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Date: Mon, 05 Mar 2007 19:24:56 +0000
From: Tom Judge <tom@tomjudge.com>
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To: aditya kiran <adityaa.kiran@gmail.com>
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Cc: freebsd-net@freebsd.org
Subject: Re: PMTU Discovery support
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aditya kiran wrote:
> Hi,
> I'm just trying to understand the PMTU Discovery support
> in FreeBSD. Is upward PMTU (increase in PMTU) is also
> discovered when PMTU Discovery is enabled?
> Thanks,
> Aditya

As I understand it, it is not possible to detect upward changes in the 
path MTU as there is no mechanism for a router to generate an error when 
a packet is small enough to be accommodated by the MTU of the link to 
the next hop.  I may be wrong though.

Tom