SDP

SDP (Session Description Protocol) is a standard for describing multimedia sessions. It contains information such as media types, transport addresses, timing, and codecs.

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 used together with protocols such as RTP and RTSP. It is also used by WebRTC to describe multimedia sessions.