"The session initiation protocol (SIP) is one of the most popular signaling protocols used in applications that require a session setup and parameter negotiation before actual communication, as well as for session management and termination. Though SIP was designed primarily for voice over IP (VoIP) telephony, it currently is used in a variety of applications, including those for multimedia conferencing and multimedia content distribution.
"SIP allows two or more participants to establish a session consisting of multiple media streams using text-based request and response messages. A user, termed a SIP endpoint, is addressed by a SIP URL in the form of an e-mail address, such as sip:alice@vocal.com or sip:alice@192.168.0.2. The application used for communication is called the user agent (UA)..."
