Using Simulcast in SDP and RTP Sessions
draft-ietf-mmusic-sdp-simulcast-13

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Network Working Group                                          B. Burman
Internet-Draft                                             M. Westerlund
Intended status: Standards Track                                Ericsson
Expires: December 29, 2018                                 S. Nandakumar
                                                               M. Zanaty
                                                                   Cisco
                                                           June 27, 2018

                Using Simulcast in SDP and RTP Sessions
                   draft-ietf-mmusic-sdp-simulcast-13

Abstract

   In some application scenarios it may be desirable to send multiple
   differently encoded versions of the same media source in different
   RTP streams.  This is called simulcast.  This document describes how
   to accomplish simulcast in RTP and how to signal it in SDP.  The
   described solution uses an RTP/RTCP identification method to identify
   RTP streams belonging to the same media source, and makes an
   extension to SDP to relate those RTP streams as being different
   simulcast formats of that media source.  The SDP extension consists
   of a new media level SDP attribute that expresses capability to send
   and/or receive simulcast RTP streams.

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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   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on December 29, 2018.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Burman, et al.          Expires December 29, 2018               [Page 1]
Internet-Draft                  Simulcast                      June 2018

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Definitions . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Requirements Language . . . . . . . . . . . . . . . . . .   5
   3.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Reaching a Diverse Set of Receivers . . . . . . . . . . .   6
     3.2.  Application Specific Media Source Handling  . . . . . . .   7
     3.3.  Receiver Media Source Preferences . . . . . . . . . . . .   7
   4.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   7
   5.  Detailed Description  . . . . . . . . . . . . . . . . . . . .  10
     5.1.  Simulcast Attribute . . . . . . . . . . . . . . . . . . .  10
     5.2.  Simulcast Capability  . . . . . . . . . . . . . . . . . .  11
     5.3.  Offer/Answer Use  . . . . . . . . . . . . . . . . . . . .  13
       5.3.1.  Generating the Initial SDP Offer  . . . . . . . . . .  13
       5.3.2.  Creating the SDP Answer . . . . . . . . . . . . . . .  13
       5.3.3.  Offerer Processing the SDP Answer . . . . . . . . . .  14
       5.3.4.  Modifying the Session . . . . . . . . . . . . . . . .  15
     5.4.  Use with Declarative SDP  . . . . . . . . . . . . . . . .  15
     5.5.  Relating Simulcast Streams  . . . . . . . . . . . . . . .  16
     5.6.  Signaling Examples  . . . . . . . . . . . . . . . . . . .  16
       5.6.1.  Single-Source Client  . . . . . . . . . . . . . . . .  17
       5.6.2.  Multi-Source Client . . . . . . . . . . . . . . . . .  18
       5.6.3.  Simulcast and Redundancy  . . . . . . . . . . . . . .  21
   6.  RTP Aspects . . . . . . . . . . . . . . . . . . . . . . . . .  23
     6.1.  Outgoing from Endpoint with Media Source  . . . . . . . .  23
     6.2.  RTP Middlebox to Receiver . . . . . . . . . . . . . . . .  23
       6.2.1.  Media-Switching Mixer . . . . . . . . . . . . . . . .  24
       6.2.2.  Selective Forwarding Middlebox  . . . . . . . . . . .  26
     6.3.  RTP Middlebox to RTP Middlebox  . . . . . . . . . . . . .  27