One document matched: draft-ietf-avtcore-5761-update-01.txt
Differences from draft-ietf-avtcore-5761-update-00.txt
Network Working Group C. Holmberg
Internet-Draft Ericsson
Updates: 5761 (if approved) August 10, 2016
Intended status: Standards Track
Expires: February 11, 2017
Updates to RFC 5761
draft-ietf-avtcore-5761-update-01.txt
Abstract
This document updates RFC 5761 by clarifying the SDP offer/answer
negotiation of RTP and RTCP multiplexing. It makes it clear that an
answerer can only include an "a=rtcp-mux" attribute in an SDP answer
if the associated SDP offer contained the attribute.
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
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 February 11, 2017.
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
Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Update to RFC 5761 . . . . . . . . . . . . . . . . . . . . . 2
3.1. Update to the sixth paragraph of section 5 . . . . . . . 2
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
7. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 5
8. Normative References . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
RFC 5761 [RFC5761] specifies how to multiplex RTP data packets and
RTP Control Protocol (RTCP) packets on a single UDP port, and how to
negotiate usage of such multiplexing using the SDP offer/answer
mechanism [RFC3264], using an "a=rtcp-mux" attribute. However, the
text is unclear on whether an answerer is allowed to include the
attribute in an answer even if the associated offer did not contain
an attribute.
This document updates RFC 5761 [RFC5761] by clarifying that an
answerer can only include an "a=rtcp-mux" attribute in an answer if
the associated offer contained the attribute. It also clarifies that
the negotiation of RTP and RTCP multiplexing is for usage in both
directions.
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. Update to RFC 5761
This section updates section 5.1.1 of RFC 5761.
3.1. Update to the sixth paragraph of section 5
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
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attribute at the media level to request multiplexing of RTP and RTCP
on a single port. 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
This offer denotes a unicast voice-over-IP session using the RTP/AVP
profile with iLBC coding. The answerer is requested to send both RTP
and RTCP to port 49170 on IPv6 address 2001:DB8::211:24ff:fea3:7a2e.
If the answerer wishes to multiplex RTP and RTCP onto a single port,
it MUST include a media-level "a=rtcp-mux" attribute in the answer.
The RTP payload types used in the answer MUST conform to the rules in
Section 4.
If the answer does not contain an "a=rtcp-mux" attribute, the offerer
MUST NOT multiplex RTP and RTCP packets on a single port. Instead,
it should send and receive RTCP on a port allocated according to the
usual port-selection rules (either the port pair, or a signalled port
if the "a=rtcp:" attribute [10] is also included). This will occur
when talking to a peer that does not understand the "a=rtcp-mux"
attribute.
When SDP is used in a declarative manner, the presence of an "a=rtcp-
mux" attribute signals that the sender will multiplex RTP and RTCP on
the same port. The receiver MUST be prepared to receive RTCP packets
on the RTP port, and any resource reservation needs to be made
including the RTCP bandwidth.
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, and the usage is always negotiated for both
directions.
If the offerer wishes to multiplex RTP and RTCP onto a single port,
the initial SDP offer MUST include the attribute at the media level to
request multiplexing of RTP and RTCP on a single port. For example:
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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
This offer denotes a unicast voice-over-IP session using the RTP/AVP
profile with iLBC coding. The answerer is requested to send both RTP
and RTCP to port 49170 on IPv6 address 2001:DB8::211:24ff:fea3:7a2e.
If the offer contains the "a=rtcp-mux" attribute, and if the answerer
wishes to multiplex RTP and RTCP onto a single port, it MUST include a
media-level "a=rtcp-mux" attribute in the answer. The RTP payload
types used in the answer MUST conform to the rules in Section 4. If
the offer does not contain the "a=rtcp-mux" attribute the answerer
MUST NOT include an "a=rtcp-mux" attribute in the answer, and the
answerer MUST NOT multiplex RTP and RTCP packets on a single port.
If the answerer includes an "a=rtcp-mux" attribute in the answer, the
offerer and answerer MUST multiplex RTP and RTCP packets on a single
port.
If the answer does not contain an "a=rtcp-mux" attribute, the offerer
and answerer MUST NOT multiplex RTP and RTCP packets on a single port.
Instead, they should send and receive RTCP on a port allocated
according to the usual port-selection rules (either the port pair, or
a signalled port if the "a=rtcp:" attribute [10] is also included).
This will occur when talking to a peer that does not understand the
"a=rtcp-mux" attribute.
When SDP is used in a declarative manner, the presence of an "a=rtcp-
mux" attribute signals that the sender will multiplex RTP and RTCP on
the same port. The receiver MUST be prepared to receive RTCP packets
on the RTP port, and any resource reservation needs to be made
including the RTCP bandwidth.
4. Security Considerations
The security considerations for RTP and RTCP multiplexing are
described in RFC 5761. This specification does not impact those
security considerations.
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5. IANA Considerations
This specifcation makes no requests from IANA.
6. Acknowledgements
Thanks to Colin Perkins, Magnus Westerlund, Paul Kyzivat, Roni Even
for providing comments on the document. Thomas Belling provided
useful input in the discussions that took place in 3GPP and resulated
in the submission of the document.
7. Change Log
[RFC EDITOR NOTE: Please remove this section when publishing]
Change from -00
o Editorial changes based on WGLC comments from Roni Even.
8. 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>.
[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
Christer Holmberg
Ericsson
Hirsalantie 11
Jorvas 02420
Finland
Email: christer.holmberg@ericsson.com
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