Multiple Synchronization Sources (SSRC) in SDP Media Descriptions
draft-westerlund-mmusic-max-ssrc-01

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Network Working Group                                      C.H. Holmberg
Internet-Draft                                           M.W. Westerlund
Intended status: Standards Track                             B.B. Burman
Expires: September 28, 2013                                 F.J. Jansson
                                                                Ericsson
                                                          March 27, 2013

   Multiple Synchronization Sources (SSRC) in SDP Media Descriptions
                draft-westerlund-mmusic-max-ssrc-01.txt

Abstract

   This document describes use-cases where endpoints, for a given media
   type, use multiple media sources.  It also describes how endpoints
   normally support media sources, and limitations associated with the
   support of multiple sources.

   This document also defines two new SDP attributes, "max-send-ssrc"
   and "max-recv-ssrc".  The attributes allows an entity to, for a given
   media description, indicate sending and receiving capabilities of
   multiple media sources, based on codec usage .

Status of This Memo

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   This Internet-Draft will expire on September 28, 2013.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   (http://trustee.ietf.org/license-info) in effect on the date of

Holmberg, et al.       Expires September 28, 2013               [Page 1]
Internet-Draft          Multiple SSRC Signalling              March 2013

   publication of this document.  Please review these documents
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Definitions . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
     2.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Multiple Media Stream Support . . . . . . . . . . . . . . . .   3
     3.1.  General . . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  Multiple Source Support Limitations . . . . . . . . . . .   4
   4.  SDP max-send-ssrc And max-recv-ssrc Attributes  . . . . . . .   4
     4.1.  Introduction  . . . . . . . . . . . . . . . . . . . . . .   4
     4.2.  Usage . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     4.3.  Syntax  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     4.4.  Use in Offer/Answer . . . . . . . . . . . . . . . . . . .   6
   5.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   An RTP session [RFC3550] contains a Synchronization Sources (SSRC)
   space.  This space can encompass a number of endpoints and network
   entities, and associated media streams, within the RTP session.  As
   defined in RFC 3550, within an RTP session, each entity may use zero,
   one or multiple SSRCs to indicate a physical media source (e.g.  a
   camera or a microphone), a conceptual source (e.g.  the most active
   speaker, selected by an RTP mixer, within a conference), or to
   identify a receiver that provides feedback and reports on reception.
   A given SSRC value is associated with a physical media source.
   Multiple SSRC values can be associated with the same source.

   The Session Description Protocol (SDP) [RFC4566] describes media
   streams using media descriptions (m- lines).  Each m- line is
   normally associated with a given media type (e.g.  audio or video).

   Multiple media streams and media sources might be associated with a
   single SDP media description.  Each media stream will share the