Subject: Re: 802.1Q & ETHER_MAX_LEN
To: Manuel Bouyer <>
From: Jason R Thorpe <>
List: tech-net
Date: 10/03/2000 07:17:33
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?

        -- Jason R. Thorpe <>