Using SSRC with WebRTC Simulcast
draft-alvestrand-mmusic-simulcast-ssrc-01

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Last updated 2019-07-06
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RTCWEB Working Group                                       H. Alvestrand
Internet-Draft                                                    Google
Intended status: Informational                             July 06, 2019
Expires: January 7, 2020

                    Using SSRC with WebRTC Simulcast
               draft-alvestrand-mmusic-simulcast-ssrc-01

Abstract

   This document describes a convention for sending "a=ssrc" attributes
   in SDP together with "a=simulcast" attributes.  This allows SFUs that
   need SSRC information to have this info easily accessible.

   Given that it is intended as an interim measure, it does not aim for
   being published as an RFC.

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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   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 January 7, 2020.

Copyright Notice

   Copyright (c) 2019 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
   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

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   3
   3.  How to represent SSRC information . . . . . . . . . . . . . .   3
   4.  How to request that SSRC information be included  . . . . . .   3
   5.  Example . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   6.  Sunsetting the interim measure  . . . . . . . . . . . . . . .   4
   7.  Open questions  . . . . . . . . . . . . . . . . . . . . . . .   4
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   6
     10.2.  Informative References . . . . . . . . . . . . . . . . .   7
   Change log  . . . . . . . . . . . . . . . . . . . . . . . . . . .   7
     A.1.  Changes from version -00 to -01 . . . . . . . . . . . . .   7
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   In developing the WebRTC specification, the IETF decided on a form of
   simulcast that doesn't require fixed SSRC allocation, but rather used
   a combination of SDP tags (a=rid) [I-D.ietf-mmusic-rid] and RTP
   header extensions (RTPStreamId) [I-D.ietf-avtext-rid] to describe the
   mapping between simulcast layers and RTP streams.

   The SDP format is described in [I-D.ietf-mmusic-sdp-simulcast].

   This posed a problem for some SFUs, which required information on
   what SSRCs the incoming streams were going to appear on in order to
   be configured correctly.

   This document gives a convention for adding information about SSRCs
   to the SDP produced by conformant WebRTC implementations in order to
   make this information available.

   This document does not specify an Internet standard.  It is an
   interim measure, intended to be useful in the time between the
   introduction of RID-based simulcast in browsers and the full support
   of RID-based simulcast by SFUs.

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2.  Conventions and Definitions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  How to represent SSRC information

   The syntax for representing SSRC information is taken from [RFC5576].
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