netdev - Re: [PATCH] tcp FRTO: in-order-only "TCP proxy" fragility workaround

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Message-ID: <20080916112411.062fa615@tux>
Date:	Tue, 16 Sep 2008 11:24:11 -0300
From:	Dâniel Fraga <fragabr@...il.com>
To:	"Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi>
Cc:	David Miller <davem@...emloft.net>, thomas.jarosch@...ra2net.com,
	billfink@...dspring.com, Netdev <netdev@...r.kernel.org>,
	Patrick Hardy <kaber@...sh.net>,
	netfilter-devel@...r.kernel.org, kadlec@...ckhole.kfki.hu
Subject: Re: [PATCH] tcp FRTO: in-order-only "TCP proxy" fragility
 workaround

On Tue, 16 Sep 2008 15:10:33 +0300 (EEST)
"Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi> wrote:

> Only thing I know to ask is, do you have any idea if your ntpd is 
> hard-stepping the time instead of adjusting the clock's rate a bit (the 
> latter should keep the clock monotonious besides potential bugs)?

	I assume it's adjusting the clock's rate a bit. Anyway, it's a
pretty simple config:

fraga@...eporto ~$ cat /etc/ntp.conf 
server ntp.usp.br
server ntp.nasa.gov
driftfile /etc/ntp.drift

	And ntpd is running without any special parameters.

	The log messages are as simple as:

Sep 15 03:56:04 teleporto ntpd[2301]: frequency initialized 5.891 PPM from /etc/ntp.drift
Sep 15 03:59:25 teleporto ntpd[2304]: frequency initialized 5.891 PPM from /etc/ntp.drift
Sep 15 04:03:49 teleporto ntpd[2304]: synchronized to 143.107.255.15, stratum 2
Sep 15 04:03:49 teleporto ntpd[2304]: kernel time sync status change 0001
Sep 15 04:10:16 teleporto ntpd[2304]: synchronized to 198.123.30.132, stratum 1
Sep 15 04:11:58 teleporto ntpd[2301]: frequency initialized 5.891 PPM from /etc/ntp.drift
Sep 15 04:16:18 teleporto ntpd[2301]: synchronized to 198.123.30.132, stratum 1
Sep 15 04:16:18 teleporto ntpd[2301]: kernel time sync status change 0001
Sep 15 12:08:53 teleporto ntpd[2301]: kernel time sync status change 4001
Sep 15 12:34:31 teleporto ntpd[2301]: kernel time sync status change 0001
Sep 15 14:34:06 teleporto ntpd[2301]: kernel time sync status change 4001
Sep 15 14:51:12 teleporto ntpd[2301]: kernel time sync status change 0001 

	If I understood correctly what do you mean, ntpd adjusts nicely the time to not 
cause huge differences in the time.

	And we're reaching the conclusion that the timer code from 2.6.25 and above 
have something wrong, since 2.6.24 and below is ok, which causes those stalls.

	But I'll wait some more time to confirm this, although I'm almost sure it's a timer
related bug which has this colateral effect of stalling connections.

	And just a question: do you use ntpd on your own desktop?
	
	Thank you!

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