Session Description Protocol (SDP) Offer/Answer Clarifications for RTP/RTCP Multiplexing
RFC 8035

Document Type RFC - Proposed Standard (November 2016; No errata)
Updates RFC 5761
Last updated 2016-11-28
Replaces draft-holmberg-avtcore-5761-update
Stream IETF
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Stream WG state Submitted to IESG for Publication
Document shepherd Roni Even
Shepherd write-up Show (last changed 2016-09-06)
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Send notices to "Roni Even" <ron.even.tlv@gmail.com>
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Internet Engineering Task Force (IETF)                       C. Holmberg
Request for Comments: 8035                                      Ericsson
Updates: 5761                                              November 2016
Category: Standards Track
ISSN: 2070-1721

     Session Description Protocol (SDP) Offer/Answer Clarifications
                       for RTP/RTCP Multiplexing

Abstract

   This document updates RFC 5761 by clarifying the SDP offer/answer
   negotiation of RTP and RTP Control Protocol (RTCP) multiplexing.  It
   makes it clear that an answerer can only include an "a=rtcp-mux"
   attribute in a Session Description Protocol (SDP) answer if the
   associated SDP offer contained the attribute.

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/rfc8035.

Holmberg                     Standards Track                    [Page 1]
RFC 8035               RTP/RTCP Mux Clarifications         November 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
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   publication of this document.  Please review these documents
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   described in the Simplified BSD License.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Holmberg                     Standards Track                    [Page 2]
RFC 8035               RTP/RTCP Mux Clarifications         November 2016

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Update to RFC 5761  . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Update to Section 5.1.1 . . . . . . . . . . . . . . . . .   4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   RFC 5761 [RFC5761] specifies how to multiplex RTP data packets and
   RTP Control Protocol (RTCP) packets on a single UDP port, and how to
   negotiate usage of such multiplexing using the SDP offer/answer
   mechanism [RFC3264] with an "a=rtcp-mux" attribute.  However, the
   text is unclear on whether an answerer is allowed to include the
   attribute in an answer even if the associated offer did not contain
   an attribute.

   This document updates RFC 5761 [RFC5761] by clarifying that an
   answerer can only include an "a=rtcp-mux" attribute in an answer if
   the associated offer contained the attribute.  It also clarifies that
   the negotiation of RTP and RTCP multiplexing is for usage in both
   directions.

2.  Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].
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