SDP: Session Description Protocol
RFC 2327

Document Type RFC - Proposed Standard (April 1998; Errata)
Obsoleted by RFC 4566
Updated by RFC 3266
Last updated 2013-03-02
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Network Working Group                                           M. Handley
Request for Comments: 2327                                     V. Jacobson
Category: Standards Track                                         ISI/LBNL
                                                                April 1998

                   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 Notice

   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 and/or the authors.

1.  Introduction

   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 1998

2.  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 [4], Session Initiation Protocol [11], Real-
   Time Streaming Protocol [12], 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.

   Session Advertisement
     See session announcement.

   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

   Session Description
     A well defined format for conveying sufficient information to
     discover and participate in a multimedia session.

3.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119.

4.  SDP Usage

4.1.  Multicast Announcements

   SDP is a session description protocol for multimedia sessions. A
   common mode of usage is for a client to announce a conference session
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