Book Review - The Internet Protocol Journal - Volume 1, No. 2

Gigabit Ethernet
Gigabit Ethernet: Technology and Applications for High-Speed LANs, by Rich Seifert, ISBN 0-201-18553-9, Addison-Wesley, 1998,

Gigabit Ethernet is storming its way onto the high-speed LAN scene. From a concept in 1984 to an emerging commercial reality in 1998, Gigabit Ethernet promises to give other high-speed LAN technologies, especially ATM, a serious run for their money. Capitalizing on the basic ease of use and deployment that has made other forms of Ethernet the most popular LAN technology of all, Gigabit Ethernet promises to add major bandwidth to such networks in a straightforward, completely compatible, and relatively affordable way. This book performs an excellent survey of the technologies, algorithms, and design principles that make Gigabit Ethernet possible, and also explains where the tremendous appeal of Gigabit Ethernet really lies. Much of the book is devoted to explaining Ethernet principles and operation in general, as well as exploring recent developments that have enabled gigabit technologies to emerge.

The book is divided into three parts. Part I explores the foundations that underpin Gigabit Ethernet, starting with a brief but cogent exploration of Ethernet before gigabit versions loomed on the horizon. The rest of Part I covers the trends in LAN usage in general, and Ethernet in particular, that laid the groundwork for Gigabit Ethernet. These trends include the move from shared media to dedicated media on many LANs, and likewise from shared LANs to dedicated LANs, and the concomitant deployment of full-duplex technologies to support bidirectional, high-bandwidth communications. Seifert, an original member of the DIX (Digital-Intel-Xerox) team that developed Ethernet, writes clearly and compellingly about complex issues, such as flow control, medium independence, and automatic configuration, as he explains what made Gigabit Ethernet possible, if not inevitable.

In Part II, Seifert turns his focus onto Gigabit Ethernet itself, beginning with an overview. In the rest of Part II, he explains how Media Access Control (MAC) works for half-duplex and full-duplex versions of Gigabit Ethernet, and makes a strong case for the essential irrelevancy of shared-media and half-duplex operation for Gigabit Ethernet. Along the way, Seifert also covers how Gigabit Ethernet networking devices, such as repeaters and switching and routing hubs, must be designed and how they work, and covers the behavior and operation of the physical layer at gigabit speeds.

He concludes this section of the book with a brief overview of the current IEEE Draft 802.3z specification that governs current Gigabit Ethernet operations, and mentions ongoing work in the 802.3ab sub-committee to define a workable implementation for Gigabit Ethernet on twisted-pair media (1000BaseT, as it will probably be known). In Part III, Seifert tackles some of the most interesting material in this book. He begins with a discussion of how LANs and computers change roles over time in acting as the bottleneck for network use. The point here is that because of its extremely high bandwidth relative to the demands of most applications and end-user requirements, Gigabit Ethernet is likely to remain a backbone or clustering technology for the foreseeable future. He also explores the performance considerations for both networks and applications involved when extreme speeds or excessive bandwidths are available, to point out how bandwidth aggregation is presently Gigabit's most immediate and compelling contribution to networking.

Finally, he explores how Gigabit Ethernet compares to other high-speed networking technologies, including Fast Ethernet, Fiber Distributed Data Interface (FDDI), High-Performance Parallel Interface (HIPPI), Fibre Channel, and ATM. His discussion of why both ATM and Gigabit Ethernet are necessary, and why neither can fully supplant the other, represents a humorous and insightful analysis of why connection-oriented and connectionless communications and applications are both good, and why the two can never truly converge.

An Outstanding Contribution
A rundown of Seifert's layout and content, however, fails to do complete justice to this book. For one thing, Seifert's work includes the funniest and most ingenious footnotes I've seen in recent publications, including some truly horrendous puns and some downright howlers. For example, when discussing how repeaters work, he comments that "A jabbering station causes carrier sense to be continuously asserted and blocks all use of a shared LAN. A repeater looks for this condition and isolates the offending station." To this last sentence, he appends the following footnote: "Research is underway to determine if this mechanism can be extended for use on politicians and university lecturers." And this is just one of dozens of such gems that help to relieve the dryness that deeply technical material can sometimes manifest.

This book is also masterful simply because the author understands his material so well, and does such an outstanding job of explaining and exploring even the most abstruse networking concepts. Although I've been working with Ethernet for 15 years, I learned a great deal of new material from Part I of the book because old concepts were explained in new ways that improved my understanding. I suspect other readers will have one or two "Aha!" experiences from this tome as well.

But it's when making the case for full-duplex Gigabit Ethernet and exploring the requirements for switching and routing behaviors in Gigabit Ethernet networking devices that this material really shines.

Without a doubt, this book is among the very best of any of the literature available on high-speed networking today. I give it an A+ rating, not only because of the breadth and depth of its technical coverage and its compilation of essential concepts and information, but also because the author's deep understanding of networking protocols and communications needs enlivens all of his discussions of matters technical, business, and political. If you want to understand Gigabit Ethernet, this book is the obvious place to begin (and for many, to end) your search for enlightenment.

But even if all you want is a good read about expensive, exotic, and high-performance technology, Seifert's book offers the opportunity for outright enjoyment of the prose, and shared delight at untangling the technical dilemmas that any good design engineer must unravel on the road between a set of requirements and working implementation thereof.

Ed Tittel
LANWrights, Inc.

More Book Reviews
We have more book reviews awaiting publication:

Internet Cryptography, by Richard E. Smith, ISBN 0-201-92480-3, Addison-Wesley, 1998. Reviewed by Fred Avolio.

Web Security: A Step-by-Step Reference Guide, by Lincoln D. Stein, ISBN 0-201-63489-9, Addison-Wesley, December 1997. Reviewed by Richard Perlman

IP Multicasting: The Complete Guide to Interactive Corporate Networks, by Dave Kosiur ISBN 0-471-24359-0, Wiley Computer Publishing, 1998. Reviewed by Neophytos Iacovou.

So, make sure you receive the next issue of The Internet Protocol Journal due out in December 1998.