RTP Header Extension for the RTP Control Protocol (RTCP) Source Description Items
RFC 7941

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Internet Engineering Task Force (IETF)                     M. Westerlund
Request for Comments: 7941                                     B. Burman
Category: Standards Track                                       Ericsson
ISSN: 2070-1721                                                  R. Even
                                                     Huawei Technologies
                                                               M. Zanaty
                                                           Cisco Systems
                                                             August 2016

                        RTP Header Extension for
        the RTP Control Protocol (RTCP) Source Description Items

Abstract

   Source Description (SDES) items are normally transported in the RTP
   Control Protocol (RTCP).  In some cases, it can be beneficial to
   speed up the delivery of these items.  The main case is when a new
   synchronization source (SSRC) joins an RTP session and the receivers
   need this source's identity, relation to other sources, or its
   synchronization context, all of which may be fully or partially
   identified using SDES items.  To enable this optimization, this
   document specifies a new RTP header extension that can carry SDES
   items.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7941.

Westerlund, et al.           Standards Track                    [Page 1]
RFC 7941                  RTP HE for RTCP SDES               August 2016

Copyright Notice

   Copyright (c) 2016 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
   (http://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 . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
     2.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Specification . . . . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  SDES Item Header Extension  . . . . . . . . . . . . . . .   5
       4.1.1.  One-Byte Format . . . . . . . . . . . . . . . . . . .   6
       4.1.2.  Two-Byte Format . . . . . . . . . . . . . . . . . . .   6
     4.2.  Usage of the SDES Item Header Extension . . . . . . . . .   6
       4.2.1.  One-Byte or Two-Byte Headers  . . . . . . . . . . . .   6
       4.2.2.  MTU and Packet Expansion  . . . . . . . . . . . . . .   7
       4.2.3.  Transmission Considerations . . . . . . . . . . . . .   8
       4.2.4.  Different Usages  . . . . . . . . . . . . . . . . . .   9
       4.2.5.  SDES Items in RTCP  . . . . . . . . . . . . . . . . .  10
       4.2.6.  Update Flaps  . . . . . . . . . . . . . . . . . . . .  10
       4.2.7.  RTP Header Compression  . . . . . . . . . . . . . . .  11
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
     5.1.  Registration of an SDES Base URN  . . . . . . . . . . . .  11
     5.2.  Creation of the "RTP SDES Compact Header Extensions"
           Sub-Registry  . . . . . . . . . . . . . . . . . . . . . .  12
     5.3.  Registration of SDES Item . . . . . . . . . . . . . . . .  12
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  14
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

Westerlund, et al.           Standards Track                    [Page 2]
RFC 7941                  RTP HE for RTCP SDES               August 2016

1.  Introduction

   This specification defines an RTP header extension [RFC3550][RFC5285]