ACM SIGCOMM ?74? Computer Communication Review Book Review: Interconnections: Bridges and Routers

Radia Perlman
ISBN 0?201?56332?0 (Hardback)
Addison?Wesley Publishing Company, Inc.

A Book Review By: Bill Warner
Senior Network Engineer
State of Ohio ? Office of Telecommunications
2151 Carmack Rd
Columbus, OH 43221
(614)466?6683
warner@ohio.gov

I found Dr. Radia Perlman's book Interconnections: Bridges and Routers thoroughly entertaining! While en? tertaining is not an adjective that usually applies to technical computer texts, this book definitely qualifies. Often while reading the book I found that I could not help but chuckle. More importantly, Dr. Perlman has the rare talent of explaining very difficult concepts in a way that makes them seem simple. In fact, often her crystal clear explanations makes you wonder why you didn't think of the idea yourself.

Dr. Perlman's many networking advances, including her work on the IEEE Spanning Tree Algorithms stan? dard and the International Standards Organization (ISO) Intermediate System to Intermediate System (IS?IS) routing protocols makes her well qualified to write this book.

Early in the book, Dr. Perlman gives an example of her "friendly" and unassuming writing style: "One should not take terminology too seriously." Another example later in the book, when discussing the differ? ences between OSI NSAPs and NETs: "I have never found the distinction interesting, useful, or completely comprehensible." Throughout the book sections are prefaced with appropriate quotations from networking giants, ranging from Woody Allen to Charles, Prince of Wales.

This book will appeal to a number of audiences. The book is a excellent introduction to computer network? ing for the novice. This does not mean that someone with more experience in the field will not find the book enlightening.

Dr. Perlman's experience with the International Standards process adds an insight into the many quirks in networking standards. Often she explains why a group of such talented network engineers can come up with standards with some very bizarre aspects.

True to it's name, the book discusses bridges and routers in depth. But in order to provide a knowledge base to discuss the topic, the first two chapters are an introduction to Local Area Networks, including both Ethernet, (and IEEE 802.3), and Token Ring (and IEEE 802.5), with a very brief discussion of Token Bus, and the IEEE 802.1 Logical Link Control (LLC).

The chapter on transparent bridging, begins discussing a simple non?learning bridge. Section by section Dr. Perlman builds on this bridge as she describes more complex bridges. In additional to a through explanation of the IEEE Transparent Bridging Spanning Tree Algorithm, she discusses possible extensions to the Algo? rithm, including Vitalink's proprietary "DLS" Protocol.

Dr. Perlman also describes the Source Route Style of bridges and the resulting Source Route Transparent bridge compromise allowing Token Rings and Ethernets to interoperate, including the quirks which result.

The router treatment includes detailed descriptions of both OSI's Connectionless Network Service (CLNS) and the Internet TCP/IP suite, with a brief discussion of the OSI Connection Oriented Network Service based on CCITT X.25.