The Session Initiation Protocol is a signaling protocol that enables the Voice Over Internet Protocol (VoIP) by defining the messages sent between endpoints and managing the actual elements of a call. SIP supports voice calls, video conferencing, instant messaging, and media distribution. Check this blog post for in-depth information on SIP architecture, messages, and methods!
SIP is just one method of deploying VoIP; its primary benefit is the fact that it provides a direct connection between private or local telephone systems (private branch exchanges, or PBX) and the public telephone network. This way, individuals and businesses don't need a legacy telephone line in order to connect.
Other VoIP deployment methods include the Real-time Transport Protocol (RTP), Real-time Transport Control Protocol (RTCP), and Session Description Protocol (SDP).
