Chapter 3 - IP Multimedia Fundamentals

Abstract

This chapter reviews the fundamental concepts around IP networks and the TCP/IP protocols and describes the architecture and the application-level Internet protocols that enable multimedia communications. The most basic service provided by the IP layer is the unreliable, connectionless packet-delivery service and the version of the IP protocol that has been in use in the Internet for more than two decades is called IPv4. A new version of the protocol, called IPv6, introduced a few new features and enlarged the address space by defining 128-bit addresses. Internet Protocol architecture can be best described by using a layered model, which is typically referred to as the TCP/IP protocol suite. The Internet layer sits on top of the data-link layers and physical layers, which are provided by the underlying network infrastructure such as Ethernet and ATM. The transport layer uses the connectionless delivery service provided by the Internet layer and offers specific transport services to the application layer. The application layer comprises the end-to-end protocols that are required to implement the end-to-end functions, and some well-known protocols sitting on it include HTTP, SMTP, POP3, IMAP4, TELNET, FTP, and DNS. SIP is also an application-layer protocol and works together with other application-level protocols such as RTP (real-time transport protocol) or SDP (session description protocol). Multimedia communication is enabled in the Internet by a myriad of IP-based application-level protocols, and among these, the signaling protocol and the media transport protocol play a predominant role. The core signaling protocol for multimedia communication is the session initiation protocol (SIP), which works in concert with the SDP.