FC2 and kernel 2.6.7 upgrade problems.

[Andreas M. Kirchwitz]

Emil Valsson <emil at netsamskipti.is> wrote:

 > After I upgraded from 2.6.6 to 2.6.7 with yum the network has been acting
 > rather weird. Speeds are very slow when uploading files to the server and
 > gradually stops after 10 seconds. Downloading from the server works fine
 > though. This problem was not present in 2.6.6 so I would appreciate someone
 > could comment on this issue. Last night when receiving Logwatch email from
 > the server this is what it reported. Any ideas or suggestions greatly
 > appreciated.

Kernel 2.6.7 uses different network parameters than kernel 2.6.6.
For example, window scaling is turned on in 2.6.7 (but it was off
on 2.6.6). This causes problems with most firewalls. Execute the
following command with root privileges, that should "fix" the
networking problem for all new connections:

	sysctl -w net.ipv4.tcp_default_win_scale=0

Put this in your /etc/rc.d/rc.local file or put
"net.ipv4.tcp_default_win_scale = 0" directly into
/etc/sysctl.conf (which is the better way, but be careful
that it doesn't get overwritten by package updates).

Actually the Linux kernel is fine, the problem is in the firewalls
and/or their configuration. If anybody knows how to configure a
Cisco (with and without inspection) to work with window scaling,
I'd be happy about some hints.

	Greetings, Andreas