Re: [AVTCORE] [rtcweb] [tsvwg] WG Last Call on changes: draft-ietf-avtcore-rtp-circuit-breakers-16
Michael Welzl <michawe@ifi.uio.no> Mon, 27 June 2016 20:52 UTC
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From: Michael Welzl <michawe@ifi.uio.no>
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To: "Black, David" <david.black@emc.com>
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Cc: "rtcweb@ietf.org" <rtcweb@ietf.org>, tsvwg <tsvwg@ietf.org>, IETF AVTCore WG <avt@ietf.org>, "De Schepper, Koen (Nokia - BE)" <koen.de_schepper@nokia-bell-labs.com>
Subject: Re: [AVTCORE] [rtcweb] [tsvwg] WG Last Call on changes: draft-ietf-avtcore-rtp-circuit-breakers-16
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David, > On 27. jun. 2016, at 22.09, Black, David <david.black@emc.com> wrote: > >> As long as an AQM is marking at the same rate as dropping > > That's an interesting assumption - it should be true for AQMs vetted > here in the past, but there are easy ways for it not to hold (e.g., if dropping > or marking is based on queue occupancy, it is possible that dropping > reduces queue occupancy in a fashion that marking does not). > > For ECN "classic" (i.e., see RFC 3168) where ECN-CE markings are treated > as drop-equivalent, that is for congestion control purposes, which is similar > to, (but not the same as) the throughput estimation usage for the RTP circuit > breaker. I'll note that ECN "classic" was designed congestion control > algorithms for react to ECN-CE marks once per RTT, independent of how > many ECN-CE marks are observed in an RTT. > > Gorry wrote: > >>> in this context we should use ECN to drive a CC algorithm and we should be >>> cautious to avoid requiring its use within a Circuit Breaker - optional >>> use, if you understand how to interpret a reaction to many CE-marks as >>> excessive congestion, are permitted. > > Something like that may be workable, starting with a clear distinction between > the use of ECN by CC (routine, active at all times) and ECN by a circuit > breaker (monitors for evidence that things have gotten bad, only activated > when things get bad). This would baseline the RTP circuit breaker on drops > and allow use of ECN as additional evidence of problems, in contrast to > congestion control where ECN-CE is effectively treated as drop-equivalent. > > I'm not quite sure how to specify "use of ECN as additional evidence" of > "excessive congestion" as drop-equivalence is about the best we have > for current guidance. I fail to parse that sentence, so maybe I’m getting you wrong, but anyway I wonder: what’s even the point of this? Why even bother considering CE-marks as information for a circuit breaker? CE-marks may *not* indicate *excessive* congestion - and since you say “additional evidence”: I don’t think that a combination of loss and CE-marks makes this any better? CE-marks may be produced by a shallow queue, which can be rather “mild” congestion, at least in the light of what a circuit breaker should consider… Cheers, Michael
- Re: [AVTCORE] [tsvwg] [rtcweb] WG Last Call on ch… Michael Welzl
- Re: [AVTCORE] [tsvwg] [rtcweb] WG Last Call on ch… De Schepper, Koen (Nokia - BE)
- Re: [AVTCORE] [rtcweb] [tsvwg] WG Last Call on ch… Colin Perkins
- Re: [AVTCORE] [rtcweb] [tsvwg] WG Last Call on ch… Black, David
- Re: [AVTCORE] [rtcweb] [tsvwg] WG Last Call on ch… Michael Welzl
- Re: [AVTCORE] [tsvwg] [rtcweb] WG Last Call on ch… Ruediger.Geib
- Re: [AVTCORE] [rtcweb] [tsvwg] WG Last Call on ch… Colin Perkins
- Re: [AVTCORE] [tsvwg] [rtcweb] WG Last Call on ch… Colin Perkins
- Re: [AVTCORE] [rtcweb] [tsvwg] WG Last Call on ch… Black, David
- Re: [AVTCORE] [tsvwg] [rtcweb] WG Last Call on ch… Fred Baker (fred)
- Re: [AVTCORE] [tsvwg] [rtcweb] WG Last Call on ch… John Leslie
- Re: [AVTCORE] [tsvwg] [rtcweb] WG Last Call on ch… Fred Baker (fred)
- Re: [AVTCORE] [rtcweb] [tsvwg] WG Last Call on ch… Michael Welzl
- Re: [AVTCORE] [rtcweb] [tsvwg] WG Last Call on ch… Colin Perkins
- Re: [AVTCORE] [rtcweb] [tsvwg] WG Last Call on ch… Michael Welzl
- Re: [AVTCORE] [tsvwg] [rtcweb] WG Last Call on ch… Black, David
- Re: [AVTCORE] [tsvwg] [rtcweb] WG Last Call on ch… Michael Welzl
- Re: [AVTCORE] [tsvwg] [rtcweb] WG Last Call on ch… De Schepper, Koen (Nokia - BE)
- Re: [AVTCORE] [tsvwg] [rtcweb] WG Last Call on ch… gorry
- Re: [AVTCORE] [tsvwg] [rtcweb] WG Last Call on ch… De Schepper, Koen (Nokia - BE)
- Re: [AVTCORE] [rtcweb] WG Last Call on changes: d… Ben Campbell
- Re: [AVTCORE] [rtcweb] WG Last Call on changes: d… Magnus Westerlund
- Re: [AVTCORE] [tsvwg] [rtcweb] WG Last Call on ch… Michael Welzl
- Re: [AVTCORE] [tsvwg] [rtcweb] WG Last Call on ch… Black, David
- Re: [AVTCORE] [tsvwg] [rtcweb] WG Last Call on ch… Gorry (erg)
- Re: [AVTCORE] [rtcweb] [tsvwg] WG Last Call on ch… Mirja Kühlewind
- Re: [AVTCORE] [rtcweb] [tsvwg] WG Last Call on ch… Black, David
- Re: [AVTCORE] [rtcweb] [tsvwg] WG Last Call on ch… Colin Perkins
- Re: [AVTCORE] [rtcweb] [tsvwg] WG Last Call on ch… John Leslie
- Re: [AVTCORE] [tsvwg] WG Last Call on changes: dr… Black, David
- Re: [AVTCORE] [tsvwg] WG Last Call on changes: dr… Colin Perkins
- Re: [AVTCORE] [rtcweb] [tsvwg] WG Last Call on ch… Michael Welzl
- Re: [AVTCORE] [tsvwg] WG Last Call on changes: dr… Black, David
- Re: [AVTCORE] [rtcweb] [tsvwg] WG Last Call on ch… John Leslie
- Re: [AVTCORE] [tsvwg] WG Last Call on changes: dr… Magnus Westerlund
- [AVTCORE] WG Last Call on changes: draft-ietf-avt… Magnus Westerlund
- Re: [AVTCORE] [tsvwg] WG Last Call on changes: dr… Black, David