SIP (Session Initiation Protocol) is the protocol used for signaling in VOIP communication. When 2 sip User agent want to communicate with each other, first they need to initiate the session. SIP is the protocol which will help in establishing that connection. Similarly when these 2 User agents want to close the connection, they will use SIP. Don’t get confused SIP with RTP. RTP is protocol used to transfer the media between two agents. In below diagram green color Sine wave represent media and being carried out by RTP protocol. Rest all the blue and Red arrow represent SIP & respective signaling code.
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