(1) Short for Session Initiation Protocol, it is an application-layer control protocol; a signaling protocol for Internet Telephony. SIP can establish sessions for features such as audio/videoconferencing, interactive gaming, and call forwarding to be deployed over IP networks, thus enabling service providers to integrate basic IP telephony services with Web, e-mail, and chat services. In addition to user authentication, redirect and registration services, SIP Server supports traditional telephony features such as personal mobility, time-of-day routing and call forwarding based on the geographical location of the person being called.
Recommended Reading: The Difference Between VoIP and PSTN Systems.
A SIP is also called a Single In-line Pin Package (SIPP).