From: Dave Taht <dave@taht.net>
To: Luca Muscariello <luca.muscariello@gmail.com>
Cc: Dave Taht <dave.taht@gmail.com>,
Jonathan Morton <chromatix99@gmail.com>,
bloat <bloat@lists.bufferbloat.net>
Subject: Re: [Bloat] when does the CoDel part of fq_codel help in the real world?
Date: Wed, 28 Nov 2018 23:20:53 -0800 [thread overview]
Message-ID: <87r2f4wdre.fsf@taht.net> (raw)
In-Reply-To: <CAHx=1M5-Qy5jH6EUTxdzDcwfy9UkkYn5QwTtT+21cx+eT6qNiw@mail.gmail.com> (Luca Muscariello's message of "Wed, 28 Nov 2018 11:48:19 +0100")
Luca Muscariello <luca.muscariello@gmail.com> writes:
> On Wed, Nov 28, 2018 at 11:40 AM Dave Taht <dave.taht@gmail.com>
> wrote:
>
> On Wed, Nov 28, 2018 at 1:56 AM Luca Muscariello
> <luca.muscariello@gmail.com> wrote:
> >
> > Dave,
> >
> > The single BDP inflight is a rule of thumb that does not account
> for fluctuations of the RTT.
> > And I am not talking about random fluctuations and noise. I am
> talking about fluctuations
> > from a control theoretic point of view to stabilise the system,
> e.g. the trajectory of the system variable that
> > gets to the optimal point no matter the initial conditions
> (Lyapunov).
>
> I have been trying all day to summon the gumption to make this
> argument:
>
> IF you have a good idea of the actual RTT...
>
> it is also nearly certain that there will be *at least* one other
> flow
> you will be competing with...
> therefore the fluctuations from every point of view are dominated
> by
> the interaction between these flows and
> the goal is, in general, is not to take up a full BDP for your
> single flow.
>
> And BBR aims for some tiny percentage less than what it thinks it
> can
> get, when, well, everybody's seen it battle it out with itself and
> with cubic. I hand it FQ at the bottleneck link and it works well.
>
> single flows exist only in the minds of theorists and labs.
>
> There's a relevant passage worth citing in the kleinrock paper, I
> thought (did he write two recently?) that talked about this
> problem...
> I *swear* when I first read it it had a deeper discussion of the
> second sentence below and had two paragraphs that went into the
> issues
> with multiple flows:
>
> "ch earlier and led to the Flow Deviation algorithm [28]. 17 The
> reason that the early work of 40 years ago took so long to make
> its
> current impact is because in [31] it was shown that the mechanism
> presented in [2] and [3] could not be implemented in a
> decentralized
> algorithm. This delayed the application of Power until the recent
> work
> by the Google team in [1] demonstrated that the key elements of
> response time and bandwidth could indeed be estimated using a
> distributed control loop sliding window spanning approximately 10
> round-trip times."
>
> but I can't find it today.
>
>
>
> Here it is
>
> https://www.lk.cs.ucla.edu/data/files/Kleinrock/Internet%20Congestion%20Control%20Using%20the%20Power%20Metric-Keep%20the%20Pipe%20Just%20Full%2C%20But%20No%20Fuller%20July%202018.pdf
Thank you that is more what I remember reading. That said, I still
remember a really two paragraph thing that went into footnote 17 of the
40+ years of history behind all this, that clicked with me about why
we're still going wrong... and I can't remember what it is. I'll go
deeper into the past and go read more refs off of this.
next prev parent reply other threads:[~2018-11-29 7:21 UTC|newest]
Thread overview: 102+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-26 19:08 Pete Heist
2018-11-26 19:28 ` Neal Cardwell
2018-11-27 20:42 ` Dave Taht
2018-11-27 20:54 ` Toke Høiland-Jørgensen
2018-11-27 21:00 ` Dave Taht
2018-11-27 21:05 ` Toke Høiland-Jørgensen
2018-11-26 21:29 ` Jonathan Morton
2018-11-27 9:24 ` Luca Muscariello
2018-11-27 10:26 ` Bless, Roland (TM)
2018-11-27 10:29 ` Luca Muscariello
2018-11-27 10:35 ` Bless, Roland (TM)
2018-11-27 10:40 ` Luca Muscariello
2018-11-27 10:50 ` Mikael Abrahamsson
2018-11-27 11:01 ` Luca Muscariello
2018-11-27 11:21 ` Mikael Abrahamsson
2018-11-27 12:17 ` Jonathan Morton
2018-11-27 13:37 ` Luca Muscariello
2018-11-27 13:49 ` Mikael Abrahamsson
2018-11-27 14:07 ` Luca Muscariello
2018-11-27 14:18 ` Mikael Abrahamsson
2018-11-27 18:44 ` Kathleen Nichols
2018-11-27 19:25 ` Dave Taht
2018-11-27 21:57 ` Roland Bless
2018-11-27 11:53 ` Bless, Roland (TM)
2018-11-27 11:58 ` Luca Muscariello
2018-11-27 12:22 ` Bless, Roland (TM)
2018-11-27 11:06 ` Jonathan Morton
2018-11-27 11:07 ` Michael Welzl
2018-11-29 7:35 ` Dave Taht
2018-11-29 18:43 ` Stephen Hemminger
2018-11-29 19:08 ` Dave Taht
2018-11-30 5:51 ` Mikael Abrahamsson
2018-11-30 19:02 ` Dave Taht
2018-11-30 19:58 ` Stephen Hemminger
2018-11-27 11:04 ` Michael Welzl
2018-11-27 12:48 ` Bless, Roland (TM)
2018-11-27 11:40 ` Bless, Roland (TM)
2018-11-27 11:43 ` Bless, Roland (TM)
2018-11-29 7:39 ` Dave Taht
2018-11-29 7:45 ` Jonathan Morton
2018-11-29 7:54 ` Dave Taht
2018-11-29 8:09 ` Luca Muscariello
2018-11-29 13:49 ` Bless, Roland (TM)
2018-11-29 8:41 ` Bless, Roland (TM)
2018-11-29 7:33 ` Dave Taht
2018-11-29 8:13 ` Bless, Roland (TM)
2018-11-29 10:00 ` Pete Heist
2018-11-29 16:09 ` Luca Muscariello
2018-11-29 17:07 ` Mario Hock
2018-11-29 22:30 ` Luca Muscariello
2018-11-30 9:55 ` Mario Hock
2018-11-30 10:32 ` Luca Muscariello
2018-11-30 11:04 ` Jonathan Morton
2018-11-30 11:53 ` jf
2018-12-03 9:42 ` Mario Hock
2018-11-27 11:52 ` Toke Høiland-Jørgensen
2018-11-28 3:37 ` [Bloat] AFD Dave Taht
2018-11-27 20:58 ` [Bloat] when does the CoDel part of fq_codel help in the real world? Dave Taht
2018-11-27 22:19 ` Luca Muscariello
2018-11-27 22:30 ` Roland Bless
2018-11-27 23:17 ` Dave Taht
2018-11-28 3:47 ` Kathleen Nichols
2018-11-28 9:56 ` Luca Muscariello
2018-11-28 10:40 ` Dave Taht
2018-11-28 10:48 ` Luca Muscariello
2018-11-28 12:10 ` Bless, Roland (TM)
2018-11-29 7:22 ` Dave Taht
2018-11-29 7:20 ` Dave Taht [this message]
2018-11-27 20:50 ` Dave Taht
2018-11-26 21:56 ` Michael Welzl
2018-11-26 22:13 ` Toke Høiland-Jørgensen
2018-11-27 8:54 ` Pete Heist
2018-11-27 9:31 ` Jonathan Morton
2018-11-27 13:19 ` Michael Richardson
2018-11-27 18:59 ` Jonathan Morton
2018-11-27 20:10 ` Dave Taht
2018-11-27 21:17 ` Michael Welzl
2018-11-27 21:20 ` Michael Welzl
2018-11-29 7:11 ` Dave Taht
2018-11-29 7:28 ` [Bloat] incremental deployment, transport and L4S (Re: when does the CoDel part of fq_codel help in the real world?) Mikael Abrahamsson
2018-11-29 7:36 ` Jonathan Morton
2018-11-29 7:46 ` Mikael Abrahamsson
2018-11-29 8:08 ` Michael Welzl
2018-11-29 10:30 ` Jonathan Morton
2018-11-29 12:06 ` Michael Welzl
2018-11-29 12:52 ` Jonathan Morton
2018-11-30 7:54 ` Michael Welzl
2019-02-03 18:20 ` Dave Taht
2018-11-29 12:12 ` Michael Welzl
2018-11-29 12:56 ` Jonathan Morton
2018-11-29 13:30 ` Mikael Abrahamsson
2018-11-29 23:27 ` Jonathan Morton
2018-11-30 6:01 ` Mikael Abrahamsson
2018-11-29 14:06 ` Bless, Roland (TM)
2018-11-29 8:09 ` Jonathan Morton
2018-11-29 8:19 ` Mikael Abrahamsson
2018-11-29 8:34 ` Jonathan Morton
2018-11-29 10:15 ` Sebastian Moeller
2018-11-29 10:53 ` Mikael Abrahamsson
2018-11-30 4:54 ` Dave Taht
2018-11-28 2:04 ` [Bloat] when does the CoDel part of fq_codel help in the real world? Pete Heist
2018-11-28 3:52 ` Dave Taht
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