Review of BGP4: Inter-Domain Routing in the Internet

BGP4: Inter-Domain Routing in the Internet
John W. Stewart III

Reviewed by Nick Christenson,

April 25, 1999

This is the first book I've seen in a new series from Addison-Wesley called the Networking Basics Series which covers a very focused topic in a brief format. Given the schedules of most information technology workers, it seems to me that the idea of covering important topics in our field with as much brevity as possible, such that our busy colleagues can gain access to this information even on their tight schedules, to be a great one. Certainly, the topic of this book, routing using the BGP4 protocol, is an excellent topic that had previously represented a considerable void in the available literature.

Stewart's book contains only four chapters, and starts, predictably enough, with an overview of IP networking. Especially in a brief book like this, it may seem tempting to forego such a topic which is almost certain to be well understood by a vast majority of its audience, and I think this is a fair consideration. On the other hand, it is certainly possible that a significant fraction of the readership may be unfamiliar with some specific aspects of the IP protocols that are especially germane to this book. For example, understanding classless addressing (CIDR) is crucial to understanding current Internetwork routing, and it's entirely conceivable that there are folks out there who would read this book that don't thoroughly understand all the issues and terminology associated with this topic. In any case, since this chapter is brief and pointed at exactly that information which is most important, I believe its inclusion is worthwhile.

Chapter two describes the BGP4 protocol in some detail. While dry, we do get all the information we need to know here and in one place. It may not be fun reading, but it does cover what we need to know. Further, it's much easier to digest than the RFCs.

Chapter three is, in my opinion, the real meat of the book. This chapter covers BGP4 operations, namely, how to construct BGP policy such that one's routing goals can be met. It covers all the most important situations, single connection to an ISP, redundant connections to one or more ISPs, interior routing with BGP, etc.. This chapter is much less dry than its predecessor, and the author speaks with authority covering the important points. However, as Stewart himself says, "It would be easy to write a whole book on multihoming [meaning, having more than one access point to one's network] and still not cover all the issues... ." I couldn't agree more, and despite the good work this book does, further elaboration on this topic, especially if it includes examples of how to implement this policy in code that a router can understand, would be of benefit to the Internet community. Perhaps for the sake of brevity, Stewart avoids the inclusion of specific implementations that include router commands, but a large audience would find it useful if someone did.

The final chapter covers commonly used extensions to the BGP4 protocol, referring to the relevant RFC and draft documents that govern the current state of their implementations. While most of the target audience of this book are unlikely to need the extensions, one's knowledge of BGP4 certainly isn't complete without understanding them, plus it gives the reader a greater insight into the logic behind the way the backbone providers organize their networks. The book concludes with a reference list, a glossary, and an index. After reading the book, there were a few things I wanted to look up to, but the index wasn't any help. I don't know if that demonstrates its inadequacy, it certainly may have been an aberration, but it wasn't helpful when I needed it.

Overall, I found this to be a very good book which achieved its aims quite well. Note that due to its small format, it is even shorter than its page count might suggest. I'd estimate that there are around half the number of words per page in this book than in most computer book formats. Because of this, I can't help but think the price, at $19.95, to be a little steep. I think a price closer to $15 would be more reasonable for the volume of information. Nonetheless, if you want to understand BGP4, this book is well worth the cost. I do worry a bit about getting value for the money from other books in this series, although I think the series itself is an excellent idea.


The best available description of BGP4 and well worth the effort for those who wish to understand this protocol. Succinct, the book achieves its aims, although there is still a great deal of room left for a more expansive book covering the intricacies of an implementation. However, the author does a fine job of indicating where the key issues are that require significant thought. If you want to know BGP4, this is the place to go.

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