SDP: Session Description Protocol

Publisher

IETF / RFC Editor

URL

https://www.rfc-editor.org/rfc/rfc8866.html

Published

2021-01-01

Updated

unknown

Accessed

2026-09-24

HTTP status

200

License

IETF Trust Legal Provisions (BCP 78); RFC text may be reproduced under IETF Trust terms; excerpts and locators only in corpus

Source notes citing this source

• RFC 8866 says that if no media direction attribute is present at session or media level sendrecv SHOULD be assumed. in context
• RFC 8866 says an RTP-based system MUST still send RTCP if RTCP is used even when a stream is inactive. in context
• RFC 8866 says a media-level direction attribute overrides a session-level one and the session-level attribute applies to media that carry none. in context
• RFC 8866 published January 2021 obsoletes RFC 4566 as the SDP specification. in context
• RFC 8866 says an RTP-based system in receive-only mode MUST still send RTCP packets. in context
• An offer using RTP/AVP sent to a peer that only accepts SRTP (or the reverse) gives the answerer no acceptable stream even when codecs match, so a profile mismatch can produce the same 488 or port-zero outcome as a codec mismatch. inferred in context
• The m= line proto field distinguishes RTP/AVP (plain RTP under the audio/video profile over UDP) from RTP/SAVP (SRTP over UDP), so the transport profile is negotiated separately from the codec list. in context
• RFC 8866 is the current SDP specification and obsoletes RFC 4566. in context
• A dynamically assigned payload type in SDP must be accompanied by an a=rtpmap attribute naming the format and its parameters. in context
• An SDP c= line carries the connection data needed to reach the media, and a media-level c= line overrides the session-level one for that media. in context
• An SDP media description line has the form m=<media> <port> <proto> <fmt> ..., giving the media type, transport port, transport protocol and format list. in context
• The SDP a=rtpmap attribute maps an RTP payload type number from the m= line to an encoding name and clock rate. in context

Cite this source record

APA

WarmTransfer. (2021, January 1). SDP: Session Description Protocol. WarmTransfer. https://warmtransfer.net/knowledge/sources/rfc-8866-sdp

BibTeX

@misc{warmtransfer-rfc-8866-sdp,
  title  = {SDP: Session Description Protocol},
  author = {{WarmTransfer}},
  year   = {2021},
  url    = {https://warmtransfer.net/knowledge/sources/rfc-8866-sdp},
  note   = {IETF / RFC Editor, accessed 2026-09-24}
}