One of the most frustrating things about Ubuntu/Kubuntu 9.10 (and 9.04) is the random but frequent 20 sec DNS lookup delay that happens when IPV6 is enabled. Apparently, the resolver first attempts an IPV6 lookup, even if no interfaces are defined. It will sit and time out, at random, for 20 seconds before attempting the IPV4 lookup.

There are a number of proposed fixes. One is to turn of IPV6 in firefox. This seems to work for a while, but then fails.

Here's a link to article about turning off IPV6 in Ubuntu:

http://www.ubuntugeek.com/how-to-disable-ipv6-in-ubuntu.html

In grub, to turn off IPV6 edit /etc/default/grub and change

GRUB_CMDLINE_LINUX_DEFAULT=quiet splash

to

GRUB_CMDLINE_LINUX_DEFAULT=ipv6.disable=1 quiet splash

 run

update-grub

and reboot.

It's not clear to me yet whether this actually works around the problem or not. Initially on reboot, opening 20 some tabs in firefox seemed much quicker than before but I did get a long hang once I brought up thunderbird. So it may not be a fix after all. Only time will tell.

To turn off IPV6 in firefox (which doesn't seem to work around the issue but is probably good to know):

Enter about:config in the URL bar then and search for:

network.dns.disableIPv6

and set it to true.

Here's a link to a very long bug report discussion on the subject:

https://bugs.launchpad.net/ubuntu/+source/eglibc/+bug/417757?comments=all

2010-02-03 Update:

Even with all these changes, I was continuing to get DNS timeouts until I came upon this bug in launchpad (which of course I found /after/ commenting on the bug above, figures:

https://bugs.launchpad.net/ubuntu/+source/nss-mdns/+bug/94940

Editing /etc/nsswitch.conf and changing

   hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4

to

   hosts: files dns

 seems to /finally/ get the DNS lookup performance I would expect.

Update 2010-02-18 - spoke too soon:

While initial network connection speeds seem to improve from the steps above, it quickly became apparent that there's still a problem with networking. This seems to happen primarily when I do multiple simultaneous network connections.

Here's a thread on the subject, which may or may not be useful:

http://ubuntuforums.org/showthread.php?t=1395866&highlight=slow+internet

Update 2010-02-21 - ok, maybe it's "fixed" now

Based on a forum post I read somewhere about the latest kernels implementing some standard too stringently, I decided to try to upgrade the firmware for my DLink DI-707 firewall gadget. It had been a firmware version 2.51. I upgraded it to version 2.57. I immediately noticed an improvement in network performance. My initial tests are not able to reproduce the problem I was seeing, but it's too early to tell for sure.

Submitted this blog to technorati.

F82AAZKE9KWM

I've upgraded the formVista install to the latest and greatest version. This version upgrades jQuery to 1.3.2 and also includes the "Share" links on blog articles making it easier to cross post things to other sites. This version also fixes yet another long standing login bug. So if you have any problems logging in please let me know.

There's alot of talk about 2012 and the end of the world. This is all clearly false. The end of the world will be on Mon Jan 18, 2038 at 22:14:07. Mark your calendars.

#include <stdio.h>
#include <time.h>
#include <limits.h>

int main(void)
        {
        time_t end_of_time;

        end_of_time = INT_MAX;

        printf("End of the world will be: %s\n",
                asctime(localtime(&end_of_time)), end_of_time );

        return(0);

        }

End of the world will be: Mon Jan 18 22:14:07 2038