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CentOS Linux 5.7 TCP Window Scaling Question

I did a clean install and use Webmin/Virtualmin.

The server seemed a little slow and I eventually figured out it was a TCP window scaling issue. At the command line I get 0 if I do "sysctl net.ipv4.tcp_window_scaling".

So I edited /etc/sysctl.conf and added this line at the end:
net.ipv4.tcp_window_scaling=1

If I do "/sbin/sysctl -p" it works. But...When I reboot, the setting is still 0 if I do "sysctl net.ipv4.tcp_window_scaling"!

How can I fix this setting so that it is permanent?
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PaliTree
Asked:
PaliTree
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1 Solution
 
pritamduttCommented:
Is the value of net.ipv4.tcp_window_scaling also changed in /etc/sysctl.conf after reboot?
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pritamduttCommented:
Because  /etc/sysctl.conf is used to permanently store the desired kernel tuning parameters for the system,  to be read in and set at boot time.

If you find the value has not changed and for some reason the changes are not reflecting, you can make a call to /sbin/sysctl in /etc/rc.local file.

Hope this helps!

Regards,
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PaliTreeAuthor Commented:
Thanks - yes I could fix the vale myself at boot. But it seems to me that there must be something wrong if the vlues of /etc/sysctl.conf are not being read-in at boot? Otherwise what is the conf file for?
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PaliTreeAuthor Commented:
I have found the problem (and it's good I didn't go the /etc/rc.local route).

I am using APF firewall. This has a setting:

# These are system control (sysctl) option changes to disable TCP features
# that can be abused in addition to tweaking other TCP features for increased
# performance and reliability.
SYSCTL_TCP="1"

And if you set this, APF does this:
echo 0 > /proc/sys/net/ipv4/tcp_window_scaling
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pritamduttCommented:
Great.. so it was a application issue..
Thanks for sharing!
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PaliTreeAuthor Commented:
In the latest version of APF this has now been fixed
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PaliTreeAuthor Commented:
Completely solved
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