Internet DRAFT - draft-holmberg-mmusic-mux-exclusive
draft-holmberg-mmusic-mux-exclusive
Network Working Group C. Holmberg
Internet-Draft Ericsson
Updates: 5761 (if approved) December 15, 2015
Intended status: Standards Track
Expires: June 17, 2016
Indicating Exclusive Support of RTP/RTCP Multiplexing using SDP
draft-holmberg-mmusic-mux-exclusive-03
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.
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
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This Internet-Draft will expire on June 17, 2016.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Update to RFC 5761 . . . . . . . . . . . . . . . . . . . . . 3
4.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 3
4.2. RFC 5761 Section 5.1.1 Update . . . . . . . . . . . . . . 3
4.3. RFC 5761 Section 5.1.3 Update . . . . . . . . . . . . . . 4
4.4. Issues And TBDs . . . . . . . . . . . . . . . . . . . . . 5
5. ICE Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
9. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 6
10. Normative References . . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
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.
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. However, the RTCWEB WG have defined that
support of the fallback is optional. Therefore, there needs to be a
mechanism for an endpoint to be able to indicate exclusive support of
RTP/RTCP multiplexing, i.e. to be able to indicate that the endpoint
only supports RTP/RTCP multiplexing and is not able to fallback to
usage of separate ports for receiving RTP and RTCP.
This document describes a mechanism, how the SDP 'rtcp-mux' attribute
[RFC5761] and the SDP 'rtcp' attribute [RFC3605] can be used to
indicate exclusive support of RTP/RTCP multiplexing. The document
updates sections 5.1.1 and 5.1.3 of [RFC5761] in order to enable
usage of the mechanism.
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. Mechanism
As as described in [RFC5761], when an offerer sends an offer, and
wants to indicate support of RTP/RTCP multiplexing, it must associate
an SDP 'rtcp-mux' attribute with each RTP-based SDP media description
("m=" line) for which support of multiplexing is indicated. In
addition, the offerer may assign an SDP 'rtcp' attribute, in order to
provide a fallback port for RTCP in case the answerer does not
support (or is not willing to use) RTP/RTCP multiplexing.
When an offerer sends an offer, and wants to indicate exclusive
support of RTP/RTCP multiplexing it MUST, in addition to the SDP
'rtcp-attribute, associate an SDP 'rtcp' attribute with each SDP
media description for which exclusive support of RTP/RTCP
multiplexing is indicated. The offerer MUST assign a port value
identical to the port value of the associated SDP media description
to the 'rtcp' attribute. The offerer MAY assign the optional IP
address part to the 'rtcp' attribute. If assigned, the IP address
part value MUST be identical to the value of the associated
connection address ("c=" line).
4. Update to RFC 5761
4.1. General
This section updates sections 5.1.1 and 5.1.3 of [RFC5761], by adding
a new paragraph in section 5.1.1 after the second paragraph, and by
modifying the second paragraph in section 5.1.3.
4.2. RFC 5761 Section 5.1.1 Update
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NEW PARAGRAPH:
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:
v=0
o=csp 1153134164 1153134164 IN IP6 2001:DB8::211:24ff:fea3:7a2e
s=-
c=IN IP6 2001:DB8::211:24ff:fea3:7a2e
t=1153134164 1153137764
m=audio 49170 RTP/AVP 97
a=rtpmap:97 iLBC/8000
a=rtcp-mux
a=rtcp: 49170
4.3. RFC 5761 Section 5.1.3 Update
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OLD TEXT:
If it is desired to use both ICE and multiplexed RTP and RTCP, the
initial offer MUST contain an "a=rtcp-mux" attribute to indicate that
RTP and RTCP multiplexing is desired and MUST contain "a=candidate:"
lines for both RTP and RTCP along with an "a=rtcp:" line indicating a
fallback port for RTCP in the case that the answerer does not support
RTP and RTCP multiplexing. This MUST be done for each media where
RTP and RTCP multiplexing is desired.
NEW TEXT:
If it is desired to use both ICE and multiplexed RTP and RTCP, the
initial offer MUST contain an "a=rtcp-mux" attribute to indicate that
RTP and RTCP multiplexing is desired. If the offerer supports
a fallback port for RTCP in the case that the answerer does not
support RTP and RTCP multiplexing, the initial offer MUST contain
"a=candidate:" lines for both RTP and RTCP along with an "a=rtcp:"
line indicating a fallback port for RTCP. If the offerer is not
able to use separate ports for RTP and RTCP the offer MUST NOT
contain "a=candidate:" lines for RTCP, and the "a=rtcp:" line
MUST indicate the RTP port. If the "a=rtcp:" line indicates the
RTP port, and if the "a=rtcp:" line also contains the optional
IP address part, the IP address part value MUST be identical to
the value of the associated "c=" line. The This MUST be done for
each media where RTP and RTCP multiplexing is desired.
4.4. 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.
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
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support of exclusive RTP/RTCP multiplexing. This document defines
such mechanism using the SDP 'rtcp-mux' and 'rtcp' 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 makes no requests from IANA.
8. Acknowledgments
Thanks to Roman Shpount, Paul Kyzivat, Ari Keraenen, Bo Burman and
Tomas Frankkila for their comments and input on the draft.
9. Change Log
[RFC EDITOR NOTE: Please remove this section when publishing]
Changes from draft-holmberg-mmusic-mux-exclusive-02
o Intended status changed to "Standards track".
Changes from draft-holmberg-mmusic-mux-exclusive-01
o Clarified that the SDP rtcp attribute may contain the optional IP
address part.
Changes from draft-holmberg-mmusic-mux-exclusive-00
o Additional updates to Section 5.1.1 of RFC 5761.
o ICE considerations added.
10. 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>.
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[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>.
[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.
Author's Address
Christer Holmberg
Ericsson
Hirsalantie 11
Jorvas 02420
Finland
Email: christer.holmberg@ericsson.com
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