conventional terminal emulation include those 
products that create a front end to terminal-based services. As an 
example, products from Apple, Avatar, and DCA offer program- 
ming interfaces so that programmers can build Macintosh applica- 
tions that have the look and feel of a Mac application, but utilize 
terminal traffic as a communications medium. 

Part Two Macintosh Netu'orking 

Other examples that build atop a terminal session are 
MacWorkStation from United Data Corporation and MitemView 
from Mitem. With MacWorkStation, a host application sends 
simple ASCII codes to a Macintosh. The Mac interprets these codes 
as commands that control various aspects of the Mac interface. 
MitemView uses standard terminal messages or MacWorkStation 
codes, together with HyperCard, to act as a front end to the host. 

Data Access Language (DAL) and 
Dther Database Services 

DAL’s purpose is to enable Macs (and other DAL clients, such as 
PCs) to uniformly access relational databases (see figure 6.9). 
Extending the SQL language, DAL provides a standard that can be 
used on different computing platforms and different databases. 

Figure 6.9 



Macintosh Client 

Host Computer 

The DAL software on the client side is implemented as an optional 
extension for System 7 (it used to be part of System 7 software, but 
Apple recently unbundled it). DAL client applications can be 
written as Mac applications or as HyperCard stacks. These stacks 
contain the DAL XCMDs that give the HyperTalk programmer 
access to the necessary DAL commands. In addition to HyperCard, 

Chapter Six Macintosh Services 

DAL is supported by other development environments, such as 
Andyne’s Graphical Query Language (GQL) and the iconic, object- 
oriented development environment from Serius. 

There are also many Mac applications that have built-in DAL client 
capabilities. Spreadsheets such as Microsoft Excel and Lotus 1-2-3 
are DAL-equipped and can be used to access and retrieve data 
managed by relational databases. Clear Access, from Fairfield 
Software, is a desk accessory that can be used to construct ad-hoc 
database queries. 

DAL servers are currendy sold by Apple, DEC, Tandem, Novell, and 
Pacer Software. Apple offers DAL servers for DEC VAX/VMS, IBM 
mainframes, IBM AS/400, and Macs running A/UX (Apple’s version 
of UNIX). The VAX/VMS version supports DEC’S Rdb, Ingres, 
Oracle, Sybase, and Informix databases. The IBM mainframe 
version supports IBM’s DB2 and Teradata’s DBC/1012 databases. 
Pacer offers a DAL seiwer for HP UNIX computers, DEC Ultrix, and 
Sun’s SPARCstation. Tandem has a DAL server for their line of 
computers, and Novell has added DAL support for NetWare’s SQL 

The appeal of DAL is that the client applications are insulated from 
the host database. This makes it easy to switch the database and 
host server as needed. DAL also provides a single standard so that 
software developers can offer database access without having to 
deal with each database vendor’s own proprietary access language. 
Since DAL uses a common-denominator approach to database 
connectivity, some specialized features, such as database triggers, 
may not be available through DAL. 

Other products get around this limitation. SequeLink (by 
TechCnosis) doesn’t rely on DAL; instead, it uses specific database 
connections for each host database. Database companies, such as 
Ingres, Oracle, and Sybase, have also gotten into the act by devel- 
oping Macintosh client tools that work with their specific database 

Part Two Macintosh Networking 

Figure 6.10 

NeiPICI of an Oracle 
database conneciion. 

languages. Figure 6.10 shows an Oracle database being accessed by 
a Macintosh client running the Oracle client software. 

Macintosh Client Host Computer 

Mail Services 

Perhaps more than any other Macintosh service, E-mail has the 
potential for truly transforming an organization. Users can finally 
quit die annoying game of telephone tag and enhance their 
communications with their co-workers. E-Mail can be used as a 
communications framework where voice, textual messages, and 
binary file attachments are sent and tracked over the entire net- 
work. In fact, many companies are now starting to view E-mail as 
the engine that will power the drive toward the elusive goal of 
workflow automation. Using custom-designed electronic mail 
forms, a company can replace its current paper-based operations 
with a system that eliminates many of the inherent shortcomings 
(time delays, manual records keeping, loss of data, transcription 
errors, and so forth) of the past. 

During the past five years, support for Macintosh E-mail has 
become widespread. As mentioned before, Apple’s AOCE initiative 
will set the foundation for a new generation of mail applications, 
where various message formats (mail, fax, voice, and video, for 

Chapter Six Macintosh Services 

example) are integrated and presented to the user within a consis- 
tent interface. AOCE will also provide the security and authentica- 
tion required by collaborative applications. 

Today, the Macintosh is supported by most of the popular 
multiplatform E-mail systems. Two of the most popular Macintosh 
mail programs are Microsoft Mail for Macintosh and CE Software’s 
QuickMail. Both of these products offer client and server compo- 
nents that work in an AppleTalk network environment (see figure 
6.1 1). The challenge begins when other mail systems, multiple 
platforms, and different transport protocols are used. 

Mac Mail Client 

Mac Mail Server 

MS Mail 
CE QuickMail 

MS Mail 
CE QuickMail 

Formats \ / 


AppleTalk 1 [ 


. Cabling ^ y 

Cabling < 

Figure 6.1 1 

services lot ilie 

Many Macintosh mail vendors offer maU gateways for their prod- 
ucts that are used to meld different mail formats or transport 
protocols. These maU gateways are similar to the other transport 
gateways mentioned earlier in this book. A mail gateway deals with 
all aspects of the mail message. This includes the formatting of the 
message as well as any changes required in the transport protocol 
used to deliver the message. 

The most common Mac and PC gateways are used to connect to 
these LAN mail systems to the UNIX mail standard SMTP (which 
stands for Simple Mail Transfer Protocol) or to the emerging 
industry-standard of X.400. Other less-common gateways provide 

Part Two Macintosh Networking 

Figure 6.12 

A Maciniosh mail server 

access to other mail environments, such as IBM PROFS, DEC All- 
In-1, MCI Mail, and Novell MHS. There are even mail gateways 
that forward mail messages to a networked fax server (see figure 
6.12)1 These mail gateways run on the computer that’s running the 
mail server application, or on a separate computer that’s con- 
nected to the mail server. 

Figure 6.13 

A Macinlosli mail server 

As an example of a shared mail server and gateway, figure 6.13 
shows a Macintosh QuickMail server that is also acting as a gate- 
way to VMS Mail running on a DEC VAX computer. In this case, the 
Macintosh users are using the AppleTalk protocol to communicate 
with the server, and the server is using the DECnet protocol to 
communicate with the VAX. The product that delivers this gateway 
capability is Alisa’s MailMate QM. 

Macintosh E-mail systems that support multiplatform access can 
be very complex — they probably deserve a separate book to 
adequately describe their capabilities. Hopefully, the descriptions 

Chapter Six Macintosh Services 

and diagrams found in Live Wired wiW place the elements of these 
systems into a clear and comprehensible form, opening the door to 
future discovery. 


Of course the services listed previously only scratch the surface. 
The Macintosh offers hundreds of networkable applications, such 
as time management, resource management, backup/archival, and 
even games that work over AppleTalk networks. Since the Mac was 
designed at the outset to operate in a networked environment, 
most Mac applications naturally take advantage of network capa- 
bilities. Today, v\ath the System 7 features of Publish and Subscribe 
and AppleEvents, the Macintosh has gone beyond mere client/ 
server applications, using tlie AppleTalk network to automatically 
update shared objects and to enable applications to directly 
control and manipulate other services available on the network. 



ften overlooked or underestimated, the data 
format is the single most crucial aspect of the 
network. More important than cabling or proto- 
cols, the formats and data structures that encode 
our file access methods, word processing docu- 
ments, spreadsheets, drawdngs, sounds, and multi- 
media presentations represent the true measure of success when it 
comes to network interoperability. 

The binarjf underpinnings of all computer formats are platform- 
independent. All computers express information in the same 
way — with binary numbers. The only difference is that computers 
and programs have different coding schemes to represent the data. 
It’s important to realize that any computer can read, write, and 
store any sequence of binary numbers. This means that any binary 
computer can read, write, and store any other binary computer’s 
data. The difficulties start to arise when one computer is able, 
through its programming, to act on and manipulate that binary 
data in a manner that another computer is unable to do. This is 
one of the central problems in computing today. 

Part Two Macintosh Networking 

For every unique computer application or service, there is usually a 
unique binary representation for its data. This is why MacWrite 
documents are different from Microsoft Word documents, even 
though they might have identical content. The choices for 
interoperability are limited: either agree on a common data 
format, or provide interchange utilities to convert one format to 
the other. In all likelihood, we will always have a mbc of these 
approaches. There will be continued pressure for data standards, 
but as innovation continues to fuel the industry, new formats and 
data structures are inevitable. Let’s look at some of the predomi- 
nant data standards and interchange utilities that are available on 
the Macintosh. 

ASCII Text and Word Processors 

As stated earlier in Chapter 2, "How Does Networking Take Place,” 
ASCII text is a standard that uses eight bits of data to encode the 
English alphabet, numbers, symbols, and special computer control 
characters (such as line feeds and carriage returns). Although text 
editors and word processors offer the ability to change the dis- 
played font of an ASCII text file, the ASCII format doesn’t support 
fonts or special attributes such as bolding or underlining. There- 
fore, using ASCII as an exchange medium will only preserve the 
text; any font information or special formatting will be lost. All 
Macintosh word processors and spreadsheets can read and write 
ASCII text. Many other Macintosh applications can also read and 
write ASCII text. For example, HyperCard can read and write ASCII 
text through its HyperTalk scripting capability. Most Macintosh 
programming environments, such as Apple’s MPW and Symantec 
Lightspeed C, also use ASCII text files for source code files. 

Chapter Seven Macintosh Formats 

Macintosh word processors usually rely on proprietary formats for 
their documents. Word processors that are available on multiple 
platforms usually use the same file format for all platforms, or 
contain built-in translators that convert one platform’s format to 
the other. Microsoft Word has translators that translate documents 
between the Mac and Windows versions of Word. Word also has 
built-in translators for other competing Macintosh word proces- 
sors, such as MacWrite and WordPerfect. Figure 7.1 shows the wide 
range of formats supported by Microsoft Word 5.1. 

rSaue File as Type- 

Normal [▼ 

leHt Only 

Te»t Only with Line Breaks 
Microsoft Mac UHord 3 .h 
I nterchange Format (RTF) 



MacLUrite II I.h 

Reuisable Form Tent (RFT-DCfl) 

Tent with Layout 
Ulord for MS-DOS 
ILIord for UMndows 1 
Ulord for lilindows 2.0 
WordPerfect 5.0 
WordPerfect 5.1 
Works 2.0 for Macintosh 

Figure 7.1 

MiciosoliWoiil can read 



Claris uses a technology' called XTND that can be used to translate 
between different word processing formats. With XTND, for 
example, MacWrite users can read and write Microsoft Word 
documents using options found in the Open and Save As dialog 

If a word processing document is truly foreign (Wang, for ex- 
ample), then a dedicated conversion program such as MacLinkPlus 
from DataViz is often required. MacLinkPlus supports hundreds of 
formats from many different platforms. 

Part Two Macintosh Networking 

MacPaint and PICT Formats 

The Macintosh introduced a number of new graphic formats. 
MacPaint was one of the first Macintosh applications. It intro- 
duced paint programs and bitmaps to the world. The MacPaint- 
style bitmap data structure is still in widespread use today. The 
original bitmap definition was 72 dots per inch and one-bit color 
(either black or white). Today, Macintosh bitmaps exist in a range 
of resolutions and millions of colors. 

Another Macintosh format is known as PICT. The PICT format is an 
outgrowth of the Macintosh imaging environment. The Macintosh 
System contains a programmers’ toolkit knowm as QuickDraw. It is 
a two dimensional, integer-based world where programmers can 
create lines, arcs, circles, rectangles, text, and Mac bitmaps. The 
QuickDraw data structures are used to display these objects on 
the Mac monitor, and to print them to QuickDraw-based printers 
such as the Apple StyleWriter II. 

A PICT file is a series of QuickDraw commands organized in a 
special resource. Thus, PICT files are limited to the objects and 
precision found in QuickDraw. Because PICT files are so intimately 
linked to the display environment of the Mac, the PICT format has 
become a standard for the storage and management of graphics. 
There are two implementations of PICT: the original, and PICT2 
(which contains color and grayscale support). 

Because the QuickDraw standard supports both object-oriented 
graphics (that is, lines, arcs, rectangles, and text) and bitmaps, die 
PICT standards support these elements as well. A PICT file can 
contain only objects, only bitmaps, or a mixture of both. One 
potential problem with PICT is its limited precision. As mentioned, 
QuickDraw is integer-based. Under certain circumstances, when 
PICT files are scaled or resized this limited precision can cause a 
certain amount of distortion. This problem doesn’t occur with 

Chapter Seven Macintosh Formats 

PostScript images, because PostScript uses a higher precision 
floating-point world. 

Since Macintosh has made inroads into the graphic and publishing 
worlds, the PICT standard has become an industry standard; many 
drawing, illustration, and publishing applications on other plat- 
forms include PICT support. 


When Apple introduced the LaserWriter, it also introduced Adobe's 
PostScript imaging language. PostScript is part programming 
language and part data sructure. PostScript instructions can be 
used to drive laser printers, display graphics on monitors, or to 
serve as a graphical format suitable for inclusion in published 
documents. PostScript soon became a standard in the computing 
world, both as a printer language and as a display language. While 
other companies (most notably NeXT) have adopted PostScript as 
a screen display language, Apple has continued to support and 
enhance QuickDraw. Because of this, Apple has two imaging 
standards; QuickDraw for the display and certain printers, and 
PostScript for other printers (see figure 7.2). PostScript, like PICT, 
can contain lines, arcs, rectangles, text and bitmaps. It uses float- 
ing point numbers to locate objects; this provides a higher degree 
of precision. 

A variation of PostScipt, called Encapsulated PostScript or EPSF, 
has become another industry standard for graphic files. EPSF files 
are essentially PostScript files with the addition of “bounding box” 
data that defines the size of the graphic. Most Mac illustration, 
drawing, and publishing programs are able to read and write the 
EPSF format. 

Part Two Macintosh Networking 

Figure 7.2 

A Maciniosli can generate 

Apple StyleWriter II Macintosh LaserWriter Server 

IMPORTANT NOTE: One word of caution about EPSF files. There are 
two versions: a generic version, and a Mac-specific version that contains a 
speciai PICT preview file resource. This additionai resource, sometimes 
referred to as a "thumbnail," is used to provide an onscreen display image 
which approximates the real PostScript image. When the file is finaliy printed, 
the reai PostScript is used. 

With many Mac appiications, if you insert an EPSF file without the PICT 
preview, you’ll only be able to see a rectangle that represents the border of the 
image. The image will still print properly. Some applications can convert 
generic EPS files into Mac-specific EPS files, and DataViz also provides a 
MacLinkPlus translator for this purpose. 


TIFF and GIF are raster formats (that is, bitmap formats) that are 
commonly supported on many platforms. T/FF (Tagged Image File 
Format) is a standard format that’s frequently used by digital 
scanners. TIFF files are often used to store high-resolution images 
that have been scanned from photographic sources. GIF (Graphic 

Chapter Seuen Macintosh Formats 

Interchange Format) is similar to the TIFF format, but it’s popular- 
ity seems to be limited to storing images of bikini-clad females on 
bulletin board services. 

Because both TIFF and GIF are raster formats, they are usually 
viewable and editable with Macintosh paint/bitmap programs 
such as Adobe Photoshop. There are also numerous viewing and 
conversion utilities (Macintosh and PC) that are able to handle 
these formats. 


By far the largest category of Macintosh formats are those that rely 
on a proprietaiy' binary' structure. Most Mac applications use their 
own binary format to store data. As more vendors start to offer 
cross-platform versions of their programs, the trend of binary 
compatibility is likely to increase. PageMaker for the Mac uses the 
same file format as PageMaker for Windows, so it’s simply a matter 
of transferring the document from one machine to the other. This 
can be done with a floppy disk, or over a network. Figure 7.3 shows 
a NetPICT of a PageMaker file that is shared between a Mac and 
PC. The real problems start when you try to exchange documents 
between incompatible applications. 

Macintosh Windows/Intel PC 

Figure 7.3 

same binary (lie fotiaai 
on both Mac and 
Windows versions. 

Part Two Macintosh Networking 

Document Interchange 

The problem can be simply stated: Most application developers 
design a unique binary file format to represent and store the data 
created within their applications. These formats are designed using 
many criteria, which include file size, application performance, 
and memory requirements. Formats are rarely designed with the 
goal of inter-vendor binary compatability. This is due to valid 
technical reasons, as well as those pragmatic business concerns 
associated witli true binary cross-vendor compatibility. However, 
there are many initiatives from vendors and industry standards 
organizations that attempt to bridge the long-standing language 
barrier betw'een different computer applications. 

Figure 7.4 

MacODA supports (lie ISO 
comppupd documents. 


MacODA attempts to solve the problem of document interchange. 
It does this not through conversion but through a standardized file 
format. MacODA is based on the Open Document Architecture, 
which is an ISO standard (standard #8613, to be precise) for the 
interchange of compound documents. (A compound document \s a 
document that contains fonts and graphics, both bitmap and 
object.) ODA preserves the formatting and structure of documents, 
so chapters, paragraphs, headers, and footers are maintained. 
Figure 7.4 uses NetPlCTs to illustrate ODA use as a common 
interchange format. 

Macintosh Foreign Host 

Chapter Seven Macintosh Formats 

The ODA standard specifies three implementation levels. 

# Level 1: Textual data 

# Level 2: Textual and Graphical (word processing) 

# Level 3: Textual and Graphical (desktop publishing) 

At the present time, Apple’s (and most other vendors’) implemen- 
tation of ODA supports Level 2, so effective transfers are limited to 
basic word processing documents. For example, at this time, 
MacODA only supports the Helvetica, Courier and Times type- 
faces. The OSI standards continue to evolve and it’s expected that 
MacODA will be continually enhanced. 

Adobe Acrobat and PDF 

Another document interchange standard is being developed by 
Adobe Systems. With Acrobat, they plan to extend their PostScript 
standard to support a new file format called the Portable Docu- 
ment Format (PDF). PDF will support fonts, graphics, text and 
color in a platform-independent file format. PDF, like ODA, will be 
a common interchange format, supported by Macs, PCs, and 
LFNIX. (A NetPICT of the PDF standard is shoum in figure 7.5.) 
Initially, PDF will be a view-only format; users won’t be able to edit 
the information contained in a PDA document. Adobe may add 
this capability sometime in the future. 

Macintosh Foreign Host 

Hgure 7.5 

IhePDf Standard fiom 
Adobe promises a unilied. 
platform independent 
interchange lormat 

Part Two Macintosh Networking 


We have just discussed one approach to document interchange; 
using a mutually agreed-upon standard that is supported by many 
applications. The other approach is to simply convert one format 
into another. 

Both approaches have their tradeoffs. With the common format 
standard mentioned before, each application must support every 
element and entity in the common format. This places quite a 
burden on the common format, as it must accept or adapt to a rich 
superset of elements used by all participating applications. This is 
why common file standards are so difficult to standardize. The 
benefit of this common format is that each vendor need only 
implement a single converter, or translator, for their application. 

The other approach is through conversion. Here, each format is 
explicitly converted into another. The advantage is that the conver- 
sions can be explicitly tailored and tweaked to accommodate the 
two participants. Explicit conversion often provides a greater 
degree of conversion accuracy. The problem is that tlie number of 
required conversions begins to multiply with each aditional 
format. We'll now look at two examples of utilities that facilitate 
the direct, seamless conversion between different applications. 

Claris XTND 

Claris's solution to the problem of file translation is an open 
exchange architecture known as XTND (pronounced “extend”). 
XTND translation has been offered with MacWrite II, and with 
most other Claris applications as well. It has also been adopted by 
other software developers because Claris has licensed the technol- 
ogy. With XTND, additional translation modules are simply added 
to a folder (figure 7.6), after which they appear in the Open and 
Save As dialog boxes (figure 7.7). XTND is also used by those Claris 

Chapter Seven Macintosh Formats 

applications that offer a Place command. For example, you can 
place an EPSF or TIFF file into a MacDrawPro document; the 
appropriate XTND translators automatically convert and import 
the graphic. 

^ Claris Translators = 

9 items 

107.4 MB in disk 

7.9 MB availa 

Claris XTND Bridge 


MacPaint 2.0 


MacOraw IM.l 


Plain Text 

MacWrite II 


MasVrite 5.0 


Figure 7.6 

XIND filters. 

Figure 7.7 

XIND Open/Save options. 

Claris' XTND architecture is modular. Each translator is a separate 
document that can be added or deleted to the “Claris” folder as 
required. Once the XTND translators are added, they automatically 
appear in the Open and Save As dialogs of XTND-compatible 

Part Two Macintosh Networking 

Apple Easy Open 

Easy Open is a new Macintosh developer’s toolkit that incorpo- 
rates seamless file translation into the operating system of the 
Macintosh. It provides a standard interface for translation software 
and alternate application support at the System level. If you’ve 
been a Mac user for some time, you’ve probably seen the plain 
document icon that produces an “application not found” message 
when you attempt to open it. Easy Open will solve this problem by 
coordinating the conversion of this document into another form, 
or by selecting an alternative application that is capable of opening 
the file. 

The translation features of Easy Open are not limited to file access. 
The Claris XTND environment will be managed under the auspices 
of Easy Open. It will also provide transparent data conversion 
during copying, pasting or publishing (System 7 Publish and 
Subscribe) operations. Easy Open also adds useful file descriptions 
and informative color icons to replace the annoying generic 
document icons. Expect to see Easy Open services used by general 
applications and specialized conversion utilities by mid- 1993. 


Perhaps more than any other computer company, Apple Com- 
puter has addressed the issue of data format portability. Starting 
with the Macintosh Clipboaid, Apple has continued to provide 
mechanisms to seamlessly share information between applications 
and platforms. Unlike its rivals, the PC-compatibles, which have a 
myriad of application-specific file formats, the Macintosh has a 
few key formats tliat are supported by many applications. 




he Transport layer is where the networking 
protocols reside. Apple’s networking protocol is 
called AppleTalk. It consists of many separate 
protocols, each performing a specific function or 
task. This chapter explains the various compo- 
nents of the AppleTalk protocol family and 
discusses why it is destined to be one of the most 
important networking protocols for the future. 

The AppleTalk Protocol Family: 

An Overview 

AppleTalk, the networking protocol, actually consists of many 
separate protocols that work in conjunction to deliver services to 
the Macintosh user. This collection of protocols is often referred to 
as the AppleTalk suite of protocols. 

Part Two Macintosh Networking 

Figure 8.1 

Ihe AppleTalk pioiQcol 

AppleTalk and the 7-Layer OSI Model 

The easiest way to describe and explain the AppleTalk protocol 
suite is to use the 7-layer OSI model. Each AppleTalk protocol 
exists at a certain layer in the stack. Sometimes, there is more than 
one protocol at a given OSI layer. The AppleTalk protocols span the 
layers from the Presentation layer down to the Data Link layer of 
the model. Remember from the printing example at the end of 
Chapter 3, “Network Diagramming with NetPICTs” that each layer 
in the stack has a client/ser\'er relationship with its neighbor. 

Figure 8.1 shows the entire suite of AppleTalk protocols, using the 
7-layer OSI model. 

Let’s take each AppleTalk protocol and describe its basic function, 
starting at the top and working our way down to the bottom. 
Unless you plan to develop and program AppleTalk applications, 
it’s not important to understand in detail each of these protocols. 
Instead, it’s only necessary to understand the basic function of the 
protocol and where it fits into the larger scheme. 

0 , 

Chapter Eight Macintosh Transport: AppleTalk 

Presentation: APR PostScript and QuickDraw 

As mentioned earlier, the OSI Presentation layer is the same as the 
NetPICT Format layer. At this layer, as shown by figure 8.2, the 
protocols deal with the format of the data. For example, Apple 
developed the AFP protocol to address the needs of shared file 
service. PostScript and QuickDraw solve the problem of device- 
independent imaging. 






Data Link 


Figure 8.2 

Ilie Apple Filing Pfoiocol 

lAFPiPoslScripl. and 






At the Session layer, the Macintosh uses ZIP, ASP, PAP, ADSP and 
ASDSP (see figure 8.3). 

Part Two Macintosh Networking 

Figure 8.3 

MacinlosI) Session layer 






Data Link 


ZIP stands for Zone Information Protocol. Its purpose is to deter- 
mine which networks are associated with which zones. To accom- 
plish this task, ZIP is used by the AppleTalk routers on the network 
to maintain a Zone Information Table (or ZIT). This table, exempli- 
fied by Table 8.1, maps networks with their corresponding zone 
names. The table is stored within each AppleTalk router on the 
network. ZIP also has the facility to make changes to the table 
when the configuration of the network is altered. A good example 
of the use of ZIP is the Macintosh Chooser. When the Chooser is 
opened on a network with zones, ZIP is used to get the current list 
of zone names from the router. 

Chapter Eight Macintosh Transport; AppleTalk 

Table 8.1 Zone Information Table 

Network Number 

Zone Name 











ASP, or the AppleTalk Session Protocol, maintains a logical network 
connection between an AppleTalk client and server. ASP is respon- 
sible for starting and stopping each session, as well as maintaining 
sequencing. ASP can be likened to the page numbers of a docu- 
ment. If I were going to send you a document by copying every 
page and sending them one at a time, you would use the page 
numbers to reassemble the document in tire correct sequence. The 
page numbers would also eliminate the potential of missing or 
duplicated pages. For example, if I sent you a 20-page document, 
and you received two copies of page 5 and didn’t receive page 6, it 
would be an easy matter for you to discard the extra page and 
request page 6 from me. 

Session management and sequencing control is crucial to main- 
tain a reliable connection between network partners. ASP doesn’t 
provide a service directly to the user; instead, it’s used by the 
higher level protocols, such as AFP, to keep things in order. 

PAP is an acronym for Printer Access Protocol. It manages commu- 
nications with network printers, usually LaserWriters. PAP is 
sandwiched between the Presentation layer of PostScript and die 
Transport layers of ATP and NBP. Basically, the function of PAP is 
to open, maintain, and close a network session with the printer. 

Part Two Macintosh Networking 

and to send the print instructions (the PostScript code). PAP is also 
responsible for determining the printer’s status. These printer 
status indicators are often displayed in the Print Monitor, or in a 
print status window that appears across the top of the Macintosh 
screen after print invocation. 

ADSP is the last of the Session protocols. It stands for Apple Data 
Stream Protocol. Because ADSP is a Session protocol, part of its job 
is to open, maintain, manage and close connections between 
tw'o network devices. In addition, ADSP provides for efficient, 
bidirectional delivery' of data vv'ithout loss or duplication. Unlike 
the other Session layer protocols, which connect to various Trans- 
port layer protocols one layer down, ADSP skips a layer and 
connects directly to the Netw'ork layer of DDP. This is because 
ADSP duplicates some of the functionality of the Transport layer. A 
new alternate version of ADSP, called ASDSP (Apple Secure Data 
Stream Protocol), has recently been added to the AppleTalk suite. 

It is part of the Apple Open Collaboration Environment (AOCE) 
and provides secure communications through encryption tech- 

In some ways, the combination of PAP and ATP (discussed next) 
provide functionality similar to tliat of ADSP (and ASDSP). PAP and 
ATP work in concert to provide a reliable, sequenced, and man- 
aged connection to printers: ADSP (and ASDSP) provide the same 
capability for general netw'ork connections. 

Transport RTMR AURR ATR NBR and AEP 

At the Transport layer, the Macintosh uses RTMP, AURP, ATP, 

NBP, and AEP (see figure 8.4). 

RTMP stands for Routing Table Maintenance Protocol. RTMP is a 
protocol spoken by AppleTalk routers, designed to keep AppleTalk 
network routing tables current. Briefly, an AppleTalk routing table 
is a listing compiled by a router, consisting of each AppleTalk 

Chapter Eight Macintosh Transport: AppleTalk 

network, its corresponding distance, which router port is used to 
access that network, and the AppleTalk node number of the 
nearest router used to access that network. RTMP packets are 
exchanged by the routers on a regular basis. 






Data Link 


Figure 8.4 

layer proiocois. 

RTMP is about to be supplanted by AURP. AURP, the Apple Update 
Routing Protocol, is a new routing protocol that only sends out 
routing tables when a network change occurs. This new protocol, 
First introduced wdth the Apple Internet Router 2.0, will make 
AppleTalk better suited for use over wide-area networks. Since 
routing is so important in an AppleTalk network, RTMP and AURP 
will be discussed in greater detail later on in the chapter. 

ATP, the Apple Transaction Protocol, provides reliable transport 
services between the source and destination sockets. Three differ- 
ent types of ATP packets ensure this delivery. First, a transaction 

Part Two Macintosh Networking 

request gets the attention of the destination socket. The destination 
socket replies back to the source witli a transaction response, and 
the source finishes the transaction with a transaction release. As an 
example, ATP is used by PAP to provide reliable printing to a 
LaserWriter. It’s as if the Mac was saying, “Here’s some PostScript,” 
followed by the LaserWriter saying, "OK, 1 got it,” followed by the 
Mac saying, “OK, here’s some more.” 

NBP is the Name Binding Protocol. It’s purpose in life is to link 
names (such as "Joe’s LaserWriter” or “Bob’s Mac”) to AppleTalk 
addresses. This protocol will be discussed in depth when we 
analyze how the Chooser works. 

AEP stands for the AppleTalk Echo Protocol. This is a simple 
protocol that is used for diagnostic and testing purposes. AEP can 
be used for two purposes: to check for the presence of another 
node, or to get an estimate of the round-trip delay time between 
two nodes on the network. A prime example of AEP is Apple’s 
Inter»PolI utility. It can be used to send a variable number of echo 
packets to another device on die network. The minimum, maxi- 
mum and average transit times are displayed. 

Network: DDP 

At the Network layer, the Macintosh uses the Datagram Delivery 
Protocol to address the message (see figure 8.5). 

The Datagram Delivery Protocol, or DDP, is the primary protocol at 
AppleTalk’s Network layer. DDP places AppleTalk communica- 
tions into a suitable "container” and addresses them for delivery 
on the internetwork. All the higher-layer data is encapsulated 
within a DDP datagram. 

The datagram is labeled with the source and destination AppleTalk 
address. This means that the datagram will have two 32-bit 
AppleTalk addresses that contain the network, node, and socket 

Chapter Eight Macintosh Transport: AppleTalk 

numbers of the sender, or source, and the recipient, or destination. 
When routers route AppleTalk packets, they look at the source and 
destination network numbers in order to determine the best way to 
route the packet. 






Data Link 


Hgure 8.5 

Maciniosli Network layei 

The datagram is independent of the cabling. Only at the next layer 
down — the Data Link layer — is the datagram placed within the 
appropriate cable-specific network frame. 

Data Link: LLARELAR and TLAP 

The various data link protocols (see figure 8.6) correspond to the 
different cabling systems supported on the Mac. 

Part Two Macintosh Networking 

Figure 8.6 

At the Data link layer, Ili8 
Macintosh uses a number 
dillerent kinds nf cabling. 






Data Link 


LLAP stands for the LocalTalk Link Access Protocol and is the built- 
in driver that comes with every Mac and networked LaserWriter, 
and with many LocalTalk peripherals. The LLAP driver takes the 
DDP datagram and places it in an LLAP frame for subsequent 
delivery over a LocalTalk network. 

ELAP stands for the EtherTalk Link Access Protocol and is present 
on Ethernet-equipped AppleTalk devices. The ELAP driver takes 
the DDP datagram and places it in the data field of an Ethernet 

TLAP stands for the TokenTalk Link Access Protocol, and places the 
DDP datagram within the data field of a Token Ring frame. 

Chapter Eight Macintosh Transport: AppleTalk 

How Does AppleTalk Work? 

As mentioned in Chapter 4, "Networking Concepts," AppleTalk 
communication is based on the premise that all devices and 
network processes are uniquely identified. For AppleTalk, this 
requires network, node, and socket numbers. 

AppleTalk Addressing 

AppleTalk network numbers are 16 bits in length: there are 65,536 
potential network numbers available for use (see figure 8.7). 

Figure 8.7 

Willi IB-bil network 
siipporis more Ilian 

In the simplest of networks, consisting of a Mac and a LaserWriter 
connected with LocalTalk, the network number is somewhat 
useless. There are no routers to maintain the network numbers, 
and therefore in this case there are no network numbers (see figure 
8.8), With a single non-routed LocalTalk (or PhoneNET) network, 
the network number is always 0. 

Figure 8.8 

neiwoik.ilie network 
numliei is always 0. 

Part Two Macintosh Networking 

In actual network transmission, the 16 bits consisting of ail zeros 
aren’t even included in the source and destination of the commu- 
nications. Why carry 32 bits of “nothing” with every transaction? 
When these all-zero network numbers are omitted from the source 
and destination of the DDP datagram, it’s known as a Short DDP. 
In cases where the network number is non-zero (and is therefore 
necessary), the DDP datagram is referred to as a Long DDP. Addi- 
tional addressing details will be covered later in this chapter, when 
AppleTalk Phase 1 and Phase 2 are described. 

The Importance of Dynamic Addressing 

Imagine moving into a new house. One of the first things you need 
to do is to get a new phone. Normally, when you get a new phone, 
the phone company assigns you a number from their registry of 
phone numbers. But imagine a phone company that doesn’t want 
to be bothered with the tedious administrative details of assigning 
unique phone numbers. 

This phone company has a system, whereby you simply dial any 
phone number at random. If someone answers the phone (see 
figure 8.9), you apologize and hang up. If there’s no answer, then 
that number becomes your new phone number. 

Figure 8.9 

Someone answers 
lire phone... 

Chapter Eight Macintosh Transport: AppleTalk 

This imaginary scenario is the mechanism that Apple uses to 
dynamically assign AppleTalk node addresses. With other proto- 
cols, such as DECnet and TCP/IP, the node ID number is deter- 
mined and assigned by a human. This human usually has a big list 
or spreadsheet of node assignments in order to determine which 
numbers are available for use. 

Apple tried to avoid this problem with AppleTalk by implementing 
a dynamic node-addressing scheme. When a LocalTalk-connected 
Macintosh boots up on a network for the first time, it chooses a 
node number at random (see figure 8.10). The Macintosh has no 
way of knowing whether this random number is already in use by 
another node, so it sends a special packet (known as an enquiry 
control packet) to the node in question. If the enquiry reaches its 
destination, the node responds to the inquiring Mac with an 
acknowledge control packet. Of course, this means that the number 
is in use and cannot be used as the node number for the new Mac 
on the network. 

Figure 8.10 

network geneiaiesiis 
own node address at 

Therefore, another random node ID and enquiry control packet is 
generated. If no acknowledge control packet is received, then the 
new Mac is free to use the number. Once a Macintosh determines a 
unique node ID for itself, it stores the number in the Mac’s PRAM. 
(The PRAM, or Parameter RAM, is special memory that is non- 
volatile — a battery is used to maintain its contents even while the 

Part Two Macintosh Networking 

Figure 8.11 

No answer — even 

Mac is turned off.) The Macintosh will use the stored node ID as an 
educated first guess the next time the machine is booted. This 
minimizes the node ID contention during startup. 

Generally, a Mac’s node number remains with a given Mac, but 
this is not alw'ays the case. Wlien a Macintosh, or any AppleTalk 
node, is turned off, it’s unable to respond to the enquiry control 
packets sent out by the other machines. Using the phone example, 
it’s as if the receiver of the message was asleep or out of the 
house — he would be unable to answer the phone (see figure 8.1 1). 

Likewise, if a new Mac is added to the network, the possibility 
exists that it could randomly guess — and steal — a node ID that is 
locked away in the PRAM of a powered-down Mac (see figure 8.12) 
Then, when this Mac is powered on, it tries to use its stored node 
ID as its first guess, and the other Mac responds with the acknowl- 
edgment packet. This causes the original Mac to establish a new 
node ID. Therefore, it’s quite possible for your Mac to be node 44 
on Monday and node 32 on Tuesday. With AppleTalk, it’s not 
important that a node number be permanently associated with a 
given Macintosh. 

Chapter Eight Macintosh Transport; AppleTalk 

Figure 8.12 

nodeil 82 onlliea 8 two(k. 
Ihe Mac oflihaleii will 
"clear the sleeping 
Mac’s npdennmbei. 

If the Mac is connected to an EtherTalk network, the process for 
establishing a unique number is a bit different. As we discussed in 
Chapter 4, "Networking Concepts,” each Ethernet card has a 
unique address stored in its hardware. AppleTalk must create a 
standard AppleTalk logical address and associate it with the 
Ethernet hardware address. Because of this, tlie Mac uses another 
protocol — the AppleTalk Address Resolution Protocol, or AARP — to 
create a logical AppleTalk address, instead of using the LEAP 
Enquiry technique. Upon booting a Mac onto an EtherTalk net- 
work, your Mac broadcasts a series of AARP probes. The AARP 
probes contain a tentative AppleTalk logical address and the 
physical hardware address of the Ethernet card. After the receiving 
nodes compare the logical addresses and report back any conflicts, 
the Macintosh obtains a unique logical AppleTalk address. 

AARP is also used to construct an Address Mapping Table (AMT), 
which links the logical AppleTalk address to the physical Ethernet 
address. This dynamically generated and updated table, exemplifi- 
ed in figure 8. 13, contains recent AppleTalk addresses and their 
corresponding Ethernet hardware addresses. 

Part Two Macintosh Networking 

Figure 8.13 

an Address Mapping 
fable, wliicliegyales 
logical Applelalk 
addresses wiihpbysical 
fibernet addresses. 

AppleTalk Logical Addresses 

AMT for 12.42 

12 . 83 : 08 - 12 - 32 - 43-91 
12 . 77 : 08 - 12 - 32 - 51-71 
12 . 81 : 08 - 12 - 32 - 41-92 
12 . 90 : 08 - 12 - 32 - 78-92 
12 . 16 : 08 - 12 - 32 - 33-71 
12 . 35 : 08 - 1 2 - 32 - 41 -88 
12 . 09 : 08 - 12 - 32 - 67-82 
12 . 132 : 06 - 12 - 32 - 91-41 

In fact, this is a very important and significant feature of the 
AppleTalk protocol. As computers get smaller and more common- 
place, and as wireless networking catches on, dynamic node 
addressing will become crucial. It would be ridiculous to have to 
stop at the front door of a company that uses a wireless LAN simply 
to receive a network node ID for your Newton personal digital 
assistant (see figure 8.14). These node numbers don’t possess any 
intrinsic meaning — they’re simply unique numbers, and it just so 
happens that computers can do an excellent job of assigning 
unique numbers. 

Figure 8.14 

I need a node number?!? 


Zone names are simply names assigned to networks. They, along 
with network numbers, are stored within the AppleTalk routers. In 

Chapter Eight Macintosh Transport: AppleTalk 

the case of LocalTalk (Phase 1 AppleTalk) networks, there can be 
only one network number and one zone name per network. 
Imagine a simple internet, figure 8.15, consisting of two LocalTalk 
networks connected by a router. Each network has a unique 
network number and different zone names. 

Figure 8.15 

Eacti network has a 
unique neiwoiknumbei 
and dilieteni tune names. 

Each network has a unique network number (10 and 20), and each 
network has a zone name (Left and Right). Here, the zone name 
Left is used to identify the devices in network number 10; Right is 
used to identify devices in network number 20. 

There’s no uniqueness requirement, however, for zone names. It’s 
perfecdy fine to have duplicate zone names in order to logically 
organize services. Therefore, networks 10 and 20 could have the 
same zone name of “CAL.” In figure 8.16, each network still has a 
unique network number, but the zone names are the same. 

When networks have the same zone name, similar devices are 
grouped together. So, if there were two LaserWriters in network 
10 and three LaserWriters in network 20, there would be 
a total of five LaserWriters in the “CAL” zone. Keep in mind. 

Part Two Macintosh Networking 

Figure 8.1 6 

Inis example, eatli 
neiwoikslill has a unique 
neiwofk number, but the 
2une names are the same. 

however, that when there’s only one zone, the Macintosh Chooser 
does not display the zone list. This is true even when there are 
multiple networks v\ath tlie same zone name. 

Network #10 

n jn n 

Zone: CAL' 

1 “ 

1 “ 

Network #20 



Zone: CAL 


Figure 8.17 

Etheinet anil Men Ring 
Applelalk networks can 
use a range nl network 

In the case of Ethernet and Token Ring networks (Phase 2 
AppleTalk), a cable segment can be assigned a range of network 
numbers and multiple zone names. In figure 8.17, the zone names 
are not associated with any specific network number. 

4.54 1.78 10.39 2.66 4.41 7.78 

Zones: Red, White, Blue 
Default Zone: Red 

With Phase 2 networks (described in the next section), the zone 
names are defined for the entire netv\^ork segment. When a 

Chapter Eight Macintosh Transport: AppleTalk 

Macintosh (or other AppleTalk node) is added to the cable, it 
automatically belongs to the Default zone. 

The Default zone is a designated zone where AppleTalk nodes 
appear by default. It’s established by choosing a zone from the list 
of defined zones maintained by the router configuration software. 
If there are multiple routers on the cable, as in figure 8.18, all 
routers must agree on the network range, zone list, and default 
zone assignment for the cable. Mismatched net numbers and zone 
lists are the most frequent causes of network problems. 

Figure 8.18 

segmenimusi agree on 
the network raimiier 
range, tones anil the 

As shown in figure 8.19, you can change your Mac's default zone 
assignment by opening the Netw'ork control panel and double- 
clicking on the EtherTalk or TokenTalk icon. A zone list will appear, 
along with a prompt to change the Mac’s zone. From then on, your 
Mac will belong to that zone — until you decide to change it again. 

If you’re unsure which zone your Mac belongs to, simply open 
the Chooser. The highlighted zone is the zone to which your 
Macintosh belongs. 

It’s important to realize that the choice of zone names can affect 
network performance. For example, consider a wide-area network 
that connects two AppleTalk-Ethernet LANs. As shown in figure 
8.20, one network is in Washington and the other is located in 

Part Two Macintosh Networking 

Little Rock. One could assign zone names geographically by 
creating a “Washington” and “Litde Rock" zone, or functionally by 
creating an “Administrative” and “Judicial” zone. However, if you 
group by function, instead of geography, there is a potential for 
increased traffic. 

Figure 8.19 

be changed by Mle- 
clicking on ibeEibeilalk 
network Cnnirol Panel. 

IP Nettuork 

Select an AppleTalk connection: 




3235BI3 Remote Only 

Please select 
this computer's 
AppleTalk zone. 

[ Cancel ] 

Figure 8.20 

Agglelalk zones can be 
set up geographically 
or lunciionally. How- 
ever, there can he a 


Net #20-50 
Zone: Washington 

» 1 

Net #70-150 
Zone: Little Rock 

Net #70-1 50 

Zones: Administrative 


Let’s look at an example of functional grouping. Suppose there are 
three LaserWriters located in Little Rock on the Administrative 

Chapter Eight Macintosh Transport: AppleTalk 

zone, and six LaserWriters located in Washington on the Adminis- 
trative zone. Every time I select the Administrative zone from a 
Mac in Washington, AppleTalk must not only poll for the printers 
in Washington, but it must also poll over the wide-area connection 
for printers in Little Rock. Eventually, I’ll see nine LaserWriters in 
my Chooser. The problem with this functional approach is that 
large AppleTalk networks over limited-bandwidth links can bog 
down with the polling traffic. If the zones are arranged geographi- 
cally, then the polling traffic remains local and doesn’t burden the 
wide-area connection. 

NOTE: Zone names can be up to 32 characters in length. They are case- 
insensitive. This means that zone “Little Rock” and zone “LITTLE ROCK” are 
the same. Zone names are much easier to read, however, if the standard 
sentence case is used. Spaces are significant, so be careful not to type an 
extra space between words or to add an unwanted space at the end of a name. 

If you’re creating a zoned network, try to establish a meaningful 
zone-naming convention prior to router installation. Remember 
that network numbers are for the computer’s convenience; zone 
names are for the users' convenience. Your zone-naming standard 
should help users find networked printers and file servers, and 
should be flexible enough to support future expansion. 

Zone names of “First Floor” and “Second Floor” only make sense 
if your organization has a single building. Avoid the practice of 
naming zones after the room number of the wiring closet where 
the router is located. Zone names should also be coordinated with 
de\dce name conventions (such as AFP servers and LaserWriters). 
If your zone-naming convention consists of a city, building num- 
ber, and floor, it’s not necessary to repeat this information at the 
device level. Instead, try to include information that pinpoints the 
final location or function of the device. 

Part Two Macintosh Networking 

AppleTalk Phase 1 and 2 

In the beginning, when Apple designed AppleTalk and LocalTalk, 
there was no distinction between Phase 1 and Phase 2. Wlien Apple 
developed EtherTalk, which is nothing more than AppleTalk 
protocols on Ethernet cabling, they simply carried the original 
AppleTalk protocol used on LocalTalk networks over to Ethernet. 

Apple developed AppleTalk Phase 2 to address certain shortcom- 
ings that were present in the initial EtherTalk implementation. 
Phase 1 EtherTalk networks were restricted to a maximum of 254 
devices and were inefficient when it came to certain aspects of 
routing and broadcasting. Phase 2 fixed these problems, and also 
provided the first version of TokenTalk, which is Apple’s imple- 
mentation of the AppleTalk protocols on Token Ring networks. 

Phase 1 

Phase 1 networks, as mentioned before, can only have a single 
network number per cable segment. Because AppleTalk only 
supports 256 potential nodes per network number, each cable 
segment was therefore limited to 256 devices (see figure 8.21). 

Figure 8.21 

Each AppleM network 
can poieniiallir support 
2S6 devices. Phase I anil 

Actually, the limit is 254 devices. With Phase 1 networks, node numbers range 
from 0 to 255. 0 is not used and 255 is reserved for broadcasts heard by all 

Chapter Eight Macintosh Transport: AppleTalk 

With LocalTalk, this is hardly a problem. LocalTalk netv\'orks have 
electrical and isolation restrictions that limit the number of nodes 
to a recommended limit of 32 devices. When Apple introduced the 
first version of EtherTalk, it too was limited to a single network 
number and 254 nodes per segment. This was bad news for large 
organizations that wanted to start populating their Ethernets with 
Macs. This was particularly bad news for those organizations that 
had bridged Ethernets that spanned many locations. They were 
limited to a grand total of 254 EtherTalk devices diroughout their 
entire organization (see figure 8.22). Apple addressed this problem 
in 1989 with the introduction of AppleTalk Phase 2. 

1.1 1.2 1.3 1.4 1.5 1.6 

Figure 8.22 

254 node limit ol 
patiiculailif will) large, 
bridged liliernei 

Phase 1 and 2 Network Number Assignment 

Phase 2 broke the 254 node limit by avoiding the restriction of a 
single network number per cable segment. Instead, the cable 
(either Ethernet or Token Ring) can be assigned a range of values. 
In a Phase 2 netw'ork, the network numbers range from 0 to 65,534. 
Zero (0) is undefined and not used. A special range, called the 
startup range, runs from 65,280 through 65,534. This leaves the 
numbers 1 through 65,279 for general assignment. 

Part Two Macintosh Networking 

Figure 8.23 

ta I Willi no routers. 

Hgure 8.24 

Phase) will) routers, 
network numbers can be 
I ibrough 05,530 

Let's review the network number assignment rules. 

• Phase 1 (LocalTalk, and the now-extinct first version of 
EtherTalk) with no routers (see figure 8.23). 

The network number is always 0. In practice the 16-bit zero 
network number is omitted from the address to conser\'e 
space. This is known as a S/torrDDP address. 

0.1 0.143 0.14 0.31 0.54 0.88 0.53 0.71 

The network number is a single number between 1 and 
65,536. Each network segment, either LocalTalk or the old 
EtherTalk, must have a single number assigned. No dupli- 
cates are permitted. 

• Phase 2 (the current version of EtherTalk and TokenTalk) 
with no routers (see figure 8.25). 

Chapter Eight Macintosh Transport: AppleTalk 

The network numbers fall in a range between 65,280 and 
65,534. This is knowm as the Startup range. There are 254 
numbers in this range that are used by AppleTalk nodes as 
they come onto the network. 

65280.1 ► 65280.253 65281 . 253 ' 


The choice of network number, like the node number, is 
made at random. One Macintosh could be in network 65,288 
and be node 23; an adjacent Mac could be in network 65,500 
and be node 23. 

NOTE: In Phase 2 networks, there is an additional reserved node number, so 
there can only be 253 nodes per network. This means that for a single, logical 
segment of Ethernet, there can be 254 networks each having 253 nodes. This 
multiplies for a total of 64,262 AppleTalk devices per segment. If you need 
more than this, an AppleTalk router will be required. 

• Phase 2 with routers (see figure 8.26). 

The network numbers are a range between 1 and 65,279. 0 is 
not used and 65,280 through 65,534 are reserved for the 
startup range. Theoretically, you could use the entire range of 
numbers for a single segment, but this would be wasteful. 
Instead, it makes sense to assign a modest range of numbers 
to a cable. This way, growth and expansion can be easily 

Rgure 8.25 

When no Mis aie 
preseni. Phase 2 devices 
assign neiwoiknembefs 
intheslarlupiange — 

Part Two Macintosh Networking 

Figure 8.26 

Phase 2 Willi Routers. 
Network numlieis can be 
1 ibrough 65.229. 

For example, in a large organization, it might make sense to 
assign ranges to the various divisional locations. Houston can 
have 1-100, Dallas 101-200 and San Antonio 201-300. Then 
local network managers can add routers using network 
numbers in their pre-assigned range. We’ll see later how 
Apple’s new routing protocol, AURP, extends this concept 
even further and provides additional flexibility in network 
number assignment. 

Phase 2 Transition Routing 

Before 1989, EtherTalk networks were Phase 1. As mentioned 
before, they were limited to a maximum of 254 AppleTalk devices. 
When Phase 2 was introduced, Apple chose a different Ethernet 
frame format and type code. From an Ethernet perspective, this 
meant the Phase 1 and Phase 2 packets could be readily distin- 
guished by network devices. It also meant that Phase 1 and Phase 2 
protocols could coexist on the same cable. 

The coexistence of Phase 1 and Phase 2 was originally deemed as 
desirable, since large organizations making the switch would find it 
difficult to upgrade all at once. The only problem with this coexist- 
ence technique was that the Phase 1 and Phase 2 devices could 

Chapter Eight Macintosh Transport: AppleTalk 

only communicate with like devices. A Phase 1 node could not 
communicate with a Phase 2 node. Apple addressed this problem 
with an interim solution called transition routing. 

A router (either a Mac running the AppleTalk Internet Router, or a 
dedicated router, such as a FastPath) could be configured as a 
transition router. The transition router’s function was to accept all 
Phase 1 packets and retransmit them as Phase 2 packets, and vice- 
versa. This unfortunately doubled the traffic, but at least the Phase 
1 and 2 nodes could communicate during the transition process. 

Today, Phase 1 EtherTalk networks are rare. Almost everj'one has 
converted to Phase 2. Those sites still running Phase 1 EtherTalk 
are at a significant disadvantage. In addition to increasing the 
number of devices and zones per segment, Apple made other 
significant improvements with Phase 2. 

Phase 1 Broadcasting versus Phase 2 Multicasting 

Starting with AppleTalk Phase 2, Apple altered the broadcasting 
mechanism (used by NBP Lookups and other AppleTalk services) 
to utilize a more specific technique known as multicasting. Let’s 
first review the concept of broadcasting, using Ethernet as an 

Often, a networking protocol (such as AppleTalk) must make an 
announcement to all the devices on the network. Imagine that you 
work at a large company and you need to contact someone. If you 
know that person’s phone number, you simply dial the number, 
but what if you don’t know that person’s number, or they don’t 
answer the phone? Then, you’ll need to have that person paged 
(see figure 8.27). Loudspeakers all over the company send out a 
“broadcast” message. Of course, this approach is somewhat 
inefficient: you're only looking for one person, but everyone in the 
company has to listen to the message. This is essentially how 
Ethernet broadcasting is implemented. 

Part Two Macintosh Networking 

iliai is trying 10 locale 
one person. 

Figure 8.27 

ithernei broadcasts are 

Compared to other protocols, it’s probably fair to say that 
AppleTalk generates more broadcast messages. In fact, in the early 
days of Phase 1 EtherTalk, AppleTalk started to get a bad reputa- 
tion for being excessively “chatty” for this very reason. What 
annoyed some people was that these AppleTalk-generated broad- 
casts were being sent to all devices on a given Ethernet — regardless 
of whether that device even spoke AppleTalk protocols. Thus, the 
owners of minicomputers, PCs, and UNIX workstations started to 
complain that their machines were spending an inordinate 
amount of time responding to broadcasts not intended for their 
machines. Just imagine how annoying it would be if the same 
group of people were being continually paged and you always had 
to listen to the messages since you sat right next to the loud- 

The solution is to be more specific with the broadcast messages. 
Imagine if the pages were made on a departmental basis (see figure 
8.28). If you need to have someone paged, the phone operator asks 
you for the department of the pagee. When the page is made, only 

Chapter Eight Macintosh Transport: AppleTalk 

those loudspeakers in the specific department are used. The rest 
of the employees are spared from having to hear the irrelevant 
message. This is the concept behind multicasting. Each networking 
protocol that supports multicasting has a unique multicasting 
address assigned. This address is similar to the department name 
used in the prior example. An AppleTalk multicast is only “heard” 
by other AppleTalk nodes. A TCP/IP multicast is only heard by 
other TCP/IP nodes. With Phase 2, AppleTalk traffic is also more 
efficient through multicasting, since Phase 2 multicasts are con- 
tained within a given zone, even though there may be only one 
cable segment containing other zones. 

Figure 8.28 

Eiheinei Multicasts are 
wide paging that is trying 

How Does the Chooser Work? 

The Chooser is one of the coolest, least understood aspects of the 
Macintosh. With it, a user can find and select network (and local) 
services in an easy and consistent manner. The Chooser does 
many interesting things behind the scenes. It dynamically gener- 
ates a list of available network zones. When you choose a particular 

Part Two Macintosh Networking 

service by clicking on an icon, the Chooser then generates a list of 
those devices that meet the selection criteria. Finally, once you’ve 
selected a particular named service, the Chooser proceeds to 
discover the AppleTalk address of the chosen service. (You see, the 
names in the Chooser are for your benefit, while the network 
addresses are for the benefit of the Macintosh.) 

Figure 8.29 

Unlike Applelalk, which 
dynamically discovers 
neiwork addresses and 
services, DECnelreqaires 
available nodes helore 

The Unknown Address 

We’ve discussed how AppleTalk dynamically assigns a node 
number to a device. This was a wonderful achievement, but Apple 
had an additional problem to solve. Each AppleTalk device auto- 
matically generates a unique node number, but initially it’s only 
known by that device. Nodes don’t automaticaUy know the node 
numbers of other devices. With other protocols, such as DECnet, 
this problem is solved manually. Someone (usually the DECnet 
administrator) uses a utility program to create a database of node 
addresses. This database, exemplified in figure 8.29, is required on 
every DECnet node in order for that node to communicate with the 
other nodes. 

Apple, desiring a plug-and-play environment, decided that this 
manual creation of node lists was not in keeping with the spirit of 
Macintosh. An alternative approach was developed to solve the 
problem of address determination. Let’s consider a Mac that needs 
to print a document to a particular LaserWriter on the network. 

Chapter Eight Macintosh Transport: AppleTalk 

The Mac doesn’t have any idea of the odter nodes on the network. 
Therefore, it must go through a process of discovery to identify the 
available services. This is done by the AppleTalk protocol knowm as 
the Name Binding Protocol, or NBP. 

The process is simple. When a user opens the Chooser and clicks 
on a service icon (such as the LaserWriter icon), the Macintosh first 
acquires a list of zones from the nearest routers with the Zone 
Information Protocol (ZIP). It then sends out a NBP Lookup 
Request packet. (Actually, it doesn’t simply send it out, it broad- 
casts — or multicasts — the request to all devices on the cable. This 
makes sense because the Mac has no idea who to send the request 
to anyway.) Essentially, the NBP Lookup Request packet contains 
information on the requested named service. A name in the 
AppleTalk system is called a Network Visible Entity, or NVE. 

AppleTalk Names and the NVE 

NVEs aren’t nodes; rather, they are the services offered by nodes. 
These services are identified by their socket numbers. One 
AppleTalk node could support a number of services, each with a 
socket number and a corresponding NVE. The NVE consists of 
three components along with delimiters and some special sym- 
bols. Each name (object, type and zone) is a 32 character case- 
insensitive alphanumeric name. The syntax is: Object:Type@Zone. 

The Object name is the name of the entity that is usually assigned 
by a person. For a Mac, the object name is defined in the 
Macintosh Name field of the Sharing Setup Control Panel. 
LaserWriter object names are established by the Namer utility 
program. Examples of object names include: Jim ' s Mac, 3rd 
Floor LaserWriter, and Joe's File Server. 

The Type name is the generic name of the service. Apple maintains 
a registry of these names. For Macs and LaserWriters, the type 
name has traditionally been the model name of the device. Some 

Part Two Macintosh Networking 

examples include Macintosh Ilci, LaserWriter Pro 630, and 
PowerBook 1 80. Other, more generic type names include 
AFPServer and PAPSpooler. Remember, since NVEs and type 
names are based on sockets, it is possible (and likely) that a single 
node will have several NVEs. 

The last field of the NVE is die zone name where die service can 
be found. Zone names, as explained earlier, are created by the 
network administrator and exist within the AppleTalk network 

Here are some examples of NVEs: 

• Jim's Mac: Quadra 950iaoffice Zone 

• The Group's Printer:LaserWriter@New York City 

In addidon to the names, there are special wildcard characters that 
can be applied to the NVE: 

• An equal sign (=) in the Object or Type fields means all 
objects, regardless of Object (or Type) names. 

• An asterisk (*) in the zone field indicates the current zone of 
the requesting node. 

Let’s review some examples of NVEs with wildcard characters. 

= : =0* means all objects, of all types, in the current zone. 

= : AFPServer0* means all objects of type AFPServer in the current 
zone. = : LaserWriter0Blue means all objects of type LaserWriter 
in the Blue zone. 

Now, with a basic understanding of the NVE, we can return to the 
Chooser. When you click on the LaserWriter icon (see figure 8.30), 
the Macintosh generates an NVE that corresponds to the service 
and the currently selected zone. The NVE takes die form 
=:LaserWriter0* . 

Chapter Eight Macintosh Transport: AppleTalk 

Hgure 8.30 

Wlten you click on ilie 
Nil! (network Visible 
Iniilvl. shown above. 
Ihis happens aiihe 
Pieseniation layer. 

Deciphering this NVE, we can establish that the Macintosh is 
looking for all names of type LaserWriter in the current selected 

This NVE is then referenced within the NBP Lookup Request (see 
figure 8.31). Remembering that NBP is a Transport layer protocol, 
the next layer dowm is the Network layer of DDP. Thus, the NBP 
Lookup Request is then handed down to DDP. 

Figure 8.31 

Ihe NVE is placed within 
an NBP lookup Nequest 
packet Ibis takes place 
in the transport layer. 

Next, the DDP datagram must be addressed. The "From" part of 
the address is easy. The sending Macintosh simply uses its own 
network and node number. A socket number is chosen at random 
from the pool of available socket numbers. The “To” part of the 
address contains the network number, the broadcast/multicast 
node number of 255, and a special reserved socket number of 2, 

Part Two Macintosh Netw'orking 

Figure 8.32 

placed williin an NBP 
lookup Bequest packet 
Iliis lakes place altlie 
Tianspoii layer. 

which is known as the Names Information Socket. The complete 
message, in a simplified form, is shown in figure 8.32. 


1^1 •••Otll 

NBP LkUp =:LaserWrlter@* 


From: 12.33.144 
To: 12.255.2 

From: 12.33.144 (the Macintosh) 

To: 12.255.2 (Anyone who will listen) 

=: LaserWriter®* 

Let’s translate this into English: 

"Hey there, all you AppleTalk nodes! This is device 12.33 commu- 
nicating over socket 144. I’m broadcasting to everyone in network 
number 12 and I’m particularly interested in names. I’m looking 
for all the names of LaserWriters in the current zone.” 

The DDP datagram, which contains the NBP request, is then 
placed in a network frame (see figure 8.33). This frame is then sent 
out over the cable to all the devices. 

Chapter Eight Macintosh Transport: AppleTalk 

± i. 







From: 12.33 
To: 12.255 

Figure 8.33 

placed inside an UAP 
ftane. Since Incallalk 
doesn't use physical 
addresses, llAP uses the 
logical Applelalk 

A device might discard tlie message if it doesn’t apply, but if the 
NBP request is sent to a device where the NVE matches, such as a 
LaserWriter, it accepts the datagram, opens it and processes the 
NBP request (see figures 8.34 through 8.40). 


From: 12.33 
To: 12.255 

Figure 8.34 

The entire conienisol 
the llAP Iratne is then 
broadcast nnto the 
cable segment 

± JL ' 



From: 12.33 
To: 12.255 

Figure 8.35 

Since the message was 
broadcast over the 
network, the laserWritet 
land other nodes) 
process the locallalk 

Part Two Macintosh Networking 

Figure 8.36 

Ilie LaserWriter inspects 
the llAPIraitie it received 
from the locallalt 



From: 12.33 
To: 12.255 

Figure 8.37 

Ihe LaserWriter strips off 
the LLAP frame to reveai 
theDDPOataoram Now 
the LaserWriter knows 
who sent Ihe message. 

.S. X ' 

I « 




From: 12.33.144 
To: 12.255.2 

Figure 8.38 

Finallif, Ihe LaserWriter 
knnws that the device 
12.33.144 is interested in 


5.. A. 




o —•••• , 

NBP LkUp =:LaserWriter(g)* 

Chapter Eight Macintosh Transport: AppleTalk 



=: Laser Wrlter(o)* 

Deb's Dreamy LaserWriter :LaserWriter(2)* 

When a LaserWriter responds to this request, it generates a NBP 
Response such as Deb ' s Dreamy LaserWriter: LaserWriter®*, 
which is shown in figure 8.41. 

Deb's Dreamy LaserWriter 

NBP Response 

Figure 8.39 

IhelaseiWritei inspects 
Ipllillilie NBP lookup 

Figure 8.40 

completes the NVE by 
adding its name to the 

Figure 8.41 

IhelaserWiiter puts the 
completed NVE into an 
NBP Besponse packet. 

Part Two Macintosh Netv\'orking 

Figure 8.42 

completed NBP Response 
inioaODPDaiagiam. Hie 
daiagiam is addressed to 
the sender of the original 

The responding devices essentially fill in the blanks of their respec- 
tive NVEs. Then, the process reverses order. After a LaserWriter 
responds, its NBP Response is placed into a DDP datagram. The 
“From" address is simply the address of the LaserWriter, which it 
already knows; the “To” address is referenced from the source 
address of the incoming request previously received. The complete 
message looks like the one shown in figure 8.42. 

NBP Resp 

Deb's Dreamy 


From: 12.33.144 
To: 12.255.2 

Thus, the response is: 

F rom : 12.144.133 (the LaserWriter) 

To: 12.33. 144 (the Macintosh) 

NBP Resp 

Deb's Dreamy LaserWriter: LaserWriter®* 

Again, let’s translate this response into English. 

“OK, I hear you, Macintosh! I’m a LaserWriter in your current zone: 
my name is “Deb’s Dreamy LaserWriter” and my address is 
12.144.133. Since you told me what address you are when you sent 
your NBP Lookup Request, I’ll send this information to you right 

Chapter Eight Macintosh Transport: AppleTalk 

Of course, multiple LaserWriters can respond to the NBP Lookup 
Request, and as they do, your Macintosh displays their names in 
the Chooser (see figure 8.43). Then, when you select a printer, the 
Macintosh simply remembers the name of the currendy selected 
printer. This name is then stored in the memory of the Macintosh 
This is why, for example, when someone moves their PowerBook 
from the office network to their home network, the office printer 
will still be selected. To solve this problem, the LaserWriter must 
be reselected from the Chooser. 

Figure 8.43 

process 10 ihe 
processes die UAPsid 
NBP anil ilieo places die 
name ol die laserWriier 
(and any Older lesponding 

This process also offers an explanation for the rare event that 
occasionally happens when someone selects a printer on Friday, 
then the network is altered over the weekend and the printer just 
so happens to choose a new node number for itself. WTien Monday 
comes, the user receives a “...can’t locate printer" message. Again, 
reselecting the printer from the Chooser solves the problem. 

This NBP request /response conversation happens every time a 
Macintosh user selects a ser\ace from the Chooser. Because the 
NBP delivery mechanism involves broadcasting (or multicasting), 
NBP traffic can be a significant part of AppleTalk network traffic. 

Part Two Macintosh Networking 

AppleTalk Routing 

Big AppleTalk internetworks are created by connecting little 
AppleTalk networks. Routers are the devices that are used to 
connect the networks. AppleTalk routers are an important part of 
many AppleTalk networks. In addition to providing a mechanism 
for growth, they also are used to provide traffic isolation and a 
means for logically grouping (organizing) network services. In this 
section, we’ll explore how AppleTalk routers accomplish these 
basic tasks. 

Routing Tables 

As discussed earlier, AppleTalk routers are used to physically and 
logically connect network segments. Each AppleTalk network that 
connects to a port on the router is assigned a number, or a range of 
numbers, that identify that particular network. These AppleTalk 
network numbers are key to the operation of the router. 

AppleTalk routers rely on tables, stored within the router, to 
fonvard AppleTalk datagrams from one netw'ork to another. The 
routing tables keep track of all networks by containing an entry for 
each network number. For each network number on the internet, 
the routing table includes the distance of each network (measured 
in hops, which is the number of routers between the router and the 
destination network), which port on the router should be used to 
connect the destination network, and the AppleTalk node ID of the 
next router. This is shown in Table 8.2. 

Table 8.2 A simple routing table. 




Next Router # 









Chapter Eight Macintosh Transport: AppleTalk 




Next Router^ 









RTMP, or the Routing Table Maintenance Protocol, was Apple’s 
only protocol that maintained routing tables among the routers of 
an AppleTalk internet. Witli RTMP, these routing tables are regu- 
larly updated every 10 seconds. This is accomplished by each 
router exchanging routing tables with the other routers on the 
network. When a router receives a new routing table, it compares it 
to the existing table. If a new network has been added, or a network 
distance has been changed, the router updates its table. 

RTMP traffic is normally present only between the routers on the 
internet, but still represents a certain percentage of the total traffic 
on the network. One of the problems with RTMP is the regular 
transmission of the routing tables, which occurs even when the 
network is stable and the network numbers and the routing tables 
remain unchanged. 

To better understand the function of RTMP, let's return to the 
classroom analogy. As shown in figure 8.44, when the students 
pass notes between themselves, they frequently have to use an 
intermediate student as a router. Let’s consider that a student is a 
two-port router (her arms represent network ports). The students 
who are acting as routers need to know the names of other stu- 
dents and the corresponding student-routers to which they are 
connected. These student-routers also need to know which hand 
(port) to use. 

Part Two Macintosh Networking 

Figure 8.44 

The siudenis in the class 
pass their messages 
thiough routers. 

Figure 8.45 

Each student router, Pat 
and Paula, has her own 
routing inlormalion that 
she uses in route the 
other students' 

To solve this problem, each student-router creates a special kind of 
note that lists all tlie note recipients, the number of intervening 
student-routers, which arm to use, and the name of the next 
student-router in the note-passing chain. Then, once all the 
student-routers have their own list, they pass it to the other stu- 
dent-routers, who check the notes for updates. These routing lists 
are shown in figure 8.45. This process continues at regular intervals 
regardless of classroom changes. 

Of course, under certain conditions, the note passing between the 
student-routers can become a problem. The same is true in the 
real AppleTalk world, as this continual RTMP traffic can become a 
burden on large networks with many routers (particularly when 
the routers are connected to WAN links of limited bandwidth). 

Chapter Eight Macintosh Transport: AppleTalk 

This routing technique, which uses a list of destination networks 
with their corresponding distances and the next router in the 
chain, is called vector-distance routing, or Bellman-Ford routing. It 
is a simple routing algorithm (as illustrated in figure 8.46), that 
attempts to find the shortest path for a datagram by minimizing 
the number of hops. Other protocols, such as DRCnet and TCP/IP, 
use other routing algorithms that may be more efficient under 
certain circumstances. Apple is currently investigating other 
routing algorithms for possible future adoption and inclusion into 

Figure 8.46 

Apiilelalk datagrams aie 
routed by aiiempiing to 
hops. In this eiample, 
dalagtams travel directly 

The problem with vector-distance routing is that minimizing the 
number of hops doesn’t always route the datagram through the 
quicker path. Consider the example shown in figure 8.47. Network 
#61-70 is one hop away from Network #11-20, but this connection 
is made through a relatively slow 9600 baud network link. If we can 
also reach Network #61-70 by making three hops over Ethernet 
connections, the throughput will be dramatically improved. With 
our student analogy, it might be faster to pass a note through the 
three hyperactive students who eat chocolate all day instead of 
waiting for one sleepy-eyed student to act. 

Part Two Macintosh Networking 

Rgure 8.47 

AppleTalk datagiams 
louie that has more hops. 

AppleTalk datagrams might go faster over a route that has more 
hops. Therefore, a method of artificial hop adjustment is often 

Some AppleTalk routers permit the artificial adjustment of a 
datagram’s hop count. Instead of the datagram’s hop count being 
increased by one when going through the router, it could be 
increased by two, which could force network traffic to take another 
less cosdy, more efficient path. Apple’s new Apple Internet Router 
(AIR) also adjusts liop counts in large networks so as not to exceed 
the limit of 15 hops (see figure 8.48). 

Remember that a key aspect of this routing technique is that the 
routers are not aware of the entire route for any given datagram 
destination. All that any given router knows for sure is the next 
router in the chain. 

Chapter Eight Macintosh Transport: AppleTalk 

houioi s<tiim 

Router Nome: Rpple Internet Router 

p ,0> Pnr.UrPcrt 
' Mo4*«t«Por! 

$ LootITtfc 
S3: Elh«rT«k 
^ y TuM>ti 




C*n*»g I-555-»234 yU ACME 96 _ 

N«(: 1000, Zortr: OMton 


3S 190 4430,80.13024 1 

i Router Setup Port Info I 

P>i«sta«1 P*rt: ^ Mo4*mPorl 
A«««ss $ Lae»rr4k 

P»rt 0»seri|itto*: 

P«rt SUtus: (i) Aetw* Q 

( Hide... ~] 

P*rt: ® S*»i O honnyi 

^ 1«”0 I 

: [ Bwto*' 

[Get Zones... ] 


Sttttottcs t«rt r»Mt 1 /1 2/93 3 ;3S Mi 


SUtistic* T*t4l E(li*ri»«t Prtatrr P*rl 

RTMP versus AURP 

To help solve the problem of excessive RTMP traffic, particularly 
on WANs, Apple has developed a new routing protocol called the 
Apple Update Routing Protocol, or AURP. AURP updates the 
routing tables only when a change has been made to the network. 
(Typically, this means whenever a new network has been added 
to the internet.) With AURP, our student-routers would only 
exchange routing notes when new students are added to the 

Figure 8.48 

Sample stieens from the 
Apple InierneiHopiei. 

Part Two Macintosh Networking 

classroom. AURP is not intended to replace RTMP, which remains 
a viable protocol for small- and medium-sized LANs; rather, AURP 
is seen as a complement to RTMP. 

.\pple describes RTMP as a “no news is bad news” type of routing 
protocol. This means that if the RTMP updates aren’t seen every 
ten seconds, then something’s wrong. Instead, AURP is categorized 
as a "no news is good news" protocol, since as long as things are 
quiet, the routing information must be okay. The AURP protocol 
also defines a method of tunneling, or encapsulating, AppleTalk 
datagrams within other netw'orking protocols. (The idea behind 
protocol encapsulation will be covered in the next section.) 

The first product to support AURP is the Apple Internet Router 
(AIR). This new product supersedes the AppleTalk Internet Router 
2.0. AIR, like its predecessor, runs on a suitably-configured 
Macintosh. System 7 is required, along with a minimum of 4 MB of 
RAM. PowerBooks are not recommended. AIR fully supports AURP 
over LAN and WAN connections using a modular approach. AIR 
also includes support for the industry standard Simple Netw'ork 
Management Protocol (SNMP) which provides for remote manage- 

The standard network supported by AIR is dial-up access over 
standard phone lines (see figure 8.49). For a dial-up connection, 
Apple recommends a minimum of a pair of V.32/9600 baud 
modems. Obviously, the faster the modem, the faster and more 
responsive the AppleTalk connection will be. Since AIR was 
developed in a modular fashion, additional capabilities can be 
simply plugged in as needed. Apple offers several optional prod- 
ucts including an AppleTalk/X.25 and AppleTalk/IP extension. 

Chapter Eight Macintosh Transport: AppleTalk 

Figure 8.49 

A MCI diagram ol the 
Apple Internet Hauler 
working over 

The AppleTalk/X.25 Wide Area Extension, shown in figure 8.50, 
enables multiple AppleTalk networks to communicate through an 
X.25 wide area network. Apple’s Serial NuBus card is required to 
connect to the X.25 service. X.25 will be covered later on; briefly, 
X.25 is a wide-area networking ser\ace that is offered by service 
providers world-wide. These providers (such as Tymnet and 
Telenet) can offer customers local phone numbers that are used to 
connect to the system. One chief advantage of X.25 connections is 
that, unlike conventional phone lines which are billed solely based 
on time regardless of traffic, X.25 uses traffic as a prime determin- 
ing factor in billing. Considering that most network traffic is not 
continual and tends to be “bursty,” X.25 is very often a cost- 
effective alternative to traditional dial-up lines. A familiar example 
of X.25 networking can be found at most banks, since many ATM 
machines use X.25 links to provide wide-area access to your 
financial data. 





Macintosh Running Apple Inlamat Router 


Macintosh Running Apple mtamal Router 

r App.aT.ik y/ x.25 ) 

r x.25 H ) 

5 Loc.rr.m ? ^ rs-2m,422 ? 

5 RS-232 422 / S LocelTalk ? 



Figure 8.50 

A HeiPICI diagram ol Hie 
Apple InieiaelRpuief 
using X.25 nelweiking. 



Part Two Macintosh Networking 

The other optional AIR module is the AppleTalk/IP Wide Area 
Extension. Diagrammed in figure 8.51, it links multiple AppleTalk 
networks over a TCP/IP network. The AppleTalk/IP extension 
is supported on Ethernet or Token Ring cabling. As with the 
X.25 option, the IP option relies on a networking trick known as 

Rgure 8.51 

Apple InierneiRouler 



Macknoth kladnloah 

Protocol Encapsulation and Tunneling 

Using figure 8.52 as an example, imagine that you want to send a 
letter to your uncle, who lives on a mountain across the country, as 
quickly as possible. You could send the letter with an overnight 
carrier, but for some reason, the carrier won’t deliver the letter up 
the mountain. The regular mail service does go up the mountain: 
unfortunately, sending it this way would take two weeks for 
delivery. You then remember that you have a cousin that lives in 
the town at the base of the mountain who can receive the over- 
night delivery service. So you proceed to address the letter to your 
uncle and affix the required postage for regular mail delivery. 

Then, you place die addressed letter inside the overnight delivery 
pouch and address it to your cousin. You don’t want to make your 
cousin go up die mountain, so you place a note inside the over- 
night pouch instructing him to simply drop the enclosed letter into 
the nearest mailbox. This way, the local mail will deliver the letter 
within a day or so. Thus, the total delivery time is only two or three 

Chapter Eight Macintosh Transport: AppleTalk 

This scenario can be directly applied to networking as well. The 
process of placing one transport protocol inside another is called 
protocol encapsulation or tunneling. Tunneling AppleTalk inside of 
another protocol, such as TCP/IP or DECnet, might be necessary 
or desirable for several reasons. 

One reason could be that an organization's wide-area network only 
supports a certain protocol. This has been fairly common in the 
past because a number of routers have only supported a single 
protocol. For example, many companies that have extensive wide- 
area DECnet networks interconnect them with DECnet-specific 
routers. For these companies to be able to offer AppleTalk services 
over the network, they would have to scrap all their existing 
DECnet routers and replace them with multiprotocol AppleTalk/ 
DECnet routers. 

Part Two Macintosh Networking 

Figure 8.53 

acis as ap AppleTalk 

Alternatively, they can tunnel AppleTalk protocols inside tlie 
DECnet protocol. In this case, an AppleTalk datagram that is 
directed to a distant network is wrapped inside a DECnet packet by 
a special device and routed over the wide-area DECnet network to 
another special device, where its AppleTalk datagram is then 
extracted from its DECnet encapsulation and then passed along 
using AppleTalk protocols to its final destination. 

In the case of AppleTalk/ DECnet tunneling, the special device 
happens to be a DEC VAX that’s running the AppleTalk for VMS 
and DECnet protocols simultaneously (see figure 8.53). The 
AppleTalk for VMS software establishes a connection with the 
DECnet software and performs the encapsulation and 
decapsulation of the AppleTalk datagrams. 




AppleTalk Net #10-20 




AppleTalk Net #21-30 


As mentioned before, with tlie new Apple Internet Router, tunnel- 
ing is also possible with X.25 and TCP/IP networks. The concept 
remains the same — AppleTalk datagrams are placed inside the 
foreign protocol and then routed accordingly to the corresponding 
Apple Internet Router (AIR) over the wide-area connection. 

Routers that link an AppleTalk network to the foreign protocol 
network are called exterior routers. Routers that perform 
AppleTalk-to-AppleTalk routing within the internetwork are called 
interior routers. 

Chapter Eight Macintosh Transport: AppleTalk 

When the AIR (or any AURP-compliant router) is used in a tunnel 
configuration, the tunnel side of the connection of the exterior 
routers appears as an end node of the encapsulating protocol. 
Using IP encapsulation as an example, when two AURP-compliant 
routers communicate over a TCP/IP link, they appear as two native 
TCP/IP devices. On the interior side of the connection, however, 
the routers must appear as Phase 2 routers that speak RTMP to the 
other interior routers. 

Wlienever an AppleTalk datagram is encapsulated in a foreign 
protocol, the AURP-compliant router adds a special AURP header 
in addition to the addressing header of the foreign protocol. This 
special variable length AURP header is called a domain header or 
DI. Technically, the AURP domain header extends the standard 
32-bit AppleTalk address (network, node and socket) and creates 
a complete AURP wade area address. 

Before AURP, one of the key rules of AppleTalk network configura- 
tion was the uniqueness of AppleTalk network numbers. With the 
addition of the AURP DI number, it is no longer a requirement that 
the network number must be globally unique (although it’s still a 
good idea). No\\f, with the addition of the DI the complete address 
is domain ( network . node . socket ) . 

Adding the DI is similar to adding an area code to a phone number. 
For example, the phone number 555-1212 is certainly not unique 
in the whole US phone system. But, by adding a unique three-digit 
area code to the beginning of the number, it becomes a valid 
directory assistance number for any area code. 

To better illustrate this point, let’s use an example of two uncon- 
nected LANs. Figure 8.54 shows one LAN in Philadelphia having a 
Phase 2 network range of 10 to 20. The other LAN in San Francisco 
has a range of 15 to 50. Under the pre-AURP Phase 2 rules, these 
two networks could not be linked together because their network 
numbers overlapped. Both LANs have a network number 15, and 


Part Two Macintosh Networking 

ngure 8.54 

With IlieAlIRP Domains, 
AppleTalk network 
numbers do not 
necessarily have to be 
uoique. In this example, 
there are two devices 
osing the 15.22.129 
address. The addition el 
the DURP Domain makes 
them unique. 

therefore a conflict would occur. With AURP Dls, each LAN could 
have a unique domain number. Philadelphia’s domain number 
could be 1 and San Francisco’s domain could be 2. This would 
create unique addresses for both sides. 1(15.22.129) is now differ- 
ent from 2(15.22.129). Of course, the Dls must be unique on the 
tunnel. If the tunnel is a TCP/IP tunnel, one sure way to insure that 
the Dls are unique is to use TCP/IP addresses as the Dls. 

2(15.22.129) 1(15.22.129) 


Domain: 2 
Net #15-20 
San Francisco 

Domain: 1 
Net #10-20 
Zone: Phiiadelphia 


The Macintosh supports a number of transport protocols. Its 
native protocol, AppleTalk, provides plug-and-play connectivity. 
AppleTalk nodes use dynamic node addressing and name binding 
to self-configure, which avoids the manual configuration required 
by other protocols such as DECnet and TCP/IP. Since its inception, 
Apple has continued to evolve AppleTalk, the most recent changes 
providing enhanced routing over wide-area networks. 



ne of the more visible aspects of a Macintosh 
network is the medium used to make the 
connection. This chapter covers the various 
connection media, such as LocalTalk and 
Ethernet. It covers the advantages and disad- 
vantages of each medium, giving you the 
knowledge to choose the right medium — or 
combination of mediums — for your network. 

LocalTalk/Phone-Type Connectors 

LocalTalk, along with its phone-type variants, is one reason for the 
popularity of Macintosh networking. Its low cost and easy instal- 
lation has set the standard for desktop networking. Although 
LocalTalk is rapidly being supplanted by Ethernet, it still offers a 
viable solution for many Macintosh users. 

Part Two Macintosh Networking 

Figure 9.1 

Apple's locallalk 
ICouriesif of Apple 


LocalTalk (see figure 9.2) was the first network cabling system 
available for tlie Macintosh. Introduced in 1985 along with the 
LaserWriter printer, LocalTalk was a low-cost plug-and-play 
solution in a world of thousand-dollar Ethernet cards. LocalTalk 
and its variants are still used today, but its use is rapidly declining. 
LocalTalk provides a bandwidth of 230.4 Kbps, which is pretty 
quick compared to a 9600 baud modem connection. Compared to 
a 10 Mbps Ethernet connection or a 100 Mbps FDDl connection, 
however, it’s pretty slow. 

The LocalTalk cabling system normally connects to a Mac’s Printer 
serial port (shov\Ti in figure 9.3), and to the appropriate LocalTalk 
ports of other devices. 

NOTE: The Modem port is not used for LocalTalk connections unless you 
intend to run router software (such as the Apple Internet Router) on your Mac 
to route between two LocalTalk segments. 


Chapter Nine Macintosh Media/Cabling 

Cabling Layer 

Figure 9.2 

locallalk resides ai Die 
Cabling layer of Uie 

Modem Port Printer Port 

The heart of LocalTalk is the small connector box which contains a 
small transformer that electrically isolates the network connection. 
It has three connections. One side of the box has a length of v\dre 
and a connector (either a circular 8-pin D1N8 connector or a D- 
shaped 9-pin DB9 connector) that is used to connect to the 
AppleTalk node. The other side of the LocalTalk box has two 
receptacles that are used to connect the node to the chain of other 
LocalTalk devices. 

Figure 9.3 

Bolb the Modem and 
Primer ports are serial 
ports; however, only ihe 
Printer port can be osed 

Part Two Macintosh Networking 

Apple’s LocalTalk connectors are rarely used today for several 
reasons. First, when a LocalTalk network is indicated, it usually 
makes sense to consider the LocalTalk-compatible phone-type 
connectors. Farallon's PhoneNET, which uses twisted-pair tele- 
phone-type wiring, is one such alternative. Another reason is that 
the LocalTalk connectors do not have a positive locking arrange- 
ment — they can be easily pulled out or disrupted. People have 
been known to wrap electrical tape around the boxes or even Crazy 
Glue the connectors in place to avoid this problem. Perhaps the 
most important reason for the decline and fall of LocalTalk is that 
it’s rapidly being replaced by Ethernet. The price of Ethernet 
connections has dropped dramatically over the past few years, so 
the cost differential is not as great as it was in the past. 

LocalTalk does have cable shielding, so in electrically noisy areas, 
LocalTalk might be better titan the unshielded twisted-pair wiring 
used by the phone-type connectors. For most small installations 
where the anticipated network traffic is modest, you’ll want to 
consider the phone-type devices. 

PhoneNET and Other Phone-Type Connectors 

Farallon was the first company to offer a functional replacement 
for LocalTalk. They replaced the DIN8 connectors of LocalTalk 
with the positive locking RJ-11 connectors found on most tele- 
phones (see figure 9.4). They also replaced the expensive shielded 
LocalTalk cable with conventional twisted-pair phone wiring. The 
PhoneNET connectors were, and remain, completely compadble 
with the LocalTalk Link Access Protocol (LLAP), so switching over 
to PhoneNET from LocalTalk requires no software changes or 
special configuration. 

Chapter Nine Macintosh Media/Cabling 

The success of PhoneNET and similar products was twofold. Small 
companies were able to create a simple, inexpensive LANs in an 
hour or so by simply going to Radio Shack and buying a spool of 
phone wire, a box of RJ-1 1 connectors, and a $15 crimping tool. 
Large companies soon found that it was possible to integrate the 
PhoneNET connectors into their existing wiring schemes — wiring 
schemes previously used for connecting “dumb" terminals to 
mainframes and minicomputers over twisted-pair RS-232 wiring. 

The PhoneNET connectors also made it possible to move to a star 
topology (or radial topoIogjO. instead of the daisy-chain topology 
of LocalTalk. PhoneNET currently supports two kinds of stars: 
passive stars, in which each of the segments is interconnected at a 
panel or junction block, and active stars, where the segments join 
at a LocalTalk repeater. Farallon’s first repeater was called the 

Hgure 9.4 




locking conneciois. 



Part Two Macintosh Networking 

Since the star topology only requires a single connection at the 
node, only one RJ-l 1 receptacle is required. When a PhoneNET 
connector is used, the extra receptacle is filled with a terminating 
resistor. Other brands are self-terminating and don’t require a 
separate resistor. Farallon also offers a single-receptacle connector 
called the StarConnector. This small connector (see figure 9.5), 
plugs directly into the printer port of a Macintosh, and is ideally 
suited for star networks. StarConnectors are also useful in pairs, 
where they can be used to connect two devices (a PowerBook and a 
desktop Mac, for example) with a single R]-l 1 cable. 

Figure 9.5 

port Used in star 
neiworks, die device is 

Today, there are many LocalTalk-compatible products. In addition 
to Farallon, there are several companies that make the phone-type 
connectors and products. 

Design Considerations 

If your network consists of a dozen or so nodes in a centralized 
location, and your bandwidth requirements are modest, then a 
LocalTalk or PhoneNET daisy-chain might make sense. With either 
device, you’ll be able to add nodes to the ends of the chain, but if 
you need to add an additional connection somewhere in the 
middle, the entire network will be disrupted. 

Chapter Nine Macintosh Media/ Cabling 

A more flexible solution for small workgroups is to use a bus 
topology. With this system, a single cable is used as a backbone. 
Each phone-type connector then plugs into the bus. Connections 
can be made and broken at any time without disruption to the 
network. This is only possible with the phone-type connectors, 
such as PhoneNET, and will not work v\qth the LocalTalk 

The next step up is to go with a star topology. The choice of a 
passive star can be limiting, with restriction on the number of 
devices and distances. In most cases, passive stars are problematic 
and not worth the trouble. The other option is to go with an active 
star. The active star involves the use of a LocalTalk multiport 
repeater. Products such as the Farallon StarController (shown in 
figure 9.6) and the Focus TurboStar avoid the problems found in 
the passive star topologies. These repeaters are a good choice for 
the LocalTalk network that is spread out through a large building. 
They’re even a better choice if you’re able to use existing twisted- 
pair wiring. 

Figure 9.6 

The Faiallon PhoneNET 
example ol a niuitipDii 
(Copriesyol Farallon 

Part Two Macintosh Networking 

Planning Ahead 

If you're going to go the tv/isted-pair phone-type connector route, be sure to 
use twisted-pair wiring that's capable of supporting twisted-pair Ethernet. 
Phone-type connectors require a single twisted pair, while twisted-pair 
Ethernet requires two twisted pairs. LocalTalk signaling will work over the 
Ethernet twisted-pair wiring, but not vice-versa. So plan for the future and wire 
for Ethernet. The additional cost of the cable should be negligible compared to 
the installation cost. Just make sure you use the appropriate twisted-pair 
wiring, as there are different kinds of wiring for different applications. 

As you consider a LocalTalk or phone-tvTJe connector network, 
keep in mind that the additional cost of die LocalTalk hub in- 
creases the per-device cost. Now that Ethernet connections are so 
inexpensive, you may want to consider spending just a bit more 
to go Ethernet. If all your de\ices — present and planned — are 
equipped with LocalTalk, then choosing it as a cabling system may 
not be a bad choice. But if you plan to add other PCs, workstations, 
or printers that don’t offer LocalTalk options, maybe it’s better to 
opt for Ethernet at the outset. 

Wlien Ethernet is chosen as a backbone cabling system, it used to 
be that the only option for connecting LocalTalk-only devices 
(such as LaserWriters) was to install a LocalTalk-EtherTalk router. 
This is an expensive cure when you may only have a limited 
number of LocalTalk devices to connect. It also adds the adminis- 
trative overhead and performance concerns of adding another 
router to the network. Several years ago Dayna Communication 
introduced a device called EtherPrint. It acted as a LocalTalk-to- 
Ethernet bridge. It essentially adapted the LocalTalk device to the 
Ethernet network. Today, these devices, diagrammed in Figure 9.7, 
have gained in popularity and functionality. 

Chapter Nine Macintosh Media/Cabling 

Figure 9.7 

Seveial companies 




used IP connect 

locallalkonly devices, 




Companies such as, Asante (AsantePrint), Compatible Systems 
(EtherWrite), Dayna (EtherPrint Plus), Farallon (LocalPath), Sonic 
Systems (SuperBridge) and Digital Products (SprintTALK) make 
LocalTalk-Ethernet bridges. The new generation of devices is able 
to connect multiple LocalTalk devices — Macs and PowerBooks 
included. The Farallon and Sonic Systems offerings are software 
solutions that run on a Mac with the appropriate network inter- 
faces. The Farallon product can even connect devices to Token 
Ring networks. Many of these devices support security features 
that can limit access to the LocalTalk device. 


At one time, Ethernet was to cabling systems what FDDI is today — 
it was expensive and offered a bandwidth well beyond the require- 
ments of most applications. Today, Ethernet is fast becoming the 
modern equivalent of RS-232. Nearly all computer systems offer 
Ethernet connections. With the advent of very large-scale 
intergration, the Ethernet components have been reduced to a 
single chip, wiiich has driven the cost of Ethernet cards down to 

Part Two Macintosh Networking 

less than $200. Fortunately, these price reductions aren’t limited to 
the PC world, as Macintosh Ethernet cards are fast becoming a hot 

Ethernet Basics 

Even though Apple developed LocalTalk to provide a basic physical 
connection between devices, Apple also recognized the need to 
provide alternative wiring choices to their customers. One of the 
most popular local area networks (LANs) is Ethernet (see figure 
9.8). Originally developed by Xerox in collaboration with Digital 
and Intel, Ethernet is used by many computer vendors as a wiring 
media for networking. Companies such as Digital and Sun use 
Ethernet to run a variety of networking protocols. In fact, Ethernet 
was developed with multiprotocol support in mind. A single 
Ethernet network can support many different protocols at the 
same time. 

Figure 9.8 

Elhernet resides at (lie 
Cabling layer of Uie 

Cabling Layer 

When AppleTalk protocols run over Ethernet cables, Apple calls 
this EtherTalk. Whereas LocalTalk cables have a bandwidth of 
230.4 Kbps, Ethernet has a bandwidth of 10 Mbps. So instead of 
being limited to 32 nodes, as with LocalTalk, EtherTalk networks 
can support thousands of devices. Theoretically, with the latest 
version of AppleTalk (Phase 2), a network can have over 16 million 

Chapter Nine Macintosh Media/Cabling 

devices. Of course, on a single cable you would run out of room to 
connect all those devices, but Ethernet cables are often “con- 
nected” by network bridges, microwave links, and even satellites to 
other Ethernet networks to create an “extended” Ethernet LAN. 
Many large companies have extensive world-wide Ethernet LANs 
with thousands of computers produced by different companies. 

The throughput of an Ethernet network is higher than LocalTalk. 
Actual transmission rates will depend on many factors, such as 
network traffic, size of the transmitted file, and performance of the 
individual Ethernet controller. On average, you can expect an 
Etliernet network to perform three to five times better than a 
LocalTalk network. \Vliy such a difference? The factors limiting 
Ethernet throughput are numerous and complex, but the speed of 
the Macintosh CPU, hard disk, and Ethernet hardware, coupled 
with network configuration, application performance, and other 
network traffic all play a role in Ethernet performance. 

All Macs and LaserWriters come standard with the hardware to 
support LocalTalk communications. Some Macs (such as the 
Quadra family) and LaserWriters (such as the LaserWriter IIG and 
LaserWriter Pro 630) come equipped with built-in Ethernet hard- 
ware. For those Macs that don’t have Ethernet, connections are 
made with the addition of a networking card. LocalTalk 
LaserWriters, such as the LaserWriter IINT, can connect to 
Ethernet with adapter devices, such as Dajma’s EtherPrint de\ice. 

Ethernet cards for Macs with card slots are made by Apple and 
other vendors (see figure 9.9). The cost varies between $200 and 
$400. Several companies also sell SCSI/Ethernet adapters for those 
Macs, such as the Classic and the PowerBook family, without card 
slots. These devices connect to the SCSI port of the Macintosh, just 
like any other SCSI device, and dien connect to the Ethernet 

Part Two Macintosh Networking 

Figure 9.9 

A sampling olEiliernet 
cards. IlieiwO'Piece 
anils are for lire 
lire one-piece pail is lor 
Farallon Computing.) 

ELAP software drivers are included with both the Ethernet cards 
and the SCSI/Ethernet devices. This software provides new net- 
work driver programs that give you the option, through the Control 
Panel, to choose between LocalTalk and EtherTalk. Unless you 
turn your Mac into a router, the AppleTalk traffic can only go 
through one port at a time. 


There are several variants of Etliernet cabling. Even though the 
cabling is different, the electrical signaling remains the same. 
Because of this, all Ethernet cable variations use the same ELAP 
drivers. The only significant difference is the cable type and the 

Thickwire 10Base-5 

Thickwire Ethernet (see figure 9. 10), is a stiff coaxial (one wire 
inside another wire) cable about 3/8" in diameter; it employs a 
15-pin D-style connector. The cable is terminated at both ends 
with special resistive fittings that minimize signal reflections that 

Chapter Nine Macintosh Media/Cabling 

would otherwise degrade communications. Usually thickwire 
Ethernet is employed as a central "backbone" running throughout 
a building, although fiber-optic Ethernet is rapidly replacing 
thickwire as a backbone media. Thickwire Ethernet permits a 
maximum of 200 devices on a 1,640 foot segment. Thickwire 
Ethernet is often referred to as lOBase-5 wiring. 

Terminator Barrel Connector Terminator 

Thickwire connections are established by clamping a device called 
a transceiverto the cable. Most transceivers are installed by drilling 
a small hole in the cable with a special tool. This is followed by 
clamping the transceiver, which pierces the cable with sharp 
contact pins that make electrical contact. This method of connec- 
tion is sometimes referred to as a "vampire tap.” These taps can 
only be made at regular interv'als along the cable. Most cables have 
indicator markings every 2.5 meters to help position die transceiv- 

Adding transceivers to a backbone cable is not difficult, but this is 
not a cost-effective way to make a single network connecUon. 
Usually transceivers are used to connect hubs (or repeaters), which 
support the connection of multiple devices through a single 
transceiver connection to the backbone. 

Figure 9.10 

Thickwire |10flase-5| 

(i.e. Computer, Hub, Router) 

Part Two Macintosh Nehvorking 

In the lOBase-5 nomenclature, the 10 refers to the bandwidth. All 
Ethernet implementations have a 10 megabit bandwidth. The term 
“Base” refers to baseband (as opposed to broadband). Baseband 
means that the cable only supports a single communications 
channel. The value of 5 refers to the maximum length of the cable 
segment, which for lOBase-5 is 500 meters. There is a specification 
for broadband Ethernet called lOBroad-36. It runs over a coaxial 
cable and has a maximum segment length of 3,800 meters. 

Figure 9.11 



Thinwire 10Base-2 

Thinwire Ethernet (see figure 9.1 1) is thinner (about3/16 ") and 
considerably more flexible than the original thickwire. It used to be 
a popular choice to connect desktop devices and workstations. 
Today, however, thinwire is being rapidly replaced by twisted-pair 
Ethernet for desktop connections. 

Terminator Tee Coaxial Cable Terminator 

Thinwire Ethernet uses BNC (twist and lock) type connections and 
allows 30 devices per 656 foot segment, over a maximum nettvork 
length of 3,281 feet. Thinvwe is often referred to as "Cheapernet," 
or its more formal name of lOBase-2. This designation is similar to 
that of thickwire: the 2 indicates a maximum segment length of 200 
meters (actually, the maximum segment length is 185 meters, but I 
guess they didn’t want to call it lOBase-1.8). 

Chapter Nine Macintosh Media/Cabling 

Connections are made with a tee connector, similar to LocalTalk. 
One branch of tlie tee connects to the network device, while the 
other two connections are used to connect to the network. When 
thinwire is connected in a daisy-chain, the free ends of the last tees 
must be terminated with special resistive end caps. Adding more 
devices to a thinwire daisy-chain disrupts the network because the 
chain must be broken. It is possible to disconnect a device at the 
attachment point without disrupting the network chain. 

Thinwire can also be configured in a star topology using a thinwire 
Ethernet repeater. Here, each tee at the end of each branch of the 
star must be terminated. The use of thinwire star topologies is 
rapidly declining, due to the arrival of the newer, more flexible 
twisted-pair Ethernet. 

Twisted Pair lOBase-T 

Lately, another Ethernet variant has started to become popular. 
Twisted-pair Ethernet (see figure 9.12) has been around for several 
years, but during the past two years it has virtually dominated 
the desktop. With this system, Ethernet can be implemented 
on standard unshielded twisted-pair wiring. Thinwire Ethernet 
requires two pairs of wires that meet certain industry 

Figure 9.12 



Part Two Macintosh Networking 

The choice of wire may depend on local building or electrical 
codes, or on the recommendations of suppliers. It’s always best to 
check with the various codes and suppliers for detailed cabling 
specifications. As mentioned earlier, it’s always wise to cable for 
thinwire Ethernet even if you’re planning to use LocalTalk. It also 
may be prudent to consider the anticipated wiring standards for 
the newer high-speed cabling systems such as FDDI (Fiber Data 
Distributed Interface). There is currently work underway to imple- 
ment FDDI over copper twisted-pair wiring and to develop a 100 
Mbps version of Ethernet that runs over four twisted-pairs. Often, 
if your wiring strategy covers the most stringent wiring scenario, 
you’ll be able to design for future growth and enhancements. 

Unlike thickwire or thinwire tliat can be connected in a bus or 
daisy-chain, twisted-pair Ethernet requires the use of a hub. These 
hubs come in a wide variety of prices and configurations with a 
varying number of ports and extra features. Some hubs offer a 
modular construction that make it easy to provide additional 
connections as required. 

All the Ethernet card vendors for die Macintosh offer twisted-pair 
Ethernet versions, with many cards offering multiple connectors 
(thick, tliin and twisted-pair) on one card. Twisted-pair Ethernet 
underwent some changes during its early years, and there have 
been several implementations, but now the standard is set and is 
widely known as lOBase-T. 

Apple s Ethernet Cabling System 

In January of 1990, Apple announced a new line of low-cost 
Ethernet cards. The two new cards (one for the Macs with NuBus 
slots and one for the Macintosh LC) use a separate attachment 
unit, known as an Apple AUI (Attachment Unit Unterface) that 
attaches to either thickwire, thinwire, or twisted-pair Ethernet (see 
figure 9.13). Resembling LocalTalk connectors, these connectors 
attach to the Mac or LaserWriter with a new style of connector. 

Chapter Nine Macintosh Media/Cabling 

This permits Apple to use these new compact connectors on the 
motherboards of all their new machines. The appropriate attach- 
ment unit (either thick, thin, or twisted-pair) is then connected to 
the device. This approach offers Apple a single, compact connector 
for their new products, while still offering the flexibility of three 
attachment options. Apple has provided the specifications for 
Apple AUl, so these new connectors are also offered by third-party 
suppliers. These new devices will bring the ease-of-installation and 
low cost of LocalTalk to Ethernet networks. 

Hgure 9.13 

Apple's EihernelNuBus 
egaippedl can canned lo 
Apple's lliick. in nr 
iwisied-pair transceivers. 

Design Considerations 

As with any network design, the physical location is an important 
determining factor. If all your AppleTalk nodes are in the same 
room, then lOBase-2 thinwire easily can be daisy-chained among 
the devices, and will most likely be the cheapest solution. The 

Part Two Macintosh Networking 

other option is to use lOBase-T twisted-pair Ethernet. If you 
choose lOBase-T, you’ll need a hub to interconnect the devices. If 
you have just a few devices to connect, there are a number of 
vendors that offer small, affordable hubs with anywhere from three 
to eight ports. The additional price of the hub may make this 
approach more expensive than thinwire, but the cabling should be 
slightly cheaper and you may be able to assemble your own cables 
more easily than thinwire. 

If your network is large and spans many rooms or floors, a back- 
bone Ethernet is probably needed. With this approach, a lOBase-5 
or fiber optic cable is strategically placed through the building. 
Often, the cable runs between wiring closets, where nebvork 
equipment such as hubs, routers, and gateways are located. These 
wiring closets are often used for phone connections as well. (Some 
networking vendors offer integrated networking equipment to 
consolidate the management of voice and data connections.) 

With most extensive EtherTalk networks, a major design consider- 
ation is the routing and isolation of traffic. Deciding where to place 
routers and how best to link EtherTalk LANs to wide-area connec- 
tions is frequently an important concern. 

Other Cabling Systems 

LocalTalk and Ethernet are the most popular cabling choices for 
the Macintosh, but the Mac also supports a wide range of other 
industry standard cabling systems. 

Token Ring 

Token Ring networks (see figure 9.14) operate using a different 
principal than Ethernet. As discussed earlier, Ethernet devices 
listen to the cable before transmitting, whereas Token Ring devices 

Chapter Nine Macintosh Media/Cabling 

wait their turn until an electronic token comes their way. Because 
of this fundamental difference, Token Ring networks enjoy certain 
benefits over Ethernet netw'orks. 

Rgure 9.14 

Token Ring MCI. 

First, when it comes to traffic. Token Ring networks are self- 
limiting. Unlike Ethernet networks, which degrade when excessive 
traffic causes collisions and retransmissions. Token Ring networks 
simply reach their maximum throughput and then level out. 
Another advantage of Token Ring is that a node is always guaran- 
teed access to the cable within a finite period of time. Ethernet 
nodes play a statistical game where access to the cable is not 
guaranteed. This makes Token Ring networks appealing for time- 
critical, real-time, and process control applications. 

Most decisions to select Token Ring technology (other than FDDI) 
are not made because of its technical advantage, but rather to 
connect to the IBM environment, where Token Ring is a popular 
choice. There are currently two implementations of Token Ring — a 
4 Mbps version and a 16 Mbps version. 

Token Ring cards are more expensive than their Ethernet counter- 
parts. Prices range from $500 to $800 per card. Apple and several 
third-party vendors offer NuBus Token Ring cards. 


Likely to succeed Ethernet, FDDI (Fiber Distributed Data Interface) 
is an ANSI and ISO standard network based on dual fiber optic 

Part Two Macintosh Networking 

Figure 9.15 


rings (see figure 9.15). FDDI has a bandwidth (data throughput 
rate) of 100 Mbps. This is 10 times the bandwadth of Ethernet. Just 
as Apple offered EtherTalk and TokenTalk drivers for Ethernet and 
Token Ring wiring systems, tliey have also developed FDDlTalk 
drivers. The Apple drivers currently support AppleTalk Phase 2 and 
MacTCP. FDDI networks can contain 1,000 nodes no more than 2 
kilometers apart, for a total aggregate distance of 100 kilometers. 

Figure 9.16 

A FDDI card lor MuS’ 

FDDI cards (see figure 9.16) are still a bit on the expensive side at 
over $ 1 ,000 per card, but just as the cost of Ethernet cards dropped, 
the price of FDDI cards will come down as well. FDDI cards are 
currently offerred by several companies; Codenoll and Impulse 
Technology are two examples. While FDDI is still rare on the 
desktop, it’s becoming increasly prevalent as a backbone cabling 

Chapter Nine Macintosh Media/Cabling 

Although FDDI is gaining in popularity, there are other upcoming 
standards vying for acceptance. A proposed “CDDI” standard 
would offer the performance of FDDI over less-costly copper 
cabling. HP and AT&T are proposing an upgrade to the Ethernet 
standard to achieve FDDI performance levels (100 Mbps) over 
lOBase-T twisted-pair wiring. Instead of two twisted pairs, this 
approach requires four twisted pairs. 

Serial RS-232/422 

Serial communications only recently have become a popular 
cabling medium for AppleTalk. Starting v\ath Apple’s Remote 
Access Protocol (ARAP), many Macintosh users are using serial 
connections and modems to dial in to remote Macintosh comput- 
ers. ARAP uses data compression and buffering techniques to coax 
the most out of the relatively slow dial-up links (see figure 9.17). 

Remote Macintosh 

Rgure 9.17 

Applelalkflemoie Access 

Part Two Macintosh Networking 

ARAP uses die client/server model to make the remote connection. 
A Macintosh running the client portion of Remote Access dials in 
to a Remote Access server. With Apple’s software, the server is a 
Macintosh. There are other servers from third-party vendors that 
use dedicated hardware devices. These servers, such as Shiva’s 
LANrover, connect to multiple dial-up lines and also make a 
network connection to LocalTalk or Ethernet networks. 

Figure 9.18 



ARCNET is a cabling system that is popular on IBM PCs (see figure 
9.18). It runs over twisted-pair or coaxial cabling at a bandwidth 
of 2.5 Mbps. A Macintosh version of this cabling system is now' 
available, along with software that provides the ARCNET data link 
drivers (ARCNET Link Access Protocol). For more detailed infor- 
mation on ARCNET, refer to Chapter 10, “Living in an Intel/DOS 


As computers get smaller and smaller, the cabling systems that 
used to connect them also tie them down to the desktop. The 
solution is to eliminate the cabiing. Wireless networks are a recent 
development that does just that. There are several wireless tech- 
nologies available for the Macintosh. 

One option for a wireless network is to use Apple’s Remote Access 
with a celluar phone/modem combination (see Figure 9.19). This 

Chapter Nine Macintosh Media/Cabling 

makes sense for wide-area network connections for a limited 
number of devices. For LAN connectivity, wireless technology may 
be useful in locations where conventional wiring is difficult or 
impossible to run. Motorola, the leading manufacturer of cellular 
telephones, has a Macintosh product called EMBARC which 
provides a one-way wireless messaging service for remote Mac 

Remote Macintosh 

Figure 9.19 



There are also options for LAN mediums such as LocalTalk and 
Ethernet. Photonics makes LocalTalk devices that use reflected 
infrared to link a number of nodes (see figure 9.20). The infrared 
devices focus their energ>' at a single point on the ceiling. 

Motorola has developed a wireless version of Ethernet called Altair 
II (see figure 9.21). These devices use low-power radio waves as a 
transmission medium. Altair’s transmission rate of 5.7 Mbps is 
somewhat less than Ethernet bandwidth. Setup is easy. Each 
Ethernet device connects to a small desktop send/ receive module. 

Part Two Macintosh Networking 

Figure 9.20 

Monies makes a 
locallalk device iliai 
conneciien medium. 

These desktop modules transmit radio waves to control modules 
that connect to walls or cubicle partitions. The send/ receive 
modules support all kinds of Ethernet adapters and cost around 
$1,200. The control module can be used alone or connected to a 
conventional Ethernet cable. These devices can handle up to 50 
wireless devices. 

Figure 9.21 

Motorola's Allaiiil 
loclinology uses radio 
waves 10 carry Eihernei 

Compared to conventional wired networks, these new technolo- 
gies are still somewhat expensive and are only cost-effective in 
those cases where wiring is difficult or where reuiring costs would 
exceed the cost of the wireless components. Expect wireless 
communications to continue to increase in popularity as Apple’s 
Newton technology and other handheld computers become 


Chapter Nine Macintosh Media/Cabling 

WAN Media 

The cabling systems mentioned previously are typically used by 
LANs. But when Macs need to be networked over longer distances, 
other technologies are needed. However, compared to the cost and 
convenience of LAN connections, WAN options are often limited 
and expensive. 

Conventional Dial-Up 

Modem access was discussed earlier in the context of remote 
access. A Macintosh user dials into a server on the LAN and con- 
nects to services using a pair of modems. This is fine for the single 
user, but what about connecting two (or more) LANs over a dial-up 

There are modem-based products that work over conventional 
analog dial-up lines that can be used to link multiple AppleTalk 
LANs. An example of this can be found in Apple’s Internet Router 
(AIR). In its standard configuration, as shown in figure 9.22, it 
offers dial-up access over standard phone lines. Apple recom- 
mends a pair of V.32/9600 baud modems as a minimum configura- 
tion. Farallon, Shiva and other companies make similar products. 

Figure 9.22 

Ihe Apple Internet Rpiiter 
can be used to link twn 
neiwptks over a dial up 

The problem with these products is the relatively slow dial-up 
connection. This type of connection is slow even for the single 

Part Two Macintosh Networking 

Remote Access user, and more so for a number of LAN users. 
Conventional dial-up connections are also plagued by noise and 
disconnections that are more likely to occur with lengthy connec- 
tion times. 

Figure 9.23 

Engage's Syncnouier can 
Dver Switched S6K lines. 

Switched 56K 

A faster and more reliable dial-up service is Switched 56K Service. 
This is a digital 56 Kbps service provided by AT&T over their 
ACCUNET system, by US Sprint, and others. Obviously this is 
much faster than a conventional 9600 baud dial-up line: it’s also 
much more reliable. This kind of service is very well suited to 
connecting remote AppleTalk LANs. Engage Communication Inc. 
offers an AppleTalk router (SyncRouter LTNT) that connects to 
Switched 56K services. A NetPICT of the SyncRouter is shown in 
figure 9.23. 


ISDN stands for Integrated Services Digital Network. The promise 
of ISDN is high-speed, digital communications that provides 
network, voice, and video to consumers. Think of ISDN as the 
digital replacement technologj^ for your telephone. Unfortunately, 
compared to other countries such as France, the United States is 
lagging in the implementation of ISDN services. This is starting to 
change as certain areas are now starting to get ISDN. 

ISDN uses three channels: two 64 Kbps “B” channels and a single 
16 Kbps “D” channel. The “B” channel carries voice and data, while 

Chapter Nine Macintosh Media/Cabling 

the “D" channel carries signalling data and can be used for lower- 
speed transmissions. As ISDN services become more readily 
available they should begin to displace conventional modems as 
means of connecting AppleTalk services. Engage Communications 
Inc. has just announced AppleTalk routers that use ISDN as a link 
(see figure 9.24). They offer a LocalTalk version that provides 64 
Kbps throughput and an EtherTalk version that uses both channels 
and can achieve a throughput of 128 Kbps. 

Figure 9.24 

Engage's SyncRoolei can 
fouling over ISDN lines. 

Leased Services 

Other high-speed services are leased for a specific period of time. 
These services are incrementally based with T1 ser\ices offering a 
bandwidth of 1.544 Mbps, T2 with 6.312 Mbps, and T3 with 44.736 
Mbps. These high speeds come with high price tags as well, making 
them suitable only for large organizations with demanding traffic 

riiese leased-line services are usually coupled with high-speed 
multiprotocol routers from companies such as Cisco, Wellfleet, 
DEC, and IBM. All these vendors provide AppleTalk routing over 
leased lines. These multiprotocol routers cost anywhere between 
S3, 000 and $20,000. They provide an>4hing from a single WAN and 
Ethernet connection to units that have multiple WAN and LAN 
connections over Ethernet, Token Ring, and FDDI. Figure 9.25 
shows a NetPICT of a T1 -connected WAN. 

Part Two Macintosh Netw'orking 

Figure 9.25 

Cisco, Wellileei, DEC, anil 
IBM) make routers that 
support higlispeed II 

X.25 Packet Switched Services 

Chances are that when you use your Automated Teller Machine 
(ATM) you’re also using the services of a packet switched network 
known as X.25. ATM machines enable customers to access their 
checking and saving accounts anywhere in the world. Obviously, 
each ATM machine doesn’t have everyone’s personal account 
information contained within; instead, it accesses your account 
information from a centralized location. Other examples of packet 
switched networks are bulletin board sei'vices such as AppleLink 
and CompuSei've. Users of these systems connect to the system 
over local phone connections. 

This is all made possible with X.25 networking. In an X.25 network, 
services are locally provided over local phone lines. Once con- 
nected, the service proxades a logical connection to anywhere on 
the entire system. 

In the past, packet switched networking was unsuited for 
AppleTalk networking because of the overhead imposed by the 
RTMP routing protocol. Now, with AURP, packet switching has 
become a viable alternative for AppleTalk WANs. X.25 routing is 
being offered as an optional extension to Apple’s Internet Router. 

One primary advantage of an X.25 connection is that the costs are 
primarily based on usage rather than connect time. In contrast, 
with a conventional dial-up line, cost is mainly based on con- 
nect time. The phone company doesn’t care whetlier you say 
anything — they’ll still bill you. This is the reason why X.25 

Chapter Nine Macintosh Media/Cabling 

AppleTalk connections have been long in coming: the continual 
RTMP traffic made their use uneconomical. X.25 bandwidths range 
from modem speeds (1200 baud) to special high-speed connec- 
tions at 2 Mbps. Figure 9.26 shows a NetPlCT of a X.25-connected 

Other Packet Switched Services 

In addition to X.25, there are other packet switched technologies 
that show promise. Frame Relay is similar to X.25 but will provide 
improved performance due to reduced overhead. SMDS (Switched 
Multimegabit Data Service) is another packet switched service that 
shows great promise. It differs from X.25 and Frame Relay by 
emplojang a datagram approach that is more in keeping with the 
AppleTalk protocol. 

Figure 9.26 

11)8 Apple inieinelfouiei 
cap be used 10 link two 


The Macintosh, LaserWriter, and many other peripherals have a 
built-in networking capability known as LocalTalk. It is a low-cost 
cabling system that works over twisted-pair cabling. AppleTalk 
protocols aren’t limited to LocalTalk; they can be sent over 
Ethernet, Token Ring, and most other media. While AppleTalk has 
been extremely popular on LANs, it has only recently begun to be 
accepted as a viable WAN protocol. 


cintosh is a team player 

;Ve^ '.V .X. an' < • . usncf '■ ■ onue 

Networks are often used to connect different computer 
systems. When it comes to multivendor networks, the 

:/!Hcli U‘:>h is a feaw pinye -. I; . u.p 

Macintosh is a team player. It supports a wide variety of 

rh twui'k Servici , H nnats, Transpc 

network Services, Formats, Transports, and Media. 

AppJnlafk is also fast 'recoining a d 

AppleTalk is also fast becoming a de-facto industry 

^ta > - • ' f that is svpj fa ted on ■; )an 

Standard that is supported on many different 

computers, fron ■ WM PC ro 

computers, from the IBM PC to DigitaPs VAX 


frif a wifla variety of 
: Services, Formats, 


<ri.s, and Media. 

Living in an 
Intei/DOS Worid 

acintosh computers and PCs, when connected, 
form the most common type of multivendor 
network. Exchanging documents and sharing 
resources between Macs and PCs is becoming 
more commonplace; software developers increas- 
ingly are offering separate Macintosh and Win- 
dows versions of their applications. With all the 
attention and focus on these two platforms, it’s not surprising that 
there are so many networking choices available. This chapter will 
describe the leading choices for putting your Macintosh computers 
and PCs on speaking terms. Since PCs are the most common 
network companions, we’ll also use this chapter to introduce some 
generic concepts and utilities diat will apply to other networked 
peers as well. 

Services; Application-Based 

During the past several years, Macs and PCs have reached an equal 
stature in the eyes of many users. Many applications and services 
are supported on both platforms, and since the advent of Microsoft 

Part Three Multivendor Networks 

Windows 3.0, the distinction between the platforms has narrowed 
considerably. Therefore, it’s hardly surprising tliat there’s a strong 
desire to share and exchange data between these two machines. 


Many new application programs are being written for both the 
Mac and PC platforms. The applications from Microsoft are the 
best example. Nearly all their products — ^Word, Excel, Mail, 
PowerPoint, Project, and even Flight Simulator — are available for 
both platforms. In the majority of cases, the binary file formats of 
these applications are the same, and therefore are interchangable. 
Other examples of this cross-platform support are Lotus 1-2-3, 
Autodesk’s AutoCAD, WordPerfect, and Claris’s FileMaker Pro and 

The application support extends beyond simple applications, as 
evidenced by Apple’s recent announcement of QuickTime for 
Windows and Microsoft’s adoption of TrueType fonts. With the 
QuickTime toolkit, Windows developers can create, edit, and 
display QuickTime files within their applications. Microsoft’s 
inclusion of TrueType might make it a bit easier to move docu- 
ments between the platforms without the font alteration that often 
occurs when competing font technologies are used. 

This cross-platform trend can only increase, as developments are 
underway to make it even easier for developers to create either 
Windows or Mac versions of their applications through the ad- 
vanced object-oriented compilers. These compilers will be able to 
substitute the appropriate platform-dependent user interface 
elements as necessary. 

Other Services 

Besides applications, there are other services that can be shared by 
both Macs and PCs (see figure 10.1). These include file, print, 

Chapter Ten Living in an Intel/ DOS World 

database, and mail services. Sharing these services is a somewhat 
more complex issue than simply sharing application files. With 
many of these services a specific format and transport layer are 
often required. For example, a PC can access an AFP file server, but 
only if equipped with the AppleTalk protocols. Both Macs and PCs 
can access an NFS file server — but only if both machines have the 
transport layer of TCP/IP. NFS and most of the other services 
common to the UNIX environment can also be installed on a 
suitably equipped PC. This chapter will just touch on a few of these 
options. For a more complete discusssion of TCP/IP services and 
protocols, refer to the next chapter. Regardless of the platform, it’s 
often a process of finding a mutually acceptable service that uses 
compatible formats, transports, and cabling. 

Macintosh PC/Windows 

Figure 10.1 

Macintosh/PC Services 

Formats: ASCII, EPS, Binary 

The ultimate success of Macintosh/PC integration is largely 
determined by the formats. Fortunately, there are many shared 
and compatible file formats. Since the advent of Windows, the 
number of applications and formats that are shared by both 
platforms has increased dramatically. There are also a number of 
mutually acceptable standards, such as Encapsulated PostScript 

Part Three Multivendor Networks 

(EPS) and Rich Text Format (RTF), that can be seamlessly moved 
between the Macintosh and PC platforms. 


The IBM PC was IBM’s first computer that used the ASCII code 
instead of their EBCDIC code. Thus, Macs and PCs speak the same 
format when it comes to text files. Both the Mac and PC have 
numerous applications that can read and write this format. The 
only occasional stumbling block is that sometimes PC text files 
have additional line feed characters at the end of each line of text. 
These line feeds can often be filtered with special utility programs 
or text editors. The key aspect of ASCII is that it’s often used as the 
basis for other higher-level formats, such as DXF, IGES, PostScript, 
and RenderMan (a 3D photorealistic rendering format). All Mac 
and PC text editors and word processors can read and write ASCII 
text files. 

Word Processing 

Many word processors, such as Microsoft Word, usually provide a 
built-in translation capability to facilitate the movement of docu- 
ments between the PC and Macintosh. Microsoft has also devel- 
oped an interchange format called Rich Text Format (RTF) that 
attempts to preserve certain formatting attributes between the 
Mac and Windows applications. If the PC word processing docu- 
ment was not created by an application that also runs on the Mac, 
or cannot be directly imported by a Mac program, then it must be 
converted. MacLinkPIus, from Data Viz, is a utility program that 
Ccm convert most PC word processing formats into formats that are 
supported on the Mac. This process is shown in figure 10.2. 

Chapter Ten Living in an Intel /DOS World 

PC/Windows Macintosh Step 1 Macintosh Step 2 Macintosh Step 3 

Of course one option, as shown in figure 10.3, is to save the Mac or PC 
document that you wish to transport as an ASCIi fiie. You’li iose ali the 
formatting, graphics, and font information, but at ieast you’il have the 
document in a form that can be universaliy read. Use this technique as a last 

Hgure 10.2 

Converting a PC 
processing document into 
Word document wiilt 

PC/WIndows Step 1 PCAIVIndows Step 2 Macintosh Step 1 Macintosh Step 2 

Figure 10.3 

neutral exchange format 
between word processors 
on the PC and Macintosh. 


When it comes to graphics, the situation gets even more compli- 
cated. There are dozens of different graphic formats that are 
supported on the Mac or PC. Some of these formats are bitmapped 
or pixel-based; others are object-oriented, containing object 
descriptions (such as line, circle, and rectangle) and coordinate 

The leading graphic formats on the Mac are: 

• MacPaint-style 72 dpi (dot per inch) bitmaps 

Part Three Multivendor Networks 

• PICT and PICT2 formats 

• EPS (Encapsulated PostScript) 

• TIFF (Tagged Image File Format) 

Of these, the MacPaint-type bitmap, PICT, and PICT2 formats are 
somewhat Macintosh-specific, although many Windows applica- 
tions support these file types directly without translation. The 
other formats — EPS and TIFF — have become industry standards: 
they’re frequendy supported by applications on both platforms. 
Just be sure to check the specific applications in question. 

On the Windows/ PC side, there are numerous graphics formats, 
and with the possible exception of EPSF, TIFF, and some 
Windows-specific formats, they are quite often specific to a par- 
ticular application. Listed below are but a few examples of the 
myriad graphics formats that you’re likely to encounter on a PC, 
along with their DOS file extensions. 

• Windows bitmap ( . BMP) 

• Windows Metafile (.WMF) 

• DrawPerfect (.WPG) 

• Computer Graphics Metafile ( . CGM) 

• Encapsulated PostScript ( . EPS) 

• Lotus 1-2-3 Graphics ( . PIC) 

• Initial Graphics Exchange Specification (. IGS) 

• AutoCAD Drawing Exchange Format ( . DXF) 

Chapter Ten Living in an Intel/DOS World 

• Micrografx Designer/Draw ( . DRW) 

• Tagged Image File (.TIF) 

With the exception of Encapsulated PostScript and Tagged Image 
File Format (TIFF) files, there are few PC/Windows graphic formats 
that are uniformly supported in the Macintosh world. Going from 
the Mac to the PC is much easier because support for the PICT 
format is common in the PC world; support for the numerous 
application-specific PC graphic formats by Macintosh applications 
is unlikely. 

One solution, shown in figure 10.4, is to use a PC graphics conver- 
sion program, such as Hijaak from Inset Systems. It can convert 
most PC formats into one of the predominant Macintosh formats 
(such as MacPaint or PICT). While Hijaak runs on the PC, the flip 
side of that approach is to do the conversion on the Mac by using 
the MacLinkPIus graphics translators. They support the conversion 
of most popular PC graphics formats into the PICT format. 

PC/Windows Step 1 PCAVindows Step 2 Macintosh 

Figure 10.4 

Hiiaakfm Intel 

For CAD/Cy\M and technical graphics, there are two formats that 
are widely supported on both the Mac and the PC. The industry 
standard IGES is a standard format that can be binary, but is 
usually ASCII text. DXF is a standard developed by Autodesk, 

Part Three Multivendor Networks 

Figure 10.5 





developers of the popular AutoCAD program. It too comes in a 
binary format, but the most popular format is regular ASCII text. 
Both of these formats are commonly supported by both Macintosh 
and PC CAD applications and utility programs. These files can 
be readily transported between the platforms. In particular, 
Macintosh /PC users desiring cross-platform conversion should 
examine the CADMOVER translation program from Kandu Soft- 
ware of Arlington, Virginia. As shown in figure 10.5, CADMOVER 
can read and write ICES and DXF and convert these formats into a 
variety of Macintosh graphic formats, such as PICT and EPSF. 

PC/Windows Step 1 Macintosh Step 1 Macintosh Step 2 

Transports: AppleTalk (PhoneNET 

Assuming your Macintosh and PCs are physically networked, what 
transport protocol will you use to logically connect the machines? 
At a certain level the choices are simple. You can equip the PC with 
the AppleTalk protocols, equip the Mac with Novell-compatible 
protocols, or be a total non-conformist and put foreign protocols 
(such as DECnet or TCP/IP) on both machines. 

Chapter Ten Living in an Intel/ DOS World 

The Choices 

The choice of a suitable transport protocol is often complicated by 
the fact that not all services support ever)' transport. Therefore, tlie 
selection of a transport often begins at the top of the stack, at the 
Service layer. If the desired service is AFP file services, then you’re 
somewhat limited to choosing AppleTalk as a transport. In most 
cases, there aren’t too many choices when it comes to transports. 
All too often, a given service only supports a single transport 
protocol. The basic choices are simple: Either make the PC speak 
the Mac transport of AppleTalk, make the Mac speak a PC trans- 
port such as Novell IPX, or make both the Mac and PC speak a 
“foreign” protocol such as TCP/IP or DECnet. The only other 
options are to use a gateway or use an intermediate computer to 
act as an exchange agent. Let’s explore the options. 

AppleTalk on the PC 

If you have a network where Macs are predominant and there are 
just a few PCs, then consider turning those PCs into AppleTalk 
nodes. One way to do this is with Farallon’s PhoneNET PC. It 
equips a DOS or Windows PC with the AppleTalk protocol stack 
and also provides the equivalent of the Chooser (see figure 10.6), so 
that the user is able to select AppleTalk network services (such as 
AFP file services. System 7 File Sharing, and PAP print services). 
PhoneNET PC works either with a LocalTalk/PhoneNET card 
(offered by Apple, Dayna, COPS Inc., and Farallon), most common 
PC Ethernet cards, and IBM Token Ring 16/4 cards. Figure 10.7 
shows various NetPICT diagrams of a PC running PhoneNET PC 
over different cabling mediums. 

Part Three Multivendor Networks 

Figure 10.6 

pals die AppleTalk 

Figure 10.7 

suppans AppleTalk aver 
dilleieni kinds al cabling. 


Chooser C 

Nttwoffc servlets: Select a server: 

AppleTalk Zones: 
4th Floor 
Sth Floor 
6th Floor 
gavel and 

ARA DIalln 

Open Window 













\ / Formats 


I 1 AppleTalk 

> Cabling 

\ Cabling < 

In addition to the AFP and PAP services supported by PhoneNET 
PC, various application services are supported by the product as 
well. A listing of the currently supported PC application appears 

• Farallon Timbuktu (PhoneNET PC is included with all ver- 
sions of Timbuktu for Windows) 

Chapter Ten Living in an Intel/DOS World 

• Microsoft Mail 3.0 and 3.1 

• QuickMail from CE Software 

• Lotus cc:Mail 

• WordPerfect Office 

• Claris FileMaker Pro 2.0 

• Blyth Omnis 7 (Can access DAL services) 

• Microsoft FoxBase+ 

As shown in figure 10.8, putting PhoneNET PC on a PC doesn’t 
restrict it from running other protocols, as PhoneNET PC runs 
concurrently with NoveU NetWare IPX and TCP/IP. One advantage 
of turning your PCs into AppleTalk nodes is that, like the 
Macintosh, your PC wall self-configure its network address. Your 
PC will also be visible to AppleTalk network management and 
troubleshooting utilities such as Apple’s Inter»Poll. 

Rgure 10.8 



PSP ol Novel IPX and 




Elheinel and Men Ring. 

Part Three Multivendor Netwrorks 

In addition to the Farallon products, another company, 
Cooperative Printing Solutions Inc. (COPS Inc.), has a number of 
AppleTalk PC solutions. COPSTalk for DOS and COPSTalk for 
Windows puts the AppleTalk protocols on a DOS- or Windows- 
equipped PC. Other products include PServe, which provides 
unified print queuing for Macs and PCs, and the COPS EasyServer, 
which turns a PC into an AFP file server. 

Yet another PC AFP solution is MacLAN Connect Gold from 
Miramar Systems Inc. This product connects LocalTalk, Ethernet, 
or Token Ring users to file and print services. It also supports the 
recently announced Microsoft Windows for Workgroups. 

Novell Solutions 

Novell, the networking giant, offers two approaches to Macintosh 
PC connectivity. First, Novell NetWare servers can be configured as 
AFP file servers. As shown in figure 10.9, Macs access these services 
with the AppleTalk transport; PC users access the same server with 
Novell IPX protocols. Normally it’s not recommended, but it is 
possible for the two environments to share a common file space. 
Thus, it is possible to share files between the two environments. 

Rgure 10.9 

Novell's NetWare lor 
suooorllo PC/Wiodows 

Chapter Ten Living in an Intel/DOS World 

Dayna offers an alternative for the Novell environment, one that 
turns a Mac into a full-fledged NetWare client running the Novell 
IPX protocol. As shown in figure 10.10, with Dayna’s NetMounter, 
the AppleTalk protocol stack is replaced with a version of Novell 
IPX. A Chooser-level driver is used to select and log on to the 
server. With this approach, the Mac appears as a PC client, so you 
won’t have to purchase the NetWare for Macintosh module. 
NetMounter also includes a utility that will assign Macintosh 
creator and type codes to particular DOS file extensions. This 
makes it possible to copy a Microsoft Excel spreadsheet from a 
NetWare DOS server and have its Macintosh icon available for 
subsequent double-clicking. 

PC/WIndows PCAWIndows Macintosh 

Figure 10.10 

equips Macs Willi (lie IPX 
enables ihem 10 direclly 
access any NeiWaie 

in the past, Novell concentrated on the file service support for the 
Mac, but Novell has recently begun to develop another approach. 
MaclPX, shown in figure 10.1 1, involves placing Novell’s IPX 
protocol on the Macintosh. Intended for developers, MaclPX will 
provide an avenue for cross-platform peer-to-peer communica- 
tions between applications on the two platforms. MaclPX should 
help the Macintosh make inroads into environments where PCs 
and Novell networks prevail. 

Part Three Multivendor Networks 

Figure 10.11 

Novell's MacIPXKanspoit 
peei'iO'peer access. 

Another Novell Macintosh solution is DataClub, which was re- 
cently acquired by Novell from International Business Software 
Inc. DataClub is a distributed file service that transparently aggre- 
gates and manages disk space from the individual workstations. 
This virtual disk space is made available to the network users as 
mountable disk volumes. DataClub was originally developed for 
Macintosh networks, but Novell plans to add support for DOS, 
Windows, and UNIX. 

Banyan Vines 

Banyan Vines, a popular enterprise-wide networking system, offers 
client support for Macintosh workstations, allowing them to share 
resources with DOS, OS/2, and Windows workstations on the same 
network. Vines supports the AppleTalk filing protocol and the 
Printer Access Protocol from their Intel /PC-based Vines server. In 
addition, AppleTalk tunneling through Vines enables disjointed 
AppleTalk networks to be connected with each other via the Vines 

DECnet on the Mac and PC 

While the appeal of DECnet is somewhat limited to those sites with 
DEC VAX computers, another transport alternative is to use 

Chapter Ten Living in an Intel/DOS World 

DECnet. Wlien DEC got into the PC clone business, they quickly 
saw the potential of integrating PCs into their network environ- 
ment. To achieve this goal, DEC created DECnet DOS, which 
equips the PC with the DECnet protocol stack. They also developed 
a number of Service layer applications so that the PC user can 
engage in terminal emulation, file copying, and printing within a 
VAX computing environment. 

DECnet for the Macintosh is now offered as a component of 
PATHWORKS for Macintosh, the product that grew out of the 
Apple/DEC alliance. DECnet for the Mac performs a similar 
function to its DOS counterpart and enables a Mac to perform 
services such as file copjang. E-mail and terminal services in a 
DECnet environment. 

Because both the Mac and PC support the DECnet transport 
protocol and the file copy services (see figure 10.12), they can use 
this mechanism to move files between the two platforms, even 
when there’s no VAX involved. It should be noted, though, that the 
common services offered by tlie Mac and PC versions of DECnet 
are somewhat basic and are likely to be of interest only to those 
who already have VAX computers and DECnet neUvorks already in 

DEC VAX PC/Windows Macintosh 

Figure 10.12 

use Digital’s DECnel 
pioiocol, either will) a 
VAX or separately. 

Part Three Multivendor Networks 

Figure 10.13 

plailorms today, ipcluding 
the Mac and PC. Sun's 
Netwfltkfilinp System is 
a common tile service 
supported by TCP/IP. 

TCP/IP on the Mac and PC 

If you're still looking to put a “foreign” transport protocol on your 
Macs and PCs, then another choice is TCP/IP. Common in UNIX 
circles, TCP/IP stands for Transmission Control Protocol/Internet 
Protocol. It is widely used in universities, government installations, 
defense contractors, and many large corporate installations. 

MacTCP is an Apple product that equips the Macintosh with the 
TCP/IP protocol. MacTCP is similar to AppleTalk, in that it’s 
useless without application services. Most of the application 
services that work with MacTCP are provided by third parties. The 
popular services are NFS file service, SLIP, and TELNET terminal 
services, and X-Windows. These services sit atop the MacTCP 
transport layer. 

Using file access as an example in figure 10.13, a Macintosh 
equipped with MacTCP and NFS (available from either 
Wollongong and InterCon) can exchange files with a similarly- 
equipped PC. PC-NFS from Sun Microsystems is a popular imple- 
mentation of NFS for DOS. FTP Software’s product called PC/TCP 
Plus provides the PC with the TCP/IP transport protocol and NFS 
in one package. For more information on TCP/IP solutions, refer to 
the next chapter, which covers UNIX connectivity. 

Chapter Ten Living in an Intel/DOS World 

Cabling Options 

The choices available for cabling systems for Mac/ PC connectivity 
are as varied as the cabling choices available for the Macintosh. 
You can choose among LocalTalk, Ethernet, Token Ring, and even 
the popular PC cabling .system, ARCNET. 


The benefits of LocalTalk expressed earlier apply to PCs as they do 
for Macs. It’s cheap and it runs over conventional tvWsted-pair 
phone wire. If you’re introducing PCs into a largely LocalTalk 
network, you’ll be able to equip your PCs with the LocalTalk 
hardware. Vendors such as Dayna, Farallon, and COPS Inc. offer 
such cards. Versions for either the ISA or MicroChannel bus are 

It probably only makes sense to consider LocalTalk cabling for 
AppleTalk-only networks. If you’re planning a multiprotocol 
network, you’re better off with Ethernet or Token Ring cabling. You 
will also find that the LocalTalk cards for PCs (see figure 10.14) are 
nearly the same price as the PC Ethernet cards. 









Figure 10.14 


Part Three Multivendor Networks 

Figure 10.15 



Ethernet is probably the best choice for a PC/ Mac cabling system 
(see Figure 10.15). It’s relatively inexpensive, comes in a variety of 
physical cable types, and (most importantly) it supports a wide 
variety of networking transport protocols. If you’re planning to use 
multiple protocols, just be sure that all your anticipated protocol 
drivers support your chosen Ethernet cards. As mentioned before, 
PhoneNET PC from Farallon supports most Ethernet cards, such as 
the EtherLink series from 3Com and Novell’s NE1000/NE2000, but 
you may Find a card that is not supported. Just be safe; double- 
check with all vendors and make sure everything’s supported. 

Macintosh PC/Windows 

Token Ring 

Compared to Ethernet, there’s less variety in Token Ring cards. 
IBM is becoming very agressive in pricing and licensing their 
Token Ring componentry (see Figure 10.16). Prices have already 
started to drop. Most of the newer cards offer both 4MB and 16MB 
transmission rates and use tlie latest integrated circuitry. As with 
Ethernet, just make sure that the transports you’ve selected are 
supported. Token Ring-equipped PCs are likely to be popular in 
IBM mainframe and minicomputer environments where Token 
Ring is already in use. 

Chapter Ten Living in an Intel/DOS World 

Macintosh PC/Windows 

Figure 10.16 

Men fling on a PC 

Apple offers a NuBus Token Ring card. This can be used to connect 
a Macintosh to a Token Ring network directly, or it can be used by 
a Mac running the Apple Internet Router. When a Mac runs the 
Apple Internet router, it can be equipped with other networking 
connections such as LocalTalk and Ethernet. In this case, the 
router can be used to protide LocalTalk- and Ethernet-equipped 
Macs access to services on the Token Ring network. 


Shortly after the IBM PC was introduced, the ARCNET network 
system was designed as a low-cost LAN (see figure 10.17). ARCNET 
is still in widespread use today as a cabling medium for PC net- 
works, particularly NetWare. ARCNET supports two different kinds 
of cabling (coaxial and twisted-pair) and has a bandwidth of 2.5 
Mbps. This places ARCNET betw'een the bandwidths of LocalTalk 
and Ethernet. 

In 1991, ACTINET Systems began to offer a line of ARCNET cards 
for Macintosh computers. Their ARCTalk cards come in three 
models: one for NuBus-equipped Macs, one for the Macintosh LC, 
and one for the SE/30 and Ilsi. Included with the cards is ARCTalk 
software which provides AppleTalk Phase 2 support. Although the 
original ARCNET specs permit both star and bus topologies, the 
ARCTalk cards only support the star topology. 

Part Three Multivendor Networks 

Figure 10.17 



Macintosh PC/Windows 

With the coaxial version of ARCNET, each cable run can be a 
maximum of 2000 feet. The twisted-pair implementation can run 
400 feet (slightly longer than twisted-pair Ethernet). In bodi cases, 
an ARCNET hub, available from third-party vendors, is required. 

The cards are certified by Novell for use with NetWare for 
Macintosh and the cards and ARCTalk software are System 7- 
complient and wili run on the Apple Internet Router. Use of the 
Apple router is important because there are no options for con- 
necting LaserWriters or other LocalTalk devices to an ARCNET 


There are more networking services, formats, transports, and 
cabling options available to connect Macs and PCs than with any 
other platform combination. The key is to first determine the 
desired services. Then, examine which protocol best delivers that 
service. Finally, choose a cabling system that balances support for 
the chosen protocol or protocols with cost and future growth and 




® hile not as prevalent as the PC or the Mac, UNIX- 
based workstations and other UNIX computers 
are very common, particularly in the engineering 
and technical environments where Macintosh is 
also very' popular. This chapter explores the 
networking options for Macintosh and UNIX 

Services: FR NFS. AFR 
X-Windows, TELNF 

Most of the services in the Macintosh/UNIX world revolve around 
file access and terminal services. To a seasoned Macintosh user, 
the services offered in the UNIX-TCP/IP world may seem a bit 
basic. Many of these services are directed at sophisticated users 
and programmers. However, new TCP/IP-conversant Macintosh 
services aimed at a more general audience are being announced 
every week. 

Part Three Multivendor Networks 

Rather than starting off talking about bringing UNIX services to the 
Mac, we’ll begin by looking at the AppleTalk-based services 
available for the UNIX environment. 

Figure 11.1 

a Sun or HP UNIX 
workstation into 
an AfP Server. 

AFP/PAP Services on UNIX Computers 

To a Macintosh user, file service means AFP. There are several 
products that provide this service on UNIX computers. Xinet sells 
K-AShare, which implements 7VFP on a Sun or HP UNIX host (see 
figure 11.1). So, just like with any other AFP server, the Macintosh 
user accesses UNIX files through the Chooser. The mounted 
volumes provide access to the UNIX files as if they were local disk 
files on the Mac. (The Sun or HP running K-AShare could also be 
set up as an NFS server, so in a sense K-AShare can be thought of 
as an AFP/NFS gateway.) 

1 ^ 

Macintosh Client Sun Workstation 

A companion product from Xinet, K-Spool, provides PAP print 
spooling services for the Macintosh user. It also acts as a print 
server and PostScript agent for the UNIX user, forwarding print 
jobs to a networked LaserWriter. 

Diagrammed in figure 11.2, K-Spool’s PAP spooler appears to the 
Macintosh user just as any other LaserWriter. It does this with a 

Chapter Eleven UNIX Connecti\nt>' 

special program — a virtual LaserWriter. This means that the 
program accepts and responds to NBP Lookup Requests and 
Responses. After the NBP process is done and a Macintosh user 
selects the virtual LaserWriter, the program accepts the PAP 
commands that contain the PostScript printing instructions. This 
printing information is placed in a file that is queued until the 
designated printer is available. This technique avoids the annoying 
background delays seen when Print Monitor is used to spool the 
print file on your local Macintosh disk. 

@ 5 ? 

This program, or This program, or 

virtual LaserWriter, virtual Macintosh, 

appears to the Mac appears to the real 

user as a real LaserWriter as a 

LaserWriter. real, printing, Mac. 

Rgure 11.2 

Xinei's ( Spool turns a 
Sun or HP UNIX 
workstation Into a PAP 
print spooler. 

Pacer Software offers PacerShare, shown in figure 1 1.3, which 
offers a similar capability for VAX computers equipped with Sun, 
HP, and DEC Ultrix (DEC’S version of UNIX). PacerShare, like K- 
AShare, maps the AFP file structure onto the native UNIX file 
structure of tlie host. PacerPrint provides for LaserWriter printer 

InterCon’s InterPrint is another printer utility that provides 
Chooser-level access to UNIX printers on TCP/IP networks. This 
utility makes it as easy for a Mac to print to a UNIX PostScript 
printer as it is to print to a LaserWriter. 

Part Three Multivendor Networks 

Figure 1 1 .3 

piovides AFP file seivices 

Macintosh Client Sun, HP, VAX Ultrix 

Figure 11 .4 

Apple and Pacef provide 
DAI dalabase seivices on 
UNIX Gompuiers. All 
UNIX DAI seiveis use 
AppleTalk as a liansppft 

Data Access Language 

DAL services provide access to relational databases on UNIX 
systems. Apple sells a version of DAL for A/UX equipped Macs, and 
Pacer offers a DAL server for HP UNIX computers, DEC Ultrix, and 
Sun’s SPARCstation (see figure 1 1.4). These services use the 
AppieTalk transport on each of their respective platforms. 

Macintosh or PC Client UNIX Host 

Chapter Eleven UNIX Connectivity 

File Transfer Protocol (FTP) 

The File Transfer Protocol (FTP) is commonly used in UNIX and 
TCP/IP networks to move files between nodes. FTP provides 
directory services, so a user can get a listing of candidate files on a 
remote machine. It also provides support for a variety of formats 
(such as ASCII and binary) and insures security by requiring login 
IDs and passwords. However, some systems offer public access to 
files witliout IDs and passwords. This service is known as Anony- 
mous FTP, and many companies, universities, and organizations 
use it to post information that they wish to distribute freely. 

Most implementations of FTP are through terminal-based com- 
mand line interfaces; any of the TCP/IP compatible terminal 
services (such as VersaTerm-Pro and NCSA Telnet) can be used to 
engage in FTP transfers (see figure 1 1.5). Since the Macintosh has 
focused attention on the user interface, a number of FTP applica- 
tion services are starting to provide sophisticated interfaces. 
There’s even a freeware HyperCard stack called HyperFTP, written 
by a Cornell student, that supports the basic set of FTP operations. 

Macintosh UNIX Host 

Figure 11.5 

piovideFIP services to 

Part Three Multivendor Networks 

Hgure 11.6 

FIP 10 provide Macs ivi 

FTPShare, from Advanced Softvc'are Concepts, is a multi-session 
FTP server (up to 20 simultaneous sessions) that runs in the 
background of the Macintosh (see figure 1 1.6). In many ways, 
FTPShare can be compared to Apple's System 7 File Sharing. The 
FTPShare setup screens, shown in figure 11.7, resemble the screens 
used under System 7 File Sharing, so it should be easy for 
Macintosh users to adapt. FTPShare also includes a monitoring 
application drat monitors the connected users and gives an indica- 
tion of FTP activity. 

Figure 11.7 

FlPSliaie puts the look 
aud Feel oFMaciniosli File 
Sharing onto FIP 

0 Jeff Dlog 

18? Connected Users Q Folder 







I FTP Share Setup ! iluHu; r-rr ^ 

ggSgSH — I [ Disconnect ] [ Trace ) 

- Netwurk Identity 


O^mr Pusword : |— — 
IP M4r*iS 


FTP Shore 

[ ] [g 

[ Settings 

FTP Shtr* (< on. Clkk Stop to prtvtnt ottt«< 
U10T5 from Mowing ttitlr Cntrg FoMor. 

enonymout I 

wl.O fron Jeff on Moo, Jon 22, IW2, 4.53:4 


In. you don‘1 hooe Urite Prioileyu 
W, I. IS, 17 

d ok. 

ted succesful ly. 

nU,U,'Au, I, IS, 18 

Chapter Eleven UNIX Connectivity 

Network Filing System (NFS) 

Developed by Sun Microsystems, NFS provides additional capa- 
bilities not found in FTP. It can be used to transfer Files between 
computers, but it also provides a mechanism for distributed 
applications that are network-aware. There are several implemen- 
tations of NFS on the Macintosh; two of the more popular products 
are NFS/Share from InterCon and Pathway NFS from Wollongong. 
Both of these products, shown in figure 1 1 .8, work with Apple’s 
MacTCP and bring NFS services to the desktop of the Macintosh, 
thus retaining the ease-of-use of the Mac. 

Figure 11.8 

Macteli. Ihey boll) use 

Partner, from IPT, takes another approach to Macintosh/UNK 
connectivity. It works in both directions between a Macintosh and 
Sun SPARC systems. Macintosh users access SPARC files as AFP 
server volumes; SPARC users access the Macintosh files as if they 
were NFS volumes (see figure 11.9). IPT also provides PAP print 
spooling with a variety of UNIX print services and a mail gateway. 
The Partner application resides on the Sun SPARC machine and 
does all the necessary transport and service layer conversion; no 
special software is required on the Macintosh. 

Part Three Multivendor Networks 

Figure 11.9 

IPI's Fanner piovidesbi- 
tlireclional access of Mac 
and Sun SPARC tiles over 
lire network. Mac users 
an AFPserver, while Sun 
users see the Mac as just 
another NFS server. 




Sun SPARCstation 

Although NFS was developed by Sun, it is supported on many 
different computing platforms. Of course, it’s most common on 
UNIX computers, but can also be found on PCs (PC-NFS), DEC 
VAX and IBM mainframes and minicomputers. Any NFS-equipped 
Mac should be able to access these other NFS platforms as well. 


The X- Window standard, also called X or XI 1, evolved from initial 
work done at the Massachusetts Institute of Technology. It is a 
client/server windowing environment that is extensible and 
customizable. DEC’S implementation of X, known as DECwindows, 
is used as their standard windowing environment on their VAX/ 
VMS computers and UNIX-based workstations. Motif is the name 
of the X implementation by the Open Software Foundation (OSF). 
However, the concept and underlying messaging used by these 
different flavors of X is the same. The user interfaces are slightly 
different, with different styles of windows, buttons and controls. 

Chapter Eleven UNIX Connectivity 

X is popular in UNIX (and tlierefore TCP/IP) networks. However, 
it should be mentioned that X is not limited to computers run- 
ning the UNIX operadng system or the TCP/IP transport. The X- 
Window service can be run on many different kinds of computers 
and network transports. 

X works on a client/server model. The computer that displays the 
image is called the server and the computer that runs the applica- 
tion code is called the client. This is a little confusing because we're 
accustomed to calling the desktop device the client, but with X 
the terms client and server reflect how the underlying software 

Many companies make X- Window terminals, or servers. These 
stand-alone devices have just enough processing power to run the 
X server display software (see figure 11.10). These terminals 
connect to X client programs running on other computers. Most 
UNIX workstations can act as both X clients and servers. Some- 
times the client and server even run on the same machine, but the 
system is flexible enough to permit connections locally or re- 

Figure 11.10 

display senms.«ioik 
diems aieHieapplicaiion 
programs, viliicli use llie 
display servers to do 
X'Window diems and 
servers can be 
network, or logeiber 00 
the same computer. 

Part Three Multivendor Networks 

There are two X- Window servers for the Macintosh: MacX from 
Apple and eXodus from White Pine Software. Either one can be 
used to connect to X- Window client applications that run on UNIX 
computers (or any other platforms that support the X standard). 
These applications make it possible to display X- Window applica- 
tions side-by-side with Macintosh windows. 

Planet X, from InterCon, is an X- Window client for the Macintosh. 

It allows a user to view and operate a Macintosh remotely from 
any X- Window server. As shown in figure 11.11, this server could 
be a UNIX workstation or even another Mac running MacX. When 
a session is established, the user operating the X- Window server 
sees the Macintosh desktop in a separate window. Planet X sup- 
ports the cutting, copying, and pasting of graphics between the two 

Figure 11.11 

Plane! X is die opposite of 
an X-Window client, 
ntakinp it accessible liom 



For all its flexibility, X has yet to really take off. The number of X 
applications continues to grow, but at a slow pace. The bulk of X 
applications can be found in the scientific and technical world 
where UNIX is an established standard. X is also reasonably 

Chapter Eleven UNIX Connectivity 

popular in its DECwindows guise, where Digital continues to 
migrate its traditionally VT terminal-based applications over to X. 

Terminal Services 

The most basic of TCP/IP services is the Telnet terminal service. 
This is a simple protocol that allows a user to remotely connect to a 
server as if he were using a local terminal. There are several popu- 
lar terminal emulators that offer Telnet and work in concert with 
MacTCP (see figure 11.12). Two examples are NCSA Telnet and 
VersaTerm Pro. With these applications, you can log on to remote 
TCP/IP hosts over a dial-up connection, or over a network connec- 
tion such as Ethernet. 

Macintosh UNIX Host 

Figure 11.12 

lelnei is a popular UNIX 
lerminal service. Many 
Macinlosli terminal 
emulaiors support it 
using MacICP as the 

Other terminal services use the Macintosh Communications 
Toolbox (MCT) with MacTCP to provide other kinds of terminal 
services. Advanced Software Concepts has an entire family of 
terminal emulation products that work through MacTCP. asc5250 
is a MCT terminal emulation tool that allows you to communicate 
with IBM AS/400 minicomputers over a TCP/IP network. asc3270 
is used to enable Macs to communicate with IBM mainfi'ames, 
using MacTCP (see figure 1 1.13). This seems weird — ^TCP/IP has 
been associated with UNIX workstations for quite a while — but it’s 

Part Three Multivendor Networks 

becoming more commonplace as TCP/IP begins to displace IBM's 
non-routable SNA protocol. 

Figure 11.13 

NelPICI of an unlikely 
funning ASCs IBM 3270 
lermioalemulaioi using 

Macintosh IBM Host 


similar to the formats supported by the PC, UNIX computers are 
able to share ASCII text files and those application formats that are 
binary compatible. As an example, let’s imagine we have three 
computers — a Mac, a Sun workstation, and a PC networked with 
Ethernet. Autodesk makes a version of their AutoCAD CAD pro- 
gram for each of these computing platforms. Each computer has 
TCP/IP and NFS file ser\dces installed. Since AutoCAD uses identi- 
cal binary formats for all platforms, we’re able to freely move 
AutoCAD files among the different computers. No translation will 
be required. 

Taking this scenario further, imagine we were using Claris CAD on 
the Macintosh instead of AutoCAD for the Macintosh. Unfortu- 
nately, Claris CAD can’t directly read the binary format of an 

Chapter Eleven UNIX Connectivity 

AutoCAD file. In this case we’ll have to translate. We can generate 
an ASCII-based DXF file from the AutoCAD application on the Sun 
or the PC (see figure 11.14). We then use NFS file services to 
transfer the DXF file to the Macintosh, where we use the Claris 
Graphics Translator to convert the DXF format into the native 
Claris CAD document. 

Sun Workstation 




Macintosh Step 1 

Macintosh Step 2 

Ctaris Graphics 

Claris Graphics 




\ / Claris CAD Format 


I 1 Transport 

V Cabling 

/ S Cabling < 


Macintosh Step 3 

Claris CAD 

' Claris CAD Format 



Many UNIX workstations, particularly those firom NeXT, use 
PostScript as an imaging format. PostScript files from these ma- 
chines (including the EPSF variety) can be easily exchanged with 
the Macintosh (see figure 11.15). But, as mentioned before, be 
aware that EPSF files generated by non-Macintosh applications 
may not have the PICT preview resource. 

NeXT Workstation 

Macintosh Step 1 

Macintosh Step 2 

Macintosh Step 3 

Figure 11.14 

A DXF file generated Oil 
a Sun workstation is 
converted into a Claris 
CAD document Willi tlie 
Claris Giaplticslranslaior. 

Figure 11.15 

A PostScript lile (without 
the Pin preview! is 
generated by a NeXI 
application, moved over 
translated into a 
PostScript hie with a PICT 
preview, and then placed 
into a PageMaker 

Part Three Multivendor Networks 

Transports: AppleTalk, TCP/IP 

Mention UNIX networking to most computerphiles and a discus- 
sion of TCP/IP will undoubtedly ensue. TCP/IP is an important 
part of Macintosh/UNIX networking. MacTCP, from Apple, puts 
the TCP/IP protocol stack onto the Macintosh, giving the 
Macintosh peer-to-peer capabilities with other IP nodes. The other 
option is to equip the UNIX machine with AppleTalk protocols. 
Computers so equipped can serve as AFP file servers, PAP print 
spoolers and DAL database servers. 

AppleTalk for UNIX 

Versions of AppleTalk for UNIX have been implemented by Xinet 
and Pacer (see figure 11.16). These products dovetail with each 
vendor’s respective services (listed previously). Xinet’s AppleTalk 
protocol suite is called K-Talk and is the underlying protocol for 
their K-AShare AFP server and their K-Spool PAP spooler. Pacer’s 
AppleTalk implementation is used for their PAP and DAL imple- 
mentations. Both implementations support AppleTalk Phase 2 and 
must be configured in accordance with the AppleTalk Phase 2 
network numbering rules and zone naming conventions. 

Hgure 11.16 

Ilie AFP file slianniL PAP 
piiQi spooling, and DAI 
by Xinet and Pacer are all 
delivered via Applelalk 

TCP/IP on the Macintosh 

The flip side of AppleTalk on UNIX is TCP/IP on the Macintosh. 
Apple’s MacTCP is widely supported by many third-party vendors 

Chapter Eleven UNIX Connectivity 

listed in this chapter — it’s the engine that is used by these vendors 
to create their applications. Figure 11.17 is a diagram of MacTCP 
transport protocol. 

Terminal, File, 
Print, Mail Svcs 





Figure 11.17 

MacKP is Apple's 

If you’re familiar with TCP/IP networks, configuring MacTCP is a 
snap. If you’re a Mac person and a TCP novice, be prepared for a 
different world. TCP/IP nodes can obtain their addresses manually 
or by a dedicated server. There is a mechanism for dynamically 
assigning addresses, but it’s somewhat limited (unlike AppleTalk). 

TCP/IP addressing, also referred to as IP addressing, uses 32-bit 
addresses. Unlike AppleTalk addresses, IP addresses can alter the 
numbers assigned to the network and host identifiers. There are 
five classes of IP addresses, Class A through E, of which classes A 
through C are commonly used. 

The fundamental difference between the classes is whether you 
create an address range that provides a small number of networks, 
each with many nodes; or a range that provides many networks, 
each with a limited number of nodes. Class A addresses use 7-bit 
network numbers and 24-bit host numbers. This adds up to 31 bits. 
(The first bit of a Class A address (0) is reserved and is not used as 
part of the address.) This provides 128 possible networks, each 
containing more than 16 million hosts. Class A networks are rare 
and are used for very large IP networks. 

Part Three Multivendor Networks 

Class B addresses split the 32 bits differently, by using 14-bit 
network numbers and 16-bit host numbers. (Here, the first two bits 
(10) are reserved.) Class B networks are common, since they strike 
a balance between the number of networks and the number of 

Class C addresses use 21-bit network numbers and 8-bit host 
numbers. The first three bits (110) are reserved. Class C addresses 
are similar to AppleTalk networks, in the sense that both number- 
ing schemes are based on a large number of networks with a 
limited number of nodes per network. 

The 32-bit IP address is usually written in a four-part decimal 
notation known as a dotted quad; an example is 1 31 . 43 . 3 . 1 8. 

Each part is eight bits (also called one byte or octet) long. With a 
Class A address, the first octet (minus the one reserved bit) repre- 
sents the network ID; the remaining three octets are the host ID. 

Class B addresses use the first two octets for the network ID (minus 
the first tv\'o bits). The remaining two octets are used for the host 

Class C addresses use the first three octets for the network number 
(less the first three bits). The remaining octet is used for the host 

.<\n exact analogy to AppleTalk addressing is difficult because IP 
addresses do not specify a particular computer. Since IP addresses 
contain network numbers and host numbers, they cannot repre- 
sent single computers that may have multiple connections to 
different networks. Therefore, an IP router or gateway will have an 
IP address for each network connection — not each computer. 

The name TCP/IP comes from the functions of different parts of 
the protocol stack. The Transmission Control Profoco/ performs the 
same tasks as the AppleTalk protocols at the Session and Transport 

Chapter Eleven UNIX Connectivity 

layers of the OSl Reference Model (see figure 11 . 18 ). TCP ensures 
the reliable, sequenced delivery of datagrams. The IP part of TCP 
stands for the Internet Protocol. This corresponds to the Network 
layer of the OSl model — the layer where AppleTalk DDP protocol 
resides. The function of this layer is the same in both cases; both IP 
and DDP are responsible for addressing the source and destination 
of the message. 

NetPICT OSl Reference Model TCP/IP 




Format > 


PostScript, FTP, 



Transmission Control Protocol 


Transmission Control Protocol 


Intarnst Protocol 

^ Cabling 

Data Link 

Data Link 



Figure 11.18 

ICP/IP gels ils name limn 
Defeience Model. 

AppleTalk DDP datagrams are addressed with network, node, and 
socket numbers of the source and destination: for example: 

DDP Datagram 

From: 12.22.128 

To: 14.43.129 

IP Datagrams are addressed with the network and host numbers of 
the source and destination; 

IP Datagram 



Part Three Multivendor Networks 

Cabling: Ethernet, LocalTalk, 

Token Ring 

By far, the majority of the UNIX workstations and computers rely 
on Ethernet as a cabling medium. There are the exceptions, such 
as an IBM AS/400 speaking TCP/IP over a Token Ring network. For 
the most part, though, Macs connecting to UNIX computers will do 
so over Ethernet. 

MOTE: It’s important to remember that the installation of MacTCP won’t 
preclude the use of AppleTalk protocols over the same network connection. 
With one Ethernet card, you’ll be able to run the AppleTalk and TCP/IP 
protocols concurrently. 

Figure 11.19 







If you decide to choose an AppleTalk-based service, you have the 
choice of LocalTalk, Ethernet, or Token Ring as the cabling me- 
dium. If you choose LocalTalk, remember that you’ll need a router 
that passes AppleTalk from LocalTalk to Ethernet (see figure 11.19). 
If you choose TCP/IP on the Mac, you’ll be able to use LocalTalk, 
Ethernet, or Token Ring, but if the UNIX computer doesn’t have 
the same cabling interface you’ll need the appropriate IP or 
multiprotocol router to make the connection (see figure 1 1.20). 

Chapter Eleven UNIX Connectivity 

Figure 1 1 .20 

locallalk Macs using 

TCP/IP 10 communicaie 

will) UNIX coinnuieis on 






The Macintosh can connect to UNIX computers at all levels. UNIX 
computers can speak the AppleTalk protocol, Macs can speak the 
TCP/IP protocol, and most UNIX computers and workstations 
utilize Ethernet cabling, so the integration process is often as 
simple as installing the right software. 


efore the famous Apple- IBM Alliance, there was 
tlie Apple-Digital Alliance. The collaboration 
between these two companies resulted in an 
architecture that combines the best of both 
worlds. Even though both the VAX and the 
F Macintosh have often been criticized for their so- 
called “closed architecture," the PATHWORKS for 
Macintosh environment illustrates that an open architecture is 
more than a common networking protocol or operating system. 

Senrices: PATHWORKS 
fat Macintosh 

The services offered by DEC’s PATHWORKS for Macintosh are a 
combination of products developed by Apple, Digital, and third- 
party vendors. They address the basic requirements of terminal 
emulation, X-Window (DECwindows) emulation, AFP File services, 
PAP print services, DEC print services, DAL database services, and 

Part Three Multivendor Networks 

Figure 12.1 

Macleiminal provides 
users connected 10 DEC 


Traditionally, VAX access has been accomplished with terminals. 
The ubiquitous VTIOO terminal standard (and subsequent versions 
that are found in nearly all Macintosh terminal emulators) is based 
on DEC products. MacTerminai is an Apple terminal emulator that 
comes bundled with PATHWORKS for Macintosh. It provides 
VT102, VT320, and TTY (an older, basic terminal standard) emula- 
tion (see figure 12.1). Compared to other third-party emulators, 
MacTerminai doesn’t offer graphics capabilities, color, macros, or 
redefinable keys. It provides basic emulation services. It, like most 
other Macintosh terminal emulators, uses the Macintosh Com- 
munications Toolbox (MCT). When purchased separately, 
MacTerminai provides the basic MCT communication tools of 
Serial and Modem. With PATHWORKS for Macintosh, additional 
MCT tools are included that permit terminal emulation over LAT 
and DECnet connections. 


Macintosh DEC VAX 


DECwindows is DEC’S implementation of the X- Window standard. 
Macs equipped with MacX appear as DECwindows terminals (see 

Chapter Twelve DEC VAX Connectivity 

figure 12.2). MacX fully supports the DECwindow character sets. If 
you’re considering using MacX, plan on picking up a three-button 
ADB mouse, available from many third-part}' suppliers (the X- 
Window system was designed for three-button mice), a minimum 
of 8 M of RAM, and an Ethernet connection. MacX uses memory 
and network bandwidth in large quantities. 

Figure 12.2 

MacX provides laiiMul 
DECwindows emulation 
example, MacX is using 

VAXshare File and Print Services 

VAXshare is the name given to AFP file services and PAP print 
services that run on a VAX. The VAXshare file server (see figure 
12.3) can be set up to support multiple servers, each potentially 
with multiple volumes. These volumes can be set up to reference 
any VMS directory. These directories can contain VMS files (either 
ASCII or binary) or foreign files, such as those from a PC. This way, 
Mac users can edit VMS text files with Mac text editors or word 
processors. They can also exchange binary application files with 
corresponding VAX or PC applications. 

Part Three Multivendor Netv^rorks 

Figure 12.3 

server lurns a VAX into 
an AfPiile server. 
Matiniosli users are able 
10 access VAX direciories 



Figure 12.4 

print services turns a VAX 
into a PAP print spooler. 
Maciniosh users are able 
to send print jobs to ibe 
VAX. Tbe VAX queues Ibe 
job and sends inn the 

The print services enable Mac users to spool LaserWriter print jobs 
to the VAX and to print to DEC PostScript printers: they also enable 
users of interactive VAX VT terminals to print to Apple LaserWriters 
through a standard VMS print queue. These are diagrammed in 
figures 12.4, 12.5, 12.6, and 12.7. 

This program, or 
virtual LaserWriter, 
appears to the Mac 
user as a real 

This program, or 
virtual Macintosh, 
appears to the real 
LaserWriter as a 
real, printing, Mac. 

Chapter Twelve DEC VAX Connectivity 

This program, or 
virtual LaserWriter, 
appears to the Mac 
user as a real 

The PostScript file 
is sent to a VMS 
print queue and 
then to a VMS 
DECnet print driver. 

Figure 12.5 

Maciniosh users aie also 
PosiScrim primers. Iliese 
primers are eillter 
Elliernet or serially 
letotioal server. 


Figure 12.6 

PosiScripi Primer. 

DEC Ttrmlnel ServM 

Terminal Server 

Termiful Server 





Async j [ 


RS-232 /S 


Figure 12.7 

VMS users (Ilrai is, 
rerorinal users) cao prim 
illliey were DEC prioiers. 



Part Three Multivendor Networks 

There are other similar AFP/PAP servers for VMS. Alisa Systems 
offers AlisaShare (Alisa licensed portions of AlisaShare to Digital, 
which eventually became VAXshare). Pacer Software has Pacer- 
Share, which, like VAXshare and AlisaShare, provides AFP file 
service and PAP print services. 

With all these AFP and PAP services, the only supported transport 
is AppleTalk for VMS. There is no support for the DECnet, LAT, or 
TCP/IP transports. 


Apple’s Data Access Language is a standard that provides a uni- 
form relational database language. Apple offers DAL servers for 
different platforms. Included with PATHWORKS for Macintosh is 
Apple’s DAL server for VMS (see figure 12.8). When purchased 
from DEC, it includes support for connections to Digital’s rela- 
tional database, Rdb. If purchased directly from Apple, it also 
supports Ingres, Oracle, Sybase, and Informix databases. (The 
support for these additional databases can be purchased directly 
from Apple.) Included are programming interfaces needed to write 
Macintosh C or Pascal programs that will support the DAL service 
and DAL-equipped HyperCard applications. The DAL VMS server 
works with the AppleTalk for VMS transport and the normal serial 
transport provided by VMS. 


PATHWORKS for Macintosh includes two mail Interfaces. Mail for 
Macintosh is a simple text-based mail application that uses a 
DECnet connection, or an AppleTalk/DECnet gateway connection, 
to VMS mail (see figure 12.9). AU-In-1 Mail for Macintosh is a more 
ambitious application. It is an X.400-compliant client/server mail 
application that supports binary enclosures, return receipts, 
priorities, and other high-end mail features. (The adherence to the 
X.400 messaging standard will make it easier to interface with 

Chapter Twelve DEC VAX Connectivity 

other foreign mail systems that also support the X.400 standard.) 
DEC also offers companion All-In- 1 clients for DECwindows and 
Windows-equipped PCs. All applications share a similar user- 


Macintosh or PC Client VAX/VMS Host 

Figure 12.8 

Apple's DAI stiver ioi 




users can access DEC'S 






□ □ 

Figure 12.9 

Digital Pliers two mail 
solutions with 

VAX siile, as a transport. 
Macs must either use the 
DECnet transport or gu 
through an Applelalk/ 
DECnet gateway. 


Similar to the formats supported by the PC and UNIX computers, 
the Mac and VAX are able to share ASCII text files and those 
application formats that are binary-compatible. 

Part Three Multivendor Networks 


The old standby, ASCII text, is an important common denominator 
between the Mac and VAX. With VAXshare, Mac users can freely 
move ASCII files back and forth. These ASCII files could be VAX 
command procedures (DCL), VMS source code, PostScript files, or 
IGES files from a VAX-based CAD/CAM system. VAXshare auto- 
matically maps Macintosh creator and type codes to VMS files 
based on their filename extensions. As an example, you might want 
all your VMS text files that have a .TXT filename extension to be 
automatically identified as Microsoft Word text files. This can be 
done by editing a configuration file that maps extensions to Mac 
creator and type codes: 







In the above example, the .TXT extension is mapped to the cre- 
ator code of Microsoft Word (MSWD). This code is assigned to 
Microsoft and identifies all Microsoft Word files. The Type indi- 
cates the specific kind of Microsoft Word file, in this case, TEXT. By 
making this assignment on the VAX, any file with the .TXT filename 
extension will be given these creator and file types (see figure 
12.10). These are used to assign the proper Microsoft Word icon to 
the file; they also tell the Finder to open the file with Microsoft 
Word when you double-click the file’s icon. 


Just as in the case with the PC and UNIX environments, more and 
more applications are using the same binary format for their 
document formats. These files can be seamlessly moved back and 
forth between the two platforms with no conversion required. 
Wlien conversion is required, there are several translation utilities 
available on the VAX. Digital has an interchange standard known 

Chapter Twelue DEC VAX Connectivity 

as DDIF (see figure 12.1 1). DDIF supports a number of standard 
Mac formats, such as MacPaint, PICT, Microsoft Word, and 
MacWrite. Once these formats are converted (on the VAX) to the 
DDIF format, they can be incorporated into DEC applications such 
as DECwrite. 




Figure 12.10 

ASCII text files can lie 




AFP Client 
Microsoft Word 

Microsoft Word 



DEC VAX (Step 1} 

AFP File Server 
DDIF Converter 

Microsoft Word 

' AppleTalk for VMS ' 


DEC VAX (Step 2) 
DDIF Converter 


AppleTalk for VMS 


DEC VAX (Step 3) 

DECwrite and 
other DDIF apps 


' AppleTalk for VMS ^ 


Figure 12.11 

DECIias a common 
intercliangefoimai called 
DDIF; OIC also offers 
(noi included wild 
conversion lonis for 
MacWriie, PICI, MacPaini 
and Microsoft Word. 

Another approach to conversion is to use explicit conversion 
utilities to convert one format to another. A good example of this 
approach can be found in the Keypak line of translators from 
Keyword Office Technologies (see figure 12.12). Keypak can be 
used to convert a VAX word processing document format such as 
WPS+ to a common Mac format such as Microsoft Word. 

Part Three Multivendor Networks 

Figure 12.12 






AFP Client 
Microsoft Word 

Microsoft Word 



DEC VAX (Step 1) 

AFP File Server 

Microsoft Word 

' AppleTalk for VMS ^ 


DEC VAX (Step 2) 

WPS+ Format 

AppleTalk for VMS^ 


DEC VAX (Step 3) 


Word Processor 

WPS+ Format 

'AppleTalk for VMS^ 


Transports: AppleTalk for VMS, 
DECnet, LAT 

In the Macintosh/VAX world, the transports of each respective 
platform are equally shared. The VAX speaks the AppleTalk proto- 
col and the Mac speaks DECnet and LAT. As we’ll discover, the 
choice of a transport for the most part is dependent on the desired 

AppleTalk for VMS 

VAXes are able to speak the AppleTalk protocol because they’re 
equipped with the AppleTalk for VMS (see figure 12.13). VAXes 
equipped with AppleTalk for VMS appear on the network as 
AppleTalk nodes. The services, VAXshare and DAL, appear as 
AppleTalk sockets within the node. AppleTalk for VMS supports 
AppleTalk routing, so VAXes with multiple Ethernet controllers can 
be set up as AppleTalk Ethernet-to-Ethernet routers. 

Chapter Twelve DEC VAX Connectivity 

AFP, PAP and 
DAL Services 


For VMS 


Figure 12.13 

Appletalk foi VMS equips 
a VAX wiitiilie Appletalk 
protocols. Appletalk is 


The most common VAX/VMS transport protocol is DECnet. VAX/ 
VMS systems usually come with DECnet, but Macs do not. So part 
of the PATHWORKS for Macintosh solution is to install DECnet on 
the Macintosh (see figure 12.14). DECnet on the Macintosh re- 
quires a configuration process that includes the assignment of a 
DECnet area and node number (similar to an AppleTalk network 
and node number) and the generation of a list of other DECnet 
nodes where communication is desired. This explicit address 
assignment and node listing is contrary to the AppleTalk philoso- 
phy of dynamic addressing and name binding using NBP. 

Figure 12.14 

poile. A Mac so equipped 
backed up by a VAX no 

Despite the extra administrative work, there are reasons for install- 
ing DECnet on your Mac. Once so equipped, the Macintosh hard 
disk can be automatically backed up through DECnet copy com- 
mands. The DECnet transport can also be used by MacX, the two 

Part Three Multivendor Networks 

mail applications, and terminal emulation. As we’ll see in the next 
section, LAT cannot be routed and therefore will not provide wide- 
area terminal services. An alternative is the CreflM protocol. Part 
of DECnet, CTERM can be used as a routable terminal protocol. 
PATHVVORKS for Macintosh includes a CTERM Communications 
Tool (see figure 12.15) that can be used with MacTerminal, or any 
other Macintosh Communication Toolbox (MCT)-compatible 
terminal emulator. 

Figure 12.15 

provide a roulable 
letminal access in lire 


If your Macs are on the same Ethernet as the VAX, you’ll be able to 
use the LAT MCT tool to directly connect to the VAX. Conventional 
VT terminals, or Macs running terminal emulators over serial lines, 
aren’t capable of speaking LAT over Ethernet; instead, they speak 
the As>mc protocol over RS-232. A device called a terminal server, 
or DECserver, is used to make the connecdon between multiple 
terminals and any LAT-speaking VAX (see figure 12.16). By speak- 
ing LAT direcdy, as shown in figure 12.17, the Macintosh can 
connect direcdy and avoid the intermediate service of the terminal 

As mentioned before, LAT cannot be routed. It was designed for 
use on a LAN. LAT is a time-critical protocol, so care must be taken 
when LAT is used on bridged Ethernet. Even though a bridged 
Ethernet logically appears as a single Ethernet LAN, if the bridge 
connection introduces a significant delay, LAT may have problems 

Chapter Twelve DEC VAX Connectivity 

maintaining connections. In these cases, and when a routed 
network exists, the DECnet CTERM protocol mentioned before 
might be a better choice. 

Figure 12.16 

tenninal users relied on 
terminal servers 10 
connect serial terminals 
tn networked VAXes. 



Figure 12.17 

Macs on [tliernet that are 
equipped with the lAI 
tool bypass the terminal 
server and can access 
any lAT host |i.e.D(C 
VAX) on Ihe Ethernet lAK. 

AppleTalk/DECnet Gateway 

The AppleTalk/DECnet Gateway converts AppleTalk protocols 
into the corresponding DECnet protocols. A prime example of 
its use is with the DECnet-based PATHWORKS mail services 

Part Three Multivendor Networks 

Figure 12.18 

Gateway conveits 
AppleTalk proipcols into 
versa. At the ntomepi. 
it's main use is to let 
Macs access DECnel 
mail services witliouttlie 
ailminisirative overhead 
oiputtinp DECnel on 

(see figure 12.18). Because the VAX mail services are only acces- 
sible through DECnet, there are two ways a client Mac can con- 
nect: by putting DECnet on the Mac, and by using AppleTalk and 
going through the gateway. The gateway is selected through the 
AppleTalk/DECnet MCT tool from within the mail applications. 

AppleTalk/LAT Gateway 

The LAT protocol is restricted to Ethernet. How do LocalTalk Macs 
connect to terminal services? They can’t use LAT directly because 
it only works over a direct Ethernet connection. You could use the 
DECnet CTERM tool and a LocalTalk/ Ethernet router that routes 
DECnet, but you would have to put DECnet on your Mac and put 
up with the extra administrative overhead associated with DECnet. 
Fortunately, Apple and DEC came up with another alternative. 

The AppleTalk/LAT Gateway runs on a Mac that has LocalTalk 
and Ethernet connections (see figure 12.19). This effectively turns 
the Macintosh into a terminal server. The Macs on the LocalTalk 
side speak the AppleTalk protocol to the server; the server speaks 

Chapter Twelve DEC VAX Connectivity 

LAT to the VAX hosts on the Ethernet. Figure 12.20 shows various 
screens from the AppleTalk/LAT Gateway as well as the client 
settings of the AppleTalk/LAT Tool. 

The gateway is also useful for dial-up users who attach to the 
network with Apple's Remote Access software (ARA). As shown in 
figure 12.21, incoming ARA Macs speak AppleTalk. By going 
through an AppleTalk/LAT Gateway, a remote Mac user can 
engage in terminal emulation with the VAX, whUe retaining the 
capability to access AppleShare file servers and LaserWriter print 

Figure 12.19 

locallalk can access lAl 
leiminal services by 
Applelalk/lAl Gateway. 

Figure 12.20 

Gateway runs on a 
llllacintosh. Client Macs 
tool to access the 

Part Three Multivendor Networks 

Figure 12.21 

Galeway lets reiooie 
lime as Ollier 
Applelalk services. 

Cabling: LocalTalk and Ethernet 

The cabling choices for Macs in a VAX environment are primarily 
LocalTalk and Ethernet. Since it’s unlikely that VAXes will ever 
sport LocalTalk interfaces, the options are few: either put Ethernet 
on the Macs, or use some sort of LocalTalk/ Ethernet router. 


The cabling choices for PATHWORKS-equipped Macs are primarily 
LocalTalk and Ethernet. Because VAX computers don’t come with 
LocalTalk interfaces, some sort of LocalTalk/Ethernet router will 
be needed (see figure 12.22). The choice of a LocalTalk router 
depends on the desired services and protocols. If you plan to use 
DECnet, then a multiprotocol router capable of routing DECnet 
will be needed. If you plan to stick to the AppleTalk services, or 
plan to access the DECnet services (such as E-mail) through 
AppleTalk, then any generic AppleTalk LocalTalk/Ethernet router 
will do. 

Because most VAX sites have extensive twisted-pair wiring that’s 
used for terminal access, you might want to adapt this wiring to the 
phone- type LocalTalk connectors, such as Farallon’s PhoneNET. 

Chapter Twelve DEC VAX Connectivity 

Figure 12.22 

Macs with ilieOECnei 
iianspoft cat) still use 
is used. 


If your VAX network is Ethernet-based, which most are, then it’s 
likely that Ethernet-equipped Macs can be easily incorporated into 
your network. Digital offers a number of desktop Ethernet prod- 
ucts that can be used to connect PCs and Macs to the network. 
Digital recently announced a line of multiprotocol routers with 
support for the AppleTalk protocol. 

Serial RS-232/Diai-Up 

With MacTerminal, Macs can take the place of VT terminals on 
Ethernet or serial connections. These connections can be made 
directly to the VAX or through a terminal server. 

With serial connections, remote MacTerminal users can use 
modems and log onto the VAX, but this connection only provides 
terminal services. Often, remote Mac/VAX users need to access 
AppleTalk services in addition to terminal services. Apple and DEC 
don’t offer a solution, but Computer Methods Corporation has a 
product called AsyncServeR that essentially turns the VAX into an 
AppleTalk Remote Access ser\'er (see figure 12.23). Most VAX sites 
have banks of dial-up modems already in place; AsyncServeR takes 
advantage of these resources by enabling any Mac with the Remote 
Access software to dial in and access not only the AppleTalk 
services on the VAX, but also the services on the entire AppleTalk 

Part Three Multivendor Networks 

Figure 12.23 

Compiiiei Meihods. uses 
basedApplelalk Remote 
Access Seiver. 


y y— ^ — T 

Remote Macintosh 


LaserWriters and other 


Digital redefined computing in the 1970s; Apple did the same in 
tire l980s. In the 1990s, Apple and Digital both realize that the 
network is the common battleground for computing services. 
Digital, with its PATHWORKS for Macintosh product, has recog- 
nized the importance of the Macintosh. They have successfully 
integrated two supposedly closed architectures by providing 
terminal emulation, DECwindows (X-Window), AFP file and print 
services, database access, and two E-mail packages. 

IBM Connectivity 

till a large part of the corporate world, IBM’s 
mainframe and minicomputers are an important 
part of Apple’s network strategy. Once again, the 
Macintosh proves its worth as the “universal 
client,” easily connecting to the Big Blue world. 

Services: Mainframe and AS/400 

The IBM computing world (PCs excluded) is comprised of the large 
mainframe computers, such as the System 370 (S/370) and 390 
(S/390), small mainframes such as the ES/9000, and midrange 
systems like the AS/400. These systems aren’t exactly showcases 
of client/server technologies, as over the years the typical user- 
interface has been through terminal emulation. 

Terminal Services 

In the past, IBM mainframe access was typically made with the 
3270 family of terminals. Today, 3270 terminal emulation is 
commonplace on PCs and Macs (see figure 13.1). As with VT-type 
terminals, the sales of so-called “dumb” terminals are declining 
while the use of intelligent workstations is increasing. 

Part Three Multivendor Networks 

Figure 13.1 

coaxial connectioa IQ 

There are a number of 3270 terminal emulators available for the 
Macintosh. These emulators enable suitably-equipped Macs to 
access IBM mainframes. Most Mac emulators add value by adding 
features such as programmable “hot keys” or macro capabilities. 
Some emulators support keyboard remapping, where 3270 keys 
can be reassigned to the Macintosh keyboard. A common feature 
in 3270 emulators is the ability to perform IND$FILE file transfers 
from within the terminal session. Four popular 3270 emulators 
include Apple’s SNA»ps 3270, DCA's IRMA Workstation for Macin- 
tosh, ASC’s asc3270, and Avatar’s MacMainFrame. 

The 3270 standard is used by the large mainframes, while the 
midrange AS/400 uses the 5250 standard. 5250 emulation on the 
Mac is not yet as common as emulation of the older 3270. 5250 
emulators offer similar features as their 3270 counterparts and are 
offered by Andrew and ASC (see figure 13.2). Conventional termi- 
nal screens can be a bit daunting: to make things a bit easier, IBM 
terminal sessions can also be front-ended with user-ft’iendly 
interfaces that interact with the terminal data stream. 

Chapter Thirteen IBM Connectivity 

Macintosh IBM AS/400 

One of the most popular IBM mainframe applications is the PROFS 
mail environment. Normally, PROFS is accessed with a conven- 
tional terminal. However, there are several Mac terminal front 
ends that put a Mac interface onto PROFS (see figure 13.3). Two of 
these — MitemVision from Mitem and Executive Workstation from 
MediaWorks — are HyperCard-based. 

IBM Host 

Macintosh i 

(Cluster Controller) 




Mail Environment 




I [ SNA 


(Apple or third party) 

^ y Coax i 

Figure 13.2 

the host 

Figure 13.3 

PROFS access wilii 
from end. 

Part Three Multivendor Networks 

HyperCard can also be used to create custom terminal front ends. 
With products from Avatar, DCA, and Mitem, developers are able 
to create HyperCard applications using custom XCMDs and XFCNs 
that provide controlled access to the terminal data stream. Other 
front-ending environments use their own development environ- 
ments to make quick work of customized interfaces. These include 
Blacksmith from CEL, SimMac from Simware, and Both from 


Apple's DAL server for IBM provides DAL clients access to IBM 
DB2 and SQL/DS relational databases (see figure 13.4). Connec- 
tions to the DAL server can be made through a 3270 terminal 
connection, serial links, or with IBM’s network transport, SNA. 

As mentioned elsewhere in this book, DAL clients can be either 
Mac- or PC-based. They can be developed from scratch with 
conventional Mac programming environments or authored with 
HyperCard or Serius. DAL clients can also be used out of the box, 
since many Macintosh applications, such as spreadsheets and 
databases, offer built-in DAL support. 

Figure 13.4 

Apple's OAL Server for 
IBM liDSis provides 
clienis access 10 IBM 
relational daiabases 

Chapter Thirteen IBM Connectivity 

Formats: Mainframe and AS/400 

Although the Mac and IBM hosts speak different fundamental 
languages (ASCII versus EBCDIC) they still enjoy a high degree of 
interoperability. This is due to the use of standardized terminal 
formats (as in the case of 3270 terminal emulations) and format 
translators that provide ASCII to EBCDIC translations in real time. 


The IBM PC was their first computer to use ASCII. Before that, IBM 
mainframes used EBCDIC (Extended Binary Coded Decimal 
Interchange Code) which, in a technique similar to that of the 
ASCII code, uses an eight-bit code to represent characters. Conver- 
sions between EBCDIC and ASCII are typically handled by protocol 
converters that can either be hardware- based (see figure 13.5) or 

Figure 13.5 

lOM'sIBCDIC codes aie 
ASCII codes Willi ilie IBM 
7171 Piolocolcomieiier. 

Transports: Mainframe and AS/400 

Traditionally, the IBM transports have been unique to the IBM 
world, focusing on terminal-based applications. During the past 
several years, as IBM has pursued a peer-to-peer environment, 
tlie rest of the industry' has started to adopt IBM’s new standards. 
Today, the Macintosh supports all of the major IBM transport 

Part Three Multivendor Networks 

Figure 13.6 

Apple's SNA*psGaiewBV 

protocols, in addition to the IBM-supported industry standards 
such as TCP/IP. 


SNA stands for System Network Architecture and is IBM’s primary 
transport protocol. When a Macintosh runs an IBM terminal 
emulator, it’s relying on a portion of the SNA protocols. SNA is only 
one part of IBM’s networking strategy, known as System Applica- 
tion Architecture (SAA). SAA defines an environment that supports 
peer-to-peer applicadon services, which is a departure from the 
traditional host-based IBM world. 

Part of IBM’s SAA/SNA plans include APPC. Standing for Advanced 
Prograrn-to-Program Communications, APPC uses a protocol 
called LU 6.2 (the LU stands for Logical Unit). Similar enhance- 
ments to SNA networking are part of IBM’s Advanced Peer-to-Peer 
Networking (APPN) protocol. APPC and APPN are still relatively 
new, but compatible applications are starting to appear. Apple’s 
SNA'ps gateway is one example (see figure 13.6). It supports both 
the APPC and APPN protocols and will undoubtedly be used as a 
development platform for future peer-to-peer applications that 
work in both the Macintosh and IBM environments. 

Chapter Thirteen IBM Connectivity 


Many companies, in an attempt to support multi-platform com- 
munications, are using the TCP/IP protocol in place of IBM’s SNA 
protocol. TCP/IP provides a common transport protocol that, 
unlike SNA, is supported on Macs, VAXes, UNIX, and many other 
platforms. Support for TCP/IP services is beginning to grow as 
companies such as ASC begin to offer Macintosh terminal emula- 
tors that use MacTCP to communicate with similarly equipped 
IBM hosts (see figure 13.7). 


IBM AS/400 

5250 Terminal 






] [ TCP/IP 

» Ethernet 

^ y Ethernet < 

Rgure 13.7 

Willi asc525D over a ICP/ 

Media: Mainframe and AS/400 

There are two primary ways that physical connections are made in 
the IBM environment. One way is through direct connections, 
which are primarily used for terminal sessions. These direct 
connections can be made over coaxial cabling or through a Syn- 
chronous Data Link Control (SDLC) connection. The other way 
connections are made is through a LAN, which can be used for a 
wide variety of services. Token Ring is currently the predominant 
LAN cabling system in the IBM world, but Ethernet is slowly 
gaining in acceptance. 

Part Three Multivendor Networks 

Direct Connections 

The most common direct connection to an IBM mainframe is 
made with a coaxial (coax) cable. Traditionally, this has been the 
method employed by IBM terminals for years; it's also used by 
Macs and PCs running terminal emulation programs. Because 
Macs don’t come with a coax connection, an expansion card is 
required. The coax card is usually connected to an intermediate 
device known as a cluster controller, which is used to connect 
multiple coax devices to the mainframe. As shown in figure 13.8, 
terminals directly connected to the IBM AS/400 midrange com- 
puter use a variation of coaxial cable called twinaxial cable. Unlike 
coaxial cable, which has a single conductor surrounded by a 
second shielding conductor, twinaxial cable has two conductors 
inside. Macintosh coax and twinax cards are available from Apple, 
Avatar, and DCA. 

Figure 13.8 

an IBM AS/4011 host wilh 

Macintosh IBM AS/400 

SDLC connections are made with high-speed synchronous mo- 
dems. As shown in Figure 13.9, an SDLC card is used to connect 
the Mac to the modem, which in turn connects to other modems 

Chapter Thirteen IBM Connectivity 

on the mainframe. Apple’s Serial NB card can be used to make 
an SDLC connection. Avatar also offers cards that perform the 

Figure 13.9 

A Maciniosh connected 
synclifonous modems and 
a SDlt connection. 

Both the coax and SDLC connections tend to be expensive, either 
because they require a number of modems (in the case of SDLC) or 
because the coax connections need available ports on the cluster 
controller. When ports on the cluster controller are no longer 
available, another controller is required. To make a number of 
cost-effective connections to the mainframe, a gateway is often tlie 
best option. 

Avatar and DCA have software that enable a Macintosh to act as a 
SNA gateway when coax connections are used. A Mac that acts as 
a SNA gateway has one coax connection to the cluster controller 
and another LAN connection to the participating Macs. These 
Macs run the appropriate vendor’s client software and can be on 
LocalTalk or Ethernet networks. A similar gateway is also used 
for SDLC connections. A Mac acts a gateway by connecting a 
LocalTalk or Ethernet LAN to a single, shared SDLC connection 
(see figure 13.10). An example of this type of gateway can be found 
in Apple’s SNA*ps gateway. In addition to Macs that act as gate- 
ways, there are also several dedicated gateway boxes drat perform 
the same function. 

Part Three Multivendor Networks 

Hgure 13.10 

SNA oaieway Willi an 

Token Ring 

Of course, Token Ring is the leading LAN technology used in the 
IBM environment. There are number of companies (Apple, Avatar, 
and DCL\) that make Token Ring cards for the Mac. Macs using 
Token Ring can be attached directly to the mainframe (see figure 
13.11), or to a gateway. 

Figure 13.11 

direci Token Ring link. 


IBM Host 

Macintosh i 

(Cluster Controller) 








Token Ring 

(Apple or third party) 

Token Ring 


Ethernet is gaining in popularity in the IBM world, particularly as 
TCP/IP continues to become more prevalent on IBM mainframes 
(see figure 13.12). The most popular means of Macintosh Ethernet 
connections is through a gateway. 

Chapter Thirteen IBM Connectivity 


IBM AS/400 Host 

Figure 13.12 





The IBM mainframe world is changing, but it is still typified by 
terminal-type applications. The Macintosh can easily adapt to this 
environment with numerous terminal emulators and front-ending 
programs. These products support IBM’s cabling (coax, twinax, or 
Token Ring) and protocols (SAA, SNA, APPC, and APPN). They also 
support non-traditional cabling and protocols such as LocalTalk, 
Ethernet, TCP/IP, and AppleTalk through the use of gateways. 

gn, implementation 


Part IV brings everything together and outlines the process of design, 

) > - j 

implementation, and management. First, in Chapter 14, dw practical issues 

i 0 1^0 1 1 Ifc r 3* iCi i) i •( t < * ' > f; •' -;J '■ 
centered around network implementation, such as wiring and maintenance, 

are examined; the NetPICT technique is used to solve specific networking 

] n ! olt'n h'?i " In : : o 


problems. Once a network is in place, the focus shifts to other 

i n ' ; Vi , ; MT; r'Ol ? 

issues — discussed in Chapter 15 — such as keeping track of users and 

services, troubleshooting, performance monitoring, and security. 

Network Design, 
and Management 

Design and 

his chapter covers the basics of network design 
and implementation. Several common 
Macintosh network scenarios will be discussed 
and analyzed. These networking scenarios 
should make it easy for you to identify your 
current (or planned) network environment. Also 
included in this chapter are tips and hints that will 
streamline your networking tasks. 

Top-Down Design Techniques 

The NetPICT diagrams used throughout this book conveniently 
break up networking into four layers. This “divide and conquer" 
approach, inherent in the layering process, makes it easy to attack 
networking problems. This is similar to the process in which 
software projects, or computer programs, are solved by breaking 
the task into smaller “digestible” components. 

Combined, the four layers represent a particular solution to the 
overall networking problem. However, each separate layer can — 
and should — be addressed on its own merits. 

Part Four Network Design, Implementation, and Management 

The process should start at the top. Simply put, this means asking, 
"What Services are required to do the job?” This should be the 
driving force behind any network plan. Unfortunately, this is not 
always the case. All too often, companies start the process from the 
bottom up. They try to dictate Cabling choices. Transport proto- 
cols, and particularly computing hardware in an attempt to 
achieve some measure of standardization. By starting at the 
Semce layer, it is much easier to stay focused on the users’ needs. 

Once the question regarding Services is asked, there are a number 
of other questions that naturally follow. "Do these Services provide 
for growth? Are we going to be locked into a specific vendor’s 

Organizations must begin to look at network Services as strategic 
decisions that can significantly affect their operations. These 
Services can be as mundane as shared printing to a laser printer, or 
as pervasive as an enterprise-wide E-mail system. Let’s use E-mail 
as an example. 

Let’s say that the Ajax company decides tliat employee communi- 
cation is a crucial aspect of their business. They decide to imple- 
ment a corporate-wide E-mail system to facilitate this communica- 
tion. They decide on an X.400-compatible mail application. One 
reason that they made this decision was because of the portability 
of the X.400 standard. They reasoned that widespread support of 
the X.400 messaging format would enhance tlieir options for future 
expansion and grov\'th. All in all, a reasonable approach. 

Once the Ajax company made the decision to go with the X.400 
standard, the rest was comparatively easy. A suitable Transport 
and Cabling decision is left as the remaining task. It should be 
obvious that while the decisions of a Transport and Cabling are 
important, they are secondary to the choice of a Service and 

Chapter Fourteen Design and Implementation 

While it’s hard to simplify and generalize all networking situations, 
here are a few suggestions that may help to organize and prioritize 
your networking plans: 

1 . Establish and evaluate the required Services. Do they meet 
your requirements? Are they supportable? 

2 . During this process, be aware of the limitations and restric- 
tions imposed by the Formats used by the Services you have 
selected. Will your data be held hostage by the application 
vendor, or can it be transported to other applications and 

3 . Once you've chosen the Services, along with their attendant 
Formats, start thinking about a Transport protocol. Because 
Services are often protocol-specific, the choice of a Transport 
protocol may be restricted. 

4 . While selecting a Transport protocol, familiarize yourself with 
the administrative requirements inherent in the protocol. 

5 . Is the candidate Transport protocol supported on likely 
Cabling mediums? 

The preceding five suggestions may be somewhat simplistic, but 
they help to illustrate and represent the general process of working 
from the top down during the network design process. 

Using NetPICTs to Help with 
Systems Integration 

This book comes with a disk that contains numerous NetPICT 
symbols. Many of the symbols are duplicated from products 

Part four Network Design, Implementation, and Management 

discussed in the book; others depict other common networking 

The disk contains a viewer application called PICTviewer. It is used 
to view the NetPICT symbols. For each NetPICT symbol there are 
two files: a PICT file that contains the graphical image, and a text 
file that contains a textual description of the image. The text file 
has the same name of the PICT, but with the addition of a “.txt” file 
extension. For example, the PICT file portion of Apple’s Internet 
Router is named “Apple Internet Router,” while the text file 
portion is named “Apple Internet Router.txt.” 

The NetPICT viewer provides an easy means for you to view and 
read informative data on hundreds of products. Of course, since 
the symbols are in the PICT format, they can be easily incorporated 
into documents made by your favorite drawing program. The same 
can be said for the text (.txt) files. These text files can be added to 
your drawings to annotate the figures. Many drawing programs, 
such as MacDraw Pro, can import text files directly. If your drawing 
program can’t directly import text files, then you’ll have to copy 
and paste with a text editor or word processor. By using a drawing 
program, you’ll be able to import those NetPICT symbols that 
represent the fundamental parts of your present or planned 
network. You’ll be able to see where bridges, routers, gateways, or 
even format translators are required. 

To use the NetPICT viewer, you’ll need HyperCard 2.1 (or the 
HyperCard viewer). You might also want to copy the NetPICT 
viewer, along with the symbol folder, to a hard disk. 

1 . Launch the NetPICT viewer by double-clicking its icon. 

2 . Click several times to close the splash screen. 

Chapter Fourteen Design and Implementation 

3. Use the pop-up folder menu to browse through the NetPICT 
symbol folder hierarchy. 

4. Once you’ve found the appropriate symbol, click once on the 
name that appears in the window directly beneath the pop- 
up menu. 

The chosen NetPICT symbol will appear in a separate win- 
dow to the right of the viewer screen. You can reposition 
this window at any time. You can even enlarge it to the 
size of your monitor by clicking on the Zoom box located 
at the upper right hand corner of the symbol window (see 
figure 14.1). 

Figure 14.1 

Hieimaoe window of the 
NeiPICI viewer can be 
repositioned as needed In 
folly view tbe NeiPICI 

5. To restore the symbol window to the right side of the viewer 
window, click once on the magnet icon. This will automati- 
cally dock the symbol window to its default position at the 
right of the viewer window (see figure 14.2). 

Part Four Network Design, Implementation, and Management 

Figure 14.2 

Hiemagnel icon re-docks 
lire PICT image at lire 
upper right corner of tlie 
viewer application 

Wiring Strategies 

As mentioned throughout this book, the Macintosh supports a 
number of cabling systems, from LocalTalk to FDDI. We’ve dis- 
cussed the pros and cons of each cabling system, but there are 
numerous issues involved with the design and implementation of 
any wiring system. While it’s hard to generalize and cover all 
possible networking situations, here are a few things to keep in 

• Don’t get locked into a specific vendor’s proprietary compo- 
nents or cabling scheme. Stay with the accepted industry 

NOTE: One exception is Apple’s Ethernet system. It uses a special 
connector to link the device with the external attachment unit. Since the 
network side of the attachment unit (either 10Base-5, 10Base-2, or 
lOBase-T) stili conforms to industry standards, it’s less important that 
the device side is somewhat non-standard. To their credit, Apple has 
published and made this standard available for any vendor to use. The 
Apple Ethernet system has already been adopted by several Macintosh 
networking vendors. Perhaps other non-Macintosh networking 
companies will follow suit. 

Chapter Fourteen Design and Implementation 

• Don’t limit your network and wiring plans just to data. 
Consider integrating your network plans with other forms of 
data, such as voice and video. You may be able to save money 
by installing these different cabling systems at the same time. 
In many cases, the different systems can use the same face- 

• Plan for the future. You may be planning to use only Local- 
Talk and Ethernet, but you should seriously consider the 
installation of twisted-pair wiring and fiber backbones that 
are capable of supporting current and future high-end 
cabling systems. 

Example 1: Four-Pair Twisted Pair . 

One such industry standard involves the use of four pairs (10Base-T 
Ethernet requires two pairs) of Unshielded Twisted-Pair (UTP) wiring. 
The most encompassing standard for UTP is published by the Elec- 
tronic Industries Association and the Telecommunications Industry 
Association (EIA/TIA). The standard is commonly referred to as EIA/TIA 
568 and TSB-36, which sets a standard for “Category 5” UTP media. 
Category 5 UTP anticipates the upcoming standards that will support 
bandwidths of 100 Mbps (Category 4 UTP supports the conventional 
Ethernet bandwidth of 10 Mbps). These standards include copper 
versions of the FDDI standard (CDDl) and 100 Mbps implementations 
of Ethernet. This cabling is also sometimes referred to as “Level 5" 

Example 2: Fiber-Optics 

Another example of planning for the future is the choice of fiber-optic 
cabling. Fiber optic cabling is becoming more commonplace as a 
medium for Ethernet backbones. In fact, a new emerging Ethernet fiber 
standard, IEEE 802.3 — lOBase-F — will be published shortly. Fiber can 
be run over great distances and is immune from most forms of 
electromagnetic interference (just don’t get it too close to a black hole). 
Fiber optic cabling is also the basis for the FDDI standard. Fortunately, 
the two standards overlap somewhat and it’s desirable to implement 

Part Four Network Design, Implementation, and Management 

fiber networks that conform to the FDDI standard (ANSI X3T9.5: FDDI) 
as well as the current and planned Ethernet fiber standards. The moral 
of this story is to plan for FDDI even though you're only going to use 
lowly Ethernet. You'll appreciate this approach in the future when FDDI 
cards sell at CompUSA for $129. 

• If it appears that your LAN will need to support more than 50 
users, plan on implementing a structured wiring approach to 
your network design. It’s money well spent. By implemen- 
ting such a system, the ongoing costs involved in support, 
troubleshooting, expansion, and equipment relocation will 
be minimized. 

• In accordance witli your budget, plan on running multiple 
cable runs to each office or cubicle. The incremental cost of 
the additional cabling is relatively small when compared to 
the minor increase in labor cost. Also, don’t scrimp on the 
number of jacks provided to an office or cubicle. You can 
choose faceplates that have a single, double, or quadruple 
complement of connectors. While it’s often possible to daisy- 
chain within a room, don’t plan on this as a part of the design. 
Consider that you might want to add printers or other 
networkable peripherals to a room at any time in the future. 
You might also need to support devices that require multiple 
connections to the LAN, such as workstations, routers, and 
gateways. A good rule of thumb is to plan for two times as 
many connections as you actually require at present. 

• Make sure that fiber and copper cable runs are within the 
specified length limitations, by carefully planning the loca- 
tion and distribution of wiring closets. Be sure to allocate 
additional cable length for vertical distances (not usually 
shown on floor plans) and the routing losses that occur when 
cable is snaked above ceilings and through walls. 

Chapter Fourteen Design and Implementation 

• Speaking of wiring closets, plan the layout and design of these 
rooms carefully. Make sure that the room is well lighted, 
ventilated, and capable of being securely locked. If the room 
is large enough, use industry standard 19" racks to contain 
the network devices. Obviously, since the room may house a 
number of routers, gateways, and other network devices, 
adequate electrical service is crucial. If you have the room, 
you may also find it convenient to install a small desk with a 
Mac that can be used for troubleshooting and maintenance. 
This Mac can also be used to maintain network configuration 
information, wiring diagrams, and problem logs. 

• Are your cables routed in such a manner as to avoid electro- 
magnetic interference and undue mechanical stress? For 
example, don’t drape cables around fluorescent light fixtures, 
and don’t hang wet laundry from cables strung from the 
ceiling. Use common sense and consult the appropriate local 
codes and requirements. 

• Plan to have your wiring tested before use. This is a particu- 
larly good idea for large, expensive installations that use 
structured wiring. The time to discover breaks or discon- 
tinuities in the cable is be/ore network deployment. If you use 
a wiring contractor, be sure to include testing and validation 
as part of the agreement. The devices used for testing can be 
rather expensive, so it’s likely that this task is better handled 
by the cable installers. 

• Adopt an adequate cable marking and identification scheme. 
Each and every cable should be unambiguously marked — in a 
location that will be visible after installation. Be sure to mark 
both ends of the cable. Make sure the marking is permanent 
and won’t easily be erased or detached. There are many 
adequate marking systems. Some utilize heat-shrinkable 
tubing, while others use labeled wiring ties. 

Part Four Network Design, Implementation, and Management 

• Document everything from the outset. Create a logical and 
physical diagram of your network. If you’re using a cabling 
system that has physical hardware addresses, such as 
Ethernet, register these numbers along v\ath their location 
and description. For this task, a spreadsheet or a simple 
database (such as FileMaker Pro) is ideal. 

• Call, without delay, the Black Box Corporation at (800) 552- 
6816. They’ll send you a free catalog that’s chock full of many 
networking products. It’s like the “Sears Catalog” for 

Using diese twelve suggestions as a guide, let’s now examine some 
common networking scenarios. These scenarios will serve severed 
purposes. First, they will expose you to a number of different 
wiring schemes, along with their benefits and disadvantages. Next, 
because the scenarios progress from the simplest to the most 
complex, you’ll be able to establish a growth path for your environ- 

Scenario la: Single LocalTalk Network 
Using a Daisy-Chain Topology 

The simplest Macintosh network is the single LocalTalk daisy- 
chain network (see figure 14.3). This network has been around 
since 1985 and in many cases is still an entirely acceptable network 
architecture. This network is inexpensive. All that is required is the 
LocalTalk (or phone-type) connectors and the necessary wiring. In 
nearly all cases, the phone-type connectors (Farallon's PhoneNET) 
are recommended. Because these connectors use the telephone- 
style RJ-11 jacks, you’ll be able to make your own cables by pur- 
chasing a spool of twisted-pair phone wire, jacks, and a crimping 
tool. Electronics stores such as Radio Shack should have everything 
you’ll need. 

Chapter Fourteen Design and Implementation 

Figure 14.3 

A single iDcallalk 
neiwoik Willi daisif-cliain 

The cost of this network is the lowest of any of the other scenarios. 
Expect to pay $25 for each LocalTalk/phone-type connector. With 
the additional cost of the wiring, the total per-node connection 
cost should be well under $50. 

With this network design, you’ll be able to provide modest band- 
widtli for any number between two and thirty devices. The maxi- 
mum distance of the network may vary somewhat, but plan on a 
maximum of 1,000 total feet of wiring. If you need more distance, 
consider the use of a LocalTalk repeater. 

The tradeoffs for this design are the low cost and ease-of- 
installation versus the limited bandwidth of LocalTalk. If you plan 
on using services that demand high bandwidth, then the simple 
LocalTalk is not for you. Applications that demand high bandwidth 
include networked databases, demanding AFP services where large 
files are frequently transferred, and demanding print jobs submit- 
ted from a number of users. As a rule of thumb, try to avoid put- 
ting more than five networked printers on a single segment of 
LocalTalk. If you need this many printers to service your users, 
then a routed scenario or a higher bandwidth cabling system is 
probably required. 

This network scenario is ideal for small offices that deal v\ith 
smaller documents and have modest print requirements. It also 
helps if the physical layout of the area to be networked can easily 
support the daisy-chain topology. If the devices are all located 
within a single room, then the daisy-chain can simply run around 

Part Four Network Design, Implementation, and Management 

the periphery of the room. On the other hand, if your network 
nodes are distributed throughout a large building that doesn’t 
provide ready wiring access, then a more structured wiring ap- 
proach might make more sense. 

One point to remember about the Lx)calTalk daisy-chain is that 
devices can be added to the ends of the chain at any time, but if 
you need to add a device somewhere in the middle, the network 
will have to be disconnected to attach the new LocalTalk connec- 
tor. This addition won’t take long, but the users will have to put up 
with a slight interrupdon in network services. 

These considerations can be summed up as follows: 

+ Ideal for small workgroups (2-20 devices) in close proximity 

+ Easy to wire 

- Limited bandwiddi and throughput 

- Network disrupted when devices are added 

- Limited to approximately 30 devices 
• Maximum cabling length of 1,000 feet 

Scenario 1b: Single Ethernet Network 
Using a Daisy-Chain Topology 

If you find the simplicity of Scenario la appealing, but you’re 
concerned about the limited bandwidth of LocalTalk, then an 
Ethernet solution may be just the ticket. In this case, we’ll use the 
thinwire variant of Ethernet known as lOBase-2 (see figure 14.4). 
Although twisted-pair Ethernet (lOBase-T) is getting all the atten- 
tion in the press, a thinwire daisy-chain is still a valid solution for 
small network installations in one compact area. 

Chapter Fourteen Design and Implementation 

Rgure 14.4 

using diinwiiellOBase-I) 

With the thinwire tee connectors, the nodes simply can be con- 
nected one after the other. The total cable length is 185 meters, or 
about 600 feet. Like the LocalTalk example in Scenario la, changes 
made to the network will cause a brief disruption of services. 
Apple’s thinwire transceivers have a unique self-terminating 
feature that engages the terminating resistor whenever the connec- 
tion is broken. With these devices, a break in the middle of a 
segment will not cause the two segments to fail. Each segment will 
continue to operate on its own. If you use the conventional 
thinwire devices, be sure that each free end of the cable has the 
terminating resistive cap in place. 

This scenario is ideal for small workgroups that require more 
bandwidth than LocalTalk. The Ethernet cabling should provide a 
300 to 500 percent improvement in throughput over the LocalTalk 
cabling. The number of nodes is still somewhat limited, as 30 is the 
recommended maximum number of devices on a single segment 
of thinwire. 

One difficulty with thinwire is the cabling. Each cable must have 
the twist-lock BNC connector fittings. You can purchase pre- 
assembled lengths of these cables, or invest in the bulk fittings and 
cable and crimp your own. You might need to go to a networking 
supply house, such as Black Box, to find these components and the 
proper crimping tools. 

The cost of a thinwire network is somewhat more than a LocalTalk 
network. If your Macs, LaserWriters and other network devices 
aren’t equipped with Ethernet, then Ethernet cards will be 

Part Four Network Design, Implementation, and Management 

required. Expect to pay $200 to $300 per card. Devices that don’t 
offer Ethernet connections (such as PowerBooks and certain 
LaserWriters) will require special Ethernet devices that connect via 
the SCSI port or through the LocalTalk port. Add the cost of the 
cables, and you’re likely to spend $300 to $400 per node. 

These considerations can be summed up as follows: 

+ Ideal for small workgroups in close proximity 

+ Easy to wire 

+ Improved throughput compared to LocalTalk 

- Network disrupted when devices are added 

- Segment limited to approximately 30 devices 

• Maximum cabling length of about 600 feet 

A similar scenario to a single Ethernet network involves the use of 
FDDl as a cabling medium. Of course, the per-node connection 
cost is considerably higher. If your network requirements are 
severe, then this approach should be considered. Perhaps you 
need to network a number of Quadras in a desktop publishing 
environment where users are continually transferring lOM 
Photoshop files, or perhaps you need to upgrade a number of CAD 
users that are continually taxing the network. In these cases, the 
extra bandwidth and throughput of Ethernet or FDDI can pay for 
itself in short order. 

If you’re planning future network growth and expansion, don’t 
invest heavily in the daisy-chain approach. If you’re planning to 
expand, consider instead scenario 3b, which uses an active 
Ethernet hub. 

Chapter Fourteen Design and Implementation 

Scenario 2: Single LocalTalk Network 
Using an Active Star Topology 

If you plan to stay with LocalTalk but would like to avoid the 
hassles associated widi daisy-chaining, then a star topology is the 
solution (see figure 14.5). Apple’s LocalTalk devices will not work 
with this topology; you’ll need to use the phone-type connectors 
(PhoneNET or equivalent). (We'll continue to use the term 
LocalTalk for convenience.) You can also use Farallon’s Star- 
Connectors. They do not require termination and are a bit less 
expensive than the conventional two-port devices. The easiest and 
cheapest LocalTalk star is known as a passive star. The passive star 
simply joins together the free ends at a common point. This can be 
a telephone-style punchdown block or a patch panel. 

Figure 14.5 

A single Locallalk 
neiwoikwiiti a passive 

This approach makes sense for a small workgroup. You may be 
able to use existing building wiring to create your passive star. 
Considering this potential for reduced wiring costs, coupled with 
the low cost of the StarConnectors, this network scenario can be 
the most affordable of all. The shortcomings of passive stars are the 
limits imposed on the number of devices (3 branches with 10 
devices each) and the limited extensibility. 

To summarize the considerations: 

+ Ideal for small workgroups in close proximity 

+ Can use existing building wiring 

Part Four Network Design, Implementation, and Management 

- Restrictive wiring limitations and limited flexibility 

- Limited to approximately 30 devices 
• Maximum cabling length of 1,000 feet 

Figure 14.6 

A single locallalk 
neiwoik using an aciive 

Scenario 3a: Single LocalTaik Network 
Using an Active Star Topology 

The alternative star topology is the active star (see figure 14.6). It 
uses a multiport LocalTaik repeater to separately feed each seg- 
ment of the star. Active stars are generally more reliable and easier 
to maintain than their passive counterparts. Each cable run has a 
maximum length of 3,000 feet. For a twelve-port repeater, the 
maximum cabling distance is 36,000 feet. Most LocalTaik star 
repeaters are equipped with management software that can enable 
or disable ports and perform basic line quality testing. 

LocalTaik Repeater 

While it’s possible to place forty (or even more) devices on an 
active star, it’s important to remember than the entire star is a 
single AppleTalk network, sharing the LocalTaik bandwidth of 
230.4 Kbps. So, unless your network demands are modest, it’s best 
to limit the number of nodes to 30 or 40. 

The cost of an active LocalTaik star network is more than the 
passive star because you must factor in the cost of the repeater. 

Chapter Fourteen Design and Implementation 

Depending on the number of nodes and the cost of the repeater, 
this could add a considerable amount to the per node cost. 

To summarize the considerations: 

+ Star topology makes it easier to add and move devices 
+ Preferred over passive star topologies in most cases 
+ Enhanced reliability 

- Limited to 30 to 40 devices 

- The cost of the repeater increases the cost per node 
• Maximum cabling length of 3,000 feet per segment 

Scenario 3b: Single Ethernet Network Using 
a Star Topology with lOBase-T Cabling 

This scenario provides the bandwidth of the thinwire scenario, 
with the flexibility of a star wiring topology (see figure 14.7). 
Twisted-pair (lOBase-T) Ethernet networks require a repeater hub. 
These hubs come in many different sizes and price points. There 
are even low-cost mini-hubs that have anywhere between four and 
eight ports. 

Figure 14.7 

A single Eilieinet network 
using a star topology and 
10Dase-I cabling. 

As in the case of the LocalTalk stars, you might be able to use 
existing building wiring, although lOBase-T wiring requires four 

Part Four Network Design, Implementation, and Management 

pairs of wires that meet certain requirements. If you must create 
your own wiring, don’t worry, it’s not too difficult — lOBase-T 
Ethernet uses a larger version (RJ-45) of the RJ- 1 1 connectors used 
by the phone-type LocalTalk connectors. You can buy the bulk 
cable, connectors, and proper crimping tools from network supply 
houses such as Black Box. (Consider the use of Level 5 wiring just 
in case you plan to migrate to a high-speed network such as 100 
Mbps Ethernet or CDDI.) 

This single hub approach makes a lot of sense when you need the 
extra bandwidth of Ethernet and are planning for future growth. 
When you require additional hubs, the hubs can be linked together 
with an Ethernet backbone. Of course, the cost of hubs add to the 
per-node cost, but that’s the price of the additional flexibility. 

The length of each twisted-pair segment cannot exceed the 100 
meter restriction, so the maximum distance between devices 
(assuming the hub is centrally located) is 200 meters. 

To summarize the considerations: 

+ The star topology makes it easier to add or move devices 

+ Uses low-cost wiring 

- Additional cost of the hub adds to the overall cost 
• Maximum lOBase-T length of about 325 feet 

Scenario 4: Single LocalTalk Network 
Using a Multiple Star Topology 

In an ideal situation, you should only place one device on each 
port of a LocalTalk star repeater. This way, you’ll be able to isolate 
problem nodes more easily. However, if you place one device per 

Chapter Fourteen Design and Implementation 

port, you will only be connecting a dozen or so devices per re- 
peater. You can extend this somewhat by linking the star repeaters 
together (see figure 14.8). For example, by interconnecting three 
12-port repeaters, you’ll be able to connect 36 LocalTalk devices 
without having multiple devices per port. 

LocalTalk Repeater 
- (Farallon, Focus) 

Figure 14.8 

A single locallalk 



Of course, this is an expensive way to connect LocalTalk nodes. In 
the example of the three linked repeaters, the per-node cost might 
exceed $100. Keep in mind that even though multiple repeaters are 
used, the resultant network is still a single logical LocalTalk seg- 
ment with a shared bandwidth of 230.4 Kbps. Due to the relatively 
high per-node cost and the inherent limitations of LocalTalk, be 
leery of this scenario. 

The considerations are: 

+ Avoids multiple devices per repeater port 

- The LocalTalk bandwidth is shared by all devices 

- Still limited in practicality to 30 to 40 devices 

- Cost per device is relatively high 

• Maximum cabling length of 3,000 feet per segment 

Part Four Network Design, Implementation, and Management 

Figure 14.9 

A single Locallalk 
neiwoik using a bridged 

Scenario 5: Single LocalTalk Network 
Using a Bridged Star Topology 

An alternative to the LocalTalk repeater is Tribe’s LocalTalk bridge 
(see Figure 14.9). This device uses packet switching technology to 
maximize the limited bandwidth of LocalTalk. If the low-cost and 
easy installation of LocalTalk appeals to you, but you’re finding the 
LocalTalk bandwidth limiting, then Tribe’s LocalSwitch might 
provide a good alternative. It increases the throughput and extends 
the number of devices that you can place on your LocalTalk 
segment. According to Tribe, you should be able to put a total of 
60 devices on the bridge. 

The considerations are: 

+ The bridge maximizes the limited LocalTalk bandwidth 
+ No router administration is required 

- Limited to 40 to 60 devices 

- Limited extensiblity without an Ethernet connection 
• Maximum cabling length of 3,000 feet per segment 

Scenario 6: Multiple LocalTalk Networks 
Using a Serially Routed Topology 

Eventually, as you continue to add LocalTalk devices to the net- 
work, you'll reach a point where separate AppleTalk networks are 
required (see figure 14.10). This might be due to the sheer number 

Chapter Fourteen Design and Implementation 

of devices or the need for traffic isolation. The key to this scenario 
is the LocalTalk-to-LocalTalk router. There are a number of com- 
panies that make such a router. The router could also be a 
Macintosh that’s running the Apple Internet Router through 
LocalTalk connectors in the modem and printer ports. In this 
example, each LocalTalk network is implemented with a repeater 
or a Tribe bridge. 

Figure 14.10 

networks serially louled. 

The router connects each LocalTalk network in a daisy-chained 
manner, but it’s wise to limit the number of connected networks to 
a maximum of 4 or 5 networks (3 or 4 routers). Anything more than 
this increases the risk of network timeouts and delays. (The router 
introduces a bit of administrative overhead due to the configura- 
tion of its network numbers and zone names.) 

This scenario makes sense as an upgrade path from the single 
LocalTalk network that is becoming burdened with traffic. This is 
particularly the case when the additional traffic can be isolated by 
the addition of the router. The only shortcoming with this ap- 
proach is that it’s somewhat limited when it comes to expansion. A 
much better approach is to use an Ethernet network as a backbone 
(see Sceneuio 7 a below). 

To summarize the considerations: 

+ The router isolates each LocalTalk segment 

• Each LocalTalk network supports 30 to 40 devices (using a 

Part Four Network Design, Implementation, and Management 

• Each LocalTalk network supports 40 to 60 devices (using a 

- Daisy-chaining networks is practically limited to 3 or 4 

- Limited expansion capability 

• Maximum cabling length of 3,000 feet per segment 

Figure 14.11 

Multiple locallalk 
neiwoiks uslnparouieil 
(not tuidoeill backbone 

Scenario 7a: Multiple LocalTalk Networks 
Using a Routed Backbone Topology 

When you outgrow your single LocalTalk network, or when you 
have to connect LocalTalk devices to Ethernet-equipped devices, 
the easiest way is to link the LocalTalk networks to an Ethernet 
backbone (see figure 14.1 1). Each LocalTalk network will connect 
to the backbone with a LocalTalk-to-Ethernet AppleTalk router. 

With this approach, you’ll be able to interconnect hundreds of 
LocalTalk devices. It still makes sense to use some kind of star 
repeater or bridge in combination with the router. Some vendors 
(such as Farallon) offer combination devices that merge a 
LocalTalk-Ethernet router with a star repeater. 

As in the prior scenario, some router administration is required. 
If you plan to connect a number of routers to the backbone, you 
may want to consider tire use of a seed router. Seed routers are 
used to load non-seed routers with network numbers and zone 

Chapter Fourteen Design and Implementation 

information. Most routers offer this seeding capability, imple- 
mented as a part of the router's configuration. The primary advan- 
tage of seeding is administrative. Changes made to the backbone’s 
network number range or zone names can be made in a single 
router instead of changing all the routers on the backbone. 

To summarize the considerations: 

+ Ethernet backbone provides high-speed path 

+ Extensible to many routers and hundreds of devices 

+ Traffic isolation with routers 

- Router administration required 

- LocalTalk bandwidth — no increase in throughput 

• Ethernet (thickwire) backbone length approximately 
1,500 feet 

Scenario 7b: Multiple LocalTalk Networks 
Using a Bridged Backbone Topology 

If you anticipate fewer than 254 devices, then another solution is 
available from Tribe (see figure 14.12). Their TribeStar bridge has 
an Ethernet connection in addition to several LocalTalk ports. The 
TribeStar has the advantage of reduced administration because 
there are no routers to configure and maintain. 


— LocalTalk-Ethernet \ f 

Bridge \ 

Rgure 14.12 

Multiple iocallalk 
bridged — not 
routed — backbone 

Part Four Network Design, Implementation, and Management 

This scenario makes sense for medium-sized LocalTalk networks 
where the maximum performance must be obtained for a mini- 
mum of administrative overhead. The Ethernet backbone provides 
a measure of extensibility, so that future bridges (assuming the 254 
node limit is not reached) and routers can be added as needed. 

The considerations are: 

+ The Ethernet backbone provides a high-speed path 
+ Extensible to many bridges and hundreds of devices 
+ No router administration required 
+ Maximizes LocalTalk bandwidth 

• Each bridge can support up to 64 devices 

- More than 254 nodes requires an AppleTalk router 

• Ethernet (thickwire) backbone length of about 1,500 feet 

Scenario 8: Ethernet Backbone with Multiple LocalTalk 
Networks and Direct AppleTalk Nodes 

Building on Scenario 7a, you can always add AppleTalk nodes 
directly to the Ethernet backbone (see figure 14.13). This approach 
can be used to connect Ethernet-equipped Macs and LaserWriters 
to the network. It is also widely used to connect other computers, 
such as UNIX workstations, DEC VAX, and PCs to the network of 

Chapter Fourteen Design and Implementation 

If AppleTalk is to be the transport of choice, then the router can be 
an AppleTalk-only unit. If other non-AppleTalk nodes are added 
to the Ethernet, then the router must be a multiprotocol router 
capable of routing the necessaiy' protocols between the LocalTalk 
and Ethernet devices. 

Keep in mind that the LocalTalk and Ethernet repeaters have 
different cabling length requirements. LocalTalk runs may ap- 
proach 3,000 feet, while lOBase-T limits are about one-tenth that 
distance (100 meters, or about 325 feet). 

The considerations are: 

+ Ethernet backbone provides a high-speed path 
+ Extensible to many routers and hundreds of devices 
+ Direct Ethernet connections with thickwire or thinwire hubs 

• Ethernet (thickwire) backbone length about 1,500 feet 

• lOBase-2 length about 600 feet; lOBase-T length about 325 

Scenario 9; Multiple Ethernet Networks Using 
a Routed Backbone and Star Topology 

As the cost of Ethernet connections continue to fail, and as Apple 
continues to offer built-in Ethernet in more and more Macintosh 
models, the trend is clearly away from LocalTalk connections. For 
this reason, solutions like Scenarios 7a and 8 are beginning to 
become less popular. The direction that most network designers 
are taking is to use Ethernet to all desktop devices, and then to use 
an Ethernet segment as a connecting backbone (see Figure 14.14). 
The key component is an Ethernet-to-Ethernet AppleTalk router. 
These devices are becoming more prevalent. Cayman, for example. 

Part Four Network Design, Implementation, and Management 

Figure 14.14 

backbone and Slat 

has just released such a router; other companies are likely to follow 
suit. The router could also be a Macintosh with two Ethernet cards 
running the Apple Internet Router. 

10Base-2(Thin) or 
10Base>T Repeater 

AppleTalk Router 

This scenario represents the most flexible and high-performance 
option for all but the most demanding applications. This scenario 
also fits in nicely with structured wiring plans, which makes it easy 
to respond to growth and redistribution of network resources; it 
also makes it easy to add routers to the network in response to 
excessive traffic. This approach lends itself to intelligent hubs and 
concentrators that work in conjunction with, or incorporate, 
AppleTalk routers. As an example, Cabletron has just announced 
their intention to incorporate die Cisco 4000 series router into their 
hubs. Standalone high-performance multiprotocol routers are also 
likely candidates, as they provide the necessary performance with 
a wide range of protocol support. These routers are supplied by 
several vendors; Cisco and Wellfleet are two popular choices. 

To summarize the considerations: 

+ Ethernet backbone provides a high-speed path 

+ Extensible to many routers and hundreds of devices 

+ Full Ethernet bandwidth between nodes 

• Ethernet (thickwire) backbone length approximately 
1,500 feet 

• lOBase-2 length about 600 feet; lOBase-T length about 
325 feet 

Chapter Fourteen Design and Implementation 

Scenario 10: Multiple Ethernet Networks 
with a FDDI Backbone 

As the number of routers increase on an Ethernet backbone, its 
ability to handle the inter-netvvork traffic plus the inter-router 
traffic can become strained. For these very large networks, replac- 
ing the Ethernet backbone with FDDI is becoming more prevalent 
(see figure 14.15). For now, the main role of FDDI is likely to be its 
use as a high-speed backbone medium. 

Figure 14.15 

networks will) a FOOl 

The latest generation of high-speed routers provide, in addition to 
Ethernet and Token Ring ports, FDDI ports that can provide the 
connection to the FDDI LAN. Since FDDI LANs can extend over 
great distances, this scenario is indicated for very large networks 
with many attached subnetworks. 

To summarize the considerations: 

+ FDDI backbone provides a high-speed path 

+ Extensible to many routers and hundreds of devices 

+ Full Ethernet bandwidth between nodes 

• FDDI supports 1,000 nodes, each up to 2km (over 1 mile) 
apart, for a total aggregate distance of 100km (over 60 miles) 

Scenario 11: Ethernet and FDDI WAN Topology 

The last wiring scenario involves the combination of Scenarios 9 
and 10 by adding a high-speed WAN connection (see figure 14.16). 

Part Four Network Design, Implementation, and Management 

These WAN connections are commonly made with the multi- 
protocol routers mentioned earlier. As mentioned before, one of 
AppleTalk’s past shortcomings was the regular transmission of 
routing table updates. These updates tended to be burdensome to 
AppleTalk WAN links. Today, there are many options to solve this 

Figure 14.16 

Etheinei and 1001 WAN 

Ethernet Backbone 

First, Apple has added the AURP routing protocol, which only 
sends routing updates when necessary. AURP support is included 
with Apple’s Internet Router, and currently being added to many 
third-party routers. Another solution for WAN AppleTalk support is 
through the encapsulation of AppleTalk within another protocol, 
such as TCP/IP. The process of IP encapsulation of AppleTalk has 
been recently defined and standardized. Lastly, many high-end 
router developers offer specialized routing protocols that can be 
applied to the routing of AppleTalk over the WAN. 

It is expected that Apple will take additional steps in the near 
future to enhance AppleTalk’s viability over wide-area networks. 
These include the support of upcoming Point-to-Point Protocol 
(PPP), which should enhance remote access and routed connec- 
tions, and the adoption of other popular routing protocols such as 
Open Shortest Path First (OSPF), which is popular in large IP 

The considerations can be summarized as follows: 

+ FDDI backbone provides a high-speed path 

Chapter Fourteen Design and Implementation 

+ Extensible to many routers and hundreds of devices 

+ Full Ethernet bandwidth between nodes 

• FDDI supports 1,000 nodes, each up to 2km (over 1 mile) 
apart, for a total aggregate distance of 100km (over 60 miles) 

Scenario 12: Structured Wiring Example 

This last example illustrates a wiring scenario that uses a technique 
sometimes referred to as a structured wiring implementation (see 
figure 14.17). In this example, a star topology is used to wire all 
offices and cubicles vdth several runs of lOBase-T (or even Level 5 
compliant) twisted-pair v\iring. All wires converge at a master 
patch panel within a wiring closet. From this patch panel, connec- 
tions are made to the appropriate wiring devices based on require- 
ments of the connected device. 

Wiring Closet Office Cubicles 

19" Rack 

LocalTalk Hub & 
Router or Bridge 

Terminal Server 

10Base-T Hub 

Figure 14.17 

situciuied wiling 

LocalTalk devices are interconnected to a LocalTalk hub and 
router; Ethernet devices are connected to an Ethernet hub. While 

Part Four Network Design, Implementation, and Management 

it’s not shown in figure 14.16, the lOBase-T hub could also be 
connected to an Ethernet-to-Ethernet router (as shown in Scenario 
9). Serially connected devices are patched to a terminal server. 
What's important about this scheme is that all devices use identical 
wiring. Changes are confined to the wiring closet. If a LocalTalk 
Mac Plus is replaced with an Ethernet Quadra, the only required 
change is to move a patch cord from the LocalTalk hub to the 
Ethernet hub. 

Some integrated hubs merge the different hubs (such as terminal 
servers, lOBase-T, and even LocalTalk) into a single, unified 
chassis. These devices make the wiring process even easier and less 
cluttered by eliminating the cross-connects that are now part of 
the hub’s backplane. 


The development and implementation of an AppleTalk network 
is not a one-time activity. It is an ongoing process; the network 
continues to evolve as users are added and technology changes. In 
this chapter, a number of network scenarios were outlined and 
discussed. Each successive scenario provided additional complex- 
ity— and additional capabilities — over the previous examples. 
Collectively, these examples delineate a full range of options for 
the reader; they also illustrate a clear and progressive growth path 
from the simplest of LocalTalk networks to the most complex 
combinations of Ethernet, Token Ring, and FDDl cabling. 

Management and 

ow many copies of MacDraw do the users own? 
H| Macs have enough memory to run System 

H iH Why can’t the users on the second floor print 

^8 to the LaserWriter? What happens to our network 

performance at 10 AM every day? Chapter 15 
discusses common questions like these — and 
provides answers to them. 

Configuration Management 

Keeping track of the software and hardware status of every 
Macintosh on a network is not an easy task. How much memory 
does Mary’s Mac have? Is everyone using the same version of 
PageMaker? Many potential problems can be avoided if every user 
on the network has the same version of important applications and 
system software, and they all use the same collection of fonts and 
font technology (TrueType or PostScript). Several products are 
now on the market that allow you to examine and even install 
software updates on another Macintosh, using the network to 
transfer the information. These products are often marketed under 

Part Four Network Design, Implemenation, and Management 

the misnomer “network management" tools, perhaps because the 
person holding the title Network Manager is often responsible for 
configuration management of every node on the network. These 
products, while quite useful, do not address the task of actually 
managing the network itself; they manage the Macs connected 
to it. 

Figure 15.1 



How Do They Work? 

A node management product (see figure 15.1) requires that you 
install a small program, usually called a responder or agent, on 
every Macintosh you will manage. The network manager’s 
Macintosh then runs an application which communicates with the 
responder using a private format. In many products, the responder 
can also handle the task of copying updated versions of system 
or application software to the correct location on the remote 
machine’s hard disk. This feature alone can justify the cost of the 
product, because it will save an enormous amount of time and 
effort every time you have to upgrade software on every node on 
your network. 

Management Node 

Managed Node 

Be sure to pick a product that can upgrade the responders, or you might still 
find yourself roaming the halls with an installer disk a few times a year. 

Chapter Fifteen Management and Troubleshooting 

Server and Account Management 

Another labor-intensive task is controlling who can use which file 
servers and printers, who can use the network’s dial-out or dial-in 
services, and reporting when or how often each one has used each 
service. These resources always have specialized requirements, so 
each has its own dedicated management tools. Whenever possible, 
select products which can be managed across the network, instead 
of those that must be managed locally. 

Network Management 

At the present time, AppleTalk network management is undergo- 
ing significant changes. In the past, AppleTalk management 
worked with any number of third-party router configuration 
programs to inspect and modify AppleTalk network numbers and 
zone names. Several years ago, Apple began development of a 
management protocol called the Apple Management Protocol, or 
AMP. During the development process, Apple made the decision to 
abandon AMP and adopt the industiy standard Simple Network 
Management Protocol, or SNMP. When the promise of SNMP for 
AppleTalk is fully realized, managers will have a consistent and 
universal interface for network management. 

Simple Network Management Protocol (SNMP) 

SNMP is a popular tool for network management in large TCP/IP 
networks. SNMP provides a means for a management station to 
query a remote device for configuration information, and in some 
cases, to load new configuration information. For example, SNMP 
can be used to examine the Address Mapping Table of an Apple- 
Talk router, or to find out how many DDP packets (or bytes) were 
sent and received by an Applet alk node. 

Part Four Network Design, Implemenation, and Management 

The information that SNMP maintains is defined in a data struc- 
ture definition called the Management Information Base (MIB). 

The complete MIB for AppleTalk is defined in an Internet Engi- 
neering Task Force Request For Comment document, RFC- 1243. 

An SNMP management station communicates with an SNMP 
agent running on a managed entity (a network node such as a 
router or gateway). In order for data to be transferred between the 
devices, it must be described within the MIB. Most MIB elements 
are currently read-only, so most of the management can be more 
accurately described as monitoring. As the security features of 
SNMP improve, more elements in the MIB will allow read-write 
access from management stations, so active management of 
AppleTalk network devices using SNMP will become a reality. 

For example, the AARP MIB defines access to the information kept 
in a node’s AppleTalk address mapping table. Each entry in the 
table matches one hardware address to one protocol address, and 
identifies the port on which the information is used. Since this is 
the only AMT information in the MIB, it is the only AMT informa- 
tion a management station can request of an SNMP-compliant 
AppleTalk node. 

Similar MIBs are defined for the other lower-layer AppleTalk 
protocols, such as DDP, RTMP, and ZIP. By examining the MIB 
definitions, you can see precisely what information is available for 
each protocol, and what configuration details (if any) can be set 

Because SNMP is a Format layer protocol, there is no reason why it 
can’t be used over AppleTalk Instead of TCP/IP. Apple now in- 
cludes SNMP protocol support in the Macintosh network drivers 
for LocalTalk, EtherTalk, and TokenTalk. This means that 
AppleTalk nodes can now maintain statistics on how busy they are 
and report that information on request to an SNMP management 

Chapter Fifteen Management and Troubleshooting 

station. Figures 15.2 and 15.3 depict where the differences lie 
between these two implementations of SNMP. 

Management Node Managed Node 

Management Node Managed Node 

Hgure 1 5.2 


Figure 15.3 

SNMP will) Applelalli 

By sending an alert to the management station, SNMP also pro- 
vides a means for nodes to notify the network management station 
of events, such as error conditions. A limited number of these 
alerts are defined in the current AppleTalk RFC, but the number is 
expected to grow. 

Currently, there is one SNMP management program, called 
WatchTower from InterCon, that runs on the Macintosh. Because 
it was developed before a standard was defined for using SNMP 
over the AppleTalk transport, it uses TCP/IP as the message 
transport protocol. As SNMP via AppleTalk becomes more popular, 
SNMP management products using AppleTalk will certainly 
become available. 

Part Four Network Design, Implemenation, and Management 


Diagnosing problems on an AppleTalk network can be a very 
complicated task. Fortunately, there are software tools that can be 
a great help in investigating and solving network problems, but no 
one tool can do the entire job. If you’re serious about diagnosing 
AppleTalk, you’ll also need a copy of Inside AppleTalk, Second 
Edition, which contains Apple’s official, definitive description of 
the AppleTalk protocol family. 

How the Chooser Really Works 

The Chooser is the user’s window onto the network, so it often 
provides the first indicadon of impending network problems. For 
example, a user might report that a machine can’t find a parUcular 
printer or some other resource in the Chooser; perhaps the 
Chooser doesn’t show any zones at all. To solve AppleTalk problem 
reports, you must know the topology of your network (how the 
routers connect everything) and you need to know where the 
affected devices are located. 

The Network Census — Who Is Out There? 

Apple Computer’s lnter»PolI is an easy-to-use network tool (see 
figure 15.4). This application uses the NBP protocols to obtain 
both the NVE (the object, type, and zone names) and the logical 
AppleTalk addresses of the AppleTalk devices found on the net- 
work. An accurate NVE and address list is a great help whenever 
you’re looking into a network problem. 

However, whenever you use Inter»Poll, keep in mind that NBP is 
an “unreliable” means of locating every node on the network. The 
list it produces may not include every node on the network be- 
cause some devices simply do not respond to NBP Lookups, while 
others may not respond if they are busy when the lookup message 

Chapter Fifteen Management and Troubleshooting 

arrives. When Inter»Poll is left to run long enough, and the 
“Unnamed Devices” option has been selected and added to the 
search list, you will usually see at least one entry (the unnamed 
socket number 4) for every active node on the network. 

-Select Zone(s);- 

Chicago, IL 




Total Zones: 5 

O nil Named Deuices 
(§) Deuices Matching: 




✓ Net 


Searching for AM Devices 
in Zone: New York, NY 

•Search Time:- 


□ Continuous 


-Select Sorttng:- 



(i) Rscending 
O Descending 


® Partial Match 

[ leaf 


ar \m 

[ Can< ei ) 

K )1 

Figure 15.4 

Apple's imei'Polluiiy. 

If the printer which could not be seen in the Chooser appears in 
lnter»PoU’s list, you can then test how long it takes to send a packet 
to the printer and back. Within lnter*Poll, this is accomplished by 
double-clicking on the line containing the name of the printer. A 
dialog box appears that enables you to send a request for the 
printer status; Inter»Poll displays the results of the test (see figure 
15.5). More importantly, you can send a series of echo packets (the 
AppleTalk Echo Protocol) to the printer, and Inter*Poll will report 
how long it took to return each one. Because NBP has a two- 
second timeout, if packets are lost or take longer Uian two seconds 
to return, the Chooser isn’t likely to display the printer in its device 
list. Notice that the display also tells you how many hops tlie reply 
message took to return to Inter* Poll. If the number of hops varies 
widely, the device may be too many router-hops away. 

Part Four Network Design, Implemenation, and Management 

Figure 15.5 

how long ii lakes to sent 
a packet loihegrinlei 
and back. 

Figure 15.6 

creates a logical network 


N*t:7097 Nod# : 158 

‘s L«s#rVrU#r - L*s#rVrit#i* - Ovol Offic# Zone 






— OEchoPkts 

Secs (i) Printer Status Packets 



s*cf O System Info Packets 

I( )l 

( Done ] 

Rovd: 8 Lost: 0 

Pockets Sent: un: 12 toui; 8 





Hops Av/eg 





DeUg (secs) 





[ Clear ] 


status ; idW 

Network Mapping Programs 

Another very helpful diagnostic tool are programs that draw a map 
of your network by interrogating devices actually on the network. 
LANsurveyor from Neon Software, and NetAdas from Farallon (see 
figure 15.6), are two Macintosh network mapping products. These 
programs can only create an accurate map if the information they 
receive from the network’s routers is correct. If a mapping program 
is unable to draw a map of your network, or if it produces some- 
thing very different than what you expected, you should determine 
the reason. This technique is often a useful diagnostic eiid. 

Chapter Fifteen Management and Troubleshooting 

Router Troubles 

As vve discussed in earlier chapters, routers play a ver>' important 
role in the operation of the Chooser, and in network performance 
in general. As the number of routers on a network increases, so 
does the challenge in tracing and diagnosing network problems. 

Remember that all routers must agree on the network number 
range and zones list configured on each router port. Every time a 
new router is added to an active network, there is a chance that it 
will conflict with the existing routers on the network. If this hap- 
pens, a product which allows you to examine the active configura- 
tion of any router on the network, such as Neon Software’s 
RouterCheck (see figure 15.8), can help you locate the source of the 
configuration conflict. RouterCheck can also notify you (either on 
screen or by text pager) whenever a trusted router experiences a 
network change, such as adding or dropping a routing table entry 
or zone. 

! Pacfcet #287 I 

FIo9S 0x80 902.3 

Statu*. 0x00 

Packet Length 64 
Tli*«*taftp 0.39:27.424 

Etrwfrn«t Heoder 

Ckij 1 1 nation 

LLC Length 

Drt t 

Source SftP: 



09:00 07 ffffifr 
08:00 90 01:73:47 





Phase 2 Broodcost 


LflftO PtW* Hooder - Datooroa DpI Ivtm f*rotoe«l 

Hop Count 
Datograe Length 
OOP Check sue 
Dest Heteork 
Sote^e heteork. 
Oest Mode 
Source Hode: 
Oest Socket 
Sois-ce Socket. 
OOP Type: 




253 0 255 


I RTrtP Socket 
I RThP Socket 
I RThP Response cr Data 

ftPPleTalk Brdcasl 

BTHP Pocket - Botitifwi Toiiie Wointenonce rrokocot 

Router's Met 


10 L*r>gth 


Router s liode 10 



RTWP Tuple «t 

RorKje St.TTt 


Range Flog; 





Ror^ie End 




RTI1P Tuple «2 

flci'ige Star*. 


Range Flog 





Range End 




BTRP Tuple «3 

lkrlxoi> l*ijfber 


Range Flog 


honex tended 



00 00 00 00 00 00 

Frane Check Sequence 0xd8o2ef4‘;1 


Figure 15.7 




Part Four Network Design, Implemenation, and Management 

Figure 15.8 

itoPeek capture Ola 
leniryRIMP packet. 
with tlie Shiva FastPaili 
louters and does not 
cause any ptoblems. 

Listen and Learn 

The most informative network diagnostic tools, sometimes called 
netivork analyzers or packet sniffers, enable you to examine the 
packets, or frames, that actually appear on the network. Until 
recently, all network analyzers were very expensive, single-purpose 
hardware instruments, beyond the budget of the typical manager 
of a small- to medium-sized network. 

Fortunately, there are now very good Macintosh-based network 
analyzers. These programs convert your ordinary Macintosh into a 
LocalTalk, Ethernet, or Token Ring network analyzer for a fraction 
of the cost of the dedicated instruments. NetMinder LocalTalk 
and NetMinder Ethernet are products of Neon Software; the AG 
Group’s network analyzers are LocalPeek, EtherPeek, and 

Chapter Fifteen Management and Troubleshooting 

TokenPeek. As their names imply, these products are Cabling 
layer- or DataLink layer-specific, and (unlike most Macintosh 
programs) they aren’t expected to work with every possible combi- 
nation of Macs and networking cards. These programs are topically 
designed to work with selected high-performance network cards 
and adapters. Confirm that the hardware requirements of the 
product match the configuration of the system you intend to use. 

A network analyzer is used to capture and examine the packets that 
are being sent over the netw'ork. This is the network equivalent of 
eavesdropping on someone else’s conversation, and we all know 
how revealing that can be. And yes, these analyzers can be used to 
read unencrypted data and perhaps learn passwords and other 
confidential information. Many applications use simple encoding 
schemes to avoid sending dear-text messages across network 
links, specifically to make reading packet contents a bit more 
difficult. This is one area where Apple’s Open Collaboration 
Environment will help. AOCE will provide a new encrypted trans- 
port protocol called Apple Secure Data Stream Protocol (ASDSP). 

A common problem when adding a new router is that the new 
router refuses to start, reporting a conflicting network range or 
zones list. Assuming that you’re sure you have configured the new 
router correctly, how can you determine the source of this conflict- 
ing information? 

If the network range is in conflict, you can simply capture the 
Routing Table Maintenance Packets (RTMP), as shown above in 
figure 15.8, and examine them for conflicting information. Every 
router broadcasts an RTMP packet every 10 seconds, so it 
shouldn’t take long to find the culprit’s physical hardware and 
logical protocol addresses. You can then use information from 
lnter»Poll, or use the hardware address, to identify the errant 
device. Simply rebooting the router may clear the problem, or it 
may be necessary to reconfigure it. 

Part Four Network Design, Implemenation, and Management 

Diagnosing Chooser Problems 

Consider a small EtherTalk network that has several Macs and a 
LaserWriter. Let’s look at what actually happens when you open 
the Chooser to select a LaserWriter. 

You may recall from Chapter 8, "Macintosh Transport: AppleTalk," 
that the Chooser loads its AppleTalk Zones window by using the 
Zone Information Protocol (ZIP) to request a list of the reachable 
zones from a local AppleTalk router. Wlien you click on tlie 
LaserWriter icon in the Chooser, it obtains the list of active printers 
in the selected zone by sending NBP Lookup messages to the 
selected zone. As NBP Response packets containing the names of 
currently active printers arrive, the printers’ names will be added 
to the list of names displayed on the right side of the Chooser. Let’s 
examine these Zone Information and Name Binding messages in 
detail to see exactly how they work. 

Figure 15.9 shows a trace (captured by NetMinder Ethernet) of all 
the messages in and out of a Macintosh as the Chooser was opened 
and the LaserWriter icon was subsequently selected. This trace is 
quite small because a filter was used to ignore all the other traffic 
that was present on the network at the same time. 

Figure 15.9 

Chooser iraflic as viewed 

Chapter Fifteen Management and Troubleshooting 

NetMinder has formatted the headers of the captured packets so 
we can easily see the address of the node sending the request 
(source), the address the message was sent to (destination), and 
the type of packet see figures 15.10 through 15.13). 

Packet 0 (figure 15.10) is a “GetZoneList” (6ZL) request, sent from 
node 1800.228 (the Macintosh) to node 1800.194 (an EtherTalk 

Figure 15.10 


lust 16 milliseconds later, the router sent Packet 1 (figure 15.1 1), a 
“ZoneInformationProtocolReply” (ZIPR), which contains the list of 
zones on this network. 

In this case, the entire list could not fit into one reply message (the 
reply contained 43 zones), so the node sent a second request 
asking for the next portion of the zone list, starting at number 44; 
this was Packet 2 (figure 15.12). 

Part Four Network Design, Implemenation, and Management 

Figure 15.11 


Pacitel I 

File Edit Search Options Filter Ullndoms nnoiysis 

NetMjnder6 Ethernet 


CED E 1 

10 3666 


1800.194 1600.228 



2 183 


1800.194 1800.228 


3 16 


1800.228 1800.194 


4 1616 


1800.194 1800.228 


5 0 


PppleJ5488d5 Rpple-d470f7 


6 0 


1800.228 1800.44 


7 1466 


1800.220 1800.228 


8 0 


1800.228 1800 44 



Total Packets 

266 Status Stopped 

Total Fittered 

0 Save File 

Total Errors 

0 Buffer Use 0% 

1 Buffered PMkats 



in Size; 602 

T <ndi>- 3603 (1/29/93 S 36:11 Pti 
Errors : Hone 

Ethornot Header 
OesUrMUon Opp I e.jd470f? 
Source C i seo_02797d 

Length $0248 

flTalk Phase 2 Header 

DSPP $oo 

ssnp $oa 

Control $03 

Protocol RTolk 

Long OOP Header 

Oest Het 
Sre Het 
Dest Mode 
Sre Node 
Dest Socket 
Sre Socket 

576 <Hops-0) 

3 <ffTP> 

RTP/ZIP Header 

CiKl/CntI $90 (TBesp EOM > 

BiMp/Seq $0 

TID $319 

Lost Flog 0 

Nua Zones 43 




Figure 15.12 


Packet 2 

File Edit Search Options Filter tilindoiiis Analysis 







1800. 194 

1800. 194 







1800 194 





1800. 194 



























NetMlndBr€' Ethernet 

mmm \asmm mumi \mmii 

1 12] Size: 64 

T <i»s)« 3866 <1/29/93 5:36:11 PH 
Errors: Hone 

Ethernet Header 
Destination Ciscoj02797d 
Source Rpple^47Qf7 

Length $00 Id 

nialk Phase 2 Header 

OSflP $oa 


Control $03 

Protocol fiTolk 

Long OOP Header 

Total Packets 




Total Filtered 


Save File 

Total Errors 


Buffer Use 


Buffered Packets 


Dest Het 
Sre Net 
Dest Hode 
_J Sre Node 
•n- Dest Socket 
Sre Socket 

21 (Kops-O) 


3 (ATP) 

RTP/ZIP Header 

Ced/CntI $40 (TPeq > 

B«op/Seq $ 1 

TIO $3ta 

Function GetZoneList 

Start Index 44 

The second reply from the router, Packet 3 (figure 15.13), con- 
tained 13 additional zones. At this point, the Chooser has enough 
information to display a complete zone list. 

Chapter Fifteen Management and Troubleshooting 

^ File Edit Search Options Filter lUindoun nnolysls 

NclMinder<) Ethernet 

mmm rnnm^ 





|[ irUr. j'.l-cfk 1 




1800 194 







1800 228 

1800. 194 




1800 19^^^ 





1600 194 

1800 228 












1800 44 






1800 228 





1800 228 

1800 44 


1 Total Packeia 

266 Status Stopped 

1 Total Filtered 

0 Save File 

1 Total Errors 

0 Buffer Use OS? 

1 Buffered Pockets 


T <iis>- 3883 (1/29/93 5:36 1 
Errors: None 









fllalk Phase 2 Head 









Long IIDP 

* Header 


172 <Hops-0> 



D«st Net 


Src Net 


Dost Node 


Src Node 


Oest Socket 


Src Socket 



3 <RTP) 

RTP/2IP Header 




Last FIo 9 
Nue Zones 

V30 <TR«sp EOtl > 


S3 In 



Figure 15.13 


A little more than a second later — 1.616 seconds, to be exact — 
when the user clicked on the LaserWriter icon, an NBP-BrRq (NBP 
Request) was sent to the router. This was Packet 4 (figure 15.14). 

Figure 15.14 

Packet 4. 

Part Four Network Design, Implemenation, and Management 

If the router is directly connected to a network in the target zone, it 
will broadcast an NBP Lookup message onto the network; all active 
LaserWriters will then send an NBP reply containing their names 
back to the Macintosh. This trace doesn’t show these broadcasts 
from the router, because for this example we have configured 
NetMinder Ethernet to capture only messages to and from the 
Macintosh running NetMinder. 

If the routing table in the router contains entries for distant net- 
works using the same zone name, it will fomard the NBP Request 
to those other networks, where a local router will convert the 
request to a broadcast message and send it out on any local 
network which is in the target zone. 

A LaserWriter on the local network (1800) has heard the router’s 
broadcast, and will now send a reply to the Mac. In order to send 
an NBP reply directly to the Mac, rather than back through the 
router, the LaserWriter must learn the correct physical hardware 
(that is, Ethernet) address to use to send a packet to the Mac’s 
logical protocol address (AppleTalk address 1800.228). 

Recall that the AppleTalk Address Resolution Protocol (AARP) is 
used to associate a node’s Ethernet address to its AppleTalk 
address. The information necessary to do this is kept in an Address 
Mapping Table (AMT) in every EtherTalk node. The LaserWriter 
checked its AMT and found that no entry exists for node 1800.228, 
so the LaserWriter broadcasts an AARP probe/request containing 
the Mac’s logical AppleTalk address. 

The Macintosh responded to the AARP request with the AARP reply 
(AARP-Rpl) shown in Packet 5 (figure 15.15). The LaserWriter 
added the information to its AMT and can now send EtherTalk 
NBP replies directly to the Macintosh. Packet 6 (figure 15.16) is the 
first of these. 

Chapter Fifteen Management and Troubleshooting 

Figure 15.15 


m FHe Edtl Search Options Filter llUndoiiis Analysis 

Netvilndei€» Etheinet 

I PacIcBt 6 I 



(cmcaa Iwinw iMSir 




I riarii 1 

81 za 

In’ki-' Ifia’.kfi 1 







1800 194 






1800 228 

1800. 194 





1800 194 






1800 228 

1800 194 





1800 194 
















1800 220 

1300 228 





1800 228 

1800 44 



1 Total Packets 

266 Status Stopped 

1 Total Fttlered 

0 Save Fite 

1 Total Errors 

0 Buffer Use OSS 

1 Buffered Packets 




RTolk Phoao 2 Header 

OSAP too 

S6AP iaa 

Corilrol 103 

Protocol RTolk 

Long DDP Header 

Oast Mat 
Src Mat 
Oast Moda 
Src Moda 
Oast Sockat 
Src Socket 

64 (Hops«0> 

2 ««P> 

HBP Header 
Control S3 (LkUp-naoly) 

Tupla Count 



HBP Tuplea 


la 44 

kat 128 

e II 

Rppla fttO <I8/60U> (L-18) 
« LosarUritar <L>1I> 
m MV Rppla RtO <L-I2> 

Rgure 15.16 


The NBP request and reply packets will continue as long as the 
Chooser remains open on the Macintosh. Under System 7, the 

Part Four Network Design, Implemenation, and Management 

longer the Chooser remains open, the less frequent the NBP 
request will be sent, eventually dropping to just one every thirty 

With a packet-level view of the network, and perhaps a trace of a 
normal example to compare against, you can often determine if a 
problem is caused by the Macintosh, a router that isn’t doing what 
its supposed to, or a device which isn’t responding as it should. If 
the printer doesn’t send the NBP reply, then the printer is obvi- 
ously the problem. If a router doesn’t send a zone list when the 
Mac requests one, then the router is the problem. In cases where 
the problem conversation crosses networks or zones, it may be 
necessary to trace the messages at each end (or even on each 
network along the way) in order to get a complete picture of what 
is happening. 


Network performance is a complex equation consisting of many 
variables. Some of these variables, such as bandwidth, are easy to 
quantify. Other variables, such as traffic, are more ambiguous. 
Networks are dynamic, unpredictable, complex systems. Optimiz- 
ing their performance requires a basic understanding of the 
underlying theory, access to traffic monitoring tools, and the 
ability to interpret — and act upon — test results. 

The Real Meaning of Bandwidth 

Everyone wants his computer to operate as quickly as possible. 

As described in previous chapters, Ethernet is not faster than 
LocalTalk at the physical level. All signals travel at nearly the speed 
of light. But not all network interfaces send and receive signals at 
the same speed. How can both of these statements be true? 

Chapter Fifteen Management and Troubleshooting 

Ethernet hardware can create and detect a single electrical state 
change (corresponding to a binary digit) in l/40th the time of 
LocalTalk. So an Ethernet can carry 40 times more information 
than LocalTalk in a given period of time. But a single Macintosh on 
Ethernet typically communicates only three or five times faster 
than on LocalTalk. Why this discrepancy? It’s because the 
Macintosh cannot send and receive data at Ethernet’s maximum 
rate. The most important performance benefit of Ethernet over 
LocalTalk is that, because each bit can be sent (and received) so 
quickly, the cable is much more likely to be idle at the moment 
your computer needs to use it, even with many more nodes on the 

Traffic Jams 

How can you tell if network traffic levels are affecting user perfor- 
mance? A relatively easy way is to use a neUvork analyzer such as 
EtherPeek or NetMinder to trace the signals on the network. After 
collecting a sample of all the traffic on your netv\'ork, these pro- 
grams will tell you exactly how busy your network really was at that 


It’s a good idea to do this occasionally when the network is operating 
normally, so as to obtain benchmarks of your normal network state. 

Another technique is to install specialized devices that listen to the 
traffic on the network and count how many packets and bytes were 
sent from each node on the network, and to what destination. 
Dayna sells specialized pods that can be connected to a segment in 
order to monitor the traffic levels. The pod can be queried by a 
program called Network Vital Signs, which uses the data reported 
by the pods to provide information about the monitored network. 

Part Four Network Design, Implemenation, and Management 

Any network which shows a high utilization is likely to force nodes 
to wait to send data often enough to affect performance. In many 
cases, network traffic may be high only a few times throughout the 
day. By learning as much as possible about these traffic peaks, you 
may be able to distribute or isolate these demands and avoid 
paying for expensive network upgrades. 

Analysis of the trace may show that the majority of the traffic is 
caused by just a few nodes that talk to each other constantly. In 
this case, moving these top talkers to their own network may bring 
performance back to acceptable levels for everyone. 

Another means to monitor network utilization by individual nodes 
is to have each device keep track of how much data they transfer 
and to report the information, upon request, to a central station 
that compiles information from many nodes to create an over-all 
picture of the network’s utilization. SNMP management stations 
can poll SNMP managed nodes regularly throughout the day and 
compile this information into a time-line analysis of network 

Traffic Cops 

On LocalTalk, adding a router between the section with the top 
talkers and the rest of the network is the most common way to 
prevent the traffic between certain nodes from delaying traffic 
among the other nodes. As an alternative, traffic can be isolated by 
adding a LocalTalk switch or bridge, such as Tribe’s LocalSwitch, 
that dynamically connects multiple LocalTalk segments only when 
the source and destination of a particular packet requires it. Tribe 
recently announced a new product called TribeStar. It has eight 
bridged LocalTalk ports and one Ethernet port. 

On Ethernet and Token Ring networks, link-layer bridges can also 
be used to isolate traffic within limited portions of the netw'ork. 
Chapter 5, “Common Network Components,” described how an 

Chapter Fifteen Management and Troubleshooting 

Ethernet bridge examines the source and destination of tlie physi- 
cal hardware addresses on every packet it hears on each port and 
maintains a table of known addresses that have been heard on 
each port. Wlien the bridge receives a packet on one port, it will 
resend it on the other port unless the destination address is known 
to be on the same port as the sender. In this case, the bridge does 
not transmit the packet on the other port, and the traffic level on 
the rest of the Etliernet is reduced. 

Traffic levels across the entire Ethernet can be significantly re- 
duced by moving top-talking pairs onto the same side of strategi- 
cally placed bridges. Afterwards, the node’s connectivity to the rest 
of the Ethernet will be unchanged. Wlienever a packet’s destina- 
tion address is on the other side of the bridge, it will be sent. In 
effect, the bridge is an imdsible gate that allows packets to pass 
through only on a need-to-go basis. 

It is sometimes possible to achieve utilization of 200% to 300% of 
Ethernet’s total bandwidth through the intelligent installation of 
Ethernet bridges (see figure 15.17). 

Hgure 15.17 

Ethernet bridoes. 

Consider the network diagram in figure 15.17. The three pairs of 
nodes. A, B, and C, each consume up to 40% of the Ethernet 
bandwidth communicating with each other, and up to 10% com- 
municating with all the other nodes on the network. Without 
bridges, this Ethernet would experience peak demands of 150% of 
the available bandwidth. But, by adding two bridges in tlie appro- 
priate places, no single section will ever see a demand higher 
that 60%. 

Part Four Network Design, Implemenation, and Management 

In Token Ring environments, Source Routing Bridges (SRBs) 
provide a similar opportunity to isolate high volume conversations 
onto their own ring. Unlike Ethernet bridges, SRBs are not entirely 
invisible at the link level. Their presence requires some additional 
overhead because ring-to-ring routing information must be added 
to every packet. But SRBs are invisible at the AppleTalk protocol 
level, so they can provide some traffic isolation which is invisible to 
the user. 

Another possible source of performance problems are the routers. 
As inter-network traffic grows, the routers will become unable to 
keep up with the demand. Most routers keep simple counters of 
how many packets are sent and received, and how many were 
ignored or discarded due to various errors. 

Figure 15.18 shows a statistic screen from an Apple Internet 
Router, running on a Macintosh Ilci. The counters indicate that 
this router is very lightly loaded, but the Recent Network Error Rate 
is extremely high; the Network Reliability is only 63.4%. Notice that 
the error counter Local Net Setup Conflicts is already 22 on the 
Ethernet port. This indicates that there is a router with a conflicting 
configuration on the Ethernet. Eliminating the conflict will reduce 
the Error Rate and Network Reliability will begin to improve. 

Figure 15.18 

Houier Errors. 

Port Statistics for Router Mo 

Packet) Routed: 

38 Network Reliability: 


Recent Activitg Rate: 

1 1 1 j i 1 1 1 1 1 1 1 1 1 1 Recent Network Error Rate; 




Low High 

Statistics last reset at: Sat, Jan 30, 1 993 

10; 12 PM 







Packets In 




Packets Out 




Name Requests In 




Name Lookups Out 




Data Link Errors 




Packet Buffer Overflow 




Unknown Network 




Hop Count Exceeded 




Routi ng Table Overflow 




Local Net Setup Conflicts 




Remote Net Range Conflicts 




Router Version Mismatch 




±1 11 

* 2 ] 

Chapter Fifteen Management and Troubleshooting 

One way to determine the source of these conflicts is to capture all 
the RTMP and ZIP packets on the segment for a few minutes. By 
examining the RTMPs sent by each router, the one sending a 
conflicting Network Range can be identified. By examining the 
Zone Information Protocol (ZIP) messages, a router sending a 
different zones list can be identified. 

On an AppleTalk network, security is primarily the responsibility 
of the individual devices. AppleTalk File Sharing and AppleTalk 
Remote Access use the "Users & Groups” file to manage access to a 
node. AppleShare servers have a more advanced version of the 
same scheme. At the other end of the spectrum, Apple Laser- 
Writers (PAP servers) don’t restrict network access at all. 

Some network devices also support additional forms of security, 
restricting what network services can be seen by a particular node. 
AppleTalk Remote Access can be configured to grant access to 
“just this node” or the entire network. Some routers can be config- 
ured to hide or show any device, or entire class of devices (for 
example “Joe’s AppleShare” or “All LaserPrinters”) based on the 
identity of the node seeking the device. Routers from Compatible 
Systems do this by forwarding NBP messages to and from your 
node only if you’ve properly identified yourself to the router and if 
the router’s manager has granted permission for your node to 
communicate with the device (or device type) of interest. 

A similar scheme is utilized by several non-Macintosh AppleTalk 
Remote Access products. One is AsyncServeR, a software ARA 
server for VAX/VMS, that supports individualized network access 
profiles for each dial-in connection account; anodier is the Shiva 
LanRover family of dedicated ARA servers. 

Part Four Network Design, Implemenation, and Management 

A few high-end routers, such as those from Cisco, can be config- 
ured to perform true zone hiding. In this case, the router hides 
zones from all die other routers on the network. Over wide-area 
connections, this feature can be used to limit Chicago’s view of 
Denver’s network to a single zone, rather than the thirty-five zones 
that actually exist in Denver. Instituting a limited view of remote 
networks can be useful in controlling which devices at one site can 
communicate with devices in other sites. It can also be used in very 
large networks to simply reduce the number of zones in the 
Chooser to a more manageable number. 

These schemes have one significant limitation. When a router 
provides the security, only connections that come through the 
router can be controlled. Access attempts originating within the 
local network remain uncontrolled and unrestricted. 

A security feature of AOCE (Apple Open Collaboradon Environ- 
ment) will provide an AppleTalk network-wide access control 
mechanism. AOCE allows a network administrator to grant or deny 
access to a network device (or type) for an individual user, or group 
of users. 


If you manage an AppleTalk network, there is no substitute for 
understanding AppleTalk, but there are quite a few tools that, 
when used together, can help reveal many of AppleTalk’s secrets to 
you. This chapter has described only a small pordon of them. 

The Future of 



ne goal of this book was to give the reader a “gut- 
level" understanding of the theories, compo- 
nents, and implementation details involved with 
Macintosh networking. Hopefully, as new 
services, formats, transports, and cabling sys- 
tems come along, you'll be better equipped to 
lentify, classify, and evaluate their suitability for 
your networking environment. 

Actually, it seems as if each week brings new networking tech- 
nologies. While it’s hard to predict the future, some trends in 
Macintosh networking are likely to continue. 

One such trend is wireless networking. You should expect an 
explosion in this technology over the next few years. This growth 
should occur throughout all the various wireless technologies — 
cellular, radio waves, and infrared. These technologies should 
primarily affect the implementation of local-area networks and 
remote users. 


Part Four Network Design, Implementation, and Management 

Another area to watch in the near future is the continued enhance- 
ment of the AppleTalk protocol stack. It’s been widely discussed by 
Apple, and in the press, that the AppleTalk Remote Access Protocol 
will be enhanced to work over the Point-to-Point Protocol (PPP). 
This will have the effect of lowering the cost and enhancing the 
performance of dial-up access. Other AppleTalk changes are likely 
to affect the routing aspects of the protocol. The newly released 
AURP routing protocol is likely to undergo continued updates; 
there’s even talk that Apple will adopt more sophisticated routing 
algorithms such as the OSPF (Open Shortest Path First) protocol. 

It’s also likely that Apple will continue the enhancement of 
AppleTalk by making some of the traditional AppleTalk services, 
such as AFP and PAP, protocol-independent. Perhaps not too far in 
the distant future, you will be able to access these services over the 
TCP/IP protocol stack instead of the AppleTalk stack. 

Even the Macintosh-compatible cabling systems are likely to 
evolve over the years. One obvious change is that Apple’s inclusion 
of Etliernet is likely to extend further down the product line into 
the midrange, and perhaps even into the low-end systems as well. 
As Ethernet finds its way into the mainstream product lines, expect 
high-bandwidth replacements for Ethernet to appear. At the 
moment, it’s somewhat unclear which of the new high-speed 
technologies — either FDDI/CDDl or 100 Mbps Ethernet — is likely 
to become the dominant LAN cabling system. In either case, the 
cost is likely to plunge as economies of scale are applied. 

All in all, when it comes to networking, Apple’s in an extremely 
strong position for the future. At every layer, Apple has continued 
to innovate. At the Service layer, Apple has pioneered dynamic 
service acquisition and continues to provide world-class services. 
The two most recent examples of this are Publish and Subscribe 
and AOCE. At the Format layer, Apple has acknowledged the 
importance of format transportability with the Clipboard, XTND, 

Chapter Sixteen The Future of Macintosh Networking 

and EasyOpen. Apple’s attention to the Transport layer is well 
known. From AppleTalk’s dynamic addressing to MacTCP’s 
integration, Apple consistendy provides transport excellence. Even 
at the Cabling layer, Apple continues to provide innovation, with 
LocalTalk, Ethernet, and with various v\ireless technologies. 

Glossary of 

O n the following section, you might notice the 

icons beside many of the definitions. The icons 
are representations of the four layers of the 
NetPlCT model: 

Services layer 

Formats layer 

Protocol layer 

Cabling layer 

Each icon indicates the layer of the NetPICT model to which the 
defined term belongs. Using these icons, you can easily determine 
where each term fits in the networking universe. If a term can be 
specifically placed within the seven-layer OSl Reference model, 
then its OSI layer is indicated within the definition. 

Live Wired 

lOBase-2 An Ethernet implementation that uses a thin 
coaxial cable. lOBase-2, like other Ethernet implementa- 
tions, has a bandwidth of 10 Mbps. The maximum cable segment 
length is 185 meters. 

lOBase-5 The original Ethernet medium, lOBase-5 uses a 
heavy shielded coaxial cable. The cable has an approxi- 
mate diameter of 3/8", It has a bandwidth of 10 Mbps. The maxi- 
mum segment length is 500 meters. 

lOBase-T An implementation of the Ethernet standard 
that runs over two pairs of unshielded twisted-pair 
wiring. Like the other Ethernet implementations, lOBase-T has a 
bandwidth of 10Mbps. The maximum segment length from the 
hub to the device is 100 meters. 

802.3 An IEEE standard that defines the CSMA/CD 
(Carrier Sense Multiple Access/Collision Detection) 
method of network access. CSMA/CD is used by Ethernet net- 

802.5 An IEEE standard that defines the Token Ring 
network access metliod. 


AARP See AppleTalk Address Resolution Protocol. 
AAUI See Apple Attachment Unit Interface. 

access privileges Controls placed upon network services 
that limit and control user access. 

Glossary of Networking Terminology 

active star A network with a multiport repeater at die 
center. Each device connects to the repeater. Active stars 
do not perform network addressing — network packets seen on one 
branch of the star are seen on all branches. 

address A sequence of bits used to identify devices on a network. 
Each network device must have a unique address. Addresses fall in 
two categories: physical hardware addresses (Ethernet), and logical 
protocol addresses (AppleTalk). 

Address Mapping Table (AMT) A table that 
associates physical hardware addresses with 
corresponding logical protocol addresses. In the case of AppleTalk, 
the AMT is updated and maintained by the AppleTalk Address 
Resolution Protocol (AARP). 

address resolution The association of physictil 
hardware addresses (Ethernet) with logical 
protocol addresses (AppleTalk). See also Address Mapping Table. 

Address Resolution Protocol (ARP) A TCP/IP 
protocol used to map logical IP addresses onto 
physical hardware addresses (Ethernet). Similar to Apple’s AARP. 

ADSP See AppleTalk Data Stream Protocol. 

AEP See AppleTalk Echo Protocol. 

AFP See AppleTalk Filing Protocol. 

amplitude The magnitude of an electrical signal. Measured by 
subtracting the minimum voltage from the maximum voltage of an 
electrical signal. 

AMT See Address Mapping Table. 

Live Wired 

analog A method of data transmission where (unlike digital 
transmissions) the data is continually modulated over an infinite 
voltage range. 

Apple Attachment Unit Interface (AAUI) Apple’s physi- 
cal Ethernet interface. AAUI uses a special connector 
and uses an external transceiver, either thickwire, thinwire, or 
twisted pair, to connect to the network. 

AppleShare file server A Macintosh product from Apple 
that runs the AppleTalk Filing Protocol (AFP). 

AppleTalk Apple’s networking software that provides reliable 
delivery of data between clients and servers. There are implemen- 
tations of AppleTalk on many different computers. 

I AppleTalk address A three-part number that uniquely 
identifies a particular network, node, and socket on an 
AppleTalk network. 

AppleTalk Address Resolution Protocol (AARP) 
Apple’s protocol that maps the logical 
AppleTalk node addresses to the physical hardware addresses. 

I AppleTalk Data Stream Protocol (ADSP) A connection- 
oriented Session layer protocol that provides a reliable, 
bi-directional stream of data between two sockets in an AppleTalk 

AppleTalk Echo Protocol (AEP) An AppleTalk Transport 
layer protocol that enables a node to send a special packet 
to another node and to receive an echoed response in return. Used 
to determine round-trip delivery times and reachability. 

Glossary' of Networking Terminology 

AppleTalk Filing Protocol (AFP) The AppleTalk Presen- 
tation layer protocol that defines shared file access. 
Platform-independent, AFP is the basis for Apple’s AppleShare 

AppleTalk for VMS An implementation of the AppleTalk network 
protocol suite that runs on a DEC VAX under the VMS operating 
system. It essentially turns a VAX into an AppleTalk node. Applica- 
tion services, such as the VAXshare file server, are seen as 
AppleTalk sockets. 

I AppleTalk Session Protocol (ASP) An AppleTalk Session 
layer protocol that provides for the creation of a network 
session. It also keeps the communications in the proper sequence. 

AppleTalk Transaction Protocol (ATP) An AppleTalk 
Transport layer protocol that manages the give and take 
of a network transaction. 

AppleTalk-LAT connection tool ACTB (Communications 
Tool Box) tool that is used in conjunction with the 
AppleTalk-LAT Gateway. It passes AppleTalk protocols to the 
gateway, where they are then converted into DEC’S LAT protocol. 
Used to access LAT terminal services over LocalTalk or AppleTalk 
Remote Access sessions. 

AppleTalk-LAT Gateway A software gateway that runs on 
a Macintosh and is used to translate AppleTalk protocols 
into LAT protocols. The AppleTalk-LAT Gateway is part of DEC’S 
PATHWORKS for Macintosh product. 

AppleTalk/DECnet Transport Gateway A software 
gateway that is included with AppleTalk for VMS. It 
provides Mac users with access to DECnet-based applications, 
such as E-mail and DECwindows. 

Live Wired 

Application layer The topmost layer of the ISO's OSI 
Reference Model; it corresponds to the Service layer of 
the NetPICT model. It defines the protocols and connections for 
applications. See OSI Reference Model. 

ARCNET Originally developed by Datapoint Corpora- 
tion, ARCNET (which stands for Attached Resource 
Computer NETwork) is a popular LAN in the IBM PC world. 
ARCNET uses a token-passing scheme and runs on coaxial or 
twisted-pair wiring. Several vendors make ARCNET cards for the 

ARP See Address Resolution Protocol. 

ASCII ASCII (which stands for American Standard Code 
for Information Interchange) is a commonly used coding 
scheme that uses 8 bits of data to encode alphanumeric characters 
and special control characters. In many ways, ASCII text files are a 
common denominator among many computers and programs. 

ASP See AppleTalk Session Protocol. 

Asynchronous communication (Also known as async 
communication.) A technique of data transmission that 
sends one character at a time without waiting for an acknowledg- 

ATP See AppleTalk Transaction Protocol. 

attenuation The loss or diminution of an electrical 
signal that occurs during transmission. 

AWG AWG (which stands for American Wire Gauge) is 
the US standard for specifying the diameter of a wire 


Glossary' of Networking Terminology' 

backbone network A network topology where devices 
connect to a single cable. Thickwire Ethernet networks 
are commonly used as backbone networks. 

bandwidth The total message-carry'ing capacity of a 
medium. Bandwidth is typically measured in bits per 
second. It is not an indication of speed. 

baseband A kind of network transmission that uses the 
entire bandwidth of a medium to transmit a signal. 
Baseband communications are commonly used by most LAN 
cabling systems, such as LocalTalk, Ethernet, and Token Ring. 

bits per second (bps) A unit that measures the message-carrying 
capacity of a medium. A kilobit per second (Kbps) is one thousand 
bits per second; a megabit per second (Mbps) is one million bits 
per second. 

bps See bits per second. 

bridge A network device used to connect two netw'orks 
at the Data Link layer. Bridges are essentially unaware of 
the logical protocol address, although some bridges can block 
protocols by filtering their type codes. 

broadband A kind of network transmission that splits 
the bandwidth of a medium to support multiple chan- 
nels of communication. This technique is used by cable television. 

broadcast transmission A network transmission that is 
sent to ail network devices. 

Live Wired 

brouter A network device that routes the 
routable protocols and bridges the non- 
routable protocols. It essentially merges the functionality of 
bridges and routers. 

bus A common network segment. Network devices 
connect to the same segment. See backbone network. 

bus topology A network scheme that uses a single cable 
to connect devices. Unlike ring topologies, the cable 
does not connect to itself. See backbone network. 


Carrier Sense Multiple Access with Collision Avoidance 
(CSMA/CA) A cable access technique used by LocalTalk. 
Devices listen for the presence of a carrier before transmitting. 
Nodes try to avoid collisions by backing off for a random period 
of time whenever a message is not successfully transmitted. 
LocalTalk doesn’t have the detection and recovery circuitry found 
in CSMA/CD networks. 

Carrier Sense Multiple Access with Collision Detection 
(CSMA/CD) A cable access technique used by Ethernet 
that allows devices to gain access to a transmission medium by 
listening for the presence of a carrier. If no carrier is detected, the 
data is transmitted. Each node is capable of detecting collisions 
and retransmitting as required. 

cheapernet A slang term describing thinwire (lOBase-2) 

Chooser The Macintosh desk accessory used to select 
AppleTalk (and other) services. 

Glossary of Networking Terminology 

client A client is a process or entity that employs the 
services of other processes or entities knowoi as servers. 
For example, a Macintosh uses AFP client software to access AFP 

client/server A term given to the interaction of software 
processes that function in a cooperative manner. Clients 
make requests of servers. 

coax See coaxial cable. 

coaxial cable A cable that contains two conductors, one 
inside the other. Coaxial cables, sometimes called coax, 
are used in thickwire and thinwire Ethernet and in IBM terminal 

collision The condition that results when two network 
devices transmit at nearly the same lime. The transmis- 
sions collide, rendering the message unusable. 

Control Panel A Macintosh utility that enables you to 
change various aspects of the Macintosh. The Netw'ork 
control panel is used to select from different network data links. 
This is where the cabling choice (such as EtherTalk, LocalTalk, 
TokenTalk, or FDDITalk) is made. 

CSMA/CA See Carrier Sense Multiple Access with Collision 

CSMA/CD See Carrier Sense Multiple Access with Collision 

Live Wired 


Data Link layer The second layer from the bottom of the 
OSI Reference Model. The Data Link layer corresponds 
to the top half of the Cabling layer of the NetPICT model. The Data 
Link layer defines the protocols that manage the creation of 
network frames, such as LLAP (LocalTalk Link Access Protocol). 
See OSI Reference Model. 

I datagram A packet of data, unique to a specific protocol. 
Datagrams are placed within network frames for delivery 
over the network. With AppleTalk, the Datagram Delivery Protocol 
(DDP) is used to encapsulate higher-level AppleTalk protocols 
within an addressable unit. 

Datagram Delivery Protocol (DDP) The Network layer 
protocol that provides the ultimate addressing of 
AppleTalk datagrams (network, node, socket) over an AppleTalk 

DECnet A suite of networking protocols developed by 
Digital Equipment Corporation for use on VAX/VMS, 
PDP-11, PCs, and other computers. Versions of DECnet are avail- 
able for the Mac from Digital and Thursby Software Systems. 

DECnet tunnel A technique used by AppleTalk for VMS 
and DECnet, which encapsulates AppleTalk datagrams 
within DECnet packets for delivery over a DECnet link. 

default zone The AppleTalk zone that a device belongs to 
by default when it’s placed on an extended (Phase 2) 
network. The default zone of a Mac can be changed by double- 
clicking on the current network icon in the Network Control Panel. 

Glossary of Networking Terminology 

dynamic node addressing A technique Apple uses 
whereby AppleTalk nodes automatically pick unique 
network addresses. This is in direct contrast to other protocols, 
such as DECnet, that maintain a listing of node addresses for each 


EBCDIC EBCDIC (which stands for Extended Binary 
Coded Decimal Interchange Code) is a coding system that 
uses 8 bits of data to represent alphanumeric characters and 
control sequences. Used by IBM mainframes. 

ELAP See EtherTalk Link Access Protocol. 

emulation See terminal emulation. 

entity type The part of an NVE (Network Visible Entity) 
that identifies the generic class to which the entity be- 
longs. Examples include "AFPServer" or “LaserWriter." The entity 
type is assigned by Apple Computer, who maintains a registry. 

Ethernet A LAN cabling system originally developed by 
Xerox, Intel, and Digital. Ethernet has a bandwidth of 
10Mbps and uses the CSMA/CD access method. Ethernet supports 
many different networking protocols, including AppleTalk. 

EtherTalk Apple’s implementation of AppleTalk proto- 
cols on Ethernet. EtherTalk places the DDP datagrams 
into Ethernet frames. 

EtherTalk Line Access Protocol (ELAP) The specific data 
link protocol used by EtherTalk. 

Live Wired 

FDDI FDDI (which stands for Fiber Distributed Data 
Interface) is a 100 Mbps LAN technology' that uses a 
token-passing access method. FDDI uses dual fiber-optic rings. 
There are several FDDI cards available for the Macintosh. A 
variation of FDDI that uses copper wiring, called CDDI, is currently 
under development. 

file server Software that provides network users with 
shared, controlled access to files. In the Macintosh 
environment, the standard for file service is the AFP file server. 

File Transfer Protocol (Fl'P) A Service layer protocol 
common in the TCP/IP world. It is used to copy files 
between network devices. 

frame A data link structure for conveying information 
over a transmission medium. 

frequency The number of times in a unit of time (usually a second) 
that a signal cycles between minimum and maximum voltage. 

FTP See File Transfer Protocol. 

gateway A device (or software process) that translates entire 
protocol stacks. 

Glossaty of Networking Terminology 

half-router A pair of routers connected with a communi- 
cation link. This tandem acts as a single routing device. 
AppleTalk half-routers require unique network numbers on each 

hardware address The unique physical address deter- 
mined at the Physical and Data Link layers. For example, 
each Ethernet card has a unique hardware address that's stored 
within the card. 

hop A unit of distance that measures the passage of a 
datagram through a router. The distance between net- 
works is often measured by tlie number of hops. 

hop count The number of routers that a datagram travels 
through on the way to its destination. AppleTalk permits a 
maximum of 15 hops, although hop count adjustment can be used 
to provide routing flexibility. 

International Standards Organization (ISO) An international 
standards-making body responsible for numerous standards, 
including film speed and the OSI Reference Model. 

internet The term applied to multiple AppleTalk networks that are 
connected by AppleTalk routers. Also called an internetwork. 

internet router (IR) A device that connects AppleTalk 
networks by using network numbering to pass, or deny 
passage of a datagram. 

Live Wired 

Internet Protocol (IP) The Network layer protocol of the 
TCP/IP protocol suite. Analogous to Apple’s DDP. 

Internetwork Packet Exchange (IPX) A Network layer 
protocol used by Novell NetWare that provides address- 
ing, routing, and switching packets. 

IP See Internet Protocol. 

IPX See Internetwork Packet Exchange. 

IR See internet router. 

ISDN ISDN (which stands for Integrated Services Digital 
Network) is a digital communications standard that 
integrates voice and data. ISDN services are just beginning to 
become common in the US. It offers the promise of affordable 
high-speed WAN communications. 

ISO See International Standards Organization. 


Kbps Kilobits per second. See bits per second. 

LAN See Local Area Network. 
LAP See Link Access Protocol. 

LLAP See LocalTalk Link Access Protocol. 

Glossary of Networking Terminology 

Local Area Network (LAN) A network in one area, such as 
a building or a group of buildings. 

Local Area Transport (LAT) DEC’S proprietary, licensed Ethernet 
protocol, used to connect terminal devices to host computers. 
Macs can speak the LAT protocol directly with the LAT Communi- 
cations Tool. At the present time, LAT’s use is limited to terminal 
emulators and terminal front-ends. 

LocalTalk Apple’s low-cost LAN network that runs over 
twisted-pair wiring. LocalTalk has a bandwidth of 
230,400 bps (230.4 Kbps). 

LocalTalk Link Access Protocol (LLAP) The Data Link 
level protocol that manages the delivery of data on a 
LocalTalk network. 

Management Information Base (MIB) A database used 
by SNMP for maintaining the status and control for a 
netw'ork device. Each network device has its own specific MIB. 

Data within the MIB is used by an SNMP agent as part of a network 
management application. AppleTalk MIBs have been recently 
defined by Apple and are currently being implemented by most 
AppleTalk networking vendors. 

Mbps Megabits per second. See bits per second. 

MIB See Management Information Base. 

live Wired 

modem A device that converts digital data from a computer into 
analog data, which can then be transmitted over a telephone line. 
This process is called modulation. It also performs the opposite 
process, demodulation, to convert incoming analog signals into 
digital data that the computer can understand. 

multicasting Multicasting is similar to broadcasting, but 
it provides a protocol-specific method of identifying 
netw'ork devices. Each protocol, such as AppleTalk, has its own 
multicast address. 


Name Binding Protocol (NBP) The AppleTalk Transport 
level protocol that maps the NVE onto the corresponding 
AppleTalk address. NBP provides AppleTalk with a way to dynami- 
cally find named services on the network. 

NBP See Name Binding Protocol. 

Network File System (NFS) A Presentation layer protocol 
developed by Sun Microsystems to provide TCP/IP 
networks with file sendees. NFS is similar in scope to Apple’s AFP. 

Network interface controller (NIC) A networking card, 
such as an Ethernet, Token Ring or FDDI, for a 

Network layer The layer of the OSI Reference Model that 
controls network addressing. The Network layer corre- 
sponds to the bottom third of the Protocol layer of the NetPICT 
model. With AppleTalk, the Network layer is defined by DDP. IP is 
the Network layer for TCP/ IP networks. 

Glossary of Networking Terminology 

network number A 16-bit number used to identify the 
AppleTalk network to which a node is assigned. Nodes 
choose their network number from an AppleTalk router; when no 
router is present they choose a number from a pre-defined range 
known as the startup range. 

network number range A range of network numbers that 
have been established within the routers for use on Phase 
2 extended network segments. Non-extended networks, such as 
LocalTalk, are restricted to single network numbers. 

Network- Visible Entity (NVE) An AppleTalk concept that 
names devices by their name, generic type, and zone. 
Examples include “My Mac:Macintosh Quadra 950@BlueZone” 
and “Joe’s Printer:LaserWriter@NYC Zone.” 

NFS See Network File System. 

node An addressable entity on a network, such as a Mac 
or a LaserWriter. 

node identifier (node ID) An 8-bit number that uniquely 
identifies each node on a single AppleTalk network 


non-extended network An AppleTalk network that supports 
addressing of up to 254 nodes and supports only one zone. A 
LocalTalk network is an example of a non-extended network. 

NVE See Network- Visible Entity. 

Live Wired 


OSl Reference Model A model put forward by the International 
Standards Organization (ISO) that provides a standard point of 
reference for networking protocols. It uses seven layers to break 
down die network process into independent processes. (OSI 
stands for Open Systems Interconnection). 

packet An organized sequence of binary data that includes data 
and control structures. 

PAP See Printer Access Protocol. 

passive star A network topology where every branch is 
connected to a common point. Unlike active stars, 
passive stars have no repeater at the center to actively retransmit 

peer A network device that is treated as the communicative equal 
to another device on the network. Networks that let devices 
communicate with each other as equals are sometimes referred to 
as peer-to-peer networks. 

Physical layer The level at which the actual delivery 
medium is realized. For example, the three different 
kinds of Ethernet and two different kinds of Token Ring cable are 
defined in this layer. The Physical layer of the OSI reference model 
corresponds to the bottom half of the Cabling layer of the NetPICT 

Glossary of Networking Terminology 

Point-to-Point Protocol (PPP) A protocol that supplants 
the Serial Line Internet Protocol (SLIP). It provides remote 
access to IP networks via asynchronous and synchronous links. It 
is similar to Apple’s Remote Access Protocol. There is some discus- 
sion that PPP might be adapted to provide remote AppleTalk 
protocol access. 

port The connection between a router and a network. 
Routers can have multiple ports. 

PPP See Point-to-Point Protocol. 

Presentation layer The layer of the OSl Reference Model 
that establishes data formats and requisite conversions. 
The Presentation layer corresponds to the Format layer of the 
NetPICT model. 

print spooler A service that queues print jobs and 
manages the submission of these jobs to the printer. This 
relieves the client workstation from this task. 

Printer Access Protocol (PAP) The AppleTalk protocol 
that controls the communication between clients (Macs) 
and print servers (LaserWriters). 

protocol A set of rules for information exchange over a 
communication medium. The set of protocols used by a 
particular networking protocol, such as AppleTalk, is called a 
family or suite of protocols. 

protocol stack (or suite) An implementation of a specific 
networking protocol consisting of multiple individual 

Liue Wired 

punchdown block A wiring device used in telephone 
and network installations for interconnecting many 
wires. Most phone- type punchdown blocks have fifty rows of four 
contacts each. The contacts accept the wires, which are “punched 
down,” to make electrical contact. A tool, called a punchdown tool, 
is used to push the wire onto the contact. 


repeater A network device that repeats the signals on a 
network. Repeaters operate at the Physical layer of the 
OSI Reference Model. Repeaters amplify weak signals from one 
segment and repeat them on another segment. 

ring topology A network organization in which all the 
nodes are connected in a ring. Data passes around tlie 
ring from node to node. Each node retransmits the messages to the 
next node in the ring. 

RIP See Routing Information Protocol. 

router A network device diat connects networks by 
maintaining logical protocol information for each 


Routing Information Protocol (RIP) A protocol used to 
update routing tables on TCP/IP networks. Similar to 
Apple's RTMP. 

routing table A table, maintained by an AppleTalk router, 
that maps the AppleTalk internet by specifying the path 
and distance (in hops) between itself and the networks. Routers 
use these tables to determine whether or not a datagram should be 

Glossary of Networking Terminology 

Routing Table Maintenance Protocol (RTMP) An 
AppleTalk protocol used by the routers to establish and 
maintain the routing tables used by the AppleTalk routers on the 
network. RTMP packets are sent at regular intervals by the routers. 
RTMP was recently supplanted by AURP, which only sends routing 
information when network changes make it nece.ssary. 

RTMP See Routing Table Maintenance Protocol. 


SDLC See Synchronous Data Link Control. 

seed router An AppleTalk router that contains the net- 
work numbers and zone information that is used by non-seed 
AppleTalk routers on the network. 

segment A length of network cable. A segment can be 
connected to the port of a repeater, bridge, router, or gateway. 

Sequenced Packet Exchange (SPX) The Transport layer 
protocol used by Novell NetWare. Provides a connection- 
oriented, guaranteed delivery link between Novell NetWare nodes. 

server A network device or process that provides a 
service to networked clients. In the AppleTalk environ- 
ment, examples of servers include AppleShare file servers and 
LaserWriter print servers. 

session A logical connection between two network 
devices. In an AppleTalk network, the AppleTalk Session 
Protocol (ASP) is used to establish, maintain, and discontinue 

Live Wired 

Session layer The layer of the OSI Reference Model that 
establishes a logical connection between netw'ork devices. 
The Session layer corresponds to the upper third of the Protocol 
layer of the NetPICT model. 

Serial Line Internet Protocol (SLIP) A TCP/IP-based 
protocol used to run IP over serial lines such as dial-up 
phone lines. Similar to Apple’s Remote Access Protocol. 

shielded cable A cable that is surrounded by a grounded 
metallic material. It minimizes disruption of the signal 
by external electrical noise and prevents the cable from emitting 
unwanted electrical signals. 

Simple Network Management Protocol (SNMP) A 
management protocol used to maintain and query 
network entities. SNMP uses agents on managed nodes to main- 
tain a database known as a MIB (Management Information Base). 
The data stored within the MIB can be transmitted to the manage- 
ment software upon request. 

Single Mail Transfer Protocol (SMTP) An electronic mail 
service common on TCP/IP networks. 

SLIP See Serial Line Internet Protocol. 

SMDS See Switched Multimegabit Data Service. 

SMTP See Single Mail Transfer Protocol. 

SNA See Systems NetworkArchitecture. 

SNMP See Simple Network Management Protocol. 

socket An addressable entity within an AppleTalk node. Sockets 
can be thought of as network processes. 

Glossary of Networking Terminology 

socket number An 8-bit number that uniquely identifies a socket. 
With AppleTalk, there are 256 sockets. 0 and 255 aren’t used, 
leaving 254 available for use. Numbers 1-127 are reserved by Apple; 
128-254 are available for use by applications. 

I split-horizon routing A technique for maintaining routing 
tables that was introduced with AppleTalk Phase 2. 
Routing information is only forwarded to those routers that can 
use the information. 

SPX See Sequenced Packet Exchange. 

SQL See Structured Query Language. 

star topology A centralized network with a hub, concen- 
trator, or repeater at the center of the network. 

Structured Query Language (SQL) A language, standardized by 
ANSI, used to manipulate relational databases. Apple’s Data 
Access Language (DAL) uses a variation of SQL to access relational 
data through DAL servers. 

Switched Multimegabit Data Service (SMDS) A relatively 
new high-speed WAN networking technology offered by 
telephone companies and service providers. 

Synchronous Data Link Control (SDLC) A Data Link 
Layer protocol used by IBM’s SNA networks. 

Systems Network Architecture (SNA) A suite of commu- 
nications protocols developed by IBM. Analogous to the 
AppleTalk protocol suite. 

Live Wired 


TCP/IP TCP/IP (which stands for Transmission Control 
Protocol/Intemet Protocol) is a set of networking proto- 
cols commonly found on, but not limited to, UNIX computers. 

TELNET A Service layer protocol common to TCP/IP 
networks that provides terminal services. 

terminal emulation A program, usually on a personal 
computer, that masquerades as a computer terminal. 
The most common terminals that are emulated are the VT series 
established by DEC and the 3270 series from IBM. 

terminator A resistive device attached to the ends of a 
cable to minimize unwanted signal reflections from the 
cable segment. 

thickwire A type of Ethernet cabling, also known as 
lOBase-5, that uses a thick (approximately 3/8") coaxial 
cable. Primarily used as a backbone to which thinwire or twisted- 
pair hubs are connected. 

thinwire A type of Ethernet cabling, also knowoi as 
lOBase-2, that uses coaxial cable and BNC connectors. 

TLAP See TokenTalk Link Access Protocol. 

Token Ring A cabling system, common in tlie IBM 
world, that connects network devices in a ring topology. 
It uses the method of token passing to enable nodes to access the 

TokenTalk Apple’s product that puts the AppleTalk 
protocols onto a Token Ring nehvork. 

Glossary of Networking Terminology^ 

TokenTalk Link Access Protocol (TLAP) The data link 
access protocol used in a TokenTalk network. TLAP puts 
AppleTalk protocols onto a Token Ring network. 

topology The physical connective structure of a network. Com- 
mon topologies include bus, ring, and star. 

transceiver An interface between a node and the 
network. Transceivers transmit and receive network 


Transport layer The layer of the OSl reference model that 
ensures that the message is correctly transmitted. If one 
portion of the communication transmission is lost or garbled, it’s 
the job of the Transport layer to retransmit the necessaiy'^ portion. 
The Transport layer of the OSI model corresponds to the middle 
third of the Protocol layer in the NetPlCT model. 

tunneling A process that enables one protocol’s datagram 
to be encapsulated within another protocol’s datagram. 

twisted-pair Wiring that consists of two insulated 
copper multi-stranded conductors twisted around each 
other to reduce electrical interference. Twisted-pair wiring can be 
used by phone-type LocalTalk connectors, Ethernet, ARCNET, and 
other cabling systems. 

VAX A line of computers manufactured by Digital Equipment 
Corporation (DEC). VAX stands for Virtual Address extension. 

VAXshare Part of DEC’S PATHWORKS for Macintosh 
software that enables a VAX to act as an AFP file server 
and PAP print spooler. 

Live Wired 

Vines Banyan’s network operating system. “Vines" is an 
acronym for Virtual NEtwork Software. 

VMS An operating system used by Digital Equipment Corporation 
for its line of VAX computers. VMS stands for Virtual Memory 

volume A disk that appears on the Mac desktop. A 
volume could be a hard disk, floppy disk, or a network file 
server disk. 


Wide Area Network (WAN) A network that spans distances beyond 
the range served by LANs. WAN distances are usually measured in 
miles instead of feet. 

ZIP See Zone Information Protocol. 
ZIT See Zone Information Table. 

zone A way of logically grouping AppleTalk nodes. Zones 
are established by AppleTalk routers. 

Zone Information Protocol (ZIP) The AppleTalk Session 
layer protocol that maintains the mapping of AppleTalk 

network numbers to zone names. ZIP is used by the Chooser to 
obtain a list of zone names. 

Glossary of Netw'orking Terminology 

Zone Information Table (ZIT) A listing of zones main- 
tained by AppleTalk routers that relates zone names to 
the ports of a router. 

zone list A listing of AppleTalk zones. Usually seen in tlie 

zone name A name assigned to an AppleTalk network 
zone. Can be 32 characters long and is case-insensitive. 




his appendix contains a sampling of key NetPICT 
diagrams that have been used throughout the 
book. These diagrams are also included on the 
disk that comes with this book. 

AppleShare Server 

AppleShare Server 

AFP Server (Ethernet) 

An AFP server on an Elliernel nelwork. snclr as a Macinlosh 
running AppleShare or a VAX running VAXshare. 

AFP Server (FDDI) 

An AFP server on a FDDI nelwork. An eiample ol such a device 
is a Macintosh running AppleShare wilh a FDDI card and the 

Live Wired 

AppleShare Server AppleShare Server 

AFP Server (LocalTalk) 

An AFP server on a locallalk network, sucit as a Macinlosli 
running AppleShare. 

LaserWriter Server 

Apple LaserWriter (Ethernet) 

Same laser printers come equippetl with Ethernet interfaces. 
Eiamples inclutle Apple's LaserWriter lip and LaserWriter 
Pro 630. 

AFP Server (Token Ring) 

An AFP server on a loken Ring network. An example wonid he 
a Macintosh rnnning AppleShare with a Token Ring card and 
the lokenlalk protocols. 

LaserWriter Server 

Apple LaserWriter (LocalTaik) 

Some Apple laser printers come eouipped with locallalk 
interfaces. Examples include Apple's oripinal LaserWriter and 
the LaserWriter IINI. 

Appendix A NetPICT Encyclopedia 

Apple Macintosh 

Apple Macintosh (Ethernet) 

Some Aople Maciniosli commiiers tome equipped wiili Eltieinei 
inieifaces as siandaid equipmeni Isuch as ilie Ooadra 9501: 
add-oo llheioei cards cao be purchased lor Macs wiihoui buili- 

Apple Macintosh 

Apple Macintosh (FDDI) 

All Apple Uatiniosh with a third panr IDDI NuBus card 
iosialled, along wiih ihe FOOIIalk proiocols. 

Apple Macintosh 

Apple Macintosh 

Apple Macintosh (LocalTalk) 

All Apple Uatifliosb compuiers come equipped wiih locallalk 
as standard equipmeoL 

Apple Macintosh (RS*422) 

Any Apple Macintosh tan use either ol its two serial ports 
mS-412) l3t asynchronous services, such as ARAP. 

Live Wired 

Apple Macintosh 

PAP Client 
AFP Client/server 



Token Ring 

Apple Macintosh (Token Ring) 

An Apple Meciniosli witli a loken Ring NuBus caid inslalled along wlUi ilie Tokenlalk pfoiocols. 

AppleTalk Ethemet-to-Ethernet Router 

An Applelalk (ouie( thai connecls Iwo (iheinei networks logeHier. (laoiples include Apple's Inlernei flooier (eguipped will) two 
[iheinei cards), or even a VAX running Applelalk for VMS over two [ihernet controllers. 

AppleTalk Ethernet-to-Token Ring Router 




Token Ring 

AppleTalk Ethemet-to-Token Ring Router 

An Applelalk router that connects an Ethernet network and a loken Bing network. Ihe best example ol such a device is Apple's 
Internet Router (equipped with an Ethernet card and a loken Ring card). 

Appendix A NetPICT Encyclopedia 

AppleTalk LocalTalk-to-Ethernet Router 

An Appletalk louiet Ihai connecis a IncalTalk network anil an Eiliernei network. Examples incluile Apple's Inieinet nooter (using a 
Incallalk connector and an EOieroet card) and dedicated routeis sucti as Stiva's FastPatlt !i. 

AppleTalk LocalTalk-to-LocalTalk Router 

An Applelalk loutet that connects two localTalk networks. Ihe best example is Apple’s Internet Hooter (using both the printer and 
modem ports lor locallalk connections). 

AppleTalk LocalTalk-to-Token Ring Router 

Ihis diagram represents an Applelalk router that connects a locallalk network and a token Ring network. Ihe best example ol 
such a device is Apple's Internet Router (equipped with a locallalk connector and a token Ring card). 

Live Wired 

Wide-Area Router (l.e. Cisco, Wellfleel) 

AppleTalk and 
other protocols 


AppleTalk and 
other protocols 

T1 and other 
WAN links 

AppleTalk multiprotocol WAN router 

An Applelalk (mulliproiocol) router that connects an [ttiernet network to a WAN connection (sucli as a II tinkl. Examples include 
multiprotocol routers from Dsco, Welllleei and IBM. 


Banyan VINES 


VINES, AppleTalk 


Banyan VINES server 

A Banyan VINES server running on a PC host. Notice that in addition to the VINES protocol the Applelalk protocol is also installed on 
the host. Ihis system also supports the encapsulation ol Applelalk within VINES datagrams. 

Cayman GatorBox 

Ihe Cayman GatorBox is an AFP-io*NFS gateway. Devices on the AFP side see the GatorBox as an AFP server, while devices on the 
NFS side see Ihe GatorBox as iust another NFS client. 

Appendix ANetPICT Encyclopedia 

Macintosh Macintosh 

Dayna NetMounter 

Ihe Dayna KeiMounier equips a Maciniosh with ihe Kovell 
iranspoii pioiocols, raakinq il appear like any other DOS client 
on lire neiwotk. this is an altetnatiye lo lire NetWare lor 
MaciniosItptoDuciltont Novell. 

DECnet for Macintosh 

Part of the PAINWODItS lot Macintosh solution is to provide the 
option to turn Macintosh computers into DECnet nodes. DECnet 
lor Mac provides E-mail, Die services, DECwindow, and backup 
services over locallalk, Elhetnei and RS-422 cabling. 

Engage SyncRouter 56K 

Engage's Applelalk router, which connects an Ethernet LAN to a switched 561! WAN link. Ibis device works to tandem with another 
identical unit. 

Engage SyncRouter ISDN 

Engage's Applelalk router, which connects an Ethernet IAN to an ISDN WAN link. Ihis device works in tandem with another 
identical unit 

live Wired 

IBM Host 

LocalTalk Bridge (Tribe LocalSwitch) 

Ihe LocalTalk bridge operaies at Ihe Data link layer. Ii does ool grovide a rooting cagabiliiy. By rapidly switching between devices 
on the LocalTalk segmeni the modest bandwidth ol LocalTalk is naiimiied. 

LocalTalk Repeater (Farallon PhoneNET Repeater) 

The LocalTalk repeater operates at the physical layer by electrically doplicaiing signals Iron one side ol the connection to the other. 
It's used to extend the range ol LocalTalk segments. 

Appendix A NetPICT Encyclopedia 

Macintosh Macintosh 

Macintosh IBM 3270 Client 

A Maciniosli 3270 leiminal emulatoi running nver a coat taid. 
An example nl iliis is lire MaclOMA emulainr and card. 


MacTerminal DECnet (CTERM) 

Here, a Macininsli is used to run a rerminal emulatinn session 
using die CIEOM protocol (pan oi ihe DECnel ptolocol) over a 
locallall: neivtotk. 01 course. Hie Eihetnei tesidenl host VAX 
compuier must be accessible through a EocallaHr lo-Ethernei 
router that routes the DECnet protocol. 

MacTerminal DECnet (CTERM) 
over Ethernet 

Here, a Macintosh is used to tun a tetniioal emulation session 
with Ihe C1EHM protocol (part ol the DECnet protocol) over an 
Eihernei network. Ihe selection of the CIEHM protocol is made 
through the Macintosh Communications loolboi. 


MacTerminal DECnet (CTERM) 

Here, a Macintosh is used to run a terminal emuladon session 
using the CIEHM protocol (part ol Ihe DECnel protocol) over a 
serial connection through the Mac's RS-422 (printer or modem) 

Live Wired 


MacTerminal Local Area 
Transport (LAT) over Ethernet 

Here, a Maciniosli is beiao used lo run a lerniinal eiaulaiioa 
session using Hie lAI ginincol ever a Etbernei neiwnrk. Ibe 
bnsi VAX is also speaking Hie LAT Iranspoit pioincol. The 
seleciion of LAI is made through the Macintosh Communica- 
tions Toolbox. 


MacTerminal Asynchronous 
Protocol over RS-422 

In Ibis diagram a Maciniosb is used to run a terminal emulation 
session using the "async" protocol over an HS-422 connec- 
tion (made through the modem or printer port). This is 
representative ol most terminal emulators that use async 

Multiprotocol Ethernet-to-Ethernet Router 





Multiprotocol Ethernet-to-Ethemet Router 

A multiprotocol router (AppleTalk, OLCnei and TCP/IP) used to connect two Tihernei segments. Examples include routers burn Cisco 

Appendix A NetPICT Encyclopedia 

Multiprotocol LocalTalk-to-Ethernet Router 





Multiprotocol LocalTalk-to-Ethemet Router 

A fliuliipiotocol rouiei (Applelalk, DECppi, anil ICP/iPI ased lo cnnaeci a Ipcallalk natwoik in an Etheinei sepmeni. Examples 
inclpde innieis liom Shiva. Wehsiei, and Cayman. 

Macintosh Macintosh 

NFS Services on a Macintosh 

A Maciniosh equipped wiih Apple's MacICP can support higher 
level protocols such as Sun's Network Eiling Sysiem (NFS). 
Implemeniaiions el NFS lor the Mat ate provided hy InierCon 
and Wollongong. 

Novell NetWare for 
Macintosh Client 

NetWare lor the Mac relies on the Applelalk iranspott to 
deliver NetWare services to the desktop. Because it uses the 
Applelalk iranspoti any cahling sysiem or router that is 
supported by both the Mac and the PC is supported by NetWare 
lot the Mac. 

Live Wired 


Novell NetWare for 
Macintosh Server 

lelWare for Macintosh seivices ate imiileiiienieil on a PC 
server with a NetWare loarlable Module (NIM). Ihe NLM also 
provides the PC wilh Ihe Aoplelallr protocol suite. 

Intel-based PC 

PC with AppleTalk and a 
LocalTalk Card (PhoneNET PC) 

fhis PC supports AFP sod PAP protocols with Ihe AppleTalk 
protocol Slack over a locallalk cooneciioo. Ihe best example 
is Farsllon's PhoneNFI PC product which supports Fthernet 
coooectiviiy (in addition to locallalk aod loken Riog). 

Intel-based PC 

PC with AppleTalk and an 
Ethernet Card (PhoneNET PC) 

This PC supports AFP and PAP protocols with the Applelalk 
protocol slack over an Fthernet connection Ihe host example 
is Farsllon's PhoneNET PC product, which supports Ethernet 
connectivity (in addition to locallalk aod Token Ring). 

Intel-based PC 

PC with AppleTalk and a Token 
Ring Card (PhoneNET PC) 

Fhis PC supports AFP and PAP protocols with Ihe Applelalk 
protocol Slack over a Token Ring conneclicn. Again, the best 
example is Farsllon's PhoneNFI PC product 

Appendix A NetPICT Encyclopedia 

Macintosh Running Appie SNA*ps Gateway 





LocalTaik or 


SNA*ps Gateway 

liiis repfesenis a Maciniosli lunning Apple's SNA*ps paieway. It is used lu conned memlieis on an AppleTalk network lo 


TCP/IP on the Macintosh 

Iliis Macinlosli has been equipped with Apple's UacICP, which 
puls ihe ItP/IP piolacol slack on the Mac, enabling ii to 
pariicipaie in IP network services nver Locallalk or Ethernet. 


Telnet Services for the Macintosh 

One popular IP service is the Telnet terminal protocol that sits 
atop the TCP/IP protocol slack. An etample ol this would be 
running the Versalerm Pro terminal emulator over TocalTalk or 

Live Wired 



Sun Workstation 

Xinet K-AShare 

linet's X'ASliare turns a Sun workstation into an AFP setvet. Notice that the Sun has the AppleTalk ptotocol slack inslalleil. 

Xinet K-Spool 

Xinei's K-Spool turns a Sun workstation into a PAP print spooler. Ihe spooler accepts Mac ptint jobs, spools then, and sends them 
to the appropriate network ptinier. 

Listing of 

3Com Corporation 

AESP, Inc. 

5400 Baj'front Plaza 

1810 NE 144th St. 

Santa Clara, CA 95052 

North Miami Beach, FL 33181 

(800) 638-3266 

(800) 446-2377 

(408) 764-5000 


(305) 944-7710 

AG Group 

22540 Camino Diablo 

Suite 202 

Walnut Creek, CA 94596 

Actinet Systems, Inc. 

360 Cowper Avenue 

(510) 937-7900 

Suite 1 1 

Alisa Systems, Inc. 

Palo Alto, CA 94301 

221 East Walnut Street 

(415) 326-1321 

Suite 175 

Pasadena, CA 91101 
(818) 792-9474 

Live Wired 

Andrew Corporation 

4301 Westbank Drive 
Suite A- 100 
Austin, TX 78746 
(800) 531-5167 
(512) 314-3000 

Apple Computer, Inc. 

20525 Mariani Avenue 
Cupertino, CA 95014 
(408) 996-1010 

Applied Engineering 

P.O. Box 5100 
Carrollton, TX 7501 1 
(800) 554-6227 

APT Communications, Inc. 

9607 Dr. Perry Road 
Ijamsville, MD 21754 
(301) 831-1182 

Artisoft Inc. 

691 River Road 
Tucson, AZ 85704 
(602) 293-4000 

Asante Technologies 

404 Tasman Drive 
Sunnyvale, CA 94089 
(408) 752-8388 


295 North Maple Avenue 
Basking Ridge, NJ 07920 
(908) 221-6153 

Avatar Corporation 

65 South Street 
Hopkinton, MA 01748 
(508) 435-3000 East 
(408) 727-3270 West 


Banyan Systems, Inc. 

120 Flanders Road 
Westboro, MA 01581 
(508) 898-1000 

Blyth Software 

1065 East Hillsdale Boulevard 
Foster City, CA 94404 
(415) 571-0222 

Brio Technology, Inc. 

444 Castro Street 
Suite 700 

Mountain View, CA 94041 
(415) 961-4110 

Appendix B Listing of Macintosh Networking Companies 

BT Tymnet 

P.O. Box 49019 
560 North First Street 
San Jose, CA 95161-9019 
(408) 922-7583 


Cabletron Systems 

35 Industrial Way 
Rochester, NH 03867 
(603) 332-9400 

Cactus Computer, Inc. 

1 120 Metrocrest Drive 
Suite 103 

Carrollton, TX 75006 
(214) 416-0525 

Caravelle Networks 

301 Moodie Drive 
Suite 306 

Nepean, ON 2H 9C4 


(613) 596-2802 

Cayman Systems, Inc. 

26 Landsdowne Street 
Cambridge, MA 02139 
(617) 494-1999 

cc:Mail, Division of 
Lotus Corporation 

2141 Landings Drive 
Mountain View, CA 94043 
(415) 961-8800 

CEL Software 

P.O. Box 8339 
Station F 

Edmonton, Alberta T6H 4W6 


(403) 463-9090 

Cisco Systems Inc. 

1525 O’Brien Drive 
Menlo Park, CA 94025 
(415) 326-1941 

Claris Corporation 

5201 Patrick Henry Drive 
Santa Clara, CA 95052 
(408) 727-8227 

Clear Access Corporation 

200 West Lowe Street 
Fairfield, lA 52556 
(515) 472-7077 
(800) 522-4252 

Codenoll Technology 

1086 North Broadway 
Yonkers, NY 10701 
(914) 965-6300 

Live Wired 

Compatible Systems 

P.O. Drawer 17220 
Boulder, CO 80308 
(800) 356-0283 
(303) 444-9532 

Computer Methods 

525 Route 73 South 
Suite 300 
Marlton, NJ 08053 
(609) 596-4360 

Connectivite Corporation 

220 White Plains Road 
Tarr)4:own, NY 10591 
(914) 631-5365 

CSG Technologies 

530 William Penn Place 
Suite 329 

Pittsburgh, PA 15219 
(412) 471-7170 
(800) 366-4622 


Data Spec 

9410 Owensmouth Avenue 
Chatsvvorth, CA 9131 1 
(818) 772-9977 


55 Corporate Drive 
Trumbull, CT 06611 
(203) 268-0030 

Dayna Communications, Inc. 

50 South Main Street 
Fifth Floor 

Salt Lake City, UT 84144 

Digital Communications 
Association, Inc. 

1000 Alderman Dr. 

Alpharetta, GA 30202 
(404) 442-4000 

Digital Equipment 

146 Main Street 
Maynard, MA 01754 
(508) 493-5111 

Digital Products Inc. 

4 1 1 Waverley Oaks Road 
Waltham, MA 02154 
(617) 647-1234 

Appendix B Listing of Macintosh Networking Companies 


EDI Communications 

20440 Town Center Lane 
Suite 4E1 

Cupertino, CA 95014 
(408) 996-1343 

EMAC Division of Everex 
Systems, Inc. 

48431 Milmont Drive 
Fremont, CA 94538 
(800) 628-3837 

Engage, Inc. 

9053 Soquel Drive 
Aptos, CA 95003 
(408) 688-1021 

Everywhere Development 

2176 Torquay Mews 
Mississaugua, ON LSN 2M6 
(416) 819-1173 


Fairfield Software, Inc. 

200 West Lowe Street 
Fairfield, lA 52556 
(515) 472-7077 

Farallon Computing, Inc. 

2000 Powell Street 
Suite 600 

Emeryville, CA 94608 
(800) 998-7761 
(510) 596-9100 

Focus, Inc. 

800 West Cummings Park 
Suite 4500 
Woburn, MAO 1801 
(800) 538-8866 
(617) 938-8088 


Hayes Microcomputer 
Products, Inc. 

P.O. Box 105203 
Atlanta, GA 30348 
(404) 840-9200 

Live Wired 

Helios USA 

10601 South DeAnza Blvd. 
Suite 103 

Cupertino, CA 95014 
(408) 864-0690 

Hewlett-Packard Co. 

5301 Stevens Creed Boulevard 
Santa Clara, CA 95052 
(800) 752-0900 

IBM Corporation 

1 133 Westchester Avenue 
White Plains, NY 10604 
(800) 426-3333 

IDEAssociates, Inc. 

29 Dunham Road 
Billerica, MA 01821 
(508) 663-6878 

impulse Technology 

210 Dahlonega Street 
Suite 206 

Cumming, GA 30130 
(404) 889-8294 

Infotek, Inc. 

56 Camille Lane 

East Patchogue, NY 1 1772 

(516) 289-9682 

InterCon Systems Corp. 

950 Herndon Parkway 
Suite 420 

Herndon, VA 22070 
(703) 709-9890 

international Transware, inc. 

1503 Grand Road 
Suite 155 

Mountain View, CA 94040 
(800) 999-6387 
(415) 903-2300 

IPT - Information 
Presentation Technologies 

555 Chorro Street 

San Luis Obispo, CA 93405 

(805) 541-3000 


Kandu Software Corp. 

2305 North Kentucky Street 
Arlington, VA 22205 
(703) 532-0213 

Appendix B Listing of Macintosh Netu'orking Companies 

Keywork Technologies 

2816 Eleventh Street, NE 
Calgary, Alberta T2E 7S7 
(403) 250-1770 

Marietta Systems 

29 El Cerrito Avenue 
San Mateo, CA 94402 
(415) 344-1519 


nil 19th Street NW 
Suite 500 

Washington, DC 20036 
(800) 444-6245 

MDG Computer Services 

634 South Dunton 
Arlington Heights, IL 
(708) 818-9991 
(708) 453-6330 

Microsoft Corporation 

One Microsoft Way 
Redmond, WA 98052-6399 
(206) 882-8080 

Miramar Systems 

201 North Salsipuedes 
Suite 204 

Santa Barbara, CA93103 
(805) 965-5161 

Mitem Corporation 

2105 Hamilton Avenue 
Suite 350 

San Jose, CA 95125 
(408) 559-8801 

Motorola Computer Group 

10700 North De Anza Boulevard 
Cupertino, CA 95014 
(800) 759-1107 Ext. MU 

MultiAccess Computing 

5350 Hollister Avenue 
Suite C 

Santa Barbara, CA 931 1 1 
(805) 964-2332 

National Semiconductor 

2900 Semiconductor Drive 
P.O. Box 58090 
Santa Clara, CA 95052-8090 

Live Wired 

Neon Software, Inc. 

1009 Oak Hill Road 
Suite 203 

Lafayette, CA 94549 
(510) 283-9771 

Network General Corporation 

4200 Bohannon Drive 
Menlo Park, CA 94025 
(415) 688-2700 

Network Resources 

736 South Hillview Drive 
Milpitas, CA 95035 
(408) 263-8100 

Nevada Western 

615 North Tasman Drive 
Sunnyvale, CA 94089-1950 
(408) 734-8727 

Novell, Inc. 

122 East 1700 South 
Provo, UT 84606 

(800) 638-9273 

(801) 379-5900 

- 0 - 

ON Technology, Inc. 

155 Second Street 
Cambridge, MA 02141 
(617) 876-0900 

Oracle Corporation 

500 Oracle Parkway 
Redwood Shores, CA 94065 
(415) 506-7000 


Pacer Software, Inc. 

7911 Herschel Avenue 
Suite 402 
La Jolla, CA 92037 
(619) 454-0565 

Photonics Corporation 

200 East Hacienda Avenue 
Campbell, CA 95008 
(408) 370-3033 

Appendix B Listing of Macintosh Networking Companies 


RacaMnterian, Inc. 

155 Swanson Road 
Foxborough, MA 01719 
(508) 263-9929 


Shiva Corporation 

One Cambridge Center 
Cambridge, MA 02142 
(800) 458-3550 
(617) 252-6300 

Sitka Corporation 

950 Marina Village Parkway 
Alameda, CA 94501 
(800) 445-8677 
(510) 769-9669 

Soft-Switch Inc. 

640 Lee Road 
Wayne, PA 19087-5698 
(215) 640-9600 

SoftWriters, Inc. 

P.O. Box 1308 
Round Rock, TX 78680 
(512) 244-3999 

Sonic Systems. Inc. 

333 West El Camino Real 
Suite 280 

Sunnyvale, CA 94087 
(800) 535-0725 
(408) 736-1900 

Standard Microsystems 

80 Arkay Drive 
Hauppauge, NY 11788 
(516) 273-3100 

StarNine Technologies. Inc. 

2126 Sixth Street 
Berkeley, CA 94710 
(510) 548-0391 

Synergy Software 

2457 Perkiomen Avenue 
Mt. Penn, PA 19606 
(215) 779-0522 


Talaris Systems. Inc. 

6059 Cornerstone Court West 
San Diego, CA 92121 
(619) 587-0787 

Live Wired 

TechGnosis Inc. 

301 Yamato Road 
Suite 2200 

Boca Raton, FL 33431 
(407) 997-6687 


4030 Broker Lane West 
Suite 350 
Austin, TX 78759 
(800) 879-7745 
(512) 794-8533 


1538 North Martel Avenue 
Suite 413 

Los Angeles, CA 90046 
(818) 446-7692 

Thomas-Conrad Corporation 

1908-R Kramer Lane 
Austin, TX 78758 
(800) 332-8683 
(512) 836-1935 

Thursby Software 
Systems, Inc. 

5840 West Interstate 20 
Suite 100 

Arlington, TX 76017 
(817) 478-5070 

Tribe Computer Works 

1195 Park Avenue 
Suite 211 

Emerj'ville, CA 94608 
(510) 547-3874 

Trik, Inc. 

400 West Cummings Park 
Suite 2350 
Woburn, MAO 1801 
(800) 766-0356 
(617) 933-8810 


Ungermann-Bass, Inc. 

3990 Freedom Circle 
P.O. Box 58030 
Santa Clara, CA 95052 
(800) 873-6381 
(408) 496-0111 

United Data Corporation 

3755 Balboa Street 
Suite 203 

San Francisco, CA 94121 
(415) 221-8931 

Appendix B Listing of Macintosh Networking Companies 

US Sprint Communications 

P.O. Box 84 17 
1200 Main St., 4th Floor 
Kansas City, MO 64105 
(800) 877-2000 


Webster Computer 

2109 O’Toole Avenue 
Suite J 

San Jose, CA 95131 
(800) 457-0903 
(408) 954-8054 

White Pine Software 

40 Simon Street 
Suite 201 

Nashua, NH 03060-3043 
(603) 886-9050 

The Wollongong Group, Inc. 

1 129 San Antonio Road 
Palo Alto, CA 94303 
(415) 962-7100 

WordPerfect Corporation 

1555 North Technology Way 
Orem, UT 84057 
(801) 225-5000 
(800) 451-5151 



2560 9th Street 
Suite 312 

Berkeley, CA 94710 
(510) 845-0555 


P.O. Box 21348 
Tulsa, OK 74121 
(800) 642-2299 

Live Wired 

A Guide to Networking Macs 


Liue Wired 


* (asterisk) wildcard character, 
with Network Visible Entities 
(NVEs), 158 
= (equal sign) wildcard 
character, with Network 
Visible Entities (NVEs), 158 
1-2-3 (Lotus), 212 

Data Access Language 
(DAL), 109 

format support, 34-35 
lOBase-2 (thinwire) Ethernet, 
92, 192-193, 195 
lOBase-5 (thickwire) Ethernet, 
93, 190-192, 196 
lOBase-T (twisted-pair) 
Etliernet, 68, 95, 193-194, 196 
single star networks, 

lOBroad-36 Ethernet, 192 
3270 terminal emulators, 106, 

3Com Corporation, 383 
EtherLink series, 228 
5250 terminal emulators, 

106, 270 

8- pin D1N8 connectors, 181 
802.3 (lOBase-F) IEEE 

standard, 289 

9- pin DB9 connectors, 181 


A/UX (Apple), DAL servers, 
109, 234 

AARP (AppleTalk Address 
Resolution Protocol), 55, 

ACCUNET system (AT&T), 204 
acknowledge control 
packets, 139 
Acrobat (Adobe), 123 
Actinet Systems, Inc., 383 
ARCTalk cards, 229 
active star topologies, 183-185 
single LocalTalk networks, 

Address Mapping Table 
(AMT), 55, 141 
Address Resolution Protocol 
(ARP), 55 
addressing, 49-50 
in AppleTalk, 137-147 
logical, 50-53 
physical, 54-55 
TCP/IP, 245-247 
Adobe Systems 
Acrobat, 123 
PostScript, 1 19 
ADSP (Apple Data Stream 
Protocol), 132 
Advanced Peer-to-Peer 
Networking (APPN), 274 
Advanced Program-to- 
Program Communications 
(APPC), 274 

Advanced Software Concepts 

asc3270, 241,270 
asc5250, 241 
FTPShare, 236 
terminal emulation 
products, 241-242 


AEP (AppleTalk Echo 
Protocol), 134 
AESP, Inc., 383 

AFP, see Apple Filing Protocol 
AG Group, 383 

EtherPeek, 322-323 
LocalPeek, 322-323 
TokenPeek, 322-323 
agent programs, 314 
AIR (Apple Internet Router), 
172-174, 203 

Aldus PageMaker, translating 
formats between versions, 


Alisa Systems, Inc., 383 
AlisaShare, 256 
MailMate QM, 112 
AlisaShare (Alisa Systems), 256 
All-In- 1 Mail for Macintosh 
(DEC), 88, 256 
mail gateways, 112 
Altair II wireless networks 
(Motorola), 201-202 
AMP (Apple Management 
Protocol), 315 
amplitude, modulating, 58 
AMT (Address Mapping 
Table), 55, 141 
analog dial-up, 203-204 
integrating Macintosh and 
DEC VAX, 267 
Andrew Corporation, 384 
Andyne’s Graphical Query 
Language (GQL) 

Data Access Language 
(DAL), 109 

Anonymous File Transfer 
Protocol (FTP), 235 

standard, 290 

AOCE (Apple Open Collabora- 
tion Environment), 105-106 

APPC (Advanced Program-to- 
Program Communications), 

Apple Computer, Inc., 384 
Apple Internet Router (AIR), 
172-174, 203 

Apple Open Collaboration 
Environment (AOCE), 

AppleShare, 99-101 
AppleTalk, see AppleTalk 
AppleTalk/ IP Wide Area 
Extension, 174 
AppleTalk/X.25 Wide Area 
Extension, 173 
Attachment Unit Interface 
(AUI) connectors, 194-195 
Data Access Language 
(DAL), see Data Access 

Easy Open file translator, 126 
Ethernet cards, 194-195 
EtherTalk, 26-27 
FDDI (Fiber Distributed 
Data Interconnect), 28-29 
future, 337-339 
Inter«Poll, 318-319 
LaserWriter printers, 104 
LocalTalk, seeLocalTalk 
Macintosh coax and twdnax 
cards, 276 
MacODA, 122-123 
MacTCP, 23-24, 226, 244-247 
MacX, 240 

Live Wired 

MPW, ASCII text. 116 
Newton, 29 

NuBus Token Ring card, 229 
Printer Access Protocol 
(PAP). 103-105, 131-132 
QuickTime for Windows, 212 
Serial NB card, 277 

3270 terminal emulator, 

gateway, 274, 277, 381 
TokenTalk, 27 
Apple Data Stream Protocol 
(ADSP), 132 
Apple Filing Protocol 
(AFP), 129 
AppleShare, 99-101 
gateways with Network 
Filing System (NFS), 87-88 
Macintosh File Sharing 
(System 7). 101-102 
on UNIX computers, 232-233 

for other platforms, 

NetPICT diagrams, 

VAXshare, 253-256 
Apple Internet Router (AIR), 

Apple Management Protocol 
(AMP), 315 

Apple Open Collaboration 
Environment (AOCE), 

Apple Remote Access (ARA), 
AppleTalk/LAT Gateway, 265 

Apple Secure Data Stream 
Protocol (ASDSP), 106, 

132, 323 

Apple Transaction Protocol 
(ATP), 133-134 

Apple Update Routing Proto- 
col (AURP), 133,171-174 
AppleShare (Apple), 99-101 
AppleShare icon, 100 
AppleTalk (Apple), 23 

AppleTalk Address Resolu- 
tion Protocol (AARP), 55 
cabling support, 26-29 
Chooser, see Chooser 
gateways, 87-90 
logical addressing, 50-53 

Network Visible Entities 
(NVEs), 157-165 
zone, 142-147 
NetPICT diagrams, 
372-374, 380 
nodes, turning PCs into, 

network, 137-138 
node, 138-142 
Phase 1 networks 
broadcasting versus 
Phase 2 multicasting, 

device limits, 148-149 
network number 
assignments, 149-152 
Phase 2 networks 
network number 
assignments, 149-152 


transition routing, 

phase development, 148 
routers, 51, 75-79, 166 
tunneling protocols, 

updating routing tables 
continuously, 166-170 
updating routing tables 
periodically, 171-174 
subdividing networks, 81-82 
suite of protocols, 127 
Data Link OSI layer, 

Network OSI layer, 

Presentation OSI 
layer, 129 

Session OSI layer, 129-132 
Transport OSI layer, 

AppleTalk Address Resolution 
Protocol (AARP), 55, 141-142 
AppleTalk Echo Protocol 
(AEP), 134 

AppleTalk for VMS, 260 
AppleTalk LAT Gateway, 88-89 
AppleTalk Remote Access 
Protocol (ARAP), 27-28 
AppleTalk Session Protocol 
(ASP), 131 

AppleTalk/DECnet Gateway, 
88, 263-264 

AppleTalk/DECnet MCT 
tool, 264 

AppleTalk/IP Wide Area 
Extension, 174 

AppleTalk/LAT Gateway, 

AppleTalk/X.25 Wide Area 
Extension, 173 
Application OSI layer, 42 
with Macintosh, 44 
Applied Engineering, 384 
APPN (Advanced Peer-to-Peer 
Networking), 274 
APT Communicadons, Inc., 384 
ARA (Apple Remote Access), 
AppleTalk/LAT Gateway, 265 
ARAP (AppleTalk Remote 
Access Protocol), 27-28 
ARCNET, 200 

integrating Macs and PCs, 

networking cards, 36 
ARCTalk cards (ACTINET 
Systems), 229 
ARP (Address Resolution 
Protocol), 55 
Artisoft Inc., 384 
AS/400 computers (IBM), 
integrating with Macintosh 
cabling systems 
direct connections, 
Ethernet, 278 
Token Ring, 278 
formats, 273 

DAL database, 272 
terminal, 269-272 
transport protocols, 273-275 
Asante Technologies, 384 
AsantePrint bridge, 187 

Live Wired 

ASC, see Advanced Software 

asc3270 (Advanced Software 
Concepts), 241, 270 
asc5250 (Advanced Software 
Concepts), 241 
ASCII (American Standard 
Code for Information 
Interchange), 20-21 
format, 116 

integrating Macintosh 
and DEC VAX, 258 
integrating Macs and 
PCs, 214 

ASDSP (Apple Secure Data 
Stream Protocol), 106, 

132, 323 

ASP (AppleTalk Session 
Protocol), 131 

asterisk (*) wildcard character, 
with Network Visible Entities 
(NVEs), 158 

Asynchronous protocol, 
NetPICT diagrams, 378 
AsyncServeR (Computer 
Methods Corporation), 28, 
267, 335 
AT&T, 384 

ACCUNET system, 204 
ATP (Apple Transaction 
Protocol), 133-134 
Attachment Unit Interface 
(AUI) connectors, 194-195 
AURP (Apple Update Routing 
Protocol), 133, 171-174 
AutoCAD (Autodesk), 212 
DXF (Drawing Exchange 
Format) format, 217-218 

Avatar Corporation, 384 
Macintosh coax and twinax 
cards, 276 
gateways, 277 
MacMainFrame, 270 


backbone (bus) topologies, 
76-77, 92-93 

bridged, multiple LocalTalk 
networks, 305-306 
Ethernet, 196 

multiple LocalTalk 
networks, 306-307 

multiple Ethernet 
networks, 309 
multiple Ethernet WAN 
networks, 309-311 
PhoneNET, 185 

multiple Ethernet 
networks, 307-308 
multiple LocalTalk 
networks, 304-305 
bandwidth, comparing 
Ethernet and LocalTalk, 

Banyan Systems, Inc., 384 
VINES, 35, 224 

NetPICT diagrams, 374 
baseband, 59, 192 
Bellman-Ford routing, 169-170 
binary data, 19 


binary formats, 121 

integrating Macintosh and 
DEC VAX, 258-259 
bitmap graphics format, 118 
bits, 19 

Black Box Corporation, 292 
Blacksmith (CEIJ, 272 
Blyth Software, 384 
BNC (twist and lock) 
connectors, 192 
Both (Connectivite), 272 
bridges, 69-71 

backbone, multiple 
LocalTalk networks, 
Ethernet, 71-72 
filtering, 70 

for LAT networks, 83-86 
isolating high-traffic nodes, 
LocalTalk, 71 
NetPICT diagrams, 376 
Source Routing Bridges 
(SRBs), 334 
star, single LocalTalk 
networks, 302 
TribeStar (Tribe), 305 
Brio Technology, Inc., 384 
broadband networking, 59 
broadcasting. Phase 1. 
versus Phase 2 multicasting, 
brouters, 85 
BT Tymnet, 385 
bus topologies, .see backbone 
bytes, 19 



anticipating wiring 
standards, 194 
coaxial (coax), 276 
fiber optic, 289-290 
twinaxial (iwinax), 276 
Unshielded Twisted-Pair 
(UTP), 289 

Cabletron Systems, 385 
Cabling NetPICT layer, 25-29 
ARCNET, 200 
conventional analog dial- 
up, 203-204 
designing, 284-285 
strategy guidelines, 

Ethernet, 187-196 
FDDI (Fiber Distributed 
Data Interface), 197-199 
integrating Macintosh 
and DEC VAX, 266-268 
and IBM mainframes/ 
midranges, 276-278 
and PCs, 227-230 
and UNIX, 248 
ISDN (Integrated Services 
Digital Network), 204-205 
leased-line services, 205 
LocalTalk, 179-187 
multiple Ethernet 
FDDI backbone, 309 
FDDI backbone WAN, 

routed backbone and 
star, 307-308 

Live Wired 

multiple LocalTalk 
bridged backbone, 

305- 306 

Ethernet backbone, 

306- 307 

routed backbone, 304-305 
serially-routed, 302-304 
packet switched, 207 
PhoneNET (Farallon), 

Serial RS-232/422, 199-200 
single Ethernet 

daisy-chain, 294-296 
twisted-pair star, 299-300 
single LocalTalk 
active star, 298-299 
bridged star, 302 
daisy-chain, 292-294 
multiple star, 300-301 
passive star, 297-298 
standard Macintosh, 33 
standard PC, 35-36 
structured wiring imple- 
mentations, 311-312 
Switched 56K Service, 204 
Token Ring, 196-197 
wireless, 200-202 
X.25 packet switched, 

Cactus Computer, Inc., 385 
Caravelle Networks 
Corporation, 385 
cards, 35-36 
Ethernet, 54 
Apple, 194-195 
cost, 187, 189 
FDDI, cost, 198 

Macintosh coax and 
twinax, 276 
Serial NB (Apple), 277 
Token Ring, cost, 197 
Carrier Sense Multiple Access/ 
Collision Avoidance (CSMA/ 

Carrier Sense Multiple Access/ 
Collision Detection (CSMA/ 
CD), 62-63 
Category 5 UTP, 289 
Cayman Systems, Inc., 385 
GatorBox gateway, NetPICT 
diagrams, 374 
cc:Mail, Division of Lotus 
Corporation, 385 
CE Software’s QuickMail, 

CEL Software, 385 
Blacksmith, 272 
Chooser, 155-156 
determining node 
addresses, 156-157 
indicating network 
problems, 318 
standard Service layer, 32 
troubleshooting, 324-330 
circuit-switched networks, 

Cisco Systems Inc., 385 
multiprotocol routers, 205 
routers, 85, 336 
Claris Corporation, 385 
ClarisWorks, 212 
FileMaker Pro, 212 
XTND data format 
translators, 117, 124-125 


Clear Access (Fairfield 
Software), 109 

Clear Access Corporation, 385 
client/server computing, 39 
Apple Filing Protocol (AFP) 
AppleShare, 99-101 
for other platforms. 

Macintosh File Sharing 
(System 7), 101-102 
Data Access Language 
(DAL), 108-110 
Printer Access Protocol 
(PAP), 103-105 
X- Window standard, 238-241 
client/server model, 18 
coaxial (coax) cable, 276 
Codenoll Technology 
Corporation, 385 
FDDI cards, 198 
collisions, 60 

common bus topologies, see 
backbone topologies 
communication layers 
Expression, 10 
Idea, 10 

matching, 13-15 
Medium, 11-12 
Transport, 11 
Compatible Systems 
Corporation, 386 
EtherWrite bridge, 187 
routers, 335 

compound documents, 122 
Computer Methods 
Corporation, 386 
AsyncServeR, 28, 267, 335 

concentrators, 90 
configuring nodes, 313-315 
Connectivity Corporation, 386 
Both, 272 

8- pin DIN8, 181 

9- pin DB9, 181 
Attachment Unit Interface 

(AUl), 194-195 
BNC (twist and lock), 192 
RJ-11, 182 

S>mchronous Data Link 
Control (SDLC), 275 
tee, 193 

transceivers, 191 
conventional analog dial-up 
networks, 203-204 
converting formats, 124-126 
Cooperative Printing 
Solutions Inc. (COPS Inc.), 
turning PCs into AppleTalk 
nodes, 222 

Altair II wireless networks 
(Motorola), 202 
Ethernet cards, 187, 189 
FDDI cards, 198 
multiprotocol routers, 205 
single Ethernet daisy-chain 
networks, 295-296 
single LocalTalk active star 
networks, 298-299 
single LocalTalk daisy- 
chain networks, 293 
single LocalTalk multiple 
star networks, 301 

Live Wired 

single LocalTaJk passive star 
networks, 297 
Token Ring cards, 197 
X.25 packet switched 
networks, 206-207 
CSG Technologies, 386 
CSMA/CA (Carrier Sense 
Multiple Access/ Collision 
Avoidance), 63 
CSMA/CD (Carrier Sense 
Multiple Access/Collision 
Detection), 62-63 
CTERM Communications 
Tool, 262 

CTERM protocol, 262 
NetPICT diagrams, 377 
cyclic redundancy checks, 57 


daisy-chain topologies, 67, 

single Ethernet networks, 

single LocalTalk networks, 

binary, 19 

formats, see formats 
Data Access Language (DAL) 
(Apple), 108-110 
for VMS, 256 
integrating Macintosh 
and UNIX, 234 
and IBM mainframes/ 
midranges, 272 

Data Link OSI layer, 41-43 
Macintosh protocols, 

with Macintosh, 45 
Data Spec, 386 
databases, relational 
accessing, 108-110 
see also Data Access 
Language (DAL) 

DataClub (Novell), 224 
Datagram Delivery Protocol 
(DDP), 134-135 
Short and Long, 138 
datagrams, 43 
Data Viz, 386 

MacLinkPlus, 117,214 
Dayna Communications, 

Inc., 386 

EtherPrint bridge, 186, 189 
EtherPrint Plus bridge, 187 
NetMounter, 223 

NetPICT diagrams, 375 
Network Vital Signs, 331-332 
DB2 databases (IBM), 
accessing, 109 
DB9 connectors, 181 
DBC/ 1012 databases 
(Teradata), accessing, 109 
DCA, see Digital Communica- 
tions Association, Inc. 

DDP (Datagram Delivery 
Protocol), 134-135, 138 
DEC (Digital Equipment 
Corporation), 386 
All-In-1 Mail for Macintosh, 
88, 1 12, 256 
DAL servers, 109 


DECnet, see DECnet 
DECwindows, 238, 252-253 
Local Area Transport (LAT), 

multiprotocol routers, 205 
PATHWORKS for Macintosh, 
88-89, 251-257 
Rdb databases, accessing, 

Ultrix, 233-234 
VAX, see VAX/ VMS 
VT-series terminals, 
emulating, 106 

DECnet (DEC), 23-24, 261-262 
AppleTalk/ DECnet 
Gateway, 263-264 
integrating Macs and PCs, 

NetPlCT diagrams, 375 
subdividing networks, 81-82 
DECservers, 262 
DECwindows (DEC), 238 
MacX, 252-253 
Default zones, 145 
designing networks 
by layers, 283-285 
cabling-system strategy 
guidelines, 288-292 
multiple Ethernet 
FDDl backbone, 309 
FDDI backbone WAN, 

routed backbone and 
star, 307-308 
multiple LocalTalk 
bridged backbone, 

Ethernet backbone, 

routed backbone, 


serially-routed, 302-304 
single Ethernet 

daisy-chain, 294-296 
twisted-pair star, 299-300 
single LocalTalk 
active star, 298-299 
bridged star, 302 
daisy-chain, 292-294 
multiple star, 300-301 
passive star, 297-298 
structured wiring imple- 
mentations, 311-312 
witii NetPlCT sjnnbols, 

dial-up networks, 203-204 
integrating Macintosh and 
DEC VAX, 267 
Digital Communications 
Association, Inc. (DCA), 386 
IRMA Workstation for 
Macintosh, 270 
Macintosh coax and twinax 
cards, 276 

Macintosh/SNA gateways, 

Digital Equipment 
Corporation, see DEC 
Digital Products Inc., 386 
SprintTALK bridge, 187 
digital signatures, 106 
D1N8 connectors, 181 
Dls (domain headers), 177-178 

Live Wired 


compound, 122 
interchanging, 122 
common format stan- 
dards versus format 
conversion, 124 
with Adobe Acrobat, 123 
with Aldus PageMaker, 

with Apple Easy Open, 

with Apple MacODA, 

with Claris XTND, 117, 

with Microsoft Word, 117 
domain headers (DIs), 177-178 
dotted quads, 246 
Drawing Exchange Format 
(DXF), 217-218 

ELAP software, 190 
FDDlTalk, 198 
dynamic node addressing, 


E-mail (electronic mail), 

PATHWORKS for Macintosh 
(DEC), 256-257 
Easy Open (Apple) file 
translator, 126 
EBCDIC (Extended Binary 
Coded Decimal Interchange 
Code), 273 

EDI Communications 
Corporation, 387 
EIA/TIA 568 and TSB-36 
standard, 289 
ELAP, see EtherTalk Link 
Access Protocol 
EMAC Division of Evcrcx 
Systems, Inc., 387 
EMBARC (Motorola), 201 
emulators, see terminal 

Encapsulated PostScript 
(EPSF), 119-120 
encapsulating protocols, 

encrypting network traffic, 106 
Engage Communications, 

Inc., 387 

ISDN AppleTalk routers, 205 

LTNT router, 204 
NetPICT diagrams, 375 
enquiry control packets, 139 
EPSF (Encapsulated 
PostScript), 119-120 
equal sign (=) wildcard charac- 
ter, with Network Visible 
Entities (NVEs), 158 
errors, cyclic redundancy 
checks, 57 

EtherLink series (3Com), 228 
Ethernet, 187-190 
lOBroad-36, 192 
Apple cards, 194-195 
AppleTalk support for, 26-27 
backbone, multiple Local- 
Talk networks, 306-307 


capacity, 66 
comparing with 
LocalTalk, 330-331 
bridges, 70-72 
broadcasts, 84 
Carrier Sense Multiple 
Access/Collision Detec- 
tion (CSMA/CD), 62-63 
design considerations, 

integrating Macintosh 
and DEC VAX, 267 
and IBM mainframes/ 
midranges, 278 
and PCs, 228 
and UNIX, 248 
isolating high-traffic nodes, 

FDDl backbone, 309 
FDDl backbone WAN, 

routed backbone and 
star, 307-308 

NetPICT diagrams, 369-373, 

network signals, 60-61 
networking cards, 36 
physical addressing, 54-55 
repeaters, 68 

daisy-chain, 294-296 
twisted-pair star, 299-300 
star topologies, 94-95 
thickwire (lOBase-5), 93, 
190-192, 196 

thinwire (lOBase-2), 92, 
192-193, 195 

twisted-pair (lOBase-T), 68, 
95, 193-194, 196 
zone names, 144-147 
EtherPeek (AG Group), 322-323 
EtherPrint bridge (Dayna 
Communication), 186, 189 
EtherPrint Plus bridge (Dayna 
Communication), 187 
EtherTalk (Apple), 26-27, 

establishing node 
numbers, 141 

EtherTalk Link Access Protocol 
(ELAP), 136 
software drivers, 190 
EtherWrite bridge (Compat- 
ible Systems), 187 
Everywhere Development 
Corporation, 387 
Excel (Microsoft), 212 
Data Access Language 
(DAL), 109 

Executive Workstation 
(MediaWorks), 271 
eXodus (Wliite Pine 
Software), 240 
Expression layer of 
communications, 10 
matching senders and 
receivers, 13-15 
Extended Binary Coded 
Decimal Interchange Code 
(EBCDIC), 273 
exterior routers, 176 

live Wired 


Fairfield Software, Inc., 387 
Clear Access, 109 
Farallon Computing, Inc., 387 
LocalPath bridge, 187 
NetAtlas, 320 
PhoneNET, 182-187 
NetPICT diagrams, 

376, 380 

PhoneNET PC, 219-221 
PhoneNET Repeater, 67 
PhoneNET Talk PC, 23 
StarController repeater, 67, 
94, 183, 185 

FastPath router (Shiva), 80-81 
FDDI (Fiber Distributed Data 
Interconnect) (Apple), 28-29, 

backbone topologies 
multiple Ethernet 
networks, 309 
multiple Ethernet WAN 
networks, 309-311 
NetPICT diagrams, 369, 371 
ring topologies, 95 
wiring standards, 194 
FDDITalk drivers, 198 
fiber optic cabling, 289-290 
File Transfer Protocol (FTP), 
integrating Macintosh and 
UNIX, 235-236 
FileMaker Pro (Claris), 212 

for NetPICT symbols, 286 
names, with mixed-plat- 
form environments, 103 


Apple Filing Protocol 
(AFP), on other 
platforms, 102-103 
AppleShare, 99-101 
Macintosh File Sharing 
(System 7), 101-102 
filtering bridges, 70 
Flight Simulator (Microsoft), 

Focus, Inc., 387 

TurboStar repeater, 68, 

94, 185 

Format NetPICT layer, 19-22 
designing, 284-285 
integrating Macintosh 
and DEC VAX, 258-259 
and IBM mainframes/ 
midranges, 273 
and PCs, 214-218 
and UNIX, 242-243 
standard Macintosh, 32-33 
standard PC, 34-35 

ASCII, 116,214, 258 
binary, 121, 258-259 
common standard, 122-123 
versus conversion, 124 
EPSF (Encapsulated 
PostScript), 119-120 
GIF (Graphic Interchange 
Format), 120-121 
graphics, 118-120,215-218 
MacPaint, 118 
ODA (Open Document 
Architecture), 122-123 
PDF (Portable Document 
Format), 123 


PICT, 118-119 
PICT2, 118 
platform differences, 
PostScript, 119 
raster, 120-121 
TIFF (Tagged Image File 
Format), 120-121 
word processing, 1 16-117, 

Frame Relay packet switched 
networks, 207 
frames, 43, 56-57 
Frequency Modulation, 58 
front-end to terminal-based 
services, 107 

FTP (File Transfer Protocol), 
integrating Macintosh and 
UNIX, 235-236 
FTP Software’s PC/TCP 
Plus, 226 

FTPShare (Advanced Software 
Concepts), 236 


gateways, 86-87 
AppleTalk, 87-90 
AppleTalk/ DCCnet, 263-264 
AppleTalk/ LAT, 264-265 
Macintosh/SNA, 277 
mail, 111-112 

NetPICT diagrams, 374, 381 
SNA»ps (Apple), 274, 277 
GatorBox gateway (Cayman), 
NetPICT diagrams, 374 

Graphic Interchange Format 
(GIF), 120-121 
Graphical Query Language 
(GQL) (Andyne), Data Access 
Language, 109 
graphics formats 
EPSF (Encapsulated 
PostScript), 119-120 
integrating Macs and PCs, 

MacPaint bitmap, 118 
PICT, 118-119 
PICT2, 118 
PostScript, 119 


Hayes Microcomputer 
Products, Inc., 387 
Helios USA, 388 
Hewlett-Packard Co., 388 
PCL format, 35 
UNIX computers 
/VFP/PAP services, 

DAL servers, 109, 234 
Hijaak (Inset Systems), 217 
hops, 76 
hubs, 90 
ASCII text, 116 
creating custom terminal 
front ends, 272 
DAL client applications, 108 
HyperFTP freeware stack, 235 

live Wired 


IBM Corporation, 388 
3270 and 5250 terminals, 
emulating, 106 
DAL servers, 109 
DB2 databases, accessing, 

mainframes/ midranges, 
integrating with 
Macintosh, 269-278 
multiprotocol routers, 205 
NetPICT diagrams, 376-377 
PROFS mail gateways, 112 
icons, AppleShare, 100 
Idea layer of communication, 

matching senders and 
receivers, 13-15 
IDEAssociates, Inc., 388 
IEEE 802.3 (lOBase-F) 
standard, 289 
IGES (Initial Graphics Ex- 
change Specification) format, 

Impulse Technology, 388 
FDDI cards, 198 
Informix databases, 
accessing, 109 
Infotek, Inc., 388 
Ingres databases, accessing, 

Initial Graphics Exchange 
Specification (IGES) format, 

Inset Systems’ Hijaak, 217 

Integrated Services Digital 
Network (ISDN), 204-205 
Inter»Poll (Apple), 318-319 
InterCon Systems Corp., 388 
InterPrint, 233 
NFS, 226 
NFS/Share, 237 
Planet X, 240 
WatchTower, 317 
interior routers, 176 
International Transware, 

Inc., 388 

Internet Protocol (IP), see 

internetworks, 51, 81 
InterPrint (InterCon), 233 
IP addressing, 245-247 
IPT (Information Presentation 
Technologies), 388 
Partner, 237 
IRMA Workstation for 
Macintosh (DCA), 270 
ISDN (Integrated Ser\ices 
Digital Network), 204-205 
ISO standards. Open 
Document Architecture 
(ODA), 122-123 


K-AShare (Xinet), 232 
NetPICT diagrams, 382 
K-Spool (Xinet), 232-233 
NetPICT diagrams, 382 
K-Talk (Xinet), 244 
Kandu Software Corp., 388 


Keywork Technologies, 389 
Keypak, 259 

Kinetics FastPath router, 75 


LAN Manager (Microsoft), 35 
LanRover (Shiva), 28, 335 
LANs, see Local Area Networks 
LANsurveyor (Neon Software), 

LaserWriter printers, 104 
NetPICT diagrams, 370 
virtual, 233 

LAT, see Local Area Transport 

Expression, 10 
idea, 10 

matching, 13-15 
Medium, 1 1-12 
Transport, 11 

Cabling, see Cabling 
NetPICT layer 
Format, see Format 
NetPICT layer 
matching, 37-38 
Transport, see Transport 
NetPICT layer 
Service, see Service 
NetPICT layer 
standard Macintosh, 

standard PC, 34-36 
swapping, 36-37 

OSl Reference Model, 40-43 
with Macintosh, 44-45 
leased-Iine services for 
WANs, 205 

Lightspeeed C (Symantec), 
ASCII text, 116 
LLAP (Local Falk Link Access 
Protocol), 136 

Local Area Netw'orks (LANs), 

ARCNET, 200, 229-230 
Ethernet, see Ethernet 
LocalTalk, seeLocalTalk 
PhoneNET, 182-187 
Serial RS-232/422, 199-200 
Token Ring, see Token Ring 
wireless, 200-202 
Local Area Transport (LAT) 
(DEC), 82-86 
AppleTalk/LAT Gateway, 

integrating Macintosh and 
DEC VAX, 262-263 
NetPICT diagrams, 378 
LocalPath bridge (Farallon), 


LocalPeek (AG Group), 322-323 
LocalSwitch bridge (Tribe), 

NetPICT diagrams, 376 
LocalTalk (Apple), 26, 179-182 
AppleTalk LAT Gateway, 

bandwidth, comparing with 
Ethernet, 330-331 
bridges, 71 

Live Wired 

Carrier Sense Multiple 
Access/Collision Avoid- 
ance (CSMA/CA), 63 
daisy-chain topologies, 91 
integrating Macintosh 
and DEC VAX, 266 
and PCs, 227 
and UNIX, 248 
isolating high-traffic nodes, 

bridged backbone, 

305- 306 

Ethernet backbone, 

306- 307 

routed backbone, 304-305 
serially-routed, 302-304 
NetPICT diagrams, 370-371, 
373, 376-377, 379-380 
network signals, 62-63 
repeaters, 67-68 

active star, 298-299 
bridged star, 302 
daisy-chain, 292-294 
multiple star, 300-301 
passive star, 297-298 
star topologies, 94 
zone names, 143-144 
LocalTalk Link Access Protocol 
(LEAP), 136 

logical addressing, 50-53 
Long DDPs, 138 
Lotus 1-2-3, 34-35, 212 
DAL (Data Access Lan- 
guage), 109 
LU 6.2 protocol, 274 

MacDraw Pro format support, 

AppleTalk transport 

addressing, 137-147 
Chooser, 155-165 
Phase 1 and 2, 148-155 
routers, 166-178 
suite of protocols, 127-136 
cabling systems 
ARCNET, 200 
conventional analog 
dial-up, 203-204 
Ethernet, 187-196 
FDDI (Fiber Distributed 
Data Interface), 197-199 
ISDN (Integrated Ser- 
vices Digital Network), 

leased-line services, 205 
LocalTalk, 179-187 
packet switched, 207 
PhoneNET, 182-187 
Serial RS-232/422, 

Switched 56K Service, 


Token Ring, 196-197 
wireless, 200-202 
X.25 packet switched, 

coax and twinax cards, 276 
E-mail, 110-113 


formats, 115-116 
binary, 121 

document interchange 
common standcird, 

document interchange 
conversion, 124-126 
graphics, 118-120 
raster, 120-121 
word processing, 116-117 

with DEC VAX, 257-267 
with IBM mainframes/ 
midranges, 269-278 
with PCs, 21 1-230 
with UNIX, 231-248 
MacPaint, 1 18 
NetPICT diagrams, 371-372, 
377, 379, 381 
QuickDraw, 118-119 

Apple Open Collabora- 
tion Environment 
(AOCE), 105-106 
database, 108-110 
file sharing, 99-103 
mail, 110-113 
printing, 103-105 
terminal, 106-108 
standard networking layers, 

Macintosh Communications 
Toolbox (MCT) 
AppleTalk/pECnet tool, 264 
AppleTalk/ 1 AT tool, 265 
CTERM Communications 
tool, 262 

integrating Macintosh and 
UNIX, 241-242 
Macintosh File Sharing, 

MaclPX (Novell), 223 
MacLAN Connect Gold 
(Miramar Systems Inc.), 222 
MacLinkPlus (DataViz), 

MacMainFrame (Avatar), 270 
MacODA (Apple), 122-123 
MacPaint (Macintosh) bitmap 
graphics format, 118 
MacTCP (Apple), 23-24, 226, 

MacTerminal (Apple), 252 
NetPICT diagrams, 377-378 
MacWorkStation (United Data 
Corporation), 108 
MacX (Apple), 25, 240, 252-253 
Mail (Microsoft), 212 
mail, electronic, see E-mail 
Mail for Macintosh 
(Microsoft), 111, 256 
MailMateQM (Alisa), 112 
mainframes (IBM), integrating 
with Macintosh 
cabling systems 
direct connections, 
Ethernet, 278 
Token Ring, 278 
formats, 273 
NetPICT diagrams, 376 

DAL database, 272 
terminal, 269-272 
transport protocols, 273-275 

Live Wired 

Management Information 
Base (MIB), 316 
mapping networks, 320 
Marietta Systems 
International, 389 

communication layers, 13-15 
networking layers, 37-38 
Mathematica, 39 
Mbps (million bits per 
second), 66 
MCI, 389 

Mail, mail gateways, 1 12 
MCT, see Macintosh Commu- 
nications Toolbox 
MDG Computer Services, 389 
MediaWorks’ Executive 
Workstation, 271 
Medium layer of 
communications, 11-15 
memory, PRAM (Parameter 
RAM), 139 
MHS (Novell), mail 
gateways, 112 
MIB (Management 
Information Base), 316 
Microsoft Corporation, 389 
applications for both Macs 
and PCs, 212 
Excel, DAL (Data Access 
Language), 109 
LAN Manager, 35 
Mail for Macintosh, 111, 256 
Word, data format 
translators, 117 
million bits per second 
(Mbps), 66 

Miramar Systems Inc., 389 
MacLAN Connect Gold, 222 
Mitem Corporation, 389 
MitemView, 108 
Mitem Vision, 271 
modem ports, 26 
modulating amplitude, 58 
Motif (Open Software 
Foundation), 238 

Altair II wireless networks, 
EMBARC, 201 
Computer Group, 389 
MPW (Apple), ASCII text, 116 
MultiAccess Computing 
Corp., 389 
multicasting, 84 

Phase 2, versus Phase 1 
broadcasting, 153-155 

Ethernet networks 
FDDI backbone, 309 
FDDI backbone WAN, 

routed backbone and 
star, 307-308 
LocalTalk networks 
bridged backbone, 

305- 306 

Ethernet backbone, 

306- 307 

routed backbone, 304-305 
serially-routed, 302-304 
star topologies, single 
LocalTalk networks, 


multiprotocol routers, 80-86 
with leased-line 
services, 205 


Name Binding Protocol (NBP), 
134, 157 

domain headers (Dls), 

Neuvork Visible Entities 
(NVEs), 157-165 
zone, AppleTalk, 142-147 
Names Information Socket, 160 
National Semiconductor 
Corporation, 389 
NBP (Name Binding Protocol), 
134, 157 

NCSA Telnet, 235, 241 
NE1000/NE2000 (Novell), 228 
Neon Software, Inc., 390 
LANsurveyor, 320 
NetMinder, 322-323 
RouterCheck, 321 
NetAtlas (Farallon), 320 
NetMinder (Neon Software), 

NetMounter (Dayna), 223 
NetPICT diagrams, 375 
NetPlCT symbols 
comparing with OSl 
Reference Model, 40 
designing networks witli, 

diagrams, 369-382 


Cabling, see Cabling 
NetPICT layer 
Format, see Format 
NetPICT layer 
matching, 37-38 
Transport, see Transport 
NetPICT layer 
Service, see Service 
NetPICT layer 
standard Macintosh, 

standard PC, 34-36 
swapping, 36-37 
NetWare (Novell), 35 
integrating Macs and 
PCs, 222 

NetPICT diagrams, 379-380 
SQLNLM, DAL support, 109 
Network Filing System (NFS) 
(Sun Microsystems), 237-238 
gateways with Apple Filing 
Protocol (AFP), 87-88 
NetPICT diagrams, 379 
Network General Corporation, 

network numbers, 51 
AppleTalk, 137-138 
Phase 1 and 2 assign- 
ments, 149-152 
Network OSI layer, 42-43 
Macintosh protocols, 

with Macintosh, 45 
Network Resources 
Corporation, 390 

Live Wired 

Network Visible Entities 
(NVEs), 157-165 
Network Vital Signs (Dayna), 

networking cards, see cards 
networking layers, see NetPICT 

addressing, 49-50 
logical, 50-53 
physical, 54-55 
analyzers (packet sniffers), 

analyzing traffic levels, 
bandwidth, 59 

comparing Ethernet and 
LocalTalk, 330-331 
broadband, 59 
circuit-switched, 47-50 
designing, see designing 
frames, 56-57 
future, 337-339 

high-traffic nodes, 
traffic, 77-78 
managing, 313-317 
mapping, 320 
packet-switched, 47-50 
security, 335-336 
serially-routed, 76 
signaling, 57-63 
Nevada Western, 390 
Newton (Apple), 29 

NFS, see Network Filing 

NFS/Share (InterCon), 237 
nodes, 50 

configuring, managing, 
numbers, 50 

AppleTalk, 138-142 
Novell, Inc., 390 
DAL servers, 109 
integrating Macs and PCs, 

MHS, mail gateways, 112 
NE1000/NE2000, 228 
NetWare, see NetWare 
NuBus Token Ring card 
(Apple), 229 
network, 51 

AppleTalk, 137-138, 
node, 50 

AppleTalk, 138-142 
socket, 51-52 

Names Information 
Socket, 160 
NVEs (Network Visible 
Entities), 157-165 


octets, 19 

ON Technology, Inc., 390 
Open Document Architecture 
(ODA) standard, 122-123 


Open Shortest Path First 
(OSPF) protocol, 310, 338 
Open Software Foundation’s 
Motif, 238 

Oracle Corporation, 390 
databases, accessing. 

OSl Reference Model 
layers, 40-43 
with Macintosh, 44-45 


Pacer Softu'are, Inc., 390 
AppleTalk implementation, 

DAL servers, 109 
PacerShare, 233, 256 
packet-switched networks, 
47-50, 206-207 

acknowledge control, 139 
enquiry control, 139 
sniffers (network analyzers), 

transaction release, 134 
transaction request, 133 
transaction response, 134 
PageMaker (Aldus), translating 
formats between versions, 


PAP, see Printer Access 

Parameter RAM (PRAM), 139 
Partner (IPT), 237 

passive star topologies. 183-185 
single LocalTalk networks, 

Pathway NFS (Wollongong), 

PATHWORKS for Macintosh 

CTERM Communications 
Tool, 262 

DAL server for VMS, 256 
DECnet, 261 
E-mail, 256-257 
gateways, 88-89 
MacTerminal terminal 
emulation, 252 
MacX X- Window 
emulation, 252-253 
terminal access, 107 
VAXshare, seeVAXshare 
PC-NFS (Sun Microsystems), 

PC/TCP Plus (FTP Softw'are), 

PCL format (Hewlett-Packard], 

PCs (personal computers) 
integrating with Macs 
services, 211-213 
cabling systems, 227-230 
formats, 213-218 
transport protocols, 

NetPlCT diagrams, 380 
standard networking layers, 

Live Wired 

PDF (Portable Document 
Format), 123 
Phase 1 networks 

broadcasting, versus Phase 
2 multicasting, 153-155 
device limits, 148-149 
network number 
assignments, 149-152 
zone names, 143-144 
Phase 2 networks 

multicasting, versus Phase 1 
broadcasting, 153-155 
network number 
assignments, 149-152 
transition routing, 152-153 
zone names, 144-147 
PhoneNET (Farallon), 182-187 
NetPlCT diagrams, 376, 380 
PhoneNET PC (Farallon), 

PhoneNET Repeater 
(Farallon), 67 
PhoneNet Talk PC 
(Farallon), 23 

Photonics Corporation, 390 
infrared devices, 201 
physical addressing, 50, 54-55 
Physical OSl layer, 41-43 
with Macintosh, 45 
PICT graphics format, 118-119 
files for NetPlCT 
symbols, 286 

P1CT2 graphics format, 1 18 
PICTviewer, 286-287 
Planet X (InterCon), 240 
Point-to-Point Protocol (PPP), 
310, 338 

Portable Document Format 
(PDF), 123 

printer serial, 180 
router, 73 
serial, 26 

PostScript (Adobe), 33, 35, 1 19 
Macintosh protocol, 129 
PowerPoint (Microsoft), 212 
PPP (Point-to-Point Protocol), 
310, 338 

PRAM (Parameter RAM), 139 
Presentation OSI layer, 41-42 
Macintosh protocols, 129 
with Macintosh, 44 
Printer Access Protocol (PAP), 
103-105, 131-132 
on UNIX computers, 

VAXshare, 253-256 
printer serial ports, 26, 180 

LaserWriter, 104 

NetPlCT diagrams, 370 
virtual, 233 
managing, 315 
PROFS (IBM), 271 
mail gateways, 112 
agent, 314 

integrating Macs and PCs, 
responder, 314 
Project (Microsoft), 212 
Protocol NetPlCT layer, see 
Transport NetPlCT layer 
protocol transparent, 66 


protocols, 11, 23 
Address Resolution 
Protocol (ARP), 55 
Advanced Peer-to-Peer 
Networking (APPN), 274 
Advanced Program-to- 
Program Communications 
(APPC), 274 

Apple Data Stream Protocol 
(ADSP), 132 

Apple Filing Protocol (AFP), 
see Apple Filing Protocol 
Apple Management 
Protocol (AMP), 315 
Apple Secure Data Stream 
Protocol (ASDSP), 106, 

132, 323 

Apple Transaction Protocol 
(ATP), 133-134 
Apple Update Routing 
Protocol (AURP), 133, 

AppleTalk Address 
Resolution Protocol 
(AARP),55, 141-142 
AppleTalk Echo Protocol 
(AEP), 134 

AppleTalk for VMS, 260 
AppleTalk Remote Access 
Protocol (ARAP), 27-28 
AppleTalk Session Protocol 
(ASP), 131 

AppleTalk suite of, 127-136 
Asynchronous, NetPlCT 
diagrams, 378 
CTERM, 262, 377 
Datagram Deliveiy Protocol 
(DDP), 134-135, 138 

EtherTalk Link Access 
Protocol (ELAP), 136, 190 
File Transfer Protocol (FTP), 
integrating Macintosh and 
UNIX, 235-236 
Local Area Transport (LAT), 
see Local Area Transport 
LocalTalk Link Access 
Protocol (LLAP), 136 
LU 6.2, 274 

Name Binding Protocol 
(NBP), 134, 157 
OSPF (Open Shortest Path 
First), 310, 338 
Printer Access Protocol 
(PAP), see Printer Access 

Point-to-Point Protocol 
(PPP),310, 338 
PostScript, 129 
QuickDraw, 129 
Routing Table Maintenance 
Protocol (RTMP), 132-133, 
167-168, 171-172 
Simple Mail Transfer 
Protocol (SMTP), 111 
Simple Network 
Management Protocol 
(SNMP), 315-317 
System Application 
Architecture (SAA), 274 
System Network Architec- 
ture (SNA), 274 
TCP/IP (Transmission 
Control Protocol/ Internet 
Protocol), seeTCP/IP 
TokenTalk Link Access 
Protocol (TIAP), 136 

Live Wired 

tunneling (encapsulating), 

Zone Information Protocol 
(ZIP), 130-131 


QuickDraw (Macintosh), 32-33 
Macintosh protocol, 129 
PICT format, 118-119 
QuickMail (CE Software), 

QuickTime for Windows 
(Apple), 212 


Racal-Interlan, Inc., 391 
racks for electronic 
equipment, 90 
radial topologies, see star 

RAM, Parameter (PRAM), 139 
ranges, startup, 149 
raster formats, 120-121 
Rdb databases (DEC), 
accessing, 109 
relational databases, 
accessing, 108-110 
repeaters, 66-67 
Ethernet, 68 
LocalTalk, 67-68 
NetPICT diagrams, 376 
responder programs, 314 
Rich Text Format (RTF), 214 

ring topologies, 95 
RJ-11 connectors, 182 
RouterCheck (Neon 
Software), 321 
routers, 51, 73-74 
AppleTalk, 75-79, 166 
updating routing tables, 

multiple Ethernet 
networks, 307-308 
multiple LocalTalk 
networks, 304-305 
exterior, 176 
interior, 176 

isolating high-traffic nodes, 

multiprotocol, 80-86 
with leased-line 
services, 205 

NetPICT diagrams, 372-375, 
seed, 304-305 
serial, multiple LocalTalk 
networks, 302-304 
troubleshooting, 321 
tunneling protocols, 174-178 

Bellman-Ford, 169-170 
transition, AppleTalk Phase 
2, 152-153 

vector-distance, 169-170 
Routing Table Maintenance 
Protocol (RTMP), 132-133, 
167-168, 171-172 
routing tables, AppleTalk, 

updating, 166-174 



NetPICT diagrams, 371, 

Serial networks, 199-200 
RTF (Rich Text Format), 214 
RTMP (Routing Table 
Maintenance Protocol), 
132-133, 167-168, 171-172 


SAA (System Application 
Architecture), 274 
SCSI /Ethernet adapters, 189 
SDLC (Synchronous Data Link 
Control) connections, 275 
security, 335-336 

Apple Open Collaboration 
Environment (AOCE), 106 
seed routers, 304-305 
SequeLink (TechGnosis), 109 
sequencing, controlling, 131 
Serial NB card (Apple), 277 
serial ports, 26 
printer, 180 
Serial RS-232 

integrating Macintosh and 
DEC VAX, 267 
networks, 199-200 
Serial RS-422 networks, 199-200 
serially- routed topologies, 76 
multiple LocalTalk networks, 

Apple Filing Protocol (AFP), 

Data Access Language 
(DAL), 108-110, 234, 272 
File Transfer Protocol (FTP), 
managing, 315 
NetPICT diagrams, 374 
Network Filing System 

terminal, 82, 241-242, 262, 

X- Window, 238-241 
see also client/server 

Service NetPICT layer, 18 
designing, 283-285 
integrating Macintosh 
and IBM mainframes/ 
midranges, 269-272 
and PCs, 211-213 
and UNIX, 232-242 
standard Macintosh, 32 
standard PC, 34 
Session OSl layer, 42 
Macintosh protocols, 

with Macintosh, 45 
Shiva Corporation, 391 
FastPath router, 80-81 
LanRover, 28, 335 
Short DDPs, 138 
signaling, 57-63 
SimMac (Simware), 272 
Simple Mail Transfer Protocol 
(SMTP), 111 

Simple Network Management 
Protocol (SNMP), 315-317 

Live Wired 

single networks 

daisy-chain, 294-296 
twisted-pair star, 299-300 

active star, 298-299 
bridged star, 302 
daisy-chain, 292-294 
multiple star, 300-301 
passive star, 297-298 
Sitka Corporation, 391 
SMDS (Switched Multimegabit 
Data Service) packet 
switched networks, 207 
SMTP (Simple Mail Transfer 
Protocol), 111 
SNA (System Network 
Architecture), 274 
SNA»ps (Apple) 

3270 terminal emulator, 270 
gateway, 274, 277 

NetPICT diagrams, 381 
SNMP (Simple Network 
Management Protocol), 

socket numbers, 51-52 
Names Information 
Socket, 160 
Soft-Switch Inc., 391 
SoftWriters, Inc., 391 
Sonic Systems, Inc., 391 
SuperBridge bridge, 187 
Source Routing Bridges 
(SRBs), 334 
SPARCstations (Sun) 

AFP/ PAP services, 232-233 
DAL servers, 109, 234 

integrating Macintosh 
and UNIX with Partner 
(IPT), 237 

speed, electromagnetic 
signals, 58 

spooling print jobs, 104-105 
SprintTALK bridge (Digital 
Products), 187 
SRBs (Source Routing 
Bridges), 334 
Standard Microsystems 
Corporation, 391 
ASCII, 20-21 
ANSI X3T9.5; FDDI, 290 
IEEE 802.3 (lOBase-F), 289 
EIA/TIA 568 andTSB-36, 

Open Document Architec- 
ture (ODA), 122-123 
Unicode, 20 

wiring, anticipating, 194 

integrating Macintosh 
and UNIX, 238-241 
MacX, 252-253 
star (radial) topologies, 93-95 
active, single LocalTalk 
networks, 298-299 
bridged, single LocalTalk 
networks, 302 

Ethernet networks, 

single LocalTalk networks, 


passive, single LocalTalk 
networks, 297-298 
single twisted-pair Ethernet 
netw'orks, 299-300 
with PhoneNET, 183-184 
StarController repeater 
(Farallon), 67, 94, 183, 185 
StarNine Technologies, 

Inc., 391 

startup ranges, 149 
structured wiring implemen- 
tations, 311-312 
substituting networking 
layers, 36-37 

suite of protocols, AppleTalk, 

Data Link OSI layer, 135-136 
Network OSI layer, 134-135 
Presentation OSI layer, 129 
Session OSI layer, 129-132 
Transport OSI layer, 132-134 
Sun Microsystems 

Network Filing System 
(NFS), 237-238 
PC-NFS, 226 
AFP/PAP services, 

DAL servers, 109, 234 
integrating Macintosh 
and UNIX, 237 
workstations, NetPICT 
diagrams, 382 
SuperBridge bridge (Sonic 
Systems), 187 
Switched 56K Service 
networks, 204 

Switched Multimegabit Data 
Service (SMDS) packet 
switched networks, 207 
Sybase databases, 
accessing, 109 
Symantec’s Lightspeeed C, 
ASCII text, 116 
Synchronous Data 
Link Control (SDLC) 
connecrions, 275 
SyncRouter (Engage 
Communications, Inc.) 

LTNT router, 204 

NetPICT diagrams, 375 
Synergy Software, 391 
System 7, Macintosh File 
Sharing, 101-102 
System Application 
Architecture (SAA), 274 
System Network Architecture 
(SNA), 274 


T1 WAN links, 66 

Address Mapping Table 
(AMT), 55, 141 

AppleTalk routing, 132-133, 

Zone Information Table 
(ZIT), 130-131 
Tagged Image File Format 
(TIFF), 120-121 
Talaris Systems, Inc., 391 
Tandem, DAL servers, 109 

Live Wired 

TCP/IP (Transmission Control 
Protocol/Internet Protocol) 
Address Resolution 
Protocol (ARP), 55 
integrating Macintosh 
and IBM mainframes/ 
midranges, 275 
and PCs, 226 
NetPICT diagrams, 381 
subdividing networks, 81-82 
on Macs, 244-247 
TechGnosis Inc., 392 
SequeLink, 109 
TechWorks, 392 
tee connectors, 193 
Tektronix graphics terminals, 
emulating, 106 
Telnet terminal service, 241 
NetPICT diagrams, 381 
Teradata's DBC/1012 
databases, accessing, 109 

emulators, 106 
3270, 269-270 
5250, 270 

Advanced Software 
Concepts (ASC), 241-242 
MacTerminal, 252 
NetPICT diagrams, 
377-378, 381 
servers, 82, 262 
services, 106-108 

integrating IBM main- 
frames/midranges with 
Macintosh, 269-272 
integrating Macintosh 
and UNIX, 241-242 
MacTerminal, 252 

Terranetics, 392 
testing network systems, 

text files for NetPICT 
symbols, 286 

thickwire (lOBase-5) Ethernet, 
93, 190-192, 196 
thinwire (lOBase-2) Ethernet, 
92, 192-193, 195 
Thomas-Conrad Corporation, 

Thursby Software Systems, 
Inc., 392 

TIFF (Tagged Image File 
Format) format, 120-121 
TLAP (TokenTalk Link Access 
Protocol), 136 
Token Ring, 196-197 

AppleTalk support for, 27 
integrating Macintosh 
and IBM mainframes/ 
midranges, 278 
and PCs, 228-229 
and UNIX, 248 
isolating high-traffic 
nodes, 334 

NetPICT diagrams, 370, 
372-373, 380 
network signals, 61-62 
networking cards, 36 
ring topologies, 95 
zone names, 144-147 
TokenPeek (AG Group), 
tokens, 61-62 
TokenTalk (Apple), 27 
TokenTalk Link Access 
Protocol (TLAP), 136 


topologies, 91 

backbone (bus), 76-77, 92-93 
bridged, multiple 
LocalTalk nettvorks, 

305- 306 

Ethernet, multiple 
LocalTalk networks, 

306- 307 

FDDl, multiple Ethernet 
networks, 309-311 
routed, multiple Ethernet 
networks, 307-308 
routed, multiple 
LocalTalk networks, 

with Ethernet, 196 
with PhoneNET, 185 
composite, 95 
daisy-chain, 91-92 

single Ethernet networks, 

single l^calTalk networks, 
ring, 95 

serially routed, 76 
multiple LocalTalk 
networks, 302-304 
star (radial), 93-95 

active, single LocalTalk 
networks, 298-299 
bridged, single LocalTalk 
networks, 302 
multiple Ethernet 
networks, 307-308 
multiple, single 
LocalTalk networks, 

passive, single LocalTalk 
networks, 297-298 
single twisted-pair 
Ethernet networks, 

with PhoneNET, 183-184 

analyzing levels, 331-332 
isolating high-talking 
nodes, 332-335 
transaction release 
packets, 134 
transaction request 
packets, 133 
transaction response 
packets, 134 
transceivers, 93, 191 
transition routing, AppleTalk 
Phase 2, 152-153 
Transmission Control 
Protocol/Internet Protocol, 
see TCP/IP 

transmission errors, cyclic 
redundancy checks, 57 
Transport NetPlCT layer, 22-25 
AppleTalk for UNIX, 244 
AppleTalk for VMS, 260 
Gateway, 263-264 
AppleTalk/LAT Gateway, 

DECnet, 261-262 
designing, 284-285 
integrating Macintosh 
and DEC VAX, 262-263 
and IBM mainframes/ 
midranges, 273-275 
and PCs, 218-226 

Live Wired 

standard Macintosh, 33 
standard PC, 35 
Transport layer of 
communications, 1 1 
matching senders and 
receivers, 13-15 
Transport OSI layer, 42-43 
Macintosh protocols, 

with Macintosh, 45 
Tribe Computer Works, 392 
LocalSwitch bridge, 71, 302 
NetPICT diagrams, 376 
TribeStar bridge, 305, 332 
Trik, Inc., 392 
Chooser, 324-330 
finding printers, 165 
mapping networks, 320 
network analyzers (packet 
sniffers), 322-323 
routers, 321 

testing systems, 318-319 
tunneling, 85-86, 174-178 
TurboStar repeater (Focus), 

68, 94, 185 

twinaxial (twinax) cable, 276 
twisted-pair (lOBase-T) 
Ethernet, 68, 95, 193-194, 196 
single star networks, 299-300 
type code, 57 


Ultrix (DEC) 

AFP/ PAP services, 233 
DAL servers, 109, 234 

Ungermann-Bass, Inc., 392 
Unicode standard, 20 
United Data Corporation, 393 
MacWorkStation, 108 

DAL servers, 109 
integrating with Macintosh 
cabling systems, 248 
formats, 242-243 
services, 231-242 
terminal protocols, 

Simple Mail Transfer 
Protocol (SMTP), 111 
Unshielded Twisted-Pair 
(UTP) wiring, 289 
upgrading network software, 

US Sprint Communications, 

vampire taps, 191 

Apple Filing Protocol (AFP) 
servers, 102-103 
DAL servers, 109 
integrating with Macintosh 
cabling systems, 266-267 
formats, 257-259 
services, 251-257 
transport protocols, 

VAXshare, 102-103,253-256 
integrating files between 
Macintosh and VAX, 258 
PAP spooler, 105 
vector-distance routing, 

VersaTerm-Pro, 235, 241 


VINES (Banyan), 35, 224 
NetPlCT diagrams, 374 
virtual LaserWriters, 233 
VMS Mail, mail gatev\'ays, 112 
VT-series terminals (DEC), 
emulating, 106 


WANs, see Wide Area Networks 
WatchTower (InterCon), 317 
Webster Computer 
Corporation, 393 
Wellfleet routers, 85 
multiprotocol, 205 
White Pine Software, 393 
eXodus, 240 

Wide Area Networks (WANs), 

conventional analog 
dial-up, 203-204 
ISDN (Integrated Services 
Digital Network), 204-205 
leased-line services, 205 
multiple Ethernet FDDI 
backbone networks, 

NetPlCT diagrams, 374 
packet switched, 207 
Switched 56K Service, 204 
X.25 packet switched, 

wildcard characters, with 
Network Visible Entities 
(NVEs), 158 
WilTel, 393 

wireless networks, 200-202 

wiring closets, 290-291 
The Wollongong Group, 

Inc., 392 
NFS, 226 

Pathway NFS, 237 
Word (Microsoft), 212 

data formal translators, 117 
word processing formats, 

integrating Macs and PCs, 

WordPerfect Corporation, 393 
WordPerfect, 212 


X-Window standard 

integrating Macintosh and 
UNIX, 238-241 
MacX, 252-253 

X.25 packet switched networks, 
Xinet, 393 

K-AShare, 232 
K-Spool, 232-233 
K-Talk, 244 

NetPlCT diagrams, 382 
XTND (Claris), data format 
translators, 117, 124-125 

Zone Information Protocol 
(ZIP), 130-131 

Zone Information Table (ZIT), 

Default, 145 
names, 78-79 

AppleTalk, 142-147 




I f youVe a Macintosh networking and communications 
professional you need to stay abreast of this fast-moving 
industry and you should be reading Connections: The 
Technical Journal of Macintosh Connectivity. Connections is 
the only publication devoted exclusively to issues that are 
important to people who design and implement Mac 
connectivity solutions. Whether you're interested in Mac to 
Mac, Mac to PC, Mac to UNIX, or Mac to mainframe 
connecti\ity. Connections has valuable information you 
cannot afford to be without. 

Connections is different because of its focus. We don’t spend 
time on video cards, monitors or spreadsheets. We talk 
about networking. This focus allows us to go beyond the 
topics found in the monthly and weekly magazines. 
Connections takes you inside the cutting-edge technology of 
such issues as Apple’s Open Collaboration Environment, 
Wide Area Networking strategies, and Enterprise Network 
Management techniques. Each issue of Connections 
provides you with approximately thirty-two pages of in- 
depth tutorials and analysis about the issues you face, and 
will be facing, on a daily basis. Connections does not accept 

any advertising, so ever>^ page contains information you 
can use. Information this focused on Macintosh 
networking is not available anwhere else. 

Connections costs just $195 a year for eight information- 
packed issues— a small price to pay for staying on top of the 
fastest-moving section of the Mac indiistr>\ 

You can try Connections: The Technical Journal of Macintosh 
Connectivity risk-free. Simply return tlie card below and 
you’ll receive your first issue absolutely free. If you decide 
Connections isn’t an outstanding resource, just write “cancel” 
on the accompanying invoice and we’ll stop the subscription 
immediately. Also, you can cancel your subscription at any 
time and we will refund the subscription fee for any 
remaining issues. 

Don’t miss another issue. Start your no-risk subscription 
today! Mail or fax a copy of the card below to: 

Winehouse Computer Company 

20 North Santa Cruz Avenue Tel: 408-354-2500 

Los Gatos, CA 95030 Fax: 408-354-2571 

I 1 

I YES! Please enter my no-risk subscription and send me o free issue of Connections. If I like what I see, HI pay SI 95 and get I 

I seven more issues for a total of eight. If not, I'll return the bill marked "cancel", keep the free issue, and owe nothing. I 

I □ Payment Enclosed □ US/Canada Subscription: $1 95 Name - 

I □ Bill Me □ Overseas Subscription: $250 Company | 

■ Charge my credit card: QVisa □ MasterCard Street ■ 

I Card Number Gty/State/ZIP ■ 

I Expires Phone Number | 

J Signature E-Mail Address j 

I I 

Making Sense of AppleTalk Networking 

Since 1986 ! 

When it comes to AppleTalk networking, few companies are as qualified as Computer 
Methods Corporation. Over the years, our organization has helped hundreds of companies 
of various types and sizes make sense of their AppleTalk networking needs. Our staff of 
highly trained AppleTalk experts can help you find answers to the tough questions like: 

"Hoiu many AppleTalk zone names can my internetwork handle?'' 

"How can I connect my Macintosh users at remote locations?" 

"What is the difference between seeding and non-seeding routers?" 

"When should I use a bridge and when should I use a router?" 

"What does the term tunneling mean and what are its implications?" 

"What are my options for wide-area AppleTalk networks?" 

"When will 1 exceed the limitatiorjs of my LocalTalk LANs?" 

"Should 1 replace them with Ethernet, Token Ring or FDDI LANs?" 



If AppleTalk networking has you confused, or if you’re interested in 
learning more about our full range of consulting services, call us today at... 

^ 800 - 969-4360 ^ 

• AppleTalk Network Integration Experts • Multivendor Systems Integrators 

• Certified Apple Developers • Members of the Apple Consultant Relations 

• Authorized Macintosh Resellers Team • Apple Training Alliance Partners 

525 Route 73 South, Suite 300, Marlton, NJ 08053 

How to Use 
the Disk 

his book comes with a disk that contains an 
entire library of the NetPICT symbols used 
throughout tlie book. For each NetPICT symbol 
there are two files: a PICT file that contains the 
graphical image, and a text file that contains a 
description of the image. The text file has the 
same name as the PICT, but with the addition of a 
“.txt” filename extension. For example, the PICT file for Apple’s 
Internet Router is named Apple Internet Router, while the text 
file is named Apple Internet Router.txt. 

The disk also contains a viewer application, Ccilled PICTviewer. 
PICT viewer is used to view both the NetPICT symbols and the 
associated text. PICTviewer provides an easy means for you to view 
and read informative data on hundreds of products. Of course, 
since the symbols are in the PICT format, they can be easily 
incorporated into documents made by your favorite drawing 
program. The same can be said for the text (.txt) files. These text 
files can be added to your drawings to annotate the figures. Many 
drawing programs, such as MacDraw Pro, can import text files 
directly. If your drawing program can’t directly import text files, 
then you’ll have to copy and paste the text using a text editor or 

word processor. By using a drawing program, you’ll be able to 
import those NetPICT symbols that represent the fundamental 
parts of your present or planned network. You’ll be able to see 
where bridges, routers, gateways, or even format translators are 



The NetPICT files are compressed to save spaa'l You will have to 
decompress them and save them to your hard disk in order to use 
them. (They will take about 3M of disk space when you have 
extracted them.) Double-click on the NetPiCTs.sea icon. You will 
be prompted to choose a location to save the extracted files. Wlien 
you have done so, click the Save button. The files will self-extract. 

To use the NetPICT viewer, you’ll need HyperCard 2.1 (or the 
HyperCard Viewer). You might also want to copy PICTviewer to 
your hard disk. 

1 . Launch the NetPICT viewer by double-clicking its icon. 

2. Click three times to close the splash screens. 

3. Use the pop-up folder menu to browse through the NetPICT 
symbol folder hierarchy. 

4. Once you’ve found the appropriate symbol, chck once on the 
name that appears in the window directly beneath the pop- 
up menu. 

The chosen NetPICT symbol will appear in a separate win- 
dow to the right of the viewer screen. You can reposition this 
window at any time. You can even enlarge it to the size of 
your monitor by clicking on the Zoom box located at the 
upper right hand corner of the symbol window. 

5. To restore the symbol window to the right side of the viewer 
window, click once on the magnet icon. This will automati- 
cally dock the symbol window to its default position at the 
right of the viewer window. 


A Guide to Net iv or king Macs 



Live Wired makes building networks as 
[clear and easy as the Mac itself. 


In this book, Mr. Anders introduces an 
^■elementary symbol language that unifies 
^Hand simplifies Macintosh network design 
vRand system integration. These symbols 
I -Uhelp make complex issues simple to 
grasp and easy to apply. Each hardware 
or software element relevant to net> 
working is explained and diagrammed — 

so you’re comfortable with their func- 

^^tions in the big picture. The result — 
properly designed, efficient networks. 


• How communication takes place 

• Necessary networking 

• How to design your own Mac 

Easy network diagramming with 

* How to network Macs and PCs 

about the author 

Jim Anders 

I Live Wired shows you more than just 
Mac-to-Mac networking. The book 
explores cross-platform networking 
.strategies with DOS, UNIX, DEC VAX, 
land various IBM platforms. Whatever 
you use, however you work with it, you 
can design your network with confidence 
using this popular method. 

He is a Senior Consulting Engineer with 
Computer Methods Corporation, specializing 
in Macintosh/VAX integration and 
CAD/CAM technologies. His reviews and arti- 
cles appear regularly in MacUser magazine. 


Disk includes the popular 
[NetPICT symbol encyclopedia 

Price: $29.95 US/$37.95 CAN 

ISBN 1-56830-015-8 





0015 :