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ports >1024 blocked, internet slow [SOLVED]
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sjeur
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PostPosted: Thu Jan 11, 2007 12:15 am    Post subject: ports >1024 blocked, internet slow [SOLVED] Reply with quote

On my network, all connections to ports >1024 are blocked. This seems to result in very slow connections.
I can't unblock those connections, so that's no option.
Browsing websites, fetching mail, etc. is extremely slow (max 7KB/s).
I have discovered that ACTIVE FTP transfers are fast (maximum speed of my ISP), although passive FTP transfers are slow.
All other protocols seem to be slow too.
Does anyone have an idea why this is, or how to get around this?

Also, this only seems to apply on Gentoo. I have tried other distros, OpenSUSE and Ubuntu for instance, they don't have this problem.
In Windows XP, there aren't any problems either.


Last edited by sjeur on Fri Jan 12, 2007 3:49 am; edited 1 time in total
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mose
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PostPosted: Thu Jan 11, 2007 12:17 am    Post subject: Reply with quote

Web browsing uses port 80, so I think that isn't related to your port blocking.
How did you realized that ports >1024 are blocked?
By the way, are you behind a router?
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sjeur
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PostPosted: Thu Jan 11, 2007 12:55 am    Post subject: Reply with quote

I am indeed behind a router. It all worked well until the network admin blocked the ports >1024, so I do think it's related.
I asked him to remove the block, it then worked good. But the ports are to be blocked here.
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mose
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PostPosted: Thu Jan 11, 2007 11:08 am    Post subject: Reply with quote

So the problem isn't with Gentoo... but with the router! Sorry, I can't help you with that :?
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sjeur
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PostPosted: Thu Jan 11, 2007 1:03 pm    Post subject: Reply with quote

I know, but why does it work on all operating systems, except for Gentoo?
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mose
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PostPosted: Thu Jan 11, 2007 1:18 pm    Post subject: Reply with quote

I don't know exactly why...
Try to post the output of
Code:

netstat

maybe we'll get some more informations
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madisonicus
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PostPosted: Thu Jan 11, 2007 3:15 pm    Post subject: Reply with quote

To be more precise, http connections are initiated on port 80 but after handshaking they move to ports above 1024. It's very unlikely that any reasonable network admin has actually blocked these ports. There are far better ways to prevent filesharing which is the usual reason for netadmins cracking down on ports.

There are a couple other possibilities that come to mind. The first is that since Gentoo is one of the few distributions which actually uses window scaling by default, that somewhere along the line there's a broken router that improperly handles it. Try doing this:
Code:
# echo 0 /proc/sys/net/ipv4/tcp_window_scaling
If that clears up your problem, you can set it as a default by adding net.ipv4.tcp_window_scaling = 0 to your /etc/sysctl.conf.

Also, you might need to go through the network parts of your kernel to make sure things are set up properly.

HTH,
m
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sjeur
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PostPosted: Fri Jan 12, 2007 3:52 am    Post subject: Reply with quote

Quote:
echo 0 /proc/sys/net/ipv4/tcp_window_scaling


Thanks, that did the trick!
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price
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PostPosted: Wed Jan 17, 2007 10:08 pm    Post subject: Reply with quote

Thanks --- this helped me solve my problem also.

Noticed a small error in the line above that tests the fix, though. I believe it should be:

Code:

echo 0 > /proc/sys/net/ipv4/tcp_window_scaling


(i.e., missing redirection.)
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