Re: IIS times out on large post requests

From: Willy Tarreau <>
Date: Thu, 24 Jul 2008 22:08:41 +0200

Hi Krzysztof,

On Thu, Jul 24, 2008 at 09:51:59PM +0200, Krzysztof Oledzki wrote:
> Hello,
> On Thu, 24 Jul 2008, Willy Tarreau wrote:
> >Hi Rainer,
> <CUT>
> >Oh you're making me think about something nasty. All 2.6.24 and 2.6.25
> >kernels had a problem with FRTO which caused some TCP connections to
> >be stuck after a few retransmits. This has been fixed in recent 2.6.25.X
> >(don't precisely remember which one, but are OK and .4 is
> >not). And it seems like some distro's 2.6.24 are not fixed. I don't
> >know if the problem pre-dates 2.6.24, but at least 2.6.22 was OK.
> >
> >So if you're on 2.6.2[45], please upgrade to (or even .12 in
> >a few days). Otherwise, maybe tcpdump will be best in order to catch
> >the real problem.
> Or simply try to disable FRTO with "sysctl net.ipv4.tcp_frto=0". It is
> interesting to know if this *workaround* helps.

Yes indeed. However, I already encountered the problem on my laptop twice while I already had frto=0. So either the other end also had the same issue (I don't know), or I was hitting another problem such as the one Ingo is currently facing with distcc since we still don't know whether its cause came after 2.6.26 or whether a recent patch triggers that old bug more often. Right now with a more recent one ( I have not encountered the issue yet (but it can take weeks or depend on the environment).

Anyway, I'd be interested in knowing if tcp_frto=0 solves it.

> BTW: is already available:

Oh cool, I had not spotted it.

Willy Received on 2008/07/24 22:08

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