ABSTRACT
The Session Initiation Protocol (SIP) is a new application level protocol that 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 to create, establish, and tear down media sessions between one or more SIP endpoints. These end-points have valid SIP addresses and form part of the information that is exchanged during SIP signaling. The end-points may reside in either the IPv4 or IPv6 domain, and application level gateways (ALGs) have been developed for the translation of the addresses inside the SIP messages.
