The Internet Protocol Journal - Volume 4, Number 1

Book Reviews

E-mail Books

Essential Email Standards: RFCs and Protocols Made Practical by Pete Loshin, ISBN 0-471-34597-0, John Wiley & Sons, Inc., 2000. www.wiley.com

Internet Email Protocols: A Developer's Guide, by Kevin Johnson, ISBN 0-201-43288-9, Addison-Wesley, 1999. www.awl.com

Deciding when to write a book about an exciting new technology is pretty easy. At first issuance of the standards for it, or emergence of a market for it, out will come the requisite texts. In 1993, when the commercial Internet started to surface, Marshall Rose produced The Internet Message: Closing The Book With Electronic Mail [Prentice Hall, 1993]; it's an excellent introduction to the core e-mail services. As the market grew, Rose and David Strom issued a more operations-oriented effort, Internet Messaging; From Desktop to the Enterprise [Prentice Hall, 1998]. For anyone serious about e-mail technology and operations, it remains required reading.

But what about straight technology exposition when the standards that have been in use for more than 20 years keep getting modified? In the case of Internet mail, this dilemma has been exacerbated by an extended recent effort to coalesce documentation for the service, compiling and clarifying the contents of many independent Internet Engineering Task Force (IETF) documents into two, one for the transfer service and one for the mail object definition. The best time to publish a book on the subject would be at the issuance of the two revisions. Unfortunately, the IETF effort has taken perhaps 3 years longer than expected, and Wiley and Addison-Wesley decided the market needed these books earlier. Hence the authors were faced with a juggling act, referring to original specifications, with appropriate nods to the new-but unstable-drafts.

Comprehensive Introductions
This tactical caveat notwithstanding, Peter Loshin's Essential Email Standards: RFC and Protocols Made Practical and Kevin Johnson's Internet Email Protocols: A Developer's Guide are credible and reasonably thorough. They introduce the reader to the technical details of Internet mail. Loshin adds detail about the standards culture that produced the specification. Johnson adds a bit of programming detail. No textbook on a technology should be used as the primary reference by someone building products, of course; and these are no exception. These are comprehensive introductions.

With such books, the criteria are simple. I look for helpful overall organization, clear language, and accurate content. These two books qualify. They summarize and restate the basic descriptions of services, data formats, protocol commands, and responses associated with the various standards.

Extra points are assigned when a book comes with commentary that provides some insight into the technical philosophy or operational pragmatics of the technology. Pleasantly, both books have a bit of these extras, too. Such texts typically also have minor technical errors; and these fit that profile, too. Since the reader is not using the book as an implementation reference, the occasional, small errors cause no harm.

Loshin's effort is 330 hardbound pages. Johnson's is about a third longer, softbound. Both books cover the core services of Submit, Simple Mail Transfer Protocol Service Extensions (ESMTP), the Post Office Protocol (POP), the Internet Mail Access Protocol (IMAP), RFC 822, and Multipurpose Internet Mail Extensions (MIME), that is, posting, relaying, and accessing e-mail, as well as description of the e-mail object. Both also discuss security. Submit is a recent spinoff from SMTP, for local user-relay posting. It began as a clone of ESMTP, but on a different port, and will permit service-to-service relaying functionality to diverge from the local, first-hop posting process. The market treats POP and IMAP as essentially competitive protocols, and both books explain their details adequately. I wish they had made the very simple architectural point that POP does last-hop delivery, to the user's PC-based message store, whereas IMAP is primarily for user access to a message store on a remote system. That is, one is for simply dumping an entire message queue onto the waiting user machine, whereas the other is for ongoing and interaction with portions of message data. On the other hand, an example of Loshin's extra credit is for noting that ISPs are reticent to support IMAP—they have not yet discovered that they could make money being a small business' back-office data store—whereas corporations like IMAP because it is an open standard that permits replacing proprietary workgroup message stores.

E-mail address resolution can be a bit tricky, requiring general understanding of the Domain Name Service and specific cleverness with MX "routing" records. Johnson devotes a useful, but very terse 2+ pages to the topic. Loshin allocates a 8+ pages.

Security
As with every other aspect of Internet standards making, e-mail security is problematic because no IETF-originated security protocol has yet gained wide deployment and use. Oddly continuing the peculiarity of security as a topic, both books are a little off-beat, albeit differently. Johnson provides a relatively extensive introduction to basic security technology, including descriptions of various algorithms, as well as a listing of the types of security attacks that can occur. He also discusses enhancements to the basic e-mail protocols for invoking security mechanisms. Loshin has a more functional systems orientation concerning overall e-mail security architecture. Although Loshin does not usually spend much time on ancient history, for some reason in this chapter he discusses two IETF failures of Privacy Enhanced Mail (PEM) and MIME Object Security Services (MOSS).

Both discuss Pretty Good Privacy (PGP), and PGP is certainly the long-standing popular choice among the technical community. Johnson discusses it in some detail; Loshin's coverage is minimal. Secure MIME (S/ MIME) has support from major industry software vendors. Loshin treats it equally as tersely as he treats PGP. Johnson barely mentions it.

Standards
Loshin spends the first 50 pages on the Internet standards community, process, and documents. His book also covers Internet News (NNTP) and some work involving standard data for business cards (vCard) and calendaring and scheduling (iCalendar). Besides being interesting topics, these last two were probably included because the Internet Mail Consortium acquired intellectual property rights to the precursor work and highlights the topics on its Web page. Loshin also ends with a chapter about the future, where he adds the topics of instant messaging and message tracking, based on continuing IETF standards work. An included CD-ROM contains a copy of the book, with Web links to cited documents such as RFCs.

Johnson's forays beyond the core services discuss messaging filtering and mailing-list processing, UNIX file issues, and generic, terse descriptions of some programming languages. He also discusses the Internet Message Support Protocol (IMSP), the Application Configuration Access Protocol (ACAP), and the Lightweight Directory Access Protocol (LDAP), protocols for accessing user configuration data. Obviously he intends that the reader take seriously the "Developer's" reference in the book title.

The Differences
Perhaps it is the programmer's orientation that caused Johnson to be so thorough with his discussions. This includes discussion of e-mail protocols that are not standards and not in use. Loshin in far more selective and reflective. And therein lies the easy distinction between the two efforts. Loshin gives an understanding of a portion of application space, providing the basic technical details tidbits of useful insight. Johnson is more mechanical and more detailed; in effect he chooses to be less selective and more detailed in what he dumps on the reader, letting the reader decide what is useful.

Dave Crocker, Brandenburg InternetWorking
dcrocker@brandenburg.com

Wireless and Mobile Network Architectures

Wireless and Mobile Network Architectures, by Yi-Bing Lin and Imrich Chlamtac, ISBN 0-471-39492-0, John Wiley & Sons, 2001.

Paging through this book, my first impressions are that it uses very little math and that it is a comprehensive standards-based overview of practical wireless systems. The authors' multidisciplinary tack&—systems, networks, and services—is evidenced by their conceptual approach to engineering design issues and their straightforward explanations of implementation issues. The primary concern of the book as a whole is: "How does it all fit together?"

Organization
The authors divide the book into five major units. The first three units covered their topics well and enhanced my understanding of wireless communications. However, the final two units fell short of my expectations. Coverage of the Wireless Application Protocol (WAP) and other up-and-coming issues in wireless networking was patchy and unbalanced.

The "PCS Network Management" section provides an overview of the concepts, definitions, and procedures used in current wireless network implementations. Basic roaming concepts including handoff geometry, detection, and queuing schemes are briefly discussed. An understanding of foundational engineering concepts is assumed as the authors provide detailed algorithmic descriptions of hard and soft handoff message flows.

The "IS-41 Mobile Systems" section provides an introductory overview of Signaling System 7 (SS7) as a supporting protocol for the IS-41 mobile communications protocol. The importance of integration between these two protocols is presented in practical example format. Intersystem handoff and authentication techniques applicable to IS-41 are then discussed. Included in this section is a functional overview of network signaling for Personal Access Communications (PACS) networks as related to IS-41. However, a general understanding of the PACS radio system is assumed.

GSM
Global System for Mobile Communication (GSM) systems are the largest focus of this book. A full ten chapters are dedicated to the concepts and applications of this technology. The section appropriately starts with a high-level overview of the GSM system architecture and moves through mobility management and roaming. Here, the authors present several alternative roaming concepts aimed at reducing the cost of roaming service. Additionally, mobile number portability mechanisms and costs are also addressed. Likewise, significant attention is given to the technical aspects of GSM networks and their integration with data networks. Full chapters are dedicated to describing the GSM network signaling software platform (MAP), operations, administration, and management functions, Voice over IP integration, and General Packet Radio Service over GSM.

For the student, Wireless and Mobile Network Architectures is a capstone reference that ties together several courses worth of technical information with a practical focus toward real-world applications. For professional IT managers, engineers, and software developers, it is a practical and handy tutorial for getting up-to-speed on second-generation wireless and mobile technologies.

Questions
Each chapter ends with a set of very open-ended and thought-provoking analysis and design questions. Reading the chapter does not necessarily prepare you to do in-depth design; rather, you gain enough knowledge to sketch out a basic approach to solving the problem. It is obvious that many of the problems would require interdisciplinary collaboration to arrive at a tenable solution. Members of such a team would contribute different perspectives based on their particular area of expertise.

Worthwile Reference
This book assumes that the reader has mastered the basics in the field of mobile communications and is seeking to implement a practical design. Throughout the book are many easy-to-follow algorithmic or flowchart explanations of various wireless communications processes. However, the information gleaned from these treatments tended to be more about functionality than design. Although a worthwhile reference, this book is by no means "all you need to design and implement a mobile services network."

Albert C. Kinney
kinney@ieee.org



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