Indicating Exclusive Support of RTP and RTP Control Protocol (RTCP) Multiplexing Using the Session Description Protocol (SDP)
RFC 8858

Document Type RFC - Proposed Standard (January 2021; No errata)
Updates RFC 5761
Author Christer Holmberg 
Last updated 2021-01-18
Replaces draft-holmberg-mmusic-mux-exclusive
Stream IETF
Formats plain text html xml pdf htmlized bibtex
Reviews
Stream WG state Submitted to IESG for Publication
Document shepherd Flemming Andreasen
Shepherd write-up Show (last changed 2016-06-10)
IESG IESG state RFC 8858 (Proposed Standard)
Consensus Boilerplate Yes
Telechat date
Responsible AD Ben Campbell
Send notices to "Flemming Andreasen" <fandreas@cisco.com>
IANA IANA review state Version Changed - Review Needed
IANA action state RFC-Ed-Ack
RFC Editor RFC Editor state AUTH48-DONE
Details


Internet Engineering Task Force (IETF)                       C. Holmberg
Request for Comments: 8858                                      Ericsson
Updates: 5761                                               January 2021
Category: Standards Track                                               
ISSN: 2070-1721

  Indicating Exclusive Support of RTP and RTP Control Protocol (RTCP)
       Multiplexing Using the Session Description Protocol (SDP)

Abstract

   This document defines a new Session Description Protocol (SDP) media-
   level attribute, 'rtcp-mux-only', that can be used by an endpoint to
   indicate exclusive support of RTP and RTP Control Protocol (RTCP)
   multiplexing.  The document also updates RFC 5761 by clarifying that
   an offerer can use a mechanism to indicate that it is not able to
   send and receive RTCP on separate ports.

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
   https://www.rfc-editor.org/info/rfc8858.

Copyright Notice

   Copyright (c) 2021 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
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction
   2.  Conventions
   3.  SDP 'rtcp-mux-only' Attribute
   4.  SDP Offer/Answer Procedures
     4.1.  General
     4.2.  Generating the Initial SDP Offer
     4.3.  Generating the Answer
     4.4.  Offerer Processing of the SDP Answer
     4.5.  Modifying the Session
   5.  Update to RFC 5761
     5.1.  General
     5.2.  Update to 4th Paragraph of Section 5.1.1
     5.3.  Update to 2nd Paragraph of Section 5.1.3
   6.  ICE Considerations
   7.  Security Considerations
   8.  IANA Considerations
   9.  References
     9.1.  Normative References
     9.2.  Informative References
   Acknowledgements
   Author's Address

1.  Introduction

   [RFC5761] defines how to multiplex RTP and RTCP on a single IP
   address and port, referred to as RTP/RTCP multiplexing.  [RFC5761]
   also defines an SDP [RFC4566] attribute, 'rtcp-mux', that can be used
   by entities to indicate support of RTP/RTCP multiplexing and
   negotiate usage of it.

   As defined in [RFC5761], if the peer endpoint does not support RTP/
   RTCP multiplexing, both endpoints should use separate ports for
   sending and receiving of RTCP (referred to as fallback to usage of
   separate ports for RTP and RTCP).

   Some newer applications that do not require backward compatibility
   with peers that cannot multiplex RTCP might choose not to implement
   separation of RTP and RTCP.  Examples of such applications are W3C
   WebRTC applications [WebRTC], which are not required to interoperate
   with non-WebRTC clients.  For such applications, this document
   defines an SDP attribute to signal intent to require multiplexing.
   The use of this attribute in SDP offers [RFC3264] may harm the
   interoperability of entities that ever need to interoperate with
   peers that do not support RTC/RTCP multiplexing.  Also, while the SDP
   answerer [RFC3264] might support, and prefer usage of, fallback to
   nonmultiplex, the attribute indicates that fallback to nonmultiplex
   cannot be enabled.  One example of where nonmultiplex is preferred is
   where an endpoint is connected to a radio interface and wants to use
   different bearers (possibly with different quality characteristics)
   for RTP and RTCP.  Another example is where one endpoint is acting as
   a gateway to a network where RTP/RTCP multiplexing cannot be used.
   In such a case, the endpoint may also prefer nonmultiplexing towards
   the other network.  Otherwise, the endpoint would have to perform
   demultiplexing of RTP and RTCP.

   This document defines a new SDP media-level attribute, 'rtcp-mux-
   only', that can be used by an endpoint to indicate exclusive support
   of RTP/RTCP multiplexing.  The document also updates [RFC5761] by
   clarifying that an offerer can use a mechanism to indicate that it is
   not able to send and receive RTCP on separate ports.
Show full document text