Cross Session Stream Identification in the Session Description Protocol
draft-alvestrand-mmusic-msid-00

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Last updated 2012-09-12
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Network Working Group                                      H. Alvestrand
Internet-Draft                                                    Google
Intended status: Standards Track                      September 12, 2012
Expires: March 16, 2013

Cross Session Stream Identification in the Session Description Protocol
                    draft-alvestrand-mmusic-msid-00

Abstract

   This document specifies a grouping mechanism for RTP media streams
   that can be used to specify relations betweeen media streams within
   different RTP sessions.

   This mechanism is used to signal the association between the RTP
   concept of SSRC and the WebRTC concept of "media stream" / "media
   stream track" using SDP signalling.

   This document is an input document for discussion.  It should be
   discussed in the RTCWEB WG list, rtcweb@ietf.org.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   This Internet-Draft will expire on March 16, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the

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   document authors.  All rights reserved.

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

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Why A New Mechanism Is Needed  . . . . . . . . . . . . . .  3
     1.2.  Application to the WEBRTC MediaStream  . . . . . . . . . .  3
   2.  The Msid Mechanism . . . . . . . . . . . . . . . . . . . . . .  4
   3.  The Msid-Semantic Attribute  . . . . . . . . . . . . . . . . .  5
   4.  Applying Msid to WebRTC Media Streams  . . . . . . . . . . . .  5
     4.1.  Handling of non-signalled tracks . . . . . . . . . . . . .  6
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  7
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  8
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     8.1.  Normative References . . . . . . . . . . . . . . . . . . .  8
     8.2.  Informative References . . . . . . . . . . . . . . . . . .  9
   Appendix A.  Design considerations, open questions and and
                alternatives  . . . . . . . . . . . . . . . . . . . .  9
   Appendix B.  Change log  . . . . . . . . . . . . . . . . . . . . . 10
     B.1.  Changes from -00 to -01  . . . . . . . . . . . . . . . . . 10
     B.2.  Changes from -01 to -02  . . . . . . . . . . . . . . . . . 10
     B.3.  Changes from rtcweb-msid-02 to mmusic-msid-00  . . . . . . 11
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 11

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1.  Introduction

1.1.  Why A New Mechanism Is Needed

   There exist cases where an application using RTP and SDP needs to
   signal some relationship between RTP media streams (packets carried
   using a single SSRC) that may be carried in either the same RTP
   session or different RTP sessions.

   When all SSRCs are carried in a single RTP session, the "a=ssrc-
   group" mechanism [RFC5576] can be used.

   When each RTP session carries one and only one SSRC, the SDP grouping
   framework [RFC5888] can be used.

   However, there are use cases (some of which are discussed in
   [I-D.westerlund-avtcore-multiplex-architecture] ) where neither of
   these approaches is appropriate; for instance, there may be a need to
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