Network Working Group M. Handley
Request for Comments: 2327 V. Jacobson
Category: Standards Track ISI/LBNL
SDP: Session Description Protocol
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright (C) The Internet Society (1998). All Rights Reserved.
This document defines the Session Description Protocol, SDP. SDP is
intended for describing multimedia sessions for the purposes of
session announcement, session invitation, and other forms of
multimedia session initiation.
This document is a product of the Multiparty Multimedia Session
Control (MMUSIC) working group of the Internet Engineering Task
Force. Comments are solicited and should be addressed to the working
group's mailing list at firstname.lastname@example.org and/or the authors.
On the Internet multicast backbone (Mbone), a session directory tool
is used to advertise multimedia conferences and communicate the
conference addresses and conference tool-specific information
necessary for participation. This document defines a session
description protocol for this purpose, and for general real-time
multimedia session description purposes. This memo does not describe
multicast address allocation or the distribution of SDP messages in
detail. These are described in accompanying memos. SDP is not
intended for negotiation of media encodings.
Handley & Jacobson Standards Track [Page 1]RFC 2327 SDP April 19982. Background
The Mbone is the part of the internet that supports IP multicast, and
thus permits efficient many-to-many communication. It is used
extensively for multimedia conferencing. Such conferences usually
have the property that tight coordination of conference membership is
not necessary; to receive a conference, a user at an Mbone site only
has to know the conference's multicast group address and the UDP
ports for the conference data streams.
Session directories assist the advertisement of conference sessions
and communicate the relevant conference setup information to
prospective participants. SDP is designed to convey such information
to recipients. SDP is purely a format for session description - it
does not incorporate a transport protocol, and is intended to use
different transport protocols as appropriate including the Session
Announcement Protocol , Session Initiation Protocol , Real-
Time Streaming Protocol , electronic mail using the MIME
extensions, and the Hypertext Transport Protocol.
SDP is intended to be general purpose so that it can be used for a
wider range of network environments and applications than just
multicast session directories. However, it is not intended to
support negotiation of session content or media encodings - this is
viewed as outside the scope of session description.
3. Glossary of Terms
The following terms are used in this document, and have specific
meaning within the context of this document.
A multimedia conference is a set of two or more communicating users
along with the software they are using to communicate.
A multimedia session is a set of multimedia senders and receivers
and the data streams flowing from senders to receivers. A
multimedia conference is an example of a multimedia session.
See session announcement.
A session announcement is a mechanism by which a session
description is conveyed to users in a proactive fashion, i.e., the
session description was not explicitly requested by the user.
Handley & Jacobson Standards Track [Page 2]RFC 2327 SDP April 1998
A well defined format for conveying sufficient information to
discover and participate in a multimedia session.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",