In this second of two companion texts by Daniel and Emma Minoli, the authors describe voice over connectionless IP-based networks, including the Internet. (The first book covers voice over connection-oriented fast-packet transport technologies, namely frame relay and ATM [1].) Here, the authors discuss the positioning of voice over IP on intranets and the Internet, and try to answer several questions: Is voice over IP a practical approach? What is the quality of voice? What are the technical challenges? and Are there standards for voice over packet networks?

The book is structured into seven chapters, an appendix, and an index. Chapter 1 is an introduction to the IP telephony technology. It highlights the motivation for voice over IP and describes approaches to IP-based voice systems.

Chapter 2 is an overview of IP technology. After a short presentation of IP (including IPv6, IP over ATM, multiprotocol over ATM, and network layer switching), the authors discuss the Resource Reservation Protocol, the signaling protocol that enables network resources to be reserved for a connectionless data stream. The Real-Time Transport Protocol (RTP) and the RTP Control Protocol (RTCP) are also presented.

Chapter 3 discusses voice characteristics that can be used in packet networks. The chapter covers some classical issues for the support of voice in general packet networks: traffic models, performance criteria, link models, and some results of optimization studies.

Chapter 4 presents adaptive differential pulse code modulation as applied to packet network environments. Some ITU recommendations that have the potential to become commercial mechanisms for voice over IP are examined in detail.

Chapter 5 includes an overview of vocoder-based compression methods used in IP. Details of G.729, G.723.1, G.728, and G.729 are given. Some applications of low-rate vocoders are discussed.

Chapter 6 is devoted to various proposals for the delivery of voice in IP environments. Some emerging product categories are described. The voice over IP Internet market and some regulatory issues related to voice on IP are also covered.

Chapter 7 presents a practical application of voice over IP technology. The appendix covers a commercial case study.

The book is intended for technology and application developers, students, vendors, researchers, consultants, and corporate network planners. This broad audience is due to the wide spectrum of problems covered, from theoretical aspects concerning the coding, decoding, and compression of speech or other audio signal components of multimedia services to practical aspects of the standardization of voice over IP. The many figures and tables included in the book give more information and help readers understand this new domain of Internet services.