RFC 2327 (rfc2327) - Page 2 of 42

SDP: Session Description Protocol

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.

   Conference
     A multimedia conference is a set of two or more communicating users
     along with the software they are using to communicate.

   Session
     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