RTP Multiplexing Architecture
draft-westerlund-avtcore-multiplex-architecture-00

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Network Working Group                                      M. Westerlund
Internet-Draft                                                 B. Burman
Intended status: BCP                                            Ericsson
Expires: April 26, 2012                                       C. Perkins
                                                   University of Glasgow
                                                        October 24, 2011

                     RTP Multiplexing Architecture
           draft-westerlund-avtcore-multiplex-architecture-00

Abstract

   RTP has always been a protocol that supports multiple participants
   each sending their own media streams in an RTP session.  Thus relying
   on the three main multiplexing points in RTP; RTP session, SSRC and
   Payload Type for their various needs.  However, most usages of RTP
   have been less complex often with a single SSRC in each direction,
   with a single RTP session per media type.  But the more complex
   usages start to be more common and thus guidance on how to use RTP in
   various complex cases are needed.  This document analyzes a number of
   cases and discusses the usage of the various multiplexing points and
   the need for functionality when defining RTP/RTCP extensions that
   utilize multiple RTP streams and multiple RTP sessions.

Status of this Memo

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Copyright Notice

   Copyright (c) 2011 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

Westerlund, et al.       Expires April 26, 2012                 [Page 1]
Internet-Draft         RTP Multiplex Architecture           October 2011

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Definitions  . . . . . . . . . . . . . . . . . . . . . . . . .  5
     2.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  5
     2.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  RTP Multiplex Points . . . . . . . . . . . . . . . . . . . . .  6
     3.1.  Session  . . . . . . . . . . . . . . . . . . . . . . . . .  6
     3.2.  SSRC . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     3.3.  CSRC . . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     3.4.  Payload Type . . . . . . . . . . . . . . . . . . . . . . .  8
   4.  Multiple Streams Alternatives  . . . . . . . . . . . . . . . .  9
   5.  RTP Topologies and Issues  . . . . . . . . . . . . . . . . . . 10
     5.1.  Point to Point . . . . . . . . . . . . . . . . . . . . . . 11
       5.1.1.  RTCP Reporting . . . . . . . . . . . . . . . . . . . . 11
       5.1.2.  Compound RTCP Packets  . . . . . . . . . . . . . . . . 12
     5.2.  Point to Multipoint Using Multicast  . . . . . . . . . . . 12
     5.3.  Point to Multipoint Using an RTP Translator  . . . . . . . 14
     5.4.  Point to Multipoint Using an RTP Mixer . . . . . . . . . . 15
     5.5.  Point to Multipoint using Multiple Unicast flows . . . . . 16
     5.6.  Decomposited End-Point . . . . . . . . . . . . . . . . . . 16
   6.  Dismissing Payload Type Multiplexing . . . . . . . . . . . . . 18
   7.  Multiple Streams Discussion  . . . . . . . . . . . . . . . . . 20
     7.1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . 20
     7.2.  RTP/RTCP Aspects . . . . . . . . . . . . . . . . . . . . . 20
       7.2.1.  The RTP Specification  . . . . . . . . . . . . . . . . 20
       7.2.2.  Multiple SSRC Legacy Considerations  . . . . . . . . . 22
       7.2.3.  RTP Specification Clarifications Needed  . . . . . . . 23
       7.2.4.  Handling Varying sets of Senders . . . . . . . . . . . 23
       7.2.5.  Cross Session RTCP requests  . . . . . . . . . . . . . 23
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