network regression using 2.6.8.x behind Cisco 1712

network regression using 2.6.8.x behind Cisco 1712

[Ondřej Surý]

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Hello,

I encountered regression in 2.6.8.1 when behind Cisco 1712 router.
There is huge network slowdown, my connections rate drops to ~10K/s on
2.6.8.1, local network is fine.  When using 2.6.7 connection rate is
~400K/s (depending on what I am downloading).

Network configuration is same on 2.6.8.1 and 2.6.7.  My .config can be
found at http://www.sury.org/kernel/config-2.6.8.1

Kernel is vanilla with MPPE+MPPC patch applied, but same behaviour has
distribution debian kernel.  Also I have tried to disable QoS and IPv6
in 2.6.8.1, but without any result.

It could be some bug in IOS, but it is triggered by some change between
2.6.7 and 2.6.8.  Any hints what should I try or where to look?
I could try some -pre and -rc kernel to locate where this was
introduced, but at least try to hint me which version should be
considered, I am not so willing to compile all -preX and -rcX, but could
do that if neccessary to hunt this regression.

Please Cc: me, I am not on list.

O.
-- 
Ondřej Surý <ondrej@sury.org>

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Re: network regression using 2.6.8.x behind Cisco 1712

[Alan Cox]

On Mer, 2004-08-18 at 09:20, Ondřej Surý wrote:
> It could be some bug in IOS, but it is triggered by some change between
> 2.6.7 and 2.6.8.  Any hints what should I try or where to look?
> I could try some -pre and -rc kernel to locate where this was
> introduced, but at least try to hint me which version should be
> considered, I am not so willing to compile all -preX and -rcX, but could
> do that if neccessary to hunt this regression.

echo "0" >/proc/sys/net/ipv4/tcp_window_scaling see if that helps. If so
then suspect somehting like the cisco or upstream router.

Re[2]: network regression using 2.6.8.x behind Cisco 1712

[Maciej Soltysiak]

echo "0" >>/proc/sys/net/ipv4/tcp_window_scaling see if that helps. If so
AC> then suspect somehting like the cisco or upstream router.
It propably is a tcp ws issue. I have the same thing.
Dave Miller & netdev friends will tell you to fix cisco.
Anyway, I belive I have isolated the changeset applied during the
developement of 2.6.8 that causes this. I might look for it (I do not
have it handy right now), so you might try to undo it before you
resolve your issue totally.
Anyway it is very cool that you say that it might be cisco. I
suspected my checkpoint fw-1 for the cause of it, but now I realize
it might be my cisco router! I will investigate that, thanks.

--
Regars,
Maciej

Re: network regression using 2.6.8.x behind Cisco 1712

[Ondřej Surý]

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On Wed, 2004-08-18 at 18:25 +0100, Alan Cox wrote:
> On Mer, 2004-08-18 at 09:20, Ondřej Surý wrote:
> > It could be some bug in IOS, but it is triggered by some change between
> > 2.6.7 and 2.6.8.  Any hints what should I try or where to look?
> > I could try some -pre and -rc kernel to locate where this was
> > introduced, but at least try to hint me which version should be
> > considered, I am not so willing to compile all -preX and -rcX, but could
> > do that if neccessary to hunt this regression.
> 
> echo "0" >/proc/sys/net/ipv4/tcp_window_scaling see if that helps.

Yep, that helped.  Thanks a lot.

> If so then suspect something like the cisco or upstream router.

I will report this to my local Cisco support partner.

O.
-- 
Ondřej Surý <ondrej@sury.org>

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Re: network regression using 2.6.8.x behind Cisco 1712

[Bastiaan Spandaw]

On Thu, 2004-08-19 at 09:16, Ondřej Surý wrote: 
> On Wed, 2004-08-18 at 18:25 +0100, Alan Cox wrote:
> > On Mer, 2004-08-18 at 09:20, Ondřej Surý wrote:
> > > It could be some bug in IOS, but it is triggered by some change between
> > > 2.6.7 and 2.6.8.  Any hints what should I try or where to look?
> > > I could try some -pre and -rc kernel to locate where this was
> > > introduced, but at least try to hint me which version should be
> > > considered, I am not so willing to compile all -preX and -rcX, but could
> > > do that if neccessary to hunt this regression.
> > 
> > echo "0" >/proc/sys/net/ipv4/tcp_window_scaling see if that helps.
> 
> Yep, that helped.  Thanks a lot.
> 
> > If so then suspect something like the cisco or upstream router.
> 
> I will report this to my local Cisco support partner.

I too have this problem. (cisco 837 running
c837-k9o3sy6-mz.123-4.XG1.bin)

Adjusting the window scaling helped me too.

If you get an answer from cisco I'd greatly appreciate hearing about it.

Regards,

Bastiaan