Minutes IETF106: rmcat
RTP Media Congestion Avoidance Techniques
||Minutes IETF106: rmcat
RTP Media Congestion Avoidance Techniques (RMCAT) Working Group
IETF 106, Singapore, 19 December 2019
Reported by Colin Perkins.
1. Working Group Status
The RMCAT working group met at IETF 106 in Singapore, in November 2019.
The meeting was chaired by Colin Perkins (in person) and Anna Brunstrom
The chairs presented the document status, noting that the requirements
for RTP congestion control, the candidate congestion control algorithms
and related drafts, and the evaluation drafts have been published or are
with the RFC Editor. The feedback message format is nearing completion
in AVTCORE, and the guidelines for providing congestion control feedback
will be updated once the feedback message format is complete. None of
the other drafts are active.
The chairs suggested updated milestones for the group. The proposed
goals are to gather evaluation results and experience for 12 months,
with meetings only if there are results to report, and then to evaluate
status and decide whether to pursue further work. There were questions
around the type of evaluation results expected, with Zahed Sarker and
Xiaoqing Zhu raising this issue during the meeting and Ingemar Johansson
making similar comments on the mailing list. Mirja Kühlewind noted that
it's important to consider carefully to ensure the candidate algorithms
are safe to use. We want experimental deployment results to show this
before the group can take candidate algorithm to Proposed Standard.
Mirja also noted that we don't have to pick a winner. The goal is to
show that a congestion control algorithm can be deployed without causing
problems, allowing it go to standards track. The goal is to show safety,
not that the candidate algorithm outperforms others. Nitin Garg and
Jonathan Lennox noted that they have some experiments and deployment
experience that will be ready to present in a future meeting, to help
support this proposal.
Jonathan Lennox reported from the Hackathon, noting that he'd been
working on adding visibility into tracing and debugging, working on a
common log format with Sergio Murillo to feed into visualisation tools.
Jonathan also noted that is would be useful to have a practical way to
turn the test case draft into concrete tests (e.g., that could be used
via mininet or Linux TC to run evaluations). The various algorithms and
test cases are written from the perspective of end points, and can be
difficult to interpret as an SFU implementer.
2. Update on NADA implementation and new evaluation results
Xiaoqing Zhu presented some NADA evaluation results. The latest
version of the draft-ietf-rmcat-nada-13 that's now been send to the RFC
Editor has some clarifications, but there have been no algorithmic
changes. The algorithm and feedback has been implemented in Firefox.
Xiaoqing showed evaluation results compared the behaviour with NADA
to that with the default congestion control for scenarios within the
US and for trans-Atlantic flows to demonstrate the behaviour of the
Nitin Garg asked about use with production traffic. Xiaoqing noted that
this has not yet been done, but that they are interested in doing so.
Another question asked about evaluating different combinations of the
default and NADA algorithms, but this has not yet been done.
The draft is with the RFC Editor. This initial implementation experience
is extremely valuable in starting to understand its behaviour.
3. RTCP feedback for congestion control
Colin Perkins briefly presented the RTP Congestion Control Feedback work
that's being done in AVTCORE(draft-ietf-avtcore-cc-feedback-message-05).
The main change has been to add an additional paragraph explaining the
relation to draft-holmer-rmcat-transport-wide-cc-extensions. There have
been no format changes. The draft is expected to go to WG last call in
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