ABSTRACT
Session Initiation Protocol (SIP) is a new application level protocol which was developed to support the exchange of information that is required for the establishment of media sessions in IP networks. It supports mobility at the application layer through its capability to establish and tear down sessions. Its main function is for creating, establishing and tearing down media sessions between one or more SIP end points. The end points have valid SIP addresses and form part of the information that is exchanged during SIP signaling. The end points may reside either in IPv4 or IPv6 domains, and Application Level Gateways (ALG) have been developed for the translation of the addresses inside the SIP messages.
