Re: [tsvwg] Comments on L4S drafts
Luca Muscariello <muscariello@ieee.org> Fri, 14 June 2019 20:10 UTC
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References: <364514D5-07F2-4388-A2CD-35ED1AE38405@akamai.com> <cc446538-cf23-4fd0-12df-7839ec6c04a2@bobbriscoe.net>
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From: Luca Muscariello <muscariello@ieee.org>
Date: Fri, 14 Jun 2019 22:10:03 +0200
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To: Bob Briscoe <ietf@bobbriscoe.net>
Cc: "Holland, Jake" <jholland@akamai.com>, "tsvwg@ietf.org" <tsvwg@ietf.org>, "ecn-sane@lists.bufferbloat.net" <ecn-sane@lists.bufferbloat.net>
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Subject: Re: [tsvwg] Comments on L4S drafts
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On Fri, Jun 7, 2019 at 8:10 PM Bob Briscoe <ietf@bobbriscoe.net> wrote: > > I'm afraid there are not the same pressures to cause rapid roll-out at > all, cos it's flakey now, jam tomorrow. (Actually ECN-DualQ-SCE has a much > greater problem - complete starvation of SCE flows - but we'll come on to > that in Q4.) > > I want to say at this point, that I really appreciate all the effort > you've been putting in, trying to find common ground. > > In trying to find a compromise, you've taken the fire that is really aimed > at the inadequacy of underlying SCE protocol - for anything other than FQ. > If the primary SCE proponents had attempted to articulate a way to use SCE > in a single queue or a dual queue, as you have, that would have taken my > fire. > > But regardless, the queue-building from classic ECN-capable endpoints that > only get 1 congestion signal per RTT is what I understand as the main > downside of the tradeoff if we try to use ECN-capability as the dualq > classifier. Does that match your understanding? > > This is indeed a major concern of mine (not as major as the starvation of > SCE explained under Q4, but we'll come to that). > > Fine-grained (DCTCP-like) and coarse-grained (Cubic-like) congestion > controls need to be isolated, but I don't see how, unless their packets are > tagged for separate queues. Without a specific fine/coarse identifier, > we're left with having to re-use other identifiers: > > - You've tried to use ECN vs Not-ECN. But that still lumps two large > incompatible groups (fine ECN and coarse ECN) together. > - The only alternative that would serve this purpose is the flow > identifier at layer-4, because it isolates everything from everything else. > FQ is where SCE started, and that seems to be as far as it can go. > > Should we burn the last unicorn for a capability needed on "carrier-scale" > boxes, but which requires FQ to work? Perhaps yes if there was no > alternative. But there is: L4S. > > I have a problem to understand why all traffic ends up to be classified as either Cubic-like or DCTCP-like. If we know that this is not true today I fail to understand why this should be the case in the future. It is also difficult to predict now how applications will change in the future in terms of the traffic mix they'll generate. I feel like we'd be moving towards more customized transport services with less predictable patterns. I do not see for instance much discussion about the presence of RTC traffic and how the dualQ system behaves when the input traffic does not respond as expected by the 2-types of sources assumed by dualQ. If my application is using simulcast or multi-stream techniques I can have several video streams in the same link, that, as far as I understand, will get significant latency in the classic queue. Unless my app starts cheating by marking packets to get into the priority queue. In both cases, i.e. my RTC app is cheating or not, I do not understand how the parametrization of the dualQ scheduler can cope with traffic that behaves in a different way to what is assumed while tuning parameters. For instance, in one instantiation of dualQ based on WRR the weights are set to 1:16. This has to necessarily change when RTC traffic is present. How? Is the assumption that a trusted marker is used as in typical diffserv deployments or that a policer identifies and punishes cheating applications? BTW I'd love to understand how dualQ is supposed to work under more general traffic assumptions. Luca
- [tsvwg] Comments on L4S drafts Holland, Jake
- Re: [tsvwg] Comments on L4S drafts Bob Briscoe
- Re: [tsvwg] Comments on L4S drafts Ingemar Johansson S
- Re: [tsvwg] Comments on L4S drafts Holland, Jake
- Re: [tsvwg] Comments on L4S drafts Holland, Jake
- Re: [tsvwg] Comments on L4S drafts Luca Muscariello
- Re: [tsvwg] Comments on L4S drafts Dave Taht
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Dave Taht
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Dave Taht
- Re: [tsvwg] Comments on L4S drafts Ingemar Johansson S
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Ingemar Johansson S
- Re: [tsvwg] Comments on L4S drafts Bob Briscoe
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Dave Taht
- Re: [tsvwg] Comments on L4S drafts Holland, Jake
- Re: [tsvwg] Comments on L4S drafts Bob Briscoe
- Re: [tsvwg] Comments on L4S drafts Luca Muscariello
- Re: [tsvwg] Comments on L4S drafts Bob Briscoe
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Bob Briscoe
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Jonathan Morton
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts De Schepper, Koen (Nokia - BE/Antwerp)
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Bob Briscoe
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Jonathan Morton
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Bob Briscoe
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts De Schepper, Koen (Nokia - BE/Antwerp)
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Jonathan Morton
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Jonathan Morton
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Luca Muscariello
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts De Schepper, Koen (Nokia - BE/Antwerp)
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Holland, Jake
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts De Schepper, Koen (Nokia - BE/Antwerp)
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Dave Taht
- Re: [tsvwg] Comments on L4S drafts Holland, Jake
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Holland, Jake
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts De Schepper, Koen (Nokia - BE/Antwerp)
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Sebastian Moeller
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts De Schepper, Koen (Nokia - BE/Antwerp)
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Gorry Fairhurst
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Dave Taht
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Sebastian Moeller
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Wesley Eddy
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Dave Taht
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Black, David
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Jonathan Morton
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Sebastian Moeller
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Sebastian Moeller
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Wesley Eddy
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Dave Taht
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Dave Taht
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Bob Briscoe
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Bob Briscoe
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Scharf, Michael
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Gorry Fairhurst
- [tsvwg] Hackathon tests Dave Taht
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Sebastian Moeller
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Jonathan Morton
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Sebastian Moeller
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Sebastian Moeller
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Black, David
- Re: [tsvwg] New Version Notification for draft-gr… alex.burr@ealdwulf.org.uk
- Re: [tsvwg] New Version Notification for draft-gr… Jonathan Morton
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Bob Briscoe
- Re: [tsvwg] New Version Notification for draft-gr… alex.burr@ealdwulf.org.uk
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Sebastian Moeller
- Re: [tsvwg] [tcpm] New Version Notification for d… Scharf, Michael
- Re: [tsvwg] [tcpm] New Version Notification for d… Jonathan Morton
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Bless, Roland (TM)
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts De Schepper, Koen (Nokia - BE/Antwerp)
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Dave Taht
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Pete Heist
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Sebastian Moeller
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Dave Taht
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts De Schepper, Koen (Nokia - BE/Antwerp)
- Re: [tsvwg] [tcpm] New Version Notification for d… Bob Briscoe
- Re: [tsvwg] [tcpm] New Version Notification for d… Scharf, Michael
- Re: [tsvwg] [tcpm] New Version Notification for d… Black, David
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Bob Briscoe
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Bob Briscoe
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Sebastian Moeller
- [tsvwg] [Ecn-sane] Compatibility with singlw queu… Sebastian Moeller
- Re: [tsvwg] [Ecn-sane] Comments on L4S drafts Pete Heist
- Re: [tsvwg] [Ecn-sane] Compatibility with singlw … Black, David
- [tsvwg] The state of l4s, bbrv2, sce? Dave Taht
- Re: [tsvwg] The state of l4s, bbrv2, sce? Dave Taht
- Re: [tsvwg] The state of l4s, bbrv2, sce? Neal Cardwell
- Re: [tsvwg] The state of l4s, bbrv2, sce? Dave Taht
- Re: [tsvwg] [Ecn-sane] Compatibility with singlw … Sebastian Moeller
- Re: [tsvwg] [Ecn-sane] Compatibility with singlw … Holland, Jake
- Re: [tsvwg] [Ecn-sane] Compatibility with singlw … Black, David
- Re: [tsvwg] [Ecn-sane] Compatibility with singlw … Black, David
- Re: [tsvwg] [Ecn-sane] Compatibility with singlw … Sebastian Moeller
- Re: [tsvwg] [Ecn-sane] Compatibility with singlw … Jonathan Morton
- Re: [tsvwg] [Ecn-sane] Compatibility with singlw … Mikael Abrahamsson
- Re: [tsvwg] [Ecn-sane] Compatibility with singlw … Mikael Abrahamsson
- Re: [tsvwg] [Ecn-sane] Compatibility with singlw … John Leslie
- Re: [tsvwg] New Version Notification for draft-gr… Rodney W. Grimes
- Re: [tsvwg] New Version Notification for draft-gr… Gorry Fairhurst
- Re: [tsvwg] New Version Notification for draft-gr… Jonathan Morton
- Re: [tsvwg] New Version Notification for draft-gr… Gorry Fairhurst
- Re: [tsvwg] New Version Notification for draft-gr… Sebastian Moeller
- Re: [tsvwg] New Version Notification for draft-gr… Gorry Fairhurst
- Re: [tsvwg] [tcpm] New Version Notification for d… Scharf, Michael
- Re: [tsvwg] New Version Notification for draft-gr… Rodney W. Grimes
- Re: [tsvwg] [tcpm] New Version Notification for d… Loganaden Velvindron
- Re: [tsvwg] [tcpm] New Version Notification for d… Black, David