SIP- a Protocol for Intelligent Network

Abstract

This article introduces the Session Initiation Protocol (SIP), which is an application layer protocol for creating, modifying and terminating interactive communication sessions among multiple users on an IP telephony network. It is the IETF protocol for VOIP and other text and multimedia sessions, like instant messaging, video, online games and other services. It easily integrates and reuses several other existing and mature Internet services and protocols such as DNS, LDP, UDP, TCP, RTP and RSTP etc. No new services have to be introduced to support the SIP infrastructure. It runs on the top of several different transport protocols. As the name implies it is used for establishing a session and the latter part is handled by the other layer protocols, in which Session Description Protocol (SDP) is the one used to hold the whole description of the session. _It uses messages to initiate a session, which can be either a request from a client to a server, or a response from a server to a client. Thus, it works · on request-response paradigm.