Session Description Protocol (SDP)

SDP is an IETF standard that allows a multimedia device to describe the kinds of media that has to offer or that it wishes to accept. As part of this description, the device will indicate the type of media (audio, video, text, etc.), the IP ports used, the protocols used (e.g., T.120), and other information necessary for a device to receive the specified media and understand how to handle that media.

SDP is defined in RFC 4566. There are additional RFCs that document extensions or enhancements to SDP.