Subject: Re: 802.1Q & ETHER_MAX_LEN
To: Manuel Bouyer <firstname.lastname@example.org>
From: Daniel Hagerty <email@example.com>
Date: 10/03/2000 14:06:58
> 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.
ISL is another "perfectly valid" encapsulation that is useful in some
legacy environments; I have some bit-rotted code that does it.
One of ISL's nasty details is the 30 byte encapsulation header/trailer
enclosing an entire L2 packet. You need 1548 bytes packets from your
ethernet to avoid an MTU reduction.