netdev - Re: [PATCH] TCP_FAILFAST: a new socket option to timeout/abort a connection quicker

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Message-ID: <4C737D15.5060400@nets.rwth-aachen.de>
Date:	Tue, 24 Aug 2010 10:04:37 +0200
From:	Arnd Hannemann <hannemann@...s.rwth-aachen.de>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	"H.K. Jerry Chu" <hkchu@...gle.com>, ilpo.jarvinen@...sinki.fi,
	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH] TCP_FAILFAST: a new socket option to timeout/abort a
 connection quicker

Am 24.08.2010 08:44, schrieb Eric Dumazet:
> Le lundi 23 août 2010 à 23:20 -0700, H.K. Jerry Chu a écrit :
>> From: Jerry Chu <hkchu@...gle.com>
>>
>> This is a TCP level socket option that takes an unsigned int to specify
>> how long in ms TCP should resend a lost data packet before giving up
>> and returning ETIMEDOUT. The normal TCP retry/abort timeout limit still
>> applies. In other words this option is only meant for those applications
>> that need to "fail faster" than the default TCP timeout. The latter
>> may take upto 20 minutes in a normal WAN environment.
>>
>> The option is disabled (by default) when set to 0. Also it does not
>> apply during the connection establishment phase.
>>
>> Signed-off-by: H.K. Jerry Chu <hkchu@...gle.com>
> 
> TCP_FAILFAST might be misleading. It reads as a boolean option, while
> its an option to cap the timeout, with a time unit, instead of the usual
> "number of retransmits".

Why not call it TCP_USERTIMEOUT?
Later you can also send it via the TCP user timeout option... (RFC5482)
Hmm... is the ms granularity really needed? Does it make sense to abort
a connection below a second?

> Its also funny you dont ask for a default value, given by a sysctl
> tunable ;)

Well retries1/2 would be the tunables, no?

Best regards,
Arnd
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