The Session Description Protocol (SDP) is a format for describing streaming media communications parameters. The IETF published the original specification as an IETF Proposed Standard in April 1998, and subsequently published a revised specification as an IETF Proposed Standard as RFC 4566 in July 2006.
SDP is used for describing multimedia communication sessions for the purposes of session announcement, session invitation, and parameter negotiation. SDP does not deliver any media by itself but is used between endpoints for negotiation of media type, format, and all associated properties. The set of properties and parameters are often called a session profile.
SDP is designed to be extensible to support new media types and formats. SDP started off as a component of the Session Announcement Protocol (SAP), but found other uses in conjunction with Real-time Transport Protocol (RTP), Real-time Streaming Protocol (RTSP), Session Initiation Protocol (SIP) and even as a standalone format for describing multicast sessions.