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Date: Sat, 1 Feb 1997 20:22:15 +1100 (EST)
From: "Daniel O'Callaghan" <danny@panda.hilink.com.au>
To: Warner Losh <imp@village.org>
cc: Brian Somers <brian@awfulhak.demon.co.uk>,
        Terry Lambert <terry@lambert.org>, dk+@ua.net,
        shocking@mailbox.uq.edu.au, freebsd-hackers@freebsd.org
Subject: Re: Setting MTU from userland ppp 
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On Fri, 31 Jan 1997, Warner Losh wrote:

> In message <199701302342.XAA20718@awfulhak.demon.co.uk> Brian Somers writes:
> : > > Don't use 256 as your MTU.  (violates the RFC)
> : > 
> : > Any chance of having the software *enforce* the RFC, then?
> : 
> : I'll have a look at the RFC.  It currently checks that 100 <= M[TR]U <= 2000.
> 
> Can someone point out where in the RFCs it says that an MTU size of
> 256 is illegal?
> 
> The closes that I've seen is a statement in the IP RFC that says that
> a remote side must be able to asssemble a packet of at least 576
> bytes, but does not disallow smaller fragment sizes.

As far as I am aware, the minimum MTU is 68 - a fully optioned IP packet 
with a single 8 octet chunk of fragment.  At least, that is for routers.

Danny