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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.


  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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