Subject: [MMUSIC] Protocol Action: Grouping of m lines in SDP to Proposed Standard

From: The IESG <[email-masked]>
Date: Mon, 26 Aug 2002 15:11:53 -0400

The IESG has approved the Internet-Draft 'Grouping of m lines in SDP' 
<draft-ietf-mmusic-fid-06.txt> as a Proposed Standard.  This document 
is the product of the Multiparty Multimedia Session Control Working 
Group.  The IESG contact persons are Allison Mankin and Scott Bradner.

Technical Summary
 
  A Session Description Protocol (SDP) description typically contains 
  a number (one or more) media lines - which are commonly known as 
  "m" lines. When a session description contains more than one "m" 
  line, SDP does not provide any means to express a particular 
  relationship between them. When an application receives an SDP 
  session description with more than one "m" line it is currently up 
  to the application to figure out what to do with them.  SDP currently 
  does not carry any information about grouping media streams.
 
  While in some environments this information can be carried out of 
  band, it would be desirable to have extensions to SDP that allowed 
  the sender to express how different media streams within a session  
  description relate to each other. This document defines such 
  extensions.
 
  Specifically, this document defines two new SDP attributes: "group" 
  and "mid". They allow a sender to group together several "m" lines 
  for two different purposes: for lip synchronization and for 
  receiving media from a single flow (several media streams), encoded 
  in different formats during a particular session, through different 
  ports and host interfaces.

  The further handling of the media for the grouping are then handling
  by the application, and the grouping in the SDP description by this
  extension is a convenince.
   
Working Group Summary
 
  The mmusic working group supported the publication of this document
  with no controversy.
 
Protocol Quality
 
  This document was reviewed for the IESG by Allison Mankin

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