[rbridge] Access-only link

[James Carlson]

Radia Perlman writes:
> I'm a little less clear on why access-only links are as important, since 
> it doesn't seem as though the traffic of
> LSP propagation would be that much. But again, I think it's simple and 
> safe, so if people think it's useful, I wouldn't
> oppose it.

The case I remember discussing (Silvano, maybe?) was with a wiring
closet.  There's a set of "backbone" links interconnecting the
RBridges, but there are a pair of RBridges that are incidentally
connected through a local access-side wiring closet.  The owner of the
wiring closet doesn't want any backbone traffic traversing it, no
matter how attractive it might look as a path.

> The idea is for the DRB to signal in its Hello "this is access-only". 
> And in the LSP for the pseudonode, the DRB
> can set the "database overflow" flag, which is a flag already in IS-IS 
> for the purpose of dealing with a router that
> can't hold the LSP database. That flag means "don't go through this node 
> unless absolutely no other path exists".
> If the "overflow" flag is set in the pseudonode's LSP, that would mean 
> that that pseudonode would not be computed
> in a path as a transit link.

I think the desire was for "no way, no how."  Not "go ahead and use
this to patch together the rest of the network if necessary."

Perhaps that's too strict a requirement, but that's what I *thought* I
understood from the lunch table discussion.  Perhaps the others
involved could pipe up and clarify whether overflow would be
sufficient.

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