[rbridge] PS Issue #12

[Gray, Eric]

--> 
--> #12 address VLAN configuration requirements

As one of the principal intentions of this effort is to allow
for configuration free operation, then inclusion of VLAN as a
preferred support goal, implies that we should make an effort
to allow for the potential of configuration free VLAN support
if and when possible.

As pointed out previously, configuration of VLAN information
is not required in conventional bridges - yet conventional
bridges are fully capable of supporting VLANs. Consequently,
as a minimum, it should be possible for a RBridge to support
VLANs in a siimlar fashion.

However, one of the additional goals of this effort is to make
use of redundant paths, and one way to accomplish this is to
use VLAN identifiers as a part of the path selection criteria.
Using VLAN identifiers ensures that traffic within a VLAN is
not subject to potential re-ordering as a result of using more
than one path, since all of the traffic sharing a common VLAN
identifier will follow the same selected path.

This use of VLAN identifiers does not require configuration of
VLAN information.

VLAN configuration is required for mapping VLAN identifiers in
different scope where an identifier used on one interface (and
in one scope) is equivalent to an identifier on other interfaces
in different scope(s).  

VLAN configuration may be required if an RBridge implementation 
supports (limited) VLAN-to-VLAN routing capabilities.

In both of these cases, this SHOULD be functionality unrelated 
to the TRILL architecture and SHOULD - therefore - be out of 
scope.  

--
Eric