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In: MissingRef
Network Working Group                                        C. Holmberg
Internet-Draft                                                  Ericsson
Intended status: Standards Track                       February 15, 2016
Expires: August 18, 2016


    Indicating Exclusive Support of RTP/RTCP Multiplexing using SDP
                   draft-ietf-mmusic-mux-exclusive-03

Abstract

   This document defines a new SDP media-level attribute, 'rtcp-mux-
   exclusive', that can be used by an endpoint to indicate exclusive
   support of RTP/RTCP multiplexing.

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
   Task Force (IETF).  Note that other groups may also distribute
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   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   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 August 18, 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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   described in the Simplified BSD License.





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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  SDP rtcp-mux-exclusive Attribute  . . . . . . . . . . . . . .   3
   4.  SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . .   4
     4.1.  General . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.2.  Generating the Initial SDP Offer  . . . . . . . . . . . .   4
     4.3.  Generating the Answer . . . . . . . . . . . . . . . . . .   4
     4.4.  Offerer Processing of the SDP Answer  . . . . . . . . . .   5
     4.5.  Modifying the Session . . . . . . . . . . . . . . . . . .   5
   5.  ICE Considerations  . . . . . . . . . . . . . . . . . . . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   6
   9.  Change Log  . . . . . . . . . . . . . . . . . . . . . . . . .   7
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   7
     10.2.  Informative References . . . . . . . . . . . . . . . . .   8
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   8

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 Session Description Protocol (SDP) [RFC4566]
   attribute, 'rtcp-mux' that can be used by entities to indicate
   support, and negotiate usage of, RTP/RTCP multiplexing.

   As defined in [RFC5761], if the peer endpoint does not support RTP/
   RTCP multiplexing, there must be a fallback to usage of separate
   ports for RTP and RTCP.

   The RTCWEB WG has defined that support of the fallback mentioned
   above is optional.  Therefore, there is a need for a mechanism that
   allows an endpoint to indicate exclusive support of RTP/RTCP
   multiplexing, meaning that endpoint only supports RTP/RTCP
   multiplexing and is not able to fallback to usage of separate ports
   for RTP and RTCP.

   This document defines a new SDP media-level attribute, 'rtcp-mux-
   exclusive', that can be used to indicate exclusive support of RTP/
   RTCP multiplexing.

   The document also describes the Interactive Connectivity
   Establishment (ICE) [I-D.ietf-ice-rfc5245bis] considerations when
   indicating exclusive support of RTP/RTCP multiplexing.




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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].

3.  SDP rtcp-mux-exclusive Attribute

   This section defines a new SDP media-level attribute, 'rtcp-mux-
   exclusive'.


          Name: rtcp-mux-exclusive

          Value: N/A

          Usage Level: media

          Charset Dependent: no

          Syntax:

              rtcp-mux-exclusive

          Example:

              a=rtcp-mux-exclusive


   In an SDP offer, the offerer uses the SDP 'rtcp-mux-exclusive'
   attribute to indicate exclusive support of RTP/RTCP multiplexing for
   the RTP-based media associated with the SDP media description ("m="
   line).

   In an SDP answer, the 'rtcp-mux-exclusive' attribute indicates that
   the answerer supports, and accepts usage of, RTP/RTCP multiplexing
   for the RTP-based media associated with the SDP media description
   ("m=" line).

   The usage of the SDP 'rtcp-mux-exclusive' attribute is only defined
   for RTP-based media.

   The mux category [I-D.ietf-mmusic-sdp-mux-attributes] for the 'rtcp-
   mux-exclusive' attribute is 'NORMAL', which means that the attribute
   can be associated with an individual media description, even if the
   media description is multiplexed with other media descriptions
   [I-D.ietf-mmusic-sdp-bundle-negotiation] with which the attribute is
   not associated.



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   The 'rtcp-mux-exclusive' attribute applies to the whole associated
   media description.  The attribute MUST NOT be defined per source
   (using the SDP 'ssrc' attribute [RFC5576]).

   The SDP offer/answer [RFC3264] procedures associated with the
   attribute are defined in Section 4

4.  SDP Offer/Answer Procedures

4.1.  General

   This section defines the SDP offer/answer [RFC3264] procedures for
   indicating exclusive support of, and negotiating usage of, RTP/RTCP
   multiplexing.

   The procedures in this section apply to individual RTP-based SDP
   media descriptions ("m=" lines).

4.2.  Generating the Initial SDP Offer

   When an offerer sends the initial offer, if the offerer wants to
   indicate exclusive RTP/RTCP multiplexing for RTP-based media, the
   offerer MUST associate an SDP 'rtcp-mux-exclusive' attribute with the
   associated SDP media description ("m=" line).

   In addition, if the offerer associates an SDP 'rtcp-mux-exclusive'
   attribute with an SDP media description ("m=" line), the offerer MUST
   also associate an SDP 'rtcp-mux' attribute with the same SDP media
   description ("m=" line), following the procedures in [RFC5761].

   If the offerer associates an SDP 'rtcp' attribute [RFC3605] with an
   SDP media description ("m=" line), and if the offerer also associates
   an SDP 'rtcp-mux-exclusive' attribute with the same SDP media
   description ("m=" line), the address and port values of the SDP
   'rtcp' attribute MUST match the corresponding values for RTP.

   NOTE: This specification does not mandate the usage of the SDP 'rtcp'
   attribute for RTP/RTCP multiplexing.

4.3.  Generating the Answer

   When an answerer receives an offer that contains an SDP 'rtcp-mux-
   exclusive' attribute, associated with an RTP-based SDP media
   description ("m=" line), if the answerer accepts the usage of RTP/
   RTCP multiplexing, the answerer MUST associate an SDP 'rtcp-mux-
   exclusive' attribute with the corresponding SDP media description
   ("m=") in the associated answer.  If the answerer does not accept the
   usage of RTP/RTCP multiplexing, the answerer MUST either reject the



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   SDP media description ("m=") by setting the port value to zero in the
   associated answer, or reject the whole offer, following the
   procedures in [RFC3264].

   In addition, if the answerer associates an SDP 'rtcp-mux-exclusive'
   attribute with an SDP media description ("m=" line) in the answer,
   the answerer MUST also associate an SDP 'rtcp-mux' attribute with the
   same SDP media description ("m=" line), following the procedures in
   [RFC5761].

4.4.  Offerer Processing of the SDP Answer

   If an offerer associated an SDP 'rtcp-mux-exclusive' attribute with
   an RTP-based SDP media description ("m=" line) in an offer, and if
   the corresponding SDP media description ("m=" line) in the associated
   answer contains an SDP 'rtcp-mux-exclusive' attribute, and/or an SDP
   'rtcp-mux' attribute, the offerer MUST apply the RTP/RTCP
   multiplexing procedures [RFC5761] to the associated RTP-based media.
   If the corresponding SDP media description ("m=" line) in the
   associated answer does not contain an SDP 'rtcp-mux-exclusive'
   attribute, nor an SDP 'rtcp-mux' attribute, the offerer MUST either
   take appropriate actions in order to disable the associated RTP-based
   media, or send a new offer without associating an SDP 'rtcp-mux-
   exclusive' attribute with the SDP media description ("m=" line).

   NOTE: This document does not mandate specific actions on how to
   terminate the RTP media.  The offerer might e.g. send a new offer,
   where the port value of the SDP media description is set to zero, in
   order to terminate the RTP media.

4.5.  Modifying the Session

   When an offerer sends a subsequent offer, if the offerer and answerer
   have previously negotiated usage of RTP/RTCP multiplexing for the
   media associated with an RTP-based SDP media description ("m=" line),
   the offerer SHOULD associate an SDP 'rtcp-mux-exclusive' attribute
   and an SDP 'rtcp-mux' attribute with the corresponding SDP media
   description ("m=" line).  If the offerer does not associate the
   attributes with the corresponding SDP media description ("m=" line)
   it is an indication that the offerer no longer wants to use RTP/RTCP
   multiplexing, and instead MUST fallback to usage of separate ports
   for RTP and RTCP once the offer has been accepted by the answerer.

   When an offerer sends a subsequent offer, if the offerer and answerer
   have not previously negotiated usage of RTP/RTCP multiplexing for the
   media associated with an RTP-based SDP media description ("m=" line),
   the offerer MAY indicate exclusive support of RTP/RTCP multiplexing,




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   following the procedures in Section 4.2.  The offerer MUST process
   the associated answer following the procedures in Section 4.4.

   NOTE: It is RECOMMENDED to not switch between usage of RTP/RTCP
   multiplexing and usage of separate ports for RTP and RTCP in a
   subsequent offer, unless there is a use-case that mandates it.

5.  ICE Considerations

   As defined in [I-D.ietf-ice-rfc5245bis], if an entity is aware that
   the remote peer supports, and is willing to use, RTP/RTCP
   multiplexing, the entity will only provide RTP candidates (component
   ID 1).  However, only providing RTP candidates does not as such imply
   exclusive support of RTP/RTCP multiplexing.  RTCP candidates would
   not be provided also in cases where RTCP is not supported at all.
   Therefore, additional information is needed in order to indicate
   support of exclusive RTP/RTCP multiplexing.  This document defines
   such mechanism using the SDP 'rtcp-mux-exclusive' attributes.

6.  Security Considerations

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

7.  IANA Considerations

   This document updates the "Session Description Protocol Parameters"
   registry as specified in Section 8.2.2 of [RFC4566].  Specifically,
   it adds the SDP 'rtcp-mux-exclusive' attribute to the table for SDP
   media level attributes.


       Attribute name: rtcp-mux-exclusive
       Type of attribute: media-level
       Subject to charset: no
       Purpose: Indicate exclusive support of RTP/RTCP multiplexing
       Appropriate Values:
       Contact name: Christer Holmberg
       Category: NORMAL



8.  Acknowledgments

   Thanks to Roman Shpount, Paul Kyzivat, Ari Keranen, Bo Burman and
   Tomas Frankkila for their comments and input on the draft.





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9.  Change Log

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

   Changes from draft-ietf-mmusic-rtcp-mux-exclusive-02

   o  Minor editorial fix.

   Changes from draft-ietf-mmusic-rtcp-mux-exclusive-01

   o  Mux category and source-specific applicability added.

   Changes from draft-ietf-mmusic-rtcp-mux-exclusive-00

   o  Defined new SDP attribute for indicating rtcp-mux-exclusive.

   o  Updates to RFC 5761 removed.

   o  IANA considerations added.

   Changes from draft-holmberg-mmusic-rtcp-mux-exclusive-03

   o  Submitted as draft-ietf-mmusic-rtcp-mux-exclusive-00.

   Changes from draft-holmberg-mmusic-rtcp-mux-exclusive-02

   o  Intended status changed to "Standards track".

   Changes from draft-holmberg-mmusic-rtcp-mux-exclusive-01

   o  Clarified that the SDP rtcp attribute may contain the optional IP
      address part.

   Changes from draft-holmberg-mmusic-rtcp-mux-exclusive-00

   o  Additional updates to Section 5.1.1 of RFC 5761.

   o  ICE considerations added.

10.  References

10.1.  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>.




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   [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>.

   [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>.

   [I-D.ietf-ice-rfc5245bis]
              Keranen, A. and J. Rosenberg, "Interactive Connectivity
              Establishment (ICE): A Protocol for Network Address
              Translator (NAT) Traversal", draft-ietf-ice-rfc5245bis-00
              (work in progress), October 2015.

10.2.  Informative References

   [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>.

   [RFC5576]  Lennox, J., Ott, J., and T. Schierl, "Source-Specific
              Media Attributes in the Session Description Protocol
              (SDP)", RFC 5576, DOI 10.17487/RFC5576, June 2009,
              <http://www.rfc-editor.org/info/rfc5576>.

   [I-D.ietf-mmusic-sdp-mux-attributes]
              Nandakumar, S., "A Framework for SDP Attributes when
              Multiplexing", draft-ietf-mmusic-sdp-mux-attributes-12
              (work in progress), January 2016.

   [I-D.ietf-mmusic-sdp-bundle-negotiation]
              Holmberg, C., Alvestrand, H., and C. Jennings,
              "Negotiating Media Multiplexing Using the Session
              Description Protocol (SDP)", draft-ietf-mmusic-sdp-bundle-
              negotiation-25 (work in progress), January 2016.

Author's Address







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   Christer Holmberg
   Ericsson
   Hirsalantie 11
   Jorvas  02420
   Finland

   Email: christer.holmberg@ericsson.com












































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