Extremely slow web page loading to only 1 site ?

[Ed Greshko]

Linuxguy123 wrote:
> On Tue, 2010-02-09 at 11:25 +0800, Ed Greshko wrote:
>
>   
>> 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.)
>>     
>
> Questions:
>
> a) does an "echo 1 /proc/sys/net/ipv4/tcp_window_scaling" put the system
> back to what it is now ?
>   
Yes.  You can "cat /proc/sys/net/ipv4/tcp_window_scaling" to see it is
set to "1" by default.
> $cat /proc/sys/net/ipv4/tcp_window_scaling
> 1
>
> b) does the command have to be issued after every reboot / login ?
>   
It is defaulted to "1" at boot.  So, if you want to have it set to "0"
you'll either have to issue the echo command or place the following in
/etc/sysctl.conf

net.ipv4.tcp_window_scaling = 0

(you need the spaces).
> c) please tell us more on resetting the network connection.
>
>   
Nothing needs to be done to reset the connection.  It will do so after a
time of inactivity between your system and the affected web site.  (The
resets are per connection).  So, if you just visited the site with
scaling set to 1 you should wait a couple of minutes after setting it to
0 before trying again.

Ed

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