Voice over IP, Second Edition (2001)

From the Book:
Preface
This book is one in a series of books called Advanced Communications Technologies. As the name of the book implies, the focus is on the Internet and the Internet Protocol (IP) in relation to the support of voice traffic.

The subject matter of this book is vast and my approach is to provide an introduction to the topic. In consonance with the intent of this series, this survey also has considerable detail but not to the level 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 considered to be at an intermediate to advanced level. As such, it assumes the reader has a background in voice and data communications and the IP suite. Notwithstanding, for the new reader, I have provided several tutorials and guide you to them in the appropriate parts of the book. I also 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 thecurrent book, yet is not a required subject 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 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 VoIP, and I have included tutorials on these subjects in the appendices at the back of this book.
EXPLANATIONS OF MESSAGES AND PROTOCOL FLOWS
This book is a survey (albeit a detailed one) of the VoIP technology. A wide variety of VoIP control messages and protocols are used to support VoIP, and the standards bodies and the Internet task 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 with references to the original specifications. In this manner, the book should provide you with a handy reference tool and act as a pointer toward more information if you so desire.
INTERNET DRAFTS: WORK IN PROGESS
A considerable portion this book is devoted to explaining many Internet-based specifications pertaining to packet telephony.

Keep in mind that the Internet drafts are works in progress, and should be viewed as such. You should not use the drafts with the expectation that they will not change. Notwithstanding, if used as general tutorials, the drafts discussed in this book are final enough to warrant their explanations. Indeed, many of my clients use these drafts in their product planning and design.

For all the Internet standards and drafts the following applies:

Copyright (c) The Internet Society (1998). All Rights Reserved.

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