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Date:      Mon, 19 Mar 2007 14:54:22 -0700
From:      Kevin Lahey <kml@patheticgeek.net>
To:        freebsd-net@freebsd.org
Subject:   Re: PMTU Discovery support
Message-ID:  <20070319145422.39bfddcd@yakko.patheticgeek.net>
In-Reply-To: <994cd1cf0703052105y375679a4t482f4e35988f9daf@mail.gmail.com>
References:  <994cd1cf0703050842r5e54daa6y5fe6af3083e15cd@mail.gmail.com> <45EC6E88.3080101@tomjudge.com> <20070305115615.W38684@orthanc.ca> <994cd1cf0703052105y375679a4t482f4e35988f9daf@mail.gmail.com>

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On Tue, 6 Mar 2007 10:35:42 +0530
"aditya kiran" <adityaa.kiran@gmail.com> wrote:

> RFC 1191 says to increase the PMTU at some itnerval (15 minutes default)

10 minutes.

> next time a packet is sent, this will be used... and if PMTU is really
> increased,
> no ICMP error will be recieved. that shows an increase in the PMTU. I'm
> trying to
> understand if this mechanism is there in freebsd. any on this is appreicated

It looks to me as though FreeBSD stores per-host MTU data in the
hostcache, which gets purged after five minutes of inactivity.  If
that's actually how it works, then, yes, FreeBSD should indeed
periodically probe for larger PMTUs.

Of course, the real test is to set up a few hosts and see what
happens, rather than speculating based on a quick perusal of the
code. :-)

Kevin
kml@patheticgeek.net



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