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Date:      Wed, 05 Jul 2000 17:56:41 +0100
From:      Tim Priebe <tim@polytechnic.edu.na>
To:        Luigi Rizzo <luigi@info.iet.unipi.it>
Cc:        David Gilbert <dgilbert@velocet.ca>, tim@iafrica.com.na, Kevin Oberman <oberman@es.net>, "Louis A. Mamakos" <louie@TransSys.COM>, Joerg Micheel <joerg@cs.waikato.ac.nz>, freebsd-stable@FreeBSD.ORG
Subject:   Re: Ethernet MTUs > 1500?
Message-ID:  <396368C9.C3C5A50F@polytechnic.edu.na>
References:  <200007051516.RAA77416@info.iet.unipi.it>

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Luigi Rizzo wrote:
> 
> > Kevin> Louis has it exactly right. 802.3 was modified a couple of
> > Kevin> years ago to allow for a maximum frame size of 1522 octets, up
> > Kevin> from the original 1518. This was to allow the VLAN information
> > Kevin> to fit in the frame.
> 
> just curious, what do we do when we have multiple encapsulation ?
> (i.e. is this allowed ?)
> 
>         cheers
>         luigi

I am not sure what you mean. If you mean "VLAN encapsulation", then it
is a misunderstanding. The standard Ethernet frame is not encapsulated.
The Ethernet header is modified. The extra 4 Bytes are not at the
begining of the frame. The frame is identical to one with
prioratization, 12 of the bits indicate the VLAN, and 4 the prority. So
there is only one VLAN value, and one priority value possible per frame.

Tim.


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