Session Initiation Protocol (SIP) is a signaling protocol used to establish, maintain, and terminate real-time sessions that include voice, video, and data communications. It is widely used for Voice over IP (VoIP) and video conferencing applications.
SIP is a text-based protocol that uses a request-response model. A client sends a request to a server, and the server responds with a response. The request and response messages are formatted using the Session Description Protocol (SDP). SDP describes the media formats and codecs that are used in the session.