draft-ietf-straw-b2bua-rtcp-16.txt   draft-ietf-straw-b2bua-rtcp-17.txt 
STRAW Working Group L. Miniero STRAW Working Group L. Miniero
Internet-Draft Meetecho Internet-Draft Meetecho
Intended status: Standards Track S. Garcia Murillo Intended status: Standards Track S. Garcia Murillo
Expires: June 19, 2017 Medooze Expires: June 25, 2017 Medooze
V. Pascual V. Pascual
Oracle Oracle
December 16, 2016 December 22, 2016
Guidelines to support RTCP end-to-end in Back-to-Back User Agents Guidelines to support RTCP end-to-end in Back-to-Back User Agents
(B2BUAs) (B2BUAs)
draft-ietf-straw-b2bua-rtcp-16 draft-ietf-straw-b2bua-rtcp-17
Abstract Abstract
SIP Back-to-Back User Agents (B2BUAs) are often designed to also be SIP Back-to-Back User Agents (B2BUAs) are often designed to also be
on the media path, rather than just intercepting signalling. This on the media path, rather than just intercepting signalling. This
means that B2BUAs often implement an RTP/RTCP stack as well, thus means that B2BUAs often implement an RTP/RTCP stack as well, thus
leading to separate multimedia sessions that the B2BUA correlates and leading to separate multimedia sessions that the B2BUA correlates and
bridges together. If not disciplined, though, this behaviour can bridges together. If not disciplined, though, this behaviour can
severely impact the communication experience, especially when severely impact the communication experience, especially when
statistics and feedback information contained in RTCP messages get statistics and feedback information contained in RTCP messages get
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 19, 2017. This Internet-Draft will expire on June 25, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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all the SSRC- and RTCP-related SDP attributes when handling a all the SSRC- and RTCP-related SDP attributes when handling a
multimedia session setup between participants: this includes multimedia session setup between participants: this includes
attributes like 'ssrc' [RFC3261], 'rtcp-fb' [RFC4585], 'rtcp-xr- attributes like 'ssrc' [RFC3261], 'rtcp-fb' [RFC4585], 'rtcp-xr-
attrib' [RFC3611] and others. However, certain SDP attributes may attrib' [RFC3611] and others. However, certain SDP attributes may
lead to call failures when forwarded by a media relay, as they have lead to call failures when forwarded by a media relay, as they have
an implied assumption that the attribute describes the immediate an implied assumption that the attribute describes the immediate
peer. A clear example of this is the 'rtcp' [RFC3605] attribute, peer. A clear example of this is the 'rtcp' [RFC3605] attribute,
which describes the expected RTCP peer port. Other attributes might which describes the expected RTCP peer port. Other attributes might
include the immediate peer's IP address, preferred transport, etc. include the immediate peer's IP address, preferred transport, etc.
In general, the guideline is to require rewriting of attributes that In general, the guideline is to require rewriting of attributes that
are implicitly describing the immediate peer. If in doubt during are implicitly describing the immediate peer. B2BUAs SHOULD forward
implementation, testing to determine whether a call failure occurs all other SDP attributes in order to avoid breaking additional
should be done. If it doesn't, B2BUAs SHOULD forward all other SDP functionality endpoints may be relying on. If implementors have
attributes in order to avoid breaking additional functionality doubts about whether this guidance applies to a specific attribute,
endpoints may be relying on. they should test to determine if call failures occur.
The cited 'rtcp' example is also relevant whenever RTP/RTCP The cited 'rtcp' example is also relevant whenever RTP/RTCP
multiplexing [RFC5761] support is being negotiated. If the B2BUA multiplexing [RFC5761] support is being negotiated. If the B2BUA
acting as a Media Relay is unaware of the specifics of the traffic it acting as a Media Relay is unaware of the specifics of the traffic it
is handling, and as such may not have RTP/RTCP parsing capabilities, is handling, and as such may not have RTP/RTCP parsing capabilities,
it SHOULD reject RTP/RTCP multiplexing by removing the 'rtcp-mux' SDP it SHOULD reject RTP/RTCP multiplexing by removing the 'rtcp-mux' SDP
attribute. If instead the Media Relay is able to parse RTP/RTCP, and attribute. If instead the Media Relay is able to parse RTP/RTCP, and
can verify that demultiplexing can be performed without any RTP can verify that demultiplexing can be performed without any RTP
Payload Type rewrites (i.e., no overlap between any RTP Payload Types Payload Type rewrites (i.e., no overlap between any RTP Payload Types
and the RTCP Payload Type space has been detected), then the B2BUA and the RTCP Payload Type space has been detected), then the B2BUA
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towards the user. towards the user.
6. IANA Considerations 6. IANA Considerations
This document has no IANA actions. This document has no IANA actions.
7. Change Summary 7. Change Summary
Note to RFC Editor: Please remove this whole section. Note to RFC Editor: Please remove this whole section.
The following are the major changes between the 16 and the 17
versions of the draft:
o Clarified the meaning of a sentence.
The following are the major changes between the 14 and the 15 The following are the major changes between the 14 and the 15
versions of the draft: versions of the draft:
o Several changes addressing the IESG review (list follows). o Several changes addressing the IESG review (list follows).
o Addressed 'rtcp-mux' in 3.1 as well, and not only 3.2. o Addressed 'rtcp-mux' in 3.1 as well, and not only 3.2.
o Clarified that, if CNAMEs are rewritten, RTP extensions o Clarified that, if CNAMEs are rewritten, RTP extensions
referencing them (e.g., [RFC7941]) should be updated too. referencing them (e.g., [RFC7941]) should be updated too.
Clarified that MTU issues can occur if the rewriting results in a Clarified that MTU issues can occur if the rewriting results in a
 End of changes. 6 change blocks. 
9 lines changed or deleted 14 lines changed or added

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