[rbridge] Proposed compromise for short/long hellos

[James Carlson]

Don Fedyk writes:
> >   2. An entire TRILL cloud looks like a single STP-speaking bridge to
> >      the regular bridges attached anywhere in the network.  TRILL DRBs
> >      are responsible for running a fraction of STP and somehow
> >      coordinating with other DRBs.
> > 
> > We've intentionally chosen (1), and I think you're suggesting we
> > switch to (2).
> 
> Not exactly I'm suggesting you make the RBridge attachment such that the
> LAN running STP decides two or more RBridges cannot be tolerated. STP
> will block the ports until you can fix things.  Rather than running STP
> in a cloud you run enough of an STP stub locally on your RBridge to
> break loops in the rare event your discovery protocol fails. Remember
> your only counting on STP iff the discovery protocol breaks. And then
> IS-IS can be your discovery protocol. 

I'm unaware of a good way to do that.  I know how to make links in the
middle of the STP topology snap apart unpredictably (reporting the
same root bridge from each RBridge ought to be enough), but I don't
offhand know how to cause STP to break off the attachment right at the
"duplicate" node.

If you've got a concrete suggestion on how to do that, I'd be
interested.  (I still doubt we can get consensus on going that way,
particularly because it'd hard to keep it from interfering with the AF
delegation behavior, but it'd be interesting nonetheless.)

-- 
James Carlson, Solaris Networking              <james.d.carlson at sun.com>
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