"Do not fragment" flag stopping Windows Update working

For a while, I have been unable to use the Windows Update website properly.
I can browse to
http://update.microsoft.com/windowsu....aspx?ln=en-us without
any problems, where I am presented with the Express and Custom buttons.
However after I click "Express" I get the "Checking for the latest updates
for your computer..." progress bar, and then after a minute or so an error
page is presented stating "The website has encountered a problem and cannot
display the page you are trying to view."

At the same time, I noticed numerous "ICMP unreachable - need to frag"
errors coming back from my router.

I re-attempted this while running a packet capture on my Windows machine,
and it appears that my system is attempting to send TLS packets to the
windows update web servers that are 1514 bytes in size and have the
do-not-fragment flag set. As the MTU on my Internet connection is 1458,
this would seem to be the reason why the windows update site is failing for
me.

Why is my browser attempting to send these large packets with the DF flag
set?

Windows XP Pro SP2, IE6.

Regards,

Jason

Jason Mann wrote:
> For a while, I have been unable to use the Windows Update website properly.
> I can browse to
> http://update.microsoft.com/windowsu....aspx?ln=en-us without
> any problems, where I am presented with the Express and Custom buttons.
> However after I click "Express" I get the "Checking for the latest updates
> for your computer..." progress bar, and then after a minute or so an error
> page is presented stating "The website has encountered a problem and cannot
> display the page you are trying to view."
>
> At the same time, I noticed numerous "ICMP unreachable - need to frag"
> errors coming back from my router.
>
> I re-attempted this while running a packet capture on my Windows machine,
> and it appears that my system is attempting to send TLS packets to the
> windows update web servers that are 1514 bytes in size and have the
> do-not-fragment flag set. As the MTU on my Internet connection is 1458,
> this would seem to be the reason why the windows update site is failing for
> me.
>
> Why is my browser attempting to send these large packets with the DF flag
> set?
>
> Windows XP Pro SP2, IE6.
>
> Regards,
>
> Jason
>
>
>

Did you try using Custom instead of Express?

Alias