Indicating Exclusive Support of RTP/RTCP Multiplexing using SDP
draft-holmberg-mmusic-mux-exclusive-00

Network Working Group                                        C. Holmberg
Internet-Draft                                                  Ericsson
Updates: 5761 (if approved)                             November 4, 2015
Intended status: Informational
Expires: May 7, 2016

    Indicating Exclusive Support of RTP/RTCP Multiplexing using SDP
                 draft-holmberg-mmusic-mux-exclusive-00

Abstract

   This document defines how an endpoint can indicate exclusive support
   of RTP/RTCP multiplexing using the Session Description Protocol
   (SDP).

   The document updates RFC 5761, by defining how the SDP 'rtcp'
   attribute is used, together with the SDP 'rtcp-mux' attribute, to
   indicate exclusive support of RTP/RTCP multiplexing.

   Editor's note: 'exclusive' is probably not the best terminology, so
   feel free to suggest something more appropriate.

Status of This Memo

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   publication of this document.  Please review these documents
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  SDP Offer/Answer Considerations . . . . . . . . . . . . . . .   3
   4.  Update to RFC 5761  . . . . . . . . . . . . . . . . . . . . .   3
     4.1.  General . . . . . . . . . . . . . . . . . . . . . . . . .   3
     4.2.  RFC 5761 Section 5.1.1 Update . . . . . . . . . . . . . .   3
     4.3.  Issues And TBDs . . . . . . . . . . . . . . . . . . . . .   3
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   4
   8.  Change Log  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .   4
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   4

1.  Introduction

   [RFC5761] defines how to multiplex RTP and RTCP on a single port,
   referred to as RTP/RTCP multiplexing.  [RFC5761] also defines an
   Session Description Protocol (SDP) [RFC4566] attribute, 'rtcp-mux'
   that can be used by entities to indicate support of RTP/RTCP
   multiplexing.

   [RFC5761] specifies that, if the peer endpoint does not support RTP/
   RTCP multiplexing, there must be a fallback to usage of different
   ports for RTP and RTCP.  However, the RTCWEB WG have defined that the
   support of using different ports is optional.  Therefor, there needs
   to be a mechanism for an endpoint to indicate exclusive support of
   RTP/RTCP multiplexing, i.e. indicate that the endpoint only supports
   RTP/RTCP multiplexing.

   The document updates section 5.1.1 of [RFC5761], by defining how the
   SDP 'rtcp' attribute is used, together with the SDP 'rtcp-mux'
   attribute, to indicate exclusive support of RTP/RTCP multiplexing.

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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3.  SDP Offer/Answer Considerations

   When an offerer sends an offer, if the offerer supports RTP/RTCP
   multiplexing, the offerer must associate an SDP 'rtcp-mux' attribute

4.  Update to RFC 5761

4.1.  General

   This section updates section 5.1.1 of [RFC5761], by replacing the
   text in the first paragraph with the new text defined in this
   section.

4.2.  RFC 5761 Section 5.1.1 Update

 OLD TEXT:

    When the Session Description Protocol (SDP) [8] is used to negotiate
    RTP sessions following the offer/answer model [9], the "a=rtcp-mux"
    attribute (see Section 8) indicates the desire to multiplex RTP and
    RTCP onto a single port.  The initial SDP offer MUST include this
    attribute at the media level to request multiplexing of RTP and RTCP
    on a single port.  For example:

 NEW TEXT:

    When the Session Description Protocol (SDP) [8] is used to negotiate
    RTP sessions following the offer/answer model [9], the "a=rtcp-mux"
    attribute (see Section 8) indicates the desire to multiplex RTP and
    RTCP onto a single port.  The initial SDP offer MUST include this
    attribute at the media level to request multiplexing of RTP and RTCP
    on a single port. If the offerer is not able to use different ports
    for RTP and RTCP, the SDP offer MUST also include the "a=rtcp"
    attribute [10] with an attribute value identical to the associated
    port value for RTP. For example:

4.3.  Issues And TBDs

   ISSUE #1: We may want to specify an explicit procedure for the
   answerer too, saying that it must select mux if it receives rtcp-mux
   and rtcp with the RTP port value.

   ISSUE #2: We may want to specify something about the case when the
   answerer only supports mux, and receives an offer without mux.

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5.  Security Considerations

   This document does not introduce new security considerations in
   additions to those specified in [RFC3605] and [RFC5761].

6.  IANA Considerations

   This document makes no requests from IANA.

7.  Acknowledgments

   TBD

8.  Change Log

   [RFC EDITOR NOTE: Please remove this section when publishing]

9.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC3264]  Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
              with Session Description Protocol (SDP)", RFC 3264,
              DOI 10.17487/RFC3264, June 2002,
              <http://www.rfc-editor.org/info/rfc3264>.

   [RFC3605]  Huitema, C., "Real Time Control Protocol (RTCP) attribute
              in Session Description Protocol (SDP)", RFC 3605,
              DOI 10.17487/RFC3605, October 2003,
              <http://www.rfc-editor.org/info/rfc3605>.

   [RFC4566]  Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
              Description Protocol", RFC 4566, DOI 10.17487/RFC4566,
              July 2006, <http://www.rfc-editor.org/info/rfc4566>.

   [RFC5761]  Perkins, C. and M. Westerlund, "Multiplexing RTP Data and
              Control Packets on a Single Port", RFC 5761,
              DOI 10.17487/RFC5761, April 2010,
              <http://www.rfc-editor.org/info/rfc5761>.

Author's Address

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   Christer Holmberg
   Ericsson
   Hirsalantie 11
   Jorvas  02420
   Finland

   Email: christer.holmberg@ericsson.com

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