IPv6 workaround - network still slow

[whatthe?]

I'm a newbie to Fedora but this problem is driving
me crazy! I've installed FC2 (2.6.5-1.358). My browser
will timeout when accessing certain websites!

I've read the various posting relating to IPv6 workarounds
and have added the following lines to /etc/modprobe.conf;

# Turn off IPv6
alias net-pf-10 off
alias ipv6 off

Also have added this to /etc/syscong/network;

NETWORKING_IPV6=no

Still no luck! This problem seems to be a greater issue than
just the DNS names resolution because if I run a
"GET ....." or "time GET ....." from the command line
I can actually watch the requested page download at an
incredibly sloooow rate. Only happens with certain sites.
I know the problem is with my machine because a
windoze PC doesn't exhibit the same slow behavour.

Any ideas? As mentioned I've tried the suggested IPv6
workarounds.

[whatthe?]

I may have found a solution to my problem. Not sure
if this is a universal fix however for others with the same
problem. I noticed that my network was fine using the
same ADSL modem but different (read: someone elses) SP.

So, I set the MTU=1400 (was 1492) on my ADSL modem.
I also set MTU=1400 (was 1500) in the /etc/sysconfig/network-scripts/ifcfg-eth0.

Network seems okay now with my orig SP.
Can get to websites now that previously I could not.

[kama]

Try this as root:

/sbin/sysctl -w net.ipv4.tcp_moderate_rcvbuf=0
/sbin/sysctl -w net.ipv4.tcp_default_win_scale=0

[pigpen]

disabling ipv6 didn't work for me either. mozilla still lags when resolving urls.
i'll try karma's way tomorrow and report back.

[pigpen]

Still no luck. Waiting for FC3...

[taylor65]

MTU shouldn't be an issue - all routers should just fragment packets if they're bigger than the MTU on their interfaces. The only time it would cause an issue is if a router is configured to not fragment packets, or if the packet has the don't fragment bit set.