The Internet Protocol Journal - Volume 4, Number 2

Book Review

Internetworking with TCP/IP
Internetworking with TCP/IP (Vol. 1): Principles, Protocols, and Architectures, Douglas E. Comer, ISBN 0-13-018380-6, Prentice Hall, 2000.

Internetworking With TCP/IP (Vol. 1): Principles, Protocols, and Archi-tectures (fourth edition) is the latest update to Comer's landmark work containing Internetworking With TCP/IP (Vol. 2): Design, Implementation, and Internals and Internetworking With TCP/IP (Vol. 3): Client-Server Programming and Applications/BSD Socket Version. As a recent engineering graduate, I wish I had read this book sooner; it is very concise and would have saved me a lot of time early in my studies.

Comer imparts Volume 1 in four sections. The first section provides a basic introduction to general networking including descriptions of typical network components. This section is most helpful for the entry-level student or casual reader. Advanced readers may want to skip right to the next section of the text, which continues with coverage of the TCP/IP networking environment from the host's point of view. Here, the organization and operation of local host protocols, addressing, and routing are thoroughly discussed. After reading this portion of the book, you will definitely understand how your desktop computer communicates on the network. Next, the global Internet architecture is laid out in a very comprehensible format. The reader is introduced to router-to-router protocols and algorithms that don't seem so complicated after this treatment. Lastly, application-level services and the client-server model of networking are covered in the final portion of the book.

Classic Reference
When reviewing one of the eminent texts in the field, it is of limited use to comment on the work chapter by chapter. However, I am compelled to comment on the quality of Chapter 11, Protocol Layering. This chapter is particularly interesting because Comer directly compares the ISO 7-layer reference model to the TCP/IP 5-layer model. As is par for this book, the comparison is clear and concise. Furthermore, the advantages and disadvantages of protocol layering are discussed in general and a realistic perspective is provided with reference to actual software implementation practices which may result in layer blurring. This is a very cogent presentation of the interaction between theory and reality in engineering. Although covering a specific topic, it could easily serve as an object lesson in a discussion of "real world" engineering techniques. In addition to Chapter 11, the chapters covering Internet routing (14 through 16) really shine as mainstays of this book. The Internet is viewed from the top down and "big network" protocols such as the Border Gateway Protocol (BGP) are given good coverage. This is an area where very few people are completely comfortable and Comer once more brings the important material forward in an easily understandable fashion. In the following paragraphs, I will highlight some of the new material included in the fourth edition.

New TCP/IP Concepts
The book's handling of Classless Inter-Domain Routing (CIDR) is very informative. In addition to explaining the inner-workings of the address space, Comer points out the requirement for new routing algorithms. This is an associated cost of adopting this new concept that is often overlooked when CIDR is presented.

Two new and important IP topics are also well-presented. Comer begins his treatment of IP Version 6 (IPv6) with a quick history of the protocol and a review of the logic behind this change. The new address space notation and allocation by type are explained very well. New advantages provided under IPv6 protocol structures are then discussed. Additionally, Mobile IP concepts and practicalities are introduced. Comer does a good job of bringing out both good news and bad news of this crucial new networking technology.

Coverage of Random Early Drop (RED) was rather brief and really needs more detail before readers can thoroughly grasp the concept. However, this would require greater mathematical sophistication on the part of the reader. Accordingly, depth of coverage is forgone in the interest of readability.

The section on Network Address Translation (NAT) does not adequately explain the dynamic nature of IP address assignment across hosts and data flows. An additional detailed example would help here.

Multimedia
In the application-level services section of the book, Comer offers a hasty explanation of how voice and video are sent over IP internets and how IP Telephony operates. The H.323 protocol is briefly mentioned as the low-bandwidth videoconferencing standard. However, it is not presented in its full importance as an umbrella recommendation from the International Telecommunications Union (ITU). A chapter explaining the roles of subordinate H.320 protocols in general would be a welcome addition to this section. Quality of Service (QoS) concepts such as Resource Reservation Protocol (RSVP), Differentiated Services (Diff-Serv), and Real Time Protocol (RTP) are likewise given short rift. However, IP Multicast is given significant treatment in one of the book's longest chapters; its concepts, mechanics, and implementation choices are thoroughly addressed.

Security
The book provides clear introductions to Virtual Private Networks (VPNs) and the IPSec set of protocols. The actual mechanics of IPSec are detailed thoroughly. Various required algorithms are introduced and pertinent RFC references are pointed out. Finally, firewall basics and implementation issues are covered. Overall, these sections clearly define the pertinent security concepts and make them simple.

Prerequisite Knowledge
This book thoroughly covers the fundamental principles of network design including implementation trade-offs and their associated foibles. However, understanding this text requires little more than a modest understanding of basic computer and networking concepts. An introductory programming course that covers computer organization, the binary number system, and basic data structures should suffice. From this point, the student can use the text for initial network familiarization as well as a future reference to ground the more abstract topics in network design.

A Must Have Reference
An extensive, concept-based overview of the TCP/IP internetworking protocols makes Comer's Volume 1 the classic introduction to TCP/IP. He makes this an enjoyable read by breaking the topic into short, digestible chapters. Additionally, Comer pauses throughout the text to intersperse review material. Recurrent, italicized summaries provide a significant advantage to the student. These asides concisely summarize key points and provide a coherent set of landmarks for quick review and study.

By itself, Volume 1 is broad enough to be complete as an introduction to IP networking protocols. Comer further extends the work by pointing the reader to very specific resources for in-depth information including web pages and specific RFC numbers for applicable topics at the end of each chapter. One of life's simple treasures is found in the Guide to RFCs (Appendix 1). Here, the first 2728 RFCs are organized by major categories and subtopics. At last, a navigable index of RFCs has been in-corporated with a superb text from which the beginner can delve the body of networking knowledge.

—Albert C. Kinney
kinney@ieee.org



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