Re: [AVTCORE] [rmcat] WGLC on draft-ietf-avtcore-cc-feedback-message-05
Colin Perkins <csp@csperkins.org> Mon, 09 March 2020 15:51 UTC
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From: Colin Perkins <csp@csperkins.org>
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Date: Mon, 09 Mar 2020 15:51:23 +0000
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Cc: Roni Even <roni.even@huawei.com>, Ingemar Johansson S <ingemar.s.johansson@ericsson.com>, "rmcat@ietf.org" <rmcat@ietf.org>, "avt@ietf.org" <avt@ietf.org>
To: Ingemar Johansson S <ingemar.s.johansson=40ericsson.com@dmarc.ietf.org>
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Subject: Re: [AVTCORE] [rmcat] WGLC on draft-ietf-avtcore-cc-feedback-message-05
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Hi Ingemar, This is a good point. I’ll add some words to Section 4 of the draft to give flexibility, and add this case to the analysis in draft-ietf-rmcat-rtp-cc-feedback. Colin > On 16 Dec 2019, at 07:07, Ingemar Johansson S <ingemar.s.johansson=40ericsson.com@dmarc.ietf.org> wrote: > > Hi > > One comment related to the feedback interval. Even though SCReAM manages relatively sparse feedback at moderate bitrates, I have observed that at high bitrates (50+ Mbps) the feedback interval needs to go down to ~2ms. > 50Mbps means ~4000 packets/s and with a 2ms feedback interval this means one feedback every 8 RTP packets which, I would say is in the same ballpark as QUIC and TCP. > In other words the feedback rate is much higher than every frame. > It is possible to reduce the feedback frequency in SCReAM with an increased headroom for the congestion window and packet pacing, the drawback is however that the delay jitter can then increase. > > > Regards > Ingemar > > From: Roni Even (A) <roni.even@huawei.com> > Sent: den 15 december 2019 09:00 > To: Colin Perkins <csp@csperkins.org> > Cc: avt@ietf.org; rmcat@ietf.org > Subject: Re: [rmcat] WGLC on draft-ietf-avtcore-cc-feedback-message-05 > > Hi Colin, > The proposed text for section 4 looks OK > Roni Even as individual > > As for submitting an updated draft please wait for the end of the WGLC (end of this week) > > Roni Even as co-chair of AVTCore WG > > From: Colin Perkins [mailto:csp@csperkins.org <mailto:csp@csperkins.org>] > Sent: Thursday, December 12, 2019 9:16 PM > To: Roni Even (A) > Cc: avt@ietf.org <mailto:avt@ietf.org>; rmcat@ietf.org <mailto:rmcat@ietf.org> > Subject: Re: [rmcat] WGLC on draft-ietf-avtcore-cc-feedback-message-05 > > > > > On 10 Dec 2019, at 12:52, Roni Even (A) <roni.even@huawei.com <mailto:roni.even@huawei.com>> wrote: > > Hi, > > Some comments as individual > > 1. in section 10 the registration of the SDP ccfb attribute need also to include mux category > > That attribute is registered by draft-ietf-mmusic-sdp-mux-attributes, which include the mux category. This draft is registering a parameter within that attribute. > > > 2. In section 4 it is says “It has been shown [I-D.ietf-rmcat-rtp-cc-feedback <https://tools.ietf.org/html/draft-ietf-avtcore-cc-feedback-message-05#ref-I-D.ietf-rmcat-rtp-cc-feedback>] that in most cases a per frame feedback is a reasonable assumption on how frequent the RTCP feedback messages can be transmitted.“ later in the section it talks about 50-200msec and say that a value in this range need to be negotiated. Looking at rmcat-rtp-cc-feedback I got the impression that a report per frame is recommended. > > I rephrased the section to: > > There is a trade-off between speed and accuracy of reporting, and the > overhead of the reports. [I-D.ietf-rmcat-rtp-cc-feedback] discusses > this trade-off, suggests desirable RTCP feedback rates, and provides > guidance on how to configure the RTCP bandwidth fraction, etc., to > make appropriate use of the reporting block described in this memo. > Specifications for RTP congestion control algorithms can also provide > guidance. > > It is generally understood that congestion control algorithms work > better with more frequent feedback. However, RTCP bandwidth and > transmission rules put some upper limits on how frequently the RTCP > feedback messages can be sent from an RTP receiver to the RTP sender. > It has been shown [I-D.ietf-rmcat-rtp-cc-feedback] that in most cases > sending feedback one per frame is an upper bound before the reporting > overhead becomes excessive. Analysis [feedback-requirements] has > also shown that candidate congestion control algorithms can operate > with less frequent feedback, using a feedback interval range of > 50-200ms. Applications need to negotiate an appropriate feedback > interval at session setup. > > The draft-ietf-rmcat-rtp-cc-feedback is trying to show that per-frame feedback is possible, with acceptable overhead, but unless the codec can adapt on a per frame basis, it’s not clear that such frequent feedback is necessary. This version is intended to give bounds, and encourage people to draft draft-ietf-rmcat-rtp-cc-feedback, which will be expanded to give more discussion over time. Does this clarify? > > > 3. A nit – please expand RTS at first occurrence, it is expanded a bit late > > Fixed. > > Let us know when you want us to submit the revised draft. > Colin > > > > > > Roni Even > > > From: avt [mailto:avt-bounces@ietf.org <mailto:avt-bounces@ietf.org>] On Behalf Of Roni Even (A) > Sent: Thursday, December 05, 2019 9:30 AM > To: avt@ietf.org <mailto:avt@ietf.org> > Cc: rmcat@ietf.org <mailto:rmcat@ietf.org> > Subject: [AVTCORE] WGLC on draft-ietf-avtcore-cc-feedback-message-05 > > Hello, all! > > As we discussed in Singapore, this is to announce a Working Group Last Call for draft-ietf-avtcore-cc-feedback-05. > > Please review this document and send comments to the AVT mailing list by Thursday, December 19, 2019. > > > If you review the document and have nothing to add, please let the list know that as well. > > Thank you! > > Roni Even > AVTCore co-chair > > > > -- > Colin Perkins > https://csperkins.org/ <https://csperkins.org/> > > > _______________________________________________ > Audio/Video Transport Core Maintenance > avt@ietf.org <mailto:avt@ietf.org> > https://www.ietf.org/mailman/listinfo/avt <https://www.ietf.org/mailman/listinfo/avt> -- Colin Perkins https://csperkins.org/
- [AVTCORE] WGLC on draft-ietf-avtcore-cc-feedback-… Roni Even (A)
- Re: [AVTCORE] WGLC on draft-ietf-avtcore-cc-feedb… Roni Even (A)
- Re: [AVTCORE] [rmcat] WGLC on draft-ietf-avtcore-… Colin Perkins
- Re: [AVTCORE] [rmcat] WGLC on draft-ietf-avtcore-… Roni Even (A)
- Re: [AVTCORE] [rmcat] WGLC on draft-ietf-avtcore-… Ingemar Johansson S
- Re: [AVTCORE] [rmcat] WGLC on draft-ietf-avtcore-… Colin Perkins