Extremely slow web page loading to only 1 site ?

[Ed Greshko]

Bruno Wolff III wrote:
> On Tue, Feb 09, 2010 at 08:21:33 +0800,
>   Ed Greshko <Ed.Greshko at greshko.com> wrote:
>   
>> In the back of my mind, from a few years ago, I remember there an issue
>> with the linux TCP/IP stack and some "mis-configured" routers.  I need
>> to get some coffee and hopefully my brain will get in gear....
>>     
>
> I believe that was ECN. (A way to signal congestion without throwing away
> packects.)
>
> There have also been problems with MTU discovery because people block ICMP
> packets indiscrimiantly.
>
>   
That is starting to stir the synapse....

The problem is related to what is in the "syn, ack" packet coming from
12.17.249.39.  In the TCP Options it is sending "Window scale: 0
(multiply by 1)".  I think this is causing problems since later packets
have the TCP data segment being only 92 bytes from 12.17.249.39.

While the same info is in the "syn, ack" the RHELv4 system seems to deal
with it OK and the TCP data segments from 12.17.249.39 are 1460 bytes.

The "problem" can be fixed by....

echo 0 > /proc/sys/net/ipv4/tcp_window_scaling

Now, while this fixes the problem for this site it may cause performance
issues with other sites.  I don't know at this point and my head hurts. 
:-)  It is hurting since my RHELv4 system has tcp_window_scaling set to
1 and it seems to deal with it.

Note: Make sure you issue the "echo" above after some quite time.  The
connection must first be rst (reset) before the sides will renegotiate
the TCP/IP settings.  (That too caused me some grief.)

I'll bugzilla it....







-- 
A handful of friends is worth more than a wagon of gold.

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