RE: [cobalt-users] Strange HTTP Problem

["Gordon." <root@xxxxxxxxxxxxxxxxxxxxxxxx>]

On Tue, 28 May 2002, Simon Pierce wrote:

> you wrote...
> 
> This problem is almost identical to one we were asked about.
> It turned out the win98 and winME machines on a network had invalid MTU
> values.
> Did a search on Google for MTU Values and found a great note on how to cure
> it.
> As soon as we set the MaxMTU values to 1454 on each of the networked
> machines
> (they were accessing the net via dsl through a winXP machine) everything was
> fine.
> We visited each of our clients with similar networks, updated the mtu values
> and there was always a noticible improvement in access times.
> (And yes, ping, traceroute all showed no error prior to the mtu update)
> 
> -------------
> 
> So can this effect you only if you're using one particular ISP, but not
> effect you if you're using any other?

Yes, ISP's using PPPeE for example, have a slightly smaller allowed 
MTU becaue of the few extra bytes needed for encapsulation, and ISP's that
are filtering out the wrong ICMP message types will break MTU discovery
making it impossible for their clients to learn that that need to
renegotiate the packet/window size.

It's also possible to break it on the other end by putting a server behind
a firewall that does the same thing btw.

gsh