n collaboration of SIP make it the signaling protocol of choice for advanced multimedia communications signaling. This fact is evidenced by its acceptance into the 3rd Generation Partnership Project (3GPP) as a signaling protocol for establishing real time multimedia sessions. SIP is continuously gaining in popularity and deployment and has been widely adopted by service providers to provide IP telephony, instant messaging, and other data services. SIP is increasingly gaining in popularity as the next generation multimedia signaling and session establishment protocol. SIP is a key technology which enables this evolution, opening new possibilities to develop multimodal communications. SIP increases the possibilities of developing integrated multimedia services and offers advantages such as independence from the underlying transport network, session establishment with the involvement of multiple devices and the support for mobility. SIP is a session-layer signaling protocol that is used for establishment, mod- ification, and release of sessions among participants. The session may involve VoIP (Voice over IP), video conference, multimedia distribution, and IMS (IP Multimedia Subsystem) applications. SIP supports five facets of establishing and terminating multimedia communications: user location, user availability, user capabilities, session setup, and session management. The SIP architec- ture is also proposed as an efficient candidate that can be reused to provide personal, terminal, and session mobility with a readily available infrastructure. SIP infrastructure is extensively deployed all over the Internet and has already been accepted as the signaling protocol of preference for many multimedia frameworks. Recently, SIP has gained widespread acceptance and deployment among wireline service providers for introducing new services such as VoIP, Tele-presence, video conferencing; within the enterprises for Instant Messag- ing and collaboration; and amongst mobile carriers for push-to-talk services. Industry acceptan