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marsques 02-08-2006 06:00 PM

strange behaviour
 
currently on an ADSL connection using slackware-current, but with some websites the ones i've noted www.ft.com and www.londonstockexchange.com after switching to a different kernel these websites get really sluggish and takes ages to load its pages, however on rebooting the router these websites load as normal until i switch kernels...

any ideas why?

jschiwal 02-08-2006 07:11 PM

I read somewhere that there is a kernel feature that will dynamically change a window the IP protocol uses. This feature should improve performance and is based on an RFC standard. The problem according to a couple posts that I read, is that some Windows based gateways don't handle this properly and throttle way down.

I'm sorry I don't remember which feature this is. Perhaps googling, you would find out. I do remember that the feature can be disabled by echoing a 0 to the appropriate /proc/net/<whatever> special file. So if this is the problem, you can simply add an echo command in a boot script to fix it rather than having to recompile the kernel.

Even if this isn't the answer, you might also zcat the /proc/config.gz file ( e.g. zcat /proc/config.gz > ~/config1) for each of the kernels, and examine both kernel configurations for features in the networking area. This may point to a solution.

Good Luck looking for a more detailed answer.

marsques 02-10-2006 12:05 PM

thanks your answer.

is there any way of knowning what kind of gateway that the website uses?

jschiwal 02-10-2006 03:17 PM

Maybe if you use nmap. However, there may be more than one gateway until your source is reached. Perhaps using routemap can provide more clues. I still don't remember which configuration option it was. The easiest solution would be to disable it when booting using an echo 0 > /proc/<target> type command.

marsques 02-12-2006 05:32 PM

how would you find out what gateway the server uses?

thank you...

jschiwal 02-13-2006 04:01 AM

It will probably be the machine before the web server.

marsques 02-14-2006 05:19 PM

re-compiled the 2.6.15.3 kernel with all the IP options configured as modules... but no luck... the two sites are still sluggish on linux...

find it strange though, how come on rebooting the router things stay fine until i start linux with a different kernel...

jschiwal 02-14-2006 10:04 PM

I don't think it is a matter of whether your IP options are configured as modules or not. I believe it depends on whether a certain feature is enabled or disabled. I wish I could remember what this was, because I can't find it any more on Google. It may even be a feature that has been dropped, and I'm on a totally wrong track. ---- I did some more Googling. Something about TCP_WINDOW_SCALING sounded familiar. http://forums.suselinuxsupport.de/lo...hp/t11895.html
Quote:

# Turn off the tcp_window_scaling if you have networking # with systems behind broken routers, otherwise keep it on (default) net.ipv4.tcp_window_scaling = 1
----

Ok, this feature isn't present in 2.6 kernels. I don't know which kernel you are using.
If both kernels are 2.6, then I've been climbing up the wrong tree.

marsques 02-15-2006 01:02 PM

the issue is with the 2.6 kernels... tried 2.6.12.1 2.6.14.4 and 2.6.15.3 in all three the problem exists with them websites...

marsques 02-15-2006 01:39 PM

did run sysctl -a before and after the reboot of the router to check for differences and the only difference was in ip_conntract_count after a few other checks it is unreliable as it seems to vary on network use.

is there a command that i can run to check the changes in the network related modules, configurations etc before and after rebooting the router as this way i might be able to narrow it down to something and work on it...

jschiwal 02-15-2006 04:54 PM

I'm not at my computer right now. There is a perl script called Sitar ( I hope I spelt that correctly ) that can gather tons of information on your computer and make a report. I believe that you can fine tune the output to deal only with IP related information.

Also, there are the sysctl -a and sysctl -p commands. ( I'm not at my computer and could be remembering 2.4 stuff ) You can use them to report rather than change options. You can also dump out the running ip_tables setting. The chkconfig program can also report back a lot.

If it's only the /proc/net/... values you are looking for, you could write a script that cats the readable values to a file, then use "diff" after you run it again to spot any differences.

Also, use zcat on each kernel to produce a config file for that kernel, e.g.:
zcat /proc/config.gz >~/config-$(uname -r).


This would be potentially more fruitful to compare values between an effected kernel and a non effected one.

marsques 02-15-2006 06:05 PM

Thanks for your info i'll give them a try...


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