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Part I: Fundamentals > Introduction - Pg. 3

CHAPTER Introduction 1 There is a growing interest, both in the Internet and in the telecommunication industries, in multimedia communication services. An increasing number of Internet users who used to just surf the web or send emails are now becoming addicted to services such as Instant Messaging (IM), online gaming, and voice and video on the Net. These are examples of multimedia communication services delivered over the Internet that are enabled by the Session Initiation Protocol (SIP) in conjunction with other protocols. In this first introductory chapter, we will explain what we mean by multime- dia communication services. We will position these services in the context of the rest of the applications provided over the Internet. We also want to give the reader a first hint of why SIP plays so crucial a role in the Internet communications space. That will lead us to dive into the importance of the signaling concept. We will underline the relevance of the signaling concept by looking at a very simple example of voice communication. SIP not only enables voice on the Internet, but also a completely new universe of Total Communication services. To let the reader grasp the possibilities of SIP, we will show some examples of services and commercial products that currently use SIP. SIP is, like any other Internet protocol, defined and developed by the Internet Engineering Task Force (IETF). More specifically, the core SIP specification is docu- mented in [RFC 3261], and we will be referring throughout this book to this and other Internet specifications. So, in this chapter, we will also try to understand a bit better the SIP-related working groups in the IETF and the specifications they produce. 1.1 IP Multimedia Communication Services A lot of very different services can be offered on top of the Internet and, in general, on top of an Internet Protocol (IP) network--a network based on the Internet Protocol. 1 It is not at all easy to find a categorization of those services 1 Internet Protocol and IP networks are reviewed in Chapter 3. 3