Minutes
of the Meeting: MMUSIC working group at IETF 83
========================================================
The
MMUSIC working group of the IETF met at IETF #83 in Paris, France. The WG met
on March 26, 2012 from 9 to 11.30.
The
meeting was chaired by Flemming Andreasen and Miguel A. Garcia.
Paul
Kyzivat, Christer Holmberg and the chairs took notes. Hadriel Kaplan acted as a
jabber scribe.
This
meeting was broadcast live and recorded by the Meetecho team. The recording of
the session is available at the following URL:
http://ietf83.conf.meetecho.com/index.php/Recorded_Sessions#MMUSIC_IETF83
Introduction
and Status Update (Chairs)
========================================
The
chairs presented the agenda:
http://www.ietf.org/proceedings/83/agenda/agenda-83-mmusic.htm
No
agenda bashing was needed.
The
chairs presented the status of the working group (see slides):
http://www.ietf.org/proceedings/83/slides/slides-83-mmusic-2.ppt
Published RFCs since last IETF
------------------------------
-
RFC 6544:
TCP Candidates with Interactive Connectivity Establishment (ICE)
No other documents are in the RFC Editor,
IESG evaluation, publication requested, or WGLC completed states.
Progress
of other work items
----------------------------
–
RFC 4566bis, draft-ietf-mmusic-rfc4566bis-05
The
document is done, we have kept it open for a while, but there are no
foreseeable changes.
–
RTSP 2.0, draft-ietf-mmusic-rfc2326bis-29
The
document was WGLCed for versions -22 (September 2009) and -23 (March 2010). The
current version -29 will start WGLC right after the IETF meeting. The focus of
this WGLC should be the changes since version -27.
–
RTSP NAT traversal, draft-ietf-mmusic-rtsp-nat-11
and RTSP NAT evaluation draft-ietf-mmusic-rtsp-nat-evaluation-04
Mostly
done, should go to WGLC right after RTSP 2.0.
–
SCTP media in SDP, draft-ietf-mmusic-sctp-sdp-01
The
document is done, waiting to start a WGLC.
–
CS descriptions in SDP, draft-ietf-mmusic-sdp-cs-10
This
draft has one issue to solve, related to the format of the correlation token if
included in the User-to-User Information element. Paul Kyzivat had a comment on
the list suggesting using the same format, since it is the same value, that is
used by draft-ietf-cuss-sip-uui-isdn.
Keith Drage indicated that there is no requirement for these two formats to be
the same. Paul and Gonzalo made argument that we need to justify being
different, not being the same.
-
Miscellaneous Capability
Negotiation, draft-ietf-mmusic-sdp-miscellaneous-caps-00.
The draft was just submitted as WG item the same day of the meeting. The
document is considered to be done.
–
Media Path Middleboxes, draft-ietf-mmusic-media-path-middleboxes-04
¥
Do we want to keep the latching text in
here or refer to the latching draft?
¥
Other than that, the document is done.
Hadriel Kaplan
indicates that he has concerns about the goal of this document and the
potential target. He sent an e-mail to the list some time ago, and he will be resending
it for comments.
–
SDP Parallax attribute, draft-ietf-mmusic-parallax-attribute-00
and SDP 3D format, draft-ietf-mmusic-signal-3d-format-00
¥
IPR of both drafts disclosed after adoption
as WG items
¥
A bit more discussion after the WG status.
–
Special mention: Media level ice-options
SDP attribute, draft-petithuguenin-mmusic-ice-attributes-level-03.txt. The author cannot promise
to work further on it. There was a request for level of interest. Cullen
expressed interest, but thought should be split into multiple drafts.
SDP directorate
---------------
The chairs announced that the SDP
directorate has been formed, http://www.ietf.org/iesg/directorate/sdp.html.
Two reviews have been carried out already.
Discussion on IPR statements related to 3D
and parallax drafts
==============================================================
The chairs continued the presentation
supported by the same slide deck used for the WG status, http://www.ietf.org/proceedings/83/slides/slides-83-mmusic-2.ppt.
The chairs indicated that both the Parallax
attribute in SDP draft-ietf-mmusic-parallax-attribute-00
and SDP 3D format, draft-ietf-mmusic-signal-3d-format-00
had IPR disclosed by the authors's affiliated companies some time after both
drafts were adopted as WG items, and long after the first version of the
individual drafts was published. Due to the previously unknown IPR disclosures,
the WG needs to re-evaluate the direction that MMUSIC wants to take with
respect to the affected drafts. The documents were adopted as WG items at IETF
82, and at that time, no IPR disclosure were known.
Gonzalo Camarillo stated that this appears
to be a violation of RFC 3979 section 6.2.1. So he proposes to reevaluate the WG
direction on these drafts. Cullen Jennings would like to take time to find
alternatives. Keith Drage thinks there should be time to see if anyone else
wants to submit an alternative solution. Stephen Wenger noted there is overlap
with work done elsewhere (mpeg) and we do not need to do this work at all.
Keith agreed that deciding not to do work is a reasonable approach. If the
expertise is elsewhere, then those groups can register suitable SDP attributes.
Cullen suggested that we un-adopt these as WG drafts, make them back to individual
drafts. Roni Even questioned why we would do that
(is it because of the IPR, or because we do
not have the expertise and others do?). Stephen argued that the IPR changes the
economics; the assertion had been that we could do something cheaper to
implement than other standards bodies. Keith says that the best thing we can do
now is reverse the adoption, and then later we can reconsider adopting
something. The chairs will ask the
authors to resubmit as individual submissions again and will remove these as WG
items. We will have another decision whether to adopt these at the next
meeting. Linyi Tian asked why we
cannot keep as WG items while alternatives are considered. But chairs prefer to
go this way. The milestone will not be affected for now.
Multiplexing Negotiation Using SDP Port
Numbers (Christer Holmberg)
===================================================================
draft-ietf-mmusic-sdp-bundle-negotiation-00.txt
Christer presented his slides.
Roni Even commented on parameters that are
affected by bundle. He said that if two video streams are bundled, then the total
bandwidth may be different than the sum of the individual streams. But this had
something to do with session level parameters, which is not the same. Christer concluded that there is need
for further discussion.
Colin Perkins commented on RTCP bandwidth
that it is affected. James Polk mentioned that Magnus has draft to specify
minimum and maximum, but it might be affected. Harald Alverstrand says we cannot
handle all parameters in all drafts, but he wants people to point out any that
they are aware of.
Flemming Andreasen commented that this is
the biggest issue (e.g. consider sdescriptons.) There must be rules for these.
What are the rules for offer/answer. He says that if we try to solve this by
identifying individual parameters it will not be good enough. We must come up
with categories of parameters that are handled equivalently, so all parameters
can be categorized.
Roni says we have rules for session level
and media level. This is essentially adding a third level, and we do not have
rules for that.
Hadriel Kaplan says we discussed last time
that there were issues doing things this way that we would not have if we
multiplexed at a lower level on the port, giving multiple RTP sessions.
Cullen requested more time to discuss this
draft in the meeting, because it is the most important issue for the group.
Chairs said more time have been already allocated, and chairs will not cut the
discussion.
Colin commented that there will be
restrictions going this way. He thinks the restrictions need to be specified
someplace else. Harald disagreed; he thinks this is an SDP issue. We just need
to figure out how to signal a single RTP session that contains multiple media
types. Colin still says we need a new AVT document about this. Roni says this
will be the first topic in the AVTCORE meeting.
Roni says bundle should cover how to
multiplex audio and video, etc. , but that there is also a more general need to
discuss how to multiplex multiple SSRCs on an RTP session.
Nobody saw reason to mandate rtcp-mux
Signalling Media Stream ID in the SDP
(Harald Alvestrand)
========================================================
draft-alvestrand-rtcweb-msid-01.txt
Harald presented his slides.
Cullen comments that he thinks there is no
need to have separate stream - CNAME has the proper semantics. Harald commented
in a way that was not understood by Cullen and others. Magnus gave an example.
Cullen says that if two things have the same sync source then they will be
placed in the same media stream. Magnus says there are ways to use CNAME, but
they will impose limitations on the API. Cullen says those are currently
planned, but others disagreed. Cullen says a media stream is a synchronization
context, and Harald says it is not. Flemming asked that this be clarified.
Roni asked why the grouping framework is
not used. There is a question whether this can work with SSRCs. Harald is concerned
that the media stream track value is so specialized it would not fit in
grouping framework.
Jonathan Lennox said SSRC grouping is
defined as part of the a=ssrc attribute, but it is only within an m-line.
Cullen commented that this (A/V)nnn thing was too specific to a particular API.
Several other people agreed.
Jonathan asked if this mechanism could work
for anything other than
RTCweb. The answer was yes. Harald took
away the recommendation to generalize this.
An Extension to the Session Description
Protocol (SDP) for Media
Loopback (Hadriel Kaplan)
================================================================
draft-ietf-mmusic-media-loopback-18.txt
Hadriel presented his slides.
Hadriel indicates that version -18 was just
submitted earlier that morning, and resolved most of the outstanding issues. The
only things left are non-technical. The main technical change was to remove
media formats from loopback-source and loopback-mirror. Nobody objected to
that.
Partha questioned constraint that mirror
must be an RTP endpoint.
Hadriel said that happened before he got
involved. Magnus said reason is that if you just sent back exactly what you
received, then a real receiving RTP stack would find all kinds of errors, e.g.,
collisions.
Hadriel said he thought doing the RTP this
way is what had to be done for the draft to approved, but in reality they are
going to implement to just echo without going thru and RTP stack and he
suggests later writing a separate draft to explain how to do that.
It was agreed that the draft is ready for WGLC.
The draft needs IANA types review, and this will be done in parallel with the
WGLC.
The 'trafficclass' Attribute (James Polk)
=========================================
draft-ietf-mmusic-traffic-class-for-sdp-01.txt
James presented his slides.
Paul Kyzivat commented that instead of
defining the values in the ABNF an IANA registry could be created.
People were requested to review the
document.
SDP Media Capabilities Negotiation
(Flemming Andreasen)
=======================================================
draft-ietf-mmusic-sdp-media-capabilities-13.txt
Flemming presented his slides.
Flemming requested that the new offer/answer
procedures be carefully reviewed. Cullen and Christer volunteered. The chairs requested
that these be done within the next four weeks. Cullen and Christer committed to
that.
Flemming thinks that there are no
implications to bundle. But there are issues for bundle that are not specific
to this. Jonathan Lennox agreed.
The document is ready for WGLC after the offer/answer
review.
Latching: Hosted NAT Traversal (HNT) for
Media in Real-Time
Communication (Emil Ivov)
===========================================================
draft-kaplan-mmusic-latching-00.txt
Emil presented his slides.
Cullen said he has commented many times on the
security problems due to port scanning. Emil replied that it is discussed in
slides and the draft.
It was clarified that the intention is not
to recommend the usage of the latching mechanism, but just the publication of
this document as an informational document.
Cullen said that restricted latching has
problems with carrier grade NATs. Hadriel said that a variation on restricted
latching solves that.
Interest was sampled on making this a WG item.
Jonathan Lennox did not think MMUSIC was the right place. Magnus suggested the
BEHAVE WG. Hadriel said that this was submitted to the MMUSIC WG because the
chairs requested it. Cullen expressed thanks to authors for writing the document.
There is support for this work to continue. Chairs will work out with the ADs
the best way for moving the document forward.
Multipath RTP (MPRTP) (Colin Perkins
presenting for Varun Singh)
================================================================
draft-singh-avtcore-mprtp-04.txt
Colin presented his slides.
As the draft is not addressed to MMUSIC, no
decision was made in the WG regarding the future of the draft. There was,
though, a general discussion about ICE and finding extra candidates.
Christer commented that the suggested in-band
mechanism could cause problems because it bypasses the offer/answer. Colin
answered that should couple, so next time an offer/answer is done, the endpoint
should include all the addresses that are being used.
Flemming agreed with separating this draft into
a core multipath doc, a separate one for ICE, others with either RTP specific
or SDP specifics.
Update on Candidate Address Selection for
ICE (Ari Keranen)
===========================================================
draft-keranen-mmusic-ice-address-selection-00.txt
Ari presented his slides.
It was clarified that the intention of the
draft is to deal only with address selection issues; it would not be a general
"ICE fix" document.
Jonathan Lennox asked if new candidate list
is subset of existing list.
More discussion is expected on list.
RTSP Extension for Substream Control (Peiyu
Yue)
================================================
draft-yue-mmusic-rtsp-substream-control-extension-01.txt
Due to lack of time, this draft was just
briefly presented (see slides).
The discussion was deferred to the mailing list.
Security Descriptions Extension for Media
Streams (Sujing Zhou)
===============================================================
draft-zhou-mmusic-sdes-keymod-00.txt
Due to lack of time, this draft was just
briefly presented (see slides).
The discussion was deferred to the mailing list.
The meeting was adjourned at 11.30.