TABLE OF CONTENTS Considerable interest has been shown during the past quarter century in supporting Voice over Packet (VoP)-based networks. Several packet technologies have been proposed, tested and deployed over the years, including Voice over X.25 (VoX25) networks, Voice over Frame Relay (VoFR) networks, Voice over Asynchronous Transfer Mode (VoATM) networks, Voice over IP (VoIP) networks, Voice over Wi-Fi/Hot-spot networks, and Voice over Multiprotocol Label Switching (VoMPLS) networks (e.g., see [MIN199801], [MIN199802], [MIN200102], [MIN200203], among other references.) Of these, VoIP has seen the largest market penetration in recent years, and it has stirred the most interest as a technology to perhaps replace the traditional circuit-switched mechanisms of the public-switched telephone network. Hence, there is keen research and commercial interest in VoIP at this time. Issues surrounding VoP/VoIP include the following six major areas:
Voice digitization/compression
Standards in the user plane (information flow) and in the control plane (call/session signaling/management)
Signaling
Numbering
Applications
Wireless deployment
This chapter provides an overview of these topics. We are not deliberately focusing on IPv6-related issues in this chapter; rather, we simply aim at establishing a baseline of the VoP space and supportive technologies before proceeding with the major topic at hand. Also, note that in Chapter 1 we have positioned the discussion (motivation) of IPv6 in part as a solution to scalability limitations of IPv4-based VoIP; hence, the discussion here and in the chapters that follow partially takes on the perspective of organizations that may have to deal with such scalability considerations, namely, service providers and telecommunication...
