Subject: [rbridge] it's time to summarize things

From: Eric.Gray at marconi.com (Gray, Eric)
Date: Thu, 15 Dec 2005 10:56:32 -0500

Stewart,

	I am not sure I understand your statement.  Maybe you 
could put together a little ASCII art picture to make it 
clearer?  :-)

	Guessing what you mean, however, I get this picture:

                   ,---> RB1 <---> *
                  /
      * <----> (?)
                  \
                   `---> RB2 <---> *

Where * = rest-of-world AND (?) = whatever-is-in-your-closet

In order to understand why RB1 and RB2 might not be able to
operate in a load distribution model, we really have to know
more about - at least - what is in the rest-of-world, from a
topology and devices perspective. Where, for instance is the
RBridge campus?

	Another picture that might apply to your question is:

                   ____
                  /    \
      * <----> (?)      RB1 <---> *
                  \____/

In this picture, we need to know a lot less about the topology
of the rest-of-world.  With STP, RB1 almost certainly will put 
one of the two interfaces to whatever-is-in-your-closet in the 
non-forwarding mode while - without STP it never has to. 

In that case, the service (efficiency) without STP is better.

The question is whether or not we can specify the behavior of
RBridges within a TRILL architecture such that the first figure
above can be made to have the simpler world-view and many of
the same advantages of the second figure above.

I believe we can, assuming that the RBridge campus extends to
the right side in such a way that RB1 and RB2 are part of the
same RBridge campus on that side.  I also believe we can if 
we can stop arguing about whether or not we should.  I am sure 
I am not misreading the WG charter when I interpret what it 
says to mean that we should look to make things work this way.

--
Eric

--> -----Original Message-----
--> From: rbridge-bounces at postel.org 
--> [mailto:rbridge-bounces at postel.org] On Behalf Of Stewart Bryant
--> Sent: Thursday, December 15, 2005 3:49 AM
--> To: Radia.Perlman at Sun.COM; Developing a hybrid router/bridge.
--> Subject: Re: [rbridge] it's time to summarize things
--> 
--> Radia
--> 
--> >
--> >It looks like the thread of whether RBridges participate
--> >in spanning tree popped up again. I thought that had been
--> >resolved.
--> >
--> >RBridges should NOT participate in spanning tree, which means
--> >they should DROP spanning tree messages.
--> >  
--> >
--> 
--> Which surely means that a dual connected wiring closet gets
--> worse service from an RBridge network than a ST network
--> (because all the traffic goes one way rather than being
--> shared over both paths).
--> 
--> Stewart
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