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RTP Media Congestion Avoidance Techniques (Active WG)
Tsv Area: Mirja K├╝hlewind, Spencer Dawkins | 2012-Sep-25 —  

IETF-103 rmcat minutes

Session 2018-11-08 1120-1220: Boromphimarn 4 - Audio stream - rmcat chatroom


minutes-103-rmcat-01 minutes

                      RTP Media Congestion Control (RMCAT) Working Group
                              IETF 103, Bangkok, 8 November 2018
          Reported by Colin Perkins
            The RMCAT working group met once at IETF 103 in Bangkok, Thailand, in
            November 2018. The meeting was chaired by Colin Perkins.
            The meeting started with a welcome, introduction, and a review of the
            working group's status.  SCReAM and SBD were previously published as
            RFCs, NADA has completed working group last call and is waiting on the
            chairs to progress, and the coupled congestion control draft is in the
            RFC Editor queue (but see below). The evaluation drafts have completed
            working group last call with only minor issued noted, and the wireless
            tests draft is ready for WG last call.
            The evaluation criteria (draft-ietf-rmcat-eval-criteria) is not on the
            agenda, but was updated earlier this week. Joerg Ott briefly summarised
            the changes, and noted that the only issue remaining is to complete the
            security consideration. It was suggested that he look at the security
            considerations for eval-test for guidance on what this should contain.
            Once this is resolved, it is expected that there will be a short WG
            call to confirm the changes are okay, before the draft is sent to the
            The congestion control feedback draft was discussed in AVTCORE earlier
            the week. There was an attempt to implement this draft at the
            with some success, but this also highlighted some issues. Jonathan
            brought one of those issues for discussion to the meeting: how should
            feedback mechanism handle duplicate packets? Gorry Fairhurst and Mirja
            Kuehlewind commented, suggesting that the arrival time of the first
            of the duplicate should be reported.  Mirja also noted that, if any
            of the duplicate was ECN-CE marked, then a ECN-CE mark should be
            for the packet. Xiaoqing Zhu confirmed that this should work for NADA.
            The chair noted that the working group milestones are outdated. It was
            proposed to update the milestones as follows:
            - to submit the requirements and evaluation criteria drafts to the
              IESG to December 2018;
            - to submit the first draft of evaluation results and the first draft
              of the standards track congestion control algorithm in July 2019;
            - to submit the standards track congestion control algorithm to the
              IESG to November 2019, along with cc-codec-interactions and the
              framework; and
            - to remove the milestones relating to techniques to detect, instrument
              or diagnose failing to meet real-time schedules, since these are both
              redundant with other mechanisms.
            There were no objections to this plan, so the chairs will made these
          Update on draft-ietf-rmcat-eval-test
            Zahed Sarker gave an update on the eval-test draft, summarising the
            changes made as a result of working group last call comments. Most
            of these were uncontroversial. Gorry Fairhurst had comments on the
            revised security considerations, suggesting it be split into two,
            and made a little more specific and detailed. Gorry will propose
            An update will be submitted to incorporate this change, and a short WG
            last call will be issued to confirm the changes are acceptable, before
            the draft is sent to the IESG.
          Update on video-traffic-model draft
            Xiaoqing Zhu gave an update on the video-traffic-model draft. She
            summarised the changes made as a result of the working group last
            call. There were no objections to these changes. A short WG last
            call will be issued on the list to confirm the changes are okay,
            before the draft is sent to the IESG.
          Update on NADA implementation in Mozilla browser
            Xiaoqing Zhu gave an update on progress with implementing NADA in the
            Firefox browser and testing against Chrome. She summarised the changes
            made, and presented results from local tests on a wireless LAN, tests
            on a real-world path within the US, and tests on an international path
            (Austin, TX to Lausanne, Switzerland). These were using an unmodified
            receiver, sending standard RTCP feedback every second without the new
            congestion control feedback extensions, so performance was limited due
            to this, but otherwise NADA looks to work as expected.
            Magnus Westerlund asked why feedback was so infrequent, given that
            supports higher rates. Xiaoqing noted that they're using the default
            the browser. There was some discussion around how to modify this,
            and it
            was noted that there was progress with implementing the congestion
            feedback extension in Firefox at the hackathon. Xiaoqing expressed the
            intent to test with higher rate feedback.
            Julius Flohr asked if the code would be made available. Xiaoqing noted
            that she hoped it would be, once it was complete and cleaned-up.
            The chair noted that it is great to see implementation experiences and
            testing of the candidates.
          NADA implementation experiences
            Julius Flohr reported on an independent implementation of NADA in the
            Omnet++ simulator. He described the implementation and test scenarios,
            and presented some initial results. These show that his implementation
            performs very similarly to the NS3 implementation of NADA, indicating
            that the specification is in good shape.
            Sergio Mena asked for clarification on what was meant by the "perfect
            video encoder" used in these tests. Sergio and the chair thanked Julius
            for implementing and testing.
          Issue with draft-ietf-rmcat-coupled-cc
            Julius Flohr has implemented draft-ietf-rmcat-coupled-cc-07 in Omnet++.
            He noted that the draft does not consider application limited scenarios
            in case of Active FSE, but does for Passive FSE, and as a result there
            are issues with multiple RTP flows with different priorities when
            application limited streams are present. He highlighted the problem
            the algorithm, showing that it results in unfair rate allocation, and
            proposed a fix.
            Michael Welzl thanked him for experimenting with this, and noted that
            this is something that was removed to simplify the draft earlier. He
            is happy to make the proposed change to address the problem, although
            he noted a minor nit with the suggested fix.
            Julius and Michael will discuss further and propose text to fix this
            problem. Since the draft is with the RFC Editor, we'll work with our
            AD and the RFC editor to figure out how to incorporate the fix.
          Other Business
            Gorry Fairhurst noted that the updated security considerations he's
            writing for eval-test might apply more broadly than the one draft, and
            asked authors of other drafts to review and consider them once
            Jonathan Lennox noted that the hackathon was successful, and asked if
            anyone wanted to repeat in Prague? People seem interested, so Jonathan
            and the chairs will follow up to arrange this.
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