SDP

SDP (Session Description Protocol) is the standard describing a peer-to-peer connection. SDP contains the codec, source address, and timing information of audio and video.

Here is a typical SDP message:

   v=0
   o=alice 2890844526 2890844526 IN IP4 host.anywhere.com
   s=
   c=IN IP4 host.anywhere.com
   t=0 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000
   m=video 51372 RTP/AVP 31
   a=rtpmap:31 H261/90000
   m=video 53000 RTP/AVP 32
   a=rtpmap:32 MPV/90000

SDP is never used alone, but by protocols like RTP and RTSP. SDP is also as component of WebRTC, which uses SDP as a way of describing a session.

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General knowledge