Preface

This book is one in a series of books called, "Emerging Communications Technologies." As the name of the book implies, the focus is on the Internet and private internets in relation to the support of voice traffic. The book is an expansion of Advanced Features of the Internet, also part of this series.

The subject matter of this book is vast and my approach is to provide an introduction to the topic. But in consonance with the intent of this series, this survey also has considerable detail but not to the level of detail needed to design a system. For that, I leave you to your project team and the various specifications that establish the standards for Internet telephony.

This book is an intermediate-to-advanced level text. As such, it assumes the reader has a background in voice and data communications and the Internet protocol suite. Notwithstanding, for the new reader, I have provided several tutorials, and I guide you to them in the appropriate parts of the book. I guide the more experienced reader away from them.

I hope you find this book a valuable addition to your library.

NOTES TO THE READER

In writing multiple books about data and voice communications systems, the author is faced with a question: How much overlap (redundancy of material) should there be among the books in the series? If the overlap is too little, the reader must buy other books in the series to fill the gaps. If the overlap is too great, the reader who has purchased other books in the series may feel cheated by spending additional money to obtain the same information.

My approach is to try to strike a compromise between the two extremes. If another book in the series contains information on a topic that is relevant to the topic of the current book, yet is not an impelling subject to know in order to read the current book, I make reference to the book. However, that is not always possible. In a few cases, it is necessary to include material from other books in the series. Otherwise, the book in question becomes a fragmented reference to other books. I have taken this approach with this book. I trust you find this an efficient and useful way to deal with this matter.

To help strike this compromise, I have included four appendices that are extracted from some of my other books. A basic knowledge of telephony signaling, the V.34 modem, ISDN, and SS7 will be very helpful as you read some of these chapters about voice over IP, and I have included tutorials on these subjects in the Appendices at the back of this book. I also have a tutorial on the V.34 and V.90 modems.

EXPLANATIONS OF MESSAGES AND PROTOCOL FLOWS

This book is a survey (albeit a detailed one) of the emerging VoIP technology. A wide variety of VoIP control messages and protocols are used to support VoIP, and the standards bodies and the Internet tasks forces are defining hundreds of messages and scores of protocol flows between VoIP gateways, call agents, and user machines. It is not the intent of this book to explain the contents of each message and each protocol flow, which would simply duplicate the VoIP specifications. Instead, I provide tutorial explanations of these messages and flows, as well as selected examples of each. In each case, I provide you references to the original specifications. In this manner, the book should provide you with a handy tutorial and reference tool, as well as a pointer toward more information if you so desire.

INTERNET DRAFTS: WORK IN PROGRESS

A considerable portion this book is devoted to explaining many Internet-based specifications pertaining to packet telephony. I had planned on waiting a year or so before writing about these specifications, but requests from my clients and publishers dictated otherwise. Indeed, some vendors are already writing code based on the specifications, even though they are not yet finished.

Keep in mind that the Internet Drafts are works in progress, and should be viewed as such. You should use the drafts with the expectation that they may change. Notwithstanding, if used as general tutorials, the Drafts discussed in this book are "final enough" to warrant their explanations.

For all the Internet standards and draft standards the following applies:

Copyright © The Internet Society (1998). All Rights Reserved.

This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English.

The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns.

THANKS TO

I would like to thank four organizations for their contributions to this book.

First, Mier Communications provided two studies on VoIP products, and this information can be found in Chapter 8. I thank Mier for their excellent work. Second, Nortel provided me with valuable information on Nortel's One Meg Modem, as well as some of their emerging IP connect technologies, found in several chapters. Third, British Telecom (BT) has been a great help in their contributions on codecs. Fourth, the various Internet Task Forces have provided much of the information on the emerging VoIP protocols.