Re: IP fragmentation problem in the 2.0 kernels ?

Olaf Titz (
Tue, 09 Sep 1997 19:51:14 +0200

> - The kernel is getting some big tcp packets from one of these web sites,
> and he must fragment it because of the MTU option
> - The kernel thus sends an ICMP packet to the web server, with the
> information about the desired MTU. Most servers correctly change their
> MTU, but some like excite dont, because they dont even get the ICMP in the
> first place (it gets blocked by their router) -

Their setup is broken. When they block ICMP, they can't reasonably do
Path MTU probing which depends on these ICMPs. More strictly, they
should set their own MTU to the minimum value.

> BTW is it an rfc compliant
> behaviour when u dont lower your MTU on an ICMP fragmentation notice ?

AFAIK, no.