[rbridge] Time to summarize "forward or block" BPDU thread

[Radia Perlman]

I'm sorry, but I don't understand your example  (in a different
email), and don't understand why you think
isolating bridges into islands that create the illusion, to RBridges, of 
a single link can be a problem.
And I don't see why having RBridges as a layer above the bridges isn't 
the same as routers
being a layer above bridges.
And I can't think of a way of explaining it any differently. Perhaps 
somoene else can try,
or perhaps I can talk to you by phone sometime. But I'm travelling again.

Radia



Joe Touch wrote:

>Radia.Perlman at sun.com wrote:
>  
>
>>It works perfectly well if RBridges block. It isolates the bridge islands.
>>
>>Routers also block bridge spanning tree, and to exactly the same
>>effect as if RBridges block BPDUs.
>>    
>>
>
>This isn't the same at all; I keep hearing the analogy, but it fails
>under all tests:
>
>	first, there are NO routers on an L2 net
>
>	all sources/sinks are the same (called nodes AFAICT)
>	and hosts and routers are just nodes,
>	identical as far as L2 is concerned
>
>	nodes block all BPDUs (we agree), but
>	nodes also block broadcast (rbridges don't)
>
>Near as I can tell, L2 has exactly three devices currently:
>
>	nodes
>
>	links
>
>	bridges (participate in SPT, interpret BPDUs)
>
>Bridges don't 'block' BPDUs, but they don't forward them to all ports
>either.
>
>Now, an rbridge can be "like" a node, a link, or a bridge and still play
>in the existing L2 specs. If it isn't 'like' any of those, then we're
>changing the definition of 802, and I didn't think that was the goal here.
>
>rbridges - at least to nodes on the L2 - are NOT 'like' hosts, since
>they don't source or sink L2 traffic to existing nodes
>
>rbridges could be 'like' links if they are TRANSPARENT
>
>rbridges could be 'like' bridges if the PARTICIPATE
>
>What exactly are rbridges 'like' if they BLOCK?
>
>They can't be 'like' routers - there are no routers in L2.
>
>??
>
>Joe
>  
>
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