[rbridge] VLAN Scoping / MAC Uniqueness

[Caitlin Bestler]

Radia Perlman wrote:

> The advantage of this is that flooding of endnode information 
> for VLAN A need not be stored by any RBridges except those
> that attach to VLAN A.

That line leapt out at me on re-read.

*If* we are going to allow RBridges to have the traditional
bridge option of using scoped or global MAC address learning,
then we do indeed have to flood endnode information about 
VLAN A. This is not so that RBridges that are not part of
VLAN A can *store* the new endnode information, it is so
they can *delete* contradictory information.

Alternatively, if we explicitly require scoped learning,
then any RBridge that is not part of VLAN A cannot have
contradictory information. Then there would be no need
to flood endnode advertisements.