Subject: [AVT] Meeting summary for AVT at 51st IETF

From: Stephen Casner <[email-masked]>
Date: Tue, 21 Aug 2001 11:17:29 -0700 (PDT)

Below is a brief summary of the AVT meeting in London.  The full
minutes will be forthcoming (Reha Civanlar graciously accepted my
request to take notes and write the minutes).  Meanwhile, there are
several action items from the meeting to be confirmed on the mailing
list.  These will be sent in separate messages to facilitate
discussion.
						-- Steve & Colin

Audio/Video Transport Working Group Summary

The AVT group had two very full sessions in London.  We identified a
few wording changes needed in the RTP specification, but then it will
be ready for publication as a draft standard RFC.  The RTP spec and
profile bundle of drafts will be submitted to the IESG shortly.  There
have been minor updates since the last meeting, mostly adding back
payload formats due to extra interoperability test results received.
The package of enhancements to CRTP and tunnel compressed RTP (for
multiplexing) is also ready, and will go to the IESG soon.  The EVRC
payload is also ready for last call.

We had a long discussion on the problems of getting RTP through NATs
and firewalls.  Proposals: relax the consecutive port rule in some
cases, use symmetric RTP where the receiver "connects" back to the
sender on the address/port where data came from.  Neither of these are
particularly controversial.  We spent much time discussing port
sharing between RTP sessions, demuxing on SSRC.  Consensus is that
this is a bad idea, but that there is a strong need for a solution.

The new Datagram Control Protocol was introduced.  There is interest
in this work, but offline discussion with various people shows
scepticism that the current set of congestion control algorithms are
appropriate for RTP.  Concern also expressed about overlap between DCP
and SCTP.

The Secure RTP draft is also progressing nicely, with the basic
protocol likely to be complete before the next meeting.  Key
management is the main task remaining, will be discussed in MSEC and
MMUSIC groups for now.  There is a strong need for this capability.

Work on extending RTCP is progressing nicely: unicast RTCP from
receivers, e.g. for SSM sessions, and extensions for retransmission.
Initial discussion of a new layered retransmission payload format to
work with the retransmission extensions showed that the proposal needs
further development.

New payload formats: phoneme/spatial animation, distributed speech
recognition, a bugfix update to RFC 2250 (MPEG 1/2 video), and time
lined static media, such as slides and subtitles.  On this last one,
there were concerns about overlap with RMT work.  A better elucidation
of the problem is sought, and discussion will likely continue.

The "generic" MPEG-4 payload format is close to completion.  An
implementation guide/applicability statement to define a simple subset
is also in progress.  We expect to submit these as a set over the
coming few months.  The main open issue with MPEG-4 is the MIME type
registrations, since there are many types, some of which overlap with
existing registrations (e.g. RFC3016).

New results on the The UXP FEC scheme were presented.  An update to
the draft is expected, clarifying the applicability of the approach.

_______________________________________________
Audio/Video Transport Working Group
[email-masked]
http://www1.ietf.org/mailman/listinfo/avt