Subject: [rbridge] Subcase for RBridges?

From: gibanez at it.uc3m.es (Guillermo Ibáñez)
Date: Fri, 28 Oct 2005 11:09:29 +0200

I have a question regarding next-hop destination RBridge addressing. It 
could be avoided whitin campus cores.
One objection that can be made to RBridges and other proposals that keep 
compatibility with bridged islands  is that  the double-encapsulated 
frame is addressed to next-hop RBridge instead of to destination 
RBridge. This is necessary as, if not, the frame could be duplicated by 
intermediate RBridges that receive  copies of  the frame.
As in some cases it is foreseable that RBridges will form the core of 
the campus network due to their advantages regarding segmentation, links 
usage, etc, I wonder whether it is worth to consider the subcase of 
confined RBridges whithin a core area formed by RBridges linked by point 
to point links. Point to point links are an standard requirement for 
RSTP protocol (required for fast convergence) and common practice in 
campus networks by performance and security reasons.
Ports of RBridges linked to RBridges ( core ports) execute RBridges 
protocol with double encapsulation and ports connected to standard 
bridges islands (sbridge ports) act as the "B1" standard bridge as 
proposed by Radia for RBridge/Bridge optional implementation.
Assuming an scenario like this, RBridges might address directly the 
encapsulated frame to destination RBridge and only the TTL field would 
need to be changed at each RBridge.
It is not the general and standard scenario, but it could be in practice 
quite common, given their advantages.
Guillermo