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Re: Very slow network - Ubuntu

A. Ben Hmeda wrote:

I have searched ubuntu forums to no avail. My network connection has
slowed down considerably since I installed Ubuntu Dapper (6.06.1 LTS) I
have disabled ipv6 in /etc/aliases and Firefox, still slow by about 50%.

My machine AMDSMP is dual boot w2k/ubuntu 6.06.1 LTS (2xAthlon 2000+ 512
RAM), network is at full speed with win2k and Fedora Core 5 (now
deleted) on this machine.

I have another Ubuntu 6.06.1 LTS machine SERVER (2xP3-500 256RAM) and a
Win2k KIDPC (P3-866 512RAM) on the same home network that do not have
this problem with the network slowdowns.

My benchmark is http://www.testmy.net/ website. Every machine on the
network has been tested separately, while other machines were turned off.

Didn't matter whether the connection was static or dhcp.
I have also noticed slowdowns (high latency) while playing on-line games
like bzflag
My /etc/network/interfaces :
auto lo
iface lo inet loopback
auto eth0
iface eth0 inet static
address 192.168.1.2
netmask 255.255.255.0
gateway 192.168.1.1

ifconfig output:

eth0      Link encap:Ethernet  HWaddr 00:04:5A:9A:8C:6E
           inet addr:192.168.1.2  Bcast:192.168.1.255  Mask:255.255.255.0
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:46508 errors:0 dropped:0 overruns:0 frame:0
           TX packets:31020 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:43829777 (41.7 MiB)  TX bytes:4368831 (4.1 MiB)

lo        Link encap:Local Loopback
           inet addr:127.0.0.1  Mask:255.0.0.0
           UP LOOPBACK RUNNING  MTU:16436  Metric:1
           RX packets:9 errors:0 dropped:0 overruns:0 frame:0
           TX packets:9 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:0
           RX bytes:472 (472.0 b)  TX bytes:472 (472.0 b)

What went wrong?


Since You are omitting some crucial details, such as the details of your LAN
and your internet connection, for the purposes of this message I will assume that your local LAN speed vastly exceeds the speed of your internet connection and you are using at least 100Mb ethernet (i.e.the typical case). Please correct me if I'm wrong. 

First I would determine if you have local throughput reduction to the
machine in question. You could try testing the throughput between machines. Unless you are using gigabit, these tests should easily saturate your local LAN and leave no doubt about the integrity of the local LAN.
If it turns out to be an ethernet issue, then given the lack of RX errors on your system, I would suspect a problem on the TX side, either in the cable or the hub/switch/router on the other end. 100mb ethernet uses two twisted pairs of wires, and problem on only the TX pair would be typically caused by a bad connection or a miswired cable (e.g. incorrectly pairing the conductors in a hand-crimped cable). Another cause is damage to RJ-45 sockets caused by plugging RJ-11 or RJ-14 plugs into RJ-45 sockets. This can bend and permanently damage some of the conductors in RJ-45 sockets.
If you find that it's not a physical layer (ethernet) issue, then it's probably an IP stack or applications bug, which would make it an extremely rare and interesting problem. I'm not a developer, but I think the developers would be be very interested in such a problem. Incidently I think you can disregard the claim, from another list member, that this is not a Debian issue. Since Ubuntu is based on Debian, any problem there could very easily apply to Etch, the next stable Debian release.
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