Sending Multiple Media Streams in a Single RTP Session
draft-ietf-avtcore-rtp-multi-stream-09

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AVTCORE                                                        J. Lennox
Internet-Draft                                                     Vidyo
Updates: 3550, 4585 (if approved)                          M. Westerlund
Intended status: Standards Track                                Ericsson
Expires: April 2, 2016                                             Q. Wu
                                                                  Huawei
                                                              C. Perkins
                                                   University of Glasgow
                                                      September 30, 2015

         Sending Multiple Media Streams in a Single RTP Session
                 draft-ietf-avtcore-rtp-multi-stream-09

Abstract

   This memo expands and clarifies the behaviour of Real-time Transport
   Protocol (RTP) endpoints that use multiple synchronization sources
   (SSRCs).  This occurs, for example, when an endpoint sends multiple
   media streams in a single RTP session.  This memo updates RFC 3550
   with regards to handling multiple SSRCs per endpoint in RTP sessions,
   with a particular focus on RTCP behaviour.  It also updates RFC 4585
   to update and clarify the calculation of the timeout of SSRCs and the
   inclusion of feedback messages.

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
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   This Internet-Draft will expire on April 2, 2016.

Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Lennox, et al.            Expires April 2, 2016                 [Page 1]
Internet-Draft  Multiple Media Streams in an RTP Session  September 2015

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Use Cases For Multi-Stream Endpoints  . . . . . . . . . . . .   3
     3.1.  Endpoints with Multiple Capture Devices . . . . . . . . .   3
     3.2.  Multiple Media Types in a Single RTP Session  . . . . . .   4
     3.3.  Multiple Stream Mixers  . . . . . . . . . . . . . . . . .   4
     3.4.  Multiple SSRCs for a Single Media Source  . . . . . . . .   4
   4.  Use of RTP by endpoints that send multiple media streams  . .   5
   5.  Use of RTCP by Endpoints that send multiple media streams . .   5
     5.1.  RTCP Reporting Requirement  . . . . . . . . . . . . . . .   5
     5.2.  Initial Reporting Interval  . . . . . . . . . . . . . . .   6
     5.3.  Aggregation of Reports into Compound RTCP Packets . . . .   7
       5.3.1.  Maintaining AVG_RTCP_SIZE . . . . . . . . . . . . . .   7
       5.3.2.  Scheduling RTCP when Aggregating Multiple SSRCs . . .   9
     5.4.  Use of RTP/AVPF or RTP/SAVPF Feedback . . . . . . . . . .  11
       5.4.1.  Choice of SSRC for Feedback Packets . . . . . . . . .  11
       5.4.2.  Scheduling an RTCP Feedback Packet  . . . . . . . . .  12
   6.  Adding and Removing SSRCs . . . . . . . . . . . . . . . . . .  14
     6.1.  Adding RTP Streams  . . . . . . . . . . . . . . . . . . .  14
     6.2.  Removing RTP Streams  . . . . . . . . . . . . . . . . . .  15
   7.  RTCP Considerations for Streams with Disparate Rates  . . . .  16
     7.1.  Timing out SSRCs  . . . . . . . . . . . . . . . . . . . .  17
       7.1.1.  Problems with the RTP/AVPF T_rr_interval Parameter  .  18
       7.1.2.  Avoiding Premature Timeout  . . . . . . . . . . . . .  19
       7.1.3.  Interoperability Between RTP/AVP and RTP/AVPF . . . .  19
       7.1.4.  Updated SSRC Timeout Rules  . . . . . . . . . . . . .  20
     7.2.  Tuning RTCP transmissions . . . . . . . . . . . . . . . .  20
       7.2.1.  RTP/AVP and RTP/SAVP  . . . . . . . . . . . . . . . .  21
       7.2.2.  RTP/AVPF and RTP/SAVPF  . . . . . . . . . . . . . . .  22