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