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Date: Fri, 13 Jul 2007 15:27:25 -0400
From: Bill Moran <wmoran@collaborativefusion.com>
To: David DeSimone <fox@verio.net>
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Subject: Re: 6.2 mtu now limits size of incomming packet
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In response to David DeSimone <fox@verio.net>:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> Bill Moran <wmoran@collaborativefusion.com> wrote:
> >
> > Let's flip the question around a bit:  why would you _want_ the TCP
> > stack to accept frames larger than the stated MTU?
> 
> If I receive a 64K frame and the TCP checksum checks out, and the
> sequence numbers match, and it passes my firewall state, why NOT receive
> it?  It is obviously valid, even if I cannot understand how my interface
> could have received it.  The packet is here, so do something useful with
> it.

But it's not here yet.  The problem is that it doesn't pass a basic
sanity check at the media layer, so it would be dropped before it ever
starts seeing checks at the TCP or IP layer.

> I agree with others that MTU means "limit what I transmit".  It does not
> mean "limit what someone else can transmit to me."

Interesting viewpoint.  I disagree with it, but I can't quote any standard
or otherwise to support my view.  You didn't either.

Does anyone know of a publicised, authoritative standard that would clear
this up?

-- 
Bill Moran
Collaborative Fusion Inc.
http://people.collaborativefusion.com/~wmoran/

wmoran@collaborativefusion.com
Phone: 412-422-3463x4023