CHAPTER 30 Voice over Internet Protocol
What You Will Learn
In this chapter, you will learn how VoIP is becoming more and more popular as an alternative to the traditional public switched telephone network (PSTN). We’ll look at one form of “softphone” that lets users make “voice” calls (voice is really many things) over an Internet connection to their PC.
You will learn about the protocols used in VoIP, especially for the “data” (RTP and RTCP) and for signaling (H.323 and SIP). We’ll put it all together and look at a complete architecture for carrying media other than data on the Internet.
In November 2006, when a person in Cardiff, Wales, made a local telephone call, no part of the British Telecom (BT) PSTN was involved. Only the “last mile” ...