Arch Linux

jw

Member

Registered: 2005-01-08

Posts: 88

Slow internet with SIS900 after moving to new network

After moving to a new house I am having internet problems on my main box. I have two computers, both of which are running archlinux:

1. My athlonxp 1700 MAIN BOX with a SIS900 onboard nic
2. An old celeron 500 LAPTOP, with an E100 onboard nic

The symptoms are similar to the "2.6.8.1 slows my internet to a crawl" problems described in the wiki.

http://wiki2.archlinux.org/index.php/Ke … 0a%20crawl!

The problems can be described as follows:

- DNS lookup is working fine
- My browser is slow when connecting to a site. After a while the page begins to load very slowly (less than 1k per second) but halts after several kilobytes
- Same thing for downloads. Download starts but halts after something like 30 k

In my house we use a shared ADSL connection, with a windows 2000 box configured as a router, and all others connected through a switch. On my LAPTOP everything is working fine. I had to do two things to get internet working properly:

1. Turn TCP Window Scaling off (echo "0" > /proc/sys/net/ipv4/tcp_window_scaling)
2. Set MTU (max transfer unit) to 1350 by adding "mtu 1350" to the eth0 line in rc.conf

However, on my main box this does not work. Since both computers are configured the same way, I am guessing the problem lies with the SIS900 driver. I did try the 2.6.11.3 as well as the old 2.4.26 kernel, but both show the same behaviour. Somehow it seems like the window scaling problem persists, even though window scaling has been turned off. By now I have spent hours trying fix this. Is there anyone that has an idea how this could be fixed?

thanks in advance
jw

jw

Member

Registered: 2005-01-08

Posts: 88

Re: Slow internet with SIS900 after moving to new network

Ok, after some more mucking about I have made some progress. By changing MTU to 100 I can get pages to load, albeit slowly. At least now I can post about this from my main box ;-).

I have noticed the following things:

- With MTU 100 pages load, but my adsl broadband is about as slow as an old modem. I get about 1Kbps on ftp downloads. After ~200K the transfer stalls.
- When using aMule i notice that my eth0 monitor (in superkaramba) indicates outward traffic of about 20 Kbps, eventhough aMule itself only indicates 5Kbps being transferred.
- When I ping my router by doing "ping 192.168.0.1" I have about 10% packet loss. This does not happen on my laptop.

* * *

So, I'm stuck with the following questions:

- Why does my internet grind to a halt when I use MTU>1000?
- Why do my downloads halt after ~100K?
- Where do I start looking for differences in my LAPTOP setup, which works fine, and my MAIN BOX, which does not?

jw

Member

Registered: 2005-01-08

Posts: 88

Re: Slow internet with SIS900 after moving to new network

[SOLVED] (google is your friend)

It turns out my router was not able to handle a 100baseTX connection, neither full-duplex nor half-duplex. I fixed the problem by doing a:

mii-tool --force=10baseT-FD

Hope this might help someone else later on..

* * *

I do have one remaining problem: For some strange reason I cannot use ifconfig to set my eth0 to 10baseT:

# ifconfig eth0 192.168.0.2 broadcast 192.168.0.255 netmask 255.255.255.0 media 10baseT up
# mii-tool -w eth0
02:03:05 eth0: negotiated 100baseTx-FD, link ok

Does anyone know another way of setting media to 10baseT at boot time?