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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This Internet-Draft will expire on May 7, 2016.
Copyright Notice
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document authors. All rights reserved.
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Provisions Relating to IETF 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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