[rbridge] VLAN Scoping / MAC Uniqueness

[Caitlin Bestler]

Silvano Gai wrote:
> Caitlin,
> 
> inline
> 
>> -----Original Message-----
>> From: Caitlin Bestler [mailto:caitlinb at broadcom.com]
>> Sent: Monday, March 19, 2007 2:50 PM
>> To: Silvano Gai; Radia Perlman
>> Cc: rbridge at postel.org; Erik Nordmark
>> Subject: RE: [rbridge] VLAN Scoping / MAC Uniqueness
>> 
>> Silvano Gai wrote:
>>> I think TRILL needs to do exactly what IEEE 802.1Q does.
>>> AN IEEE 802.1Q bridge has M VIDs and N FIDs with M >= 1, N >=1, M
>>> =N. 
>>> 
>>> N is never advertised outside the bridge, and the mapping of M to N
>>> is never advertised outside the bridge. TRILL must do the same.
>>> 
>>> Learning is done on {VID, MAC-address} pairs. TRILL must do the
>>> same. 
>>> 
>> My reading of Appendix B is that Shared Learning is allowed, where
>> VID is not a key field (i.e, there is only one FID supported).
>> Appendix B details some of the problems this creates. I believe the
>> problems for RBridges are even greater than for simple Bridges. This
>> probably justifies restricting RBridges to the Independent Learning
>> model, but any such additional restriction should be explicitly
>> stated. 
> 
> I am not saying I want to restrict, I am saying that in
> bridges what triggers learning is always the reception of a
> frame that has a {VID, MAC-address} pair. The fact that the
> VID, on that particular bridge, shares the FID with other
> VIDs is what causes shared learning. But shared learning
> NEVER propagates. TRILL MUST NOT propagate shared learning.
> IT MUST always propagate {VID, MAC-address}. Recipients may
> decide to do individual or shared learning.
> 
> -- Silvano

>From a standards point of view I could see stating that all
TRILL-related protocols MUST be based on Independent Learning,
but that an RBridge MAY use Shared Learning for its local ports
when acting as a Bridge. And I suppose if you literally grafted
an RBridge as an add-on module to an existing Bridge with shared
learning it might even make sense.

Effectively, however, it is requiring RBridges to use Independent
Learning. I see that requirement as inevitable, and therefore best
stated explicitly.