The MPLS WG Archive

[Kireeti Kompella <kireeti@juniper.net>]

Hi John,

> What's needed is a way for you to ask for a lightpath that's physically
> diverse from one or more other lightpaths, whether or not the other
> lightpaths have the same terminals as the new lightpath.

Yes, that is correct.

> This is done
> routinely at DS3 and (I think) OC-n levels today by PL services like
> AT&T's EDRO (Enhanced Diversity Routing Option).

Are you (or others) proposing the mechanisms to do this in the
UNI/GMPLS framework?

> The heuristics to simultaneously route a number of circuits simultaneously
> subject to diversity constraints essentially require zillions of calls
> to a Dijkstra algorithm and so don't seem to lend themselves to incorporation
> in the control plane.

In the IP world, I see the use for simultaneous set up of a small
number of disjoint paths, basically, a primary and one or more
backups for an LSP.  So, this may not be an issue.  What is the
requirement driving having lots of simultaneous diverse paths in
the telephony world?

> I'd be interested in hearing more about the drivers for your example. I would
> expect that if you want physical diversity you are setting up lightpaths that
> are going to be around for a while.

Yes, but as I said above, I visualize lots of LSPs, each requiring
two or three diverse paths, not hundreds of diverse paths.  So, this
should not be an issue.

> There's a book by Ramesh Bhandari that addresses some of the algorithm issues.
> I don't believe that the heuristics used for services like EDRO are in the
> public domain though.

More's the pity :-)

Kireeti.

PS. BTW, your mail replies are MIME encoded, even when they are
simple ASCII.