From: Dave Taht <dave.taht@gmail.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: "Steinar H. Gunderson" <sgunderson@bigfoot.com>,
bloat <bloat@lists.bufferbloat.net>
Subject: Re: [Bloat] "BBR" TCP patches submitted to linux kernel
Date: Thu, 27 Oct 2016 10:59:26 -0700 [thread overview]
Message-ID: <CAA93jw6a_FfiDDnU+eC4X-uXQ8Yoy20F+RBtqPFhnQZ5-QU9OQ@mail.gmail.com> (raw)
In-Reply-To: <1477590728.7065.231.camel@edumazet-glaptop3.roam.corp.google.com>
On Thu, Oct 27, 2016 at 10:52 AM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On Thu, 2016-10-27 at 10:33 -0700, Dave Taht wrote:
>
>> At the moment my biggest beef with BBR is that it ignores ECN entirely
>> (and yet negotiates it).
>
> Note that switching cubic to any other CC like BBR is allowed at any
> time, way after ECN was negotiated.
>
> So BBR can not solve the issue you mention in a reliable way.
>
> There must be a reason sysctl_tcp_ecn default value is 2 on linux [1],
> don't you think ???
>
> _You_ chose to change this sysctl, do not blame BBR for being silly !
While I chose to do so on portions of my deployment, there is the larger
problem that Apple has enabled it nearly universally on iOS and OSX
over the past year.
> ECN was a nice attempt, but suffers from implementation bugs.
Believe me, I'm not huge on it either!
>
> For a start, linux does not implement RFC 3540.
>
> If someone cares enough of ECN, then it should cook linux patches to
> implement RFC 3540. Hint hint hint.
>
> Then you need to make sure all the nodes between your peers are not
> messing with ECN.
>
> BBR simply works, because it is a sender side thing.
> You do not have to fix everything in the Internet.
>
> [1]
> Documentation/networking/ip-sysctl.txt
> tcp_ecn - INTEGER
> Control use of Explicit Congestion Notification (ECN) by TCP.
> ECN is used only when both ends of the TCP connection indicate
> support for it. This feature is useful in avoiding losses due
> to congestion by allowing supporting routers to signal
> congestion before having to drop packets.
> Possible values are:
> 0 Disable ECN. Neither initiate nor accept ECN.
> 1 Enable ECN when requested by incoming connections and
> also request ECN on outgoing connection attempts.
> 2 Enable ECN when requested by incoming connections
> but do not request ECN on outgoing connections.
> Default: 2
>
>
--
Dave Täht
Let's go make home routers and wifi faster! With better software!
http://blog.cerowrt.org
next prev parent reply other threads:[~2016-10-27 17:59 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-16 21:04 Dave Taht
2016-09-16 21:11 ` Steinar H. Gunderson
2016-09-16 21:14 ` Eric Dumazet
2016-09-16 22:29 ` Dave Taht
2016-09-29 11:24 ` Mário Sérgio Fujikawa Ferreira
2016-09-29 19:43 ` Dave Täht
2016-09-29 20:35 ` Aaron Wood
2016-09-30 8:12 ` Mikael Abrahamsson
2016-09-30 14:16 ` Aaron Wood
2016-09-29 21:23 ` Steinar H. Gunderson
2016-09-30 1:54 ` Mario Ferreira
2016-09-30 3:50 ` Dave Täht
2016-09-30 4:29 ` Aaron Wood
2016-09-29 23:26 ` Benjamin Cronce
2016-09-30 1:58 ` Mario Ferreira
2016-10-21 8:47 ` Steinar H. Gunderson
2016-10-21 10:28 ` Eric Dumazet
2016-10-21 10:42 ` Steinar H. Gunderson
2016-10-21 10:47 ` Steinar H. Gunderson
2016-10-21 10:55 ` Eric Dumazet
2016-10-21 10:52 ` Eric Dumazet
2016-10-21 11:03 ` Steinar H. Gunderson
2016-10-21 11:40 ` Eric Dumazet
2016-10-21 11:45 ` Steinar H. Gunderson
2016-10-27 17:04 ` Steinar H. Gunderson
2016-10-27 17:31 ` Eric Dumazet
2016-10-27 17:33 ` Dave Taht
2016-10-27 17:52 ` Eric Dumazet
2016-10-27 17:59 ` Dave Taht [this message]
2016-10-27 17:57 ` Yuchung Cheng
2016-10-27 18:14 ` Dave Taht
2016-10-27 21:30 ` [Bloat] [bbr-dev] " Yuchung Cheng
2016-11-01 23:13 ` Yuchung Cheng
2016-11-01 23:49 ` Jonathan Morton
2016-11-02 9:27 ` Mikael Abrahamsson
2016-11-02 17:21 ` Klatsky, Carl
2016-11-02 18:48 ` Dave Täht
2016-11-25 12:51 ` [Bloat] " Bernd Paysan
2016-10-21 10:50 ` Zhen Cao
2016-10-27 19:25 Ingemar Johansson S
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