very slow external network access

[Scott Smedley]

Accessing the non-local network with Ubuntu 7.04 installed on my laptop is approximately 50x slower than it should be.

I have an almost identical network configuration to my desktop (RH9) with which to compare. Also, my laptop is able to run Fedora 4 (dual boot) which achieves much better network throughput.

I have disabled IPv6 & iptables (as a precaution), but observed no improvement.

The following command downloads ~1.8Mb from an external site & takes < 1 second on my (RH9) desktop:

time wget http://mirror.aarnet.edu.au/pub/CPAN/modules/by-category/02_Language_Extensions/Module/Language-Haskell-0.01.tar.gz

The same command on Ubuntu 7.04 takes over 1 minute!

scp'ing a 16Mb file from my desktop (RH9) to my laptop (Ubuntu) takes < 1 second, suggesting local network performance is very good.

Here is ifconfig & route output on Ubuntu which is effectively the same as on Fedora:

lapss# ifconfig
eth0 Link encap:Ethernet HWaddr 00:12:3F:E1:4C:8C
          inet addr:192.231.167.147 Bcast:192.231.167.255 Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          RX packets:52977 errors:0 dropped:0 overruns:0 frame:0
          TX packets:18182 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:14151823 (13.4 MiB) TX bytes:2253348 (2.1 MiB)
          Interrupt:19

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:14 errors:0 dropped:0 overruns:0 frame:0
          TX packets:14 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:1140 (1.1 KiB) TX bytes:1140 (1.1 KiB)

lapss# route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.231.167.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
169.254.0.0 0.0.0.0 255.255.0.0 U 1000 0 0 eth0
0.0.0.0 192.231.167.250 0.0.0.0 UG 0 0 0 eth0
lapss# cat /etc/resolv.conf
search aao.gov.au
nameserver 192.231.167.202
nameserver 192.231.167.2

My laptop is a Dell Inspiron 9300.

My colleague just installed Ubuntu on his Dell Latitude D610 laptop & has similar (poor) performance when accessing a non-local network.

I also tried Ubuntu 6.06 Live CD on my laptop. Non-local network throughput was fine! (~ 4 seconds for aforementioned 'wget' command to complete.)

Please let me know what else I can do to help diagnose this problem.

Scott.

[Scott Smedley (ss-aao)]

Here's the output from 'dmesg' in case it's of interest.

Scott.

[Scott Smedley (ss-aao)]

One more thing I forgot to mention.

I tried using the eth1 (wireless) interface. Non-local network throughput was just as bad. Suggesting it's not a bug in the b44 network driver & probably some sort of system problem?

Scott.

[Scott Smedley (ss-aao)]

It's only taken 6 months, but it turns out the problem is with a recent modification to the TCP networking subsystem of the Linux kernel. Appeared in 2.6.20 I think.

Some old routers (ie. our firewall) can't handle the increased TCP window sizes.

Solution: edit /etc/sysctl.conf & add the line:
net.ipv4.tcp_window_scaling = 0

Then: sysctl -p /etc/sysctl.conf

In the aim of constructive criticism: it seems a bit rude to have submitted a bug report to an official Ubuntu website & not have had any response whatsoever after 6 months.

[Adam Niedling (krychek)]

Can this bug be closed now? If you want to keep it open you should change the bug summary, now that you know what's causing the problem. You should also find the package that this bug is related to. Possible linux-source-2.6.24 .

[Leann Ogasawara (leannogasawara)]

The Ubuntu Kernel Team is planning to move to the 2.6.27 kernel for the upcoming Intrepid Ibex 8.10 release. As a result, the kernel team would appreciate it if you could please test this newer 2.6.27 Ubuntu kernel. There are one of two ways you should be able to test:

1) If you are comfortable installing packages on your own, the linux-image-2.6.27-* package is currently available for you to install and test.

--or--

2) The upcoming Alpha5 for Intrepid Ibex 8.10 will contain this newer 2.6.27 Ubuntu kernel. Alpha5 is set to be released Thursday Sept 4. Please watch http://www.ubuntu.com/testing for Alpha5 to be announced. You should then be able to test via a LiveCD.

Please let us know immediately if this newer 2.6.27 kernel resolves the bug reported here or if the issue remains. More importantly, please open a new bug report for each new bug/regression introduced by the 2.6.27 kernel and tag the bug report with 'linux-2.6.27'. Also, please specifically note if the issue does or does not appear in the 2.6.26 kernel. Thanks again, we really appreicate your help and feedback.

[Leann Ogasawara (leannogasawara)]

*This is an automated response*

This bug report is being closed because we received no response to the previous request for information. Please reopen this if it is still an issue in the actively developed pre-release of Jaunty Jackalope 9.04 - http://cdimage.ubuntu.com/releases/jaunty . To reopen the bug report simply change the Status of the "linux" task back to "New".