netdev - Re: [PATCH] tcp: ECN blackhole should not force quickack mode

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Message-ID: <alpine.DEB.2.00.1109232215420.10441@melkinpaasi.cs.helsinki.fi>
Date:	Fri, 23 Sep 2011 22:17:42 +0300 (EEST)
From:	"Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi>
To:	Eric Dumazet <eric.dumazet@...il.com>
cc:	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>, Jerry Chu <hkchu@...gle.com>,
	Jamal Hadi Salim <jhs@...atatu.com>,
	Jim Gettys <jg@...edesktop.org>,
	Dave Taht <dave.taht@...il.com>
Subject: Re: [PATCH] tcp: ECN blackhole should not force quickack mode

On Fri, 23 Sep 2011, 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.
> 
> Refine this heuristic and apply it only if we seen ECT in a previous
> segment, to detect ECN blackhole at IP level.

This seems sensible thing to do.

Acked-by: Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>


-- 
 i.