On Tue, Oct 03, 2000 at 07:17:33AM -0700, Jason R Thorpe wrote:
> On Tue, Oct 03, 2000 at 03:12:10PM +0200, Manuel Bouyer wrote:
> 
>  > Is there other case where we need something like this (different MTU at
>  > the hardware level depending on the frame type) ? If not maybe we could just
>  > hack something simpler: change ifnet (or maybe, really if_data) to include
>  > the max frame length the HW can do; which may be bigger than
>  > if_mtu + if_hdrlen. Then extra encap layers such as 802.1Q can use it to
>  > recompute a MTU. Anyway we won't be able to have a completely clean separation
>  > between 802.1Q and ethernet.
> 
> How is this problem really any different than e.g. FDDI using a different
> MTU for IP than it does for anything else?

How is this handled ?

The difference I can see if that, with fddi, we know the max len; for IP and
for anything else. In our case, the driver needs to inform if_vlan whenever
it can do 1522 or only 1518. Not all ethernet boards can do 1522.

--
Manuel Bouyer, LIP6, Universite Paris VI.           Manuel.Bouyer@lip6.fr
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