SIP – Session Initiation Protocol
The Session Initiation Protocol (SIP) is a signalling protocol used for establishing sessions in an IP network. It’s a network communications protocol commonly employed for Voice over IP (VoIP) signaling. In VoIP networking, SIP is an alternative approach to signaling using the H.323 protocol standards. SIP was designed to support the calling features of traditional telephone systems as well as to be a general-purpose way to set up real-time multimedia sessions between groups of participants. In addition to simple telephone calls, SIP can also be used to set up video and audio multicast meetings, or instant messaging conferences.
SIP works in roughly the same way as other common protocols like HTTP or SMTP. It carries out the signaling by sending small messages, consisting of a header and a body. SIP is an open-source protocol meaning that many developers have access to the protocol source code. It is developed therefore by a large group of people, both commercial and non-commercial. It’s an organic protocol under constant development and improvement.
