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From: Jamal Hadi Salim <jhs@mojatatu.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: "David Miller" <davem@davemloft.net>,
	netdev <netdev@vger.kernel.org>, "Jerry Chu" <hkchu@google.com>,
	"Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>,
	"Jim Gettys" <jg@freedesktop.org>,
	"Dave Taht" <dave.taht@gmail.com>
Subject: Re: [PATCH] tcp: ECN blackhole should not force quickack mode
Date: Fri, 23 Sep 2011 20:55:45 -0400	[thread overview]
Message-ID: <1316825745.1865.24.camel@mojatatu> (raw)
In-Reply-To: <1316757739.2560.12.camel@edumazet-laptop>

On Fri, 2011-09-23 at 08:02 +0200, Eric Dumazet wrote:
> While playing with a new ADSL box at home, I discovered that ECN
> blackhole can trigger suboptimal quickack mode on linux : We send one
> ACK for each incoming data frame, without any delay and eventual
> piggyback.
>
> This is because TCP_ECN_check_ce() considers that if no ECT is seen on a
> segment, this is because this segment was a retransmit.

If you have Linux as the sender, that assumption is legit (i.e we never
set ECT on retransmits).

> Refine this heuristic and apply it only if we seen ECT in a previous
> segment, to detect ECN blackhole at IP level.

So  small confusion for me, Eric:
Is theres some middlebox clearing the ECT but allowing the TCP header
ECN flags to be set during SYN echange?  If yes, why would not allowing
quickack help?

cheers,
jamal

  parent reply	other threads:[~2011-09-24  0:59 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-09-23  6:02 [PATCH] tcp: ECN blackhole should not force quickack mode Eric Dumazet
2011-09-23 17:47 ` David Miller
2011-09-23 19:17 ` Ilpo Järvinen
2011-09-24  0:55 ` Jamal Hadi Salim [this message]
2011-09-25 19:24   ` Eric Dumazet
2011-09-26  1:07     ` jamal
2011-09-26  1:13       ` jamal
2011-09-26  8:26         ` Eric Dumazet
2011-09-26 12:00           ` jamal
2011-09-26 12:44             ` Eric Dumazet
2011-09-27  4:59 ` David Miller
2011-09-27  6:00   ` [PATCH net-next] tcp: unalias tcp_skb_cb flags and ip_dsfield Eric Dumazet
2011-09-27  6:20     ` David Miller
2011-09-27  7:37       ` Christoph Paasch
2011-09-27  8:01         ` Eric Dumazet
2011-09-27  8:08         ` David Miller
2011-09-27  8:38           ` Christoph Paasch
2011-09-27  9:23             ` Eric Dumazet
2011-09-27  9:28               ` Christoph Paasch
2011-09-27  9:40                 ` Eric Dumazet
2011-09-27  9:51       ` [PATCH net-next] tcp: rename tcp_skb_cb flags Eric Dumazet
2011-09-27 17:25         ` David Miller

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