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Hi Igor hi Greg, I think this is a
very interesting discussion. IMHO the point Igor raised is on the
boundary between network planning and circuit provisioning I mean the decision to
have a node with/without conversion capability is a planning decision, likely
dependent by a given traffic forecast and a physical topology. Moreover the
same consideration applies for 3R capabilities I mean is possible that an LSP
needs 3R due to optical impairments. A possible solution to say that loopback
are not allowed and thus if an LSP for some reason needs a loopback the PCE must
return an error. This information can be used to improve the wavelength conversion/3R
capability of the network e.g. planning the deployment of more wavelength converter.
The other solution is to allow loopback. Best Regards
From: owner-ccamp@ops.ietf.org [mailto:owner-ccamp@ops.ietf.org] On Behalf Of Greg Bernstein Very good catch Igor. See in line.
2. Considering wavelength conversion
inevitably brings to the problem of looped paths, which is a completely new ball
game in path computation, and I am surprised that the issue was never mentioned
in the draft. --> How is this different from the
"looping" that can occur with a TDM multiplexer in a drop and
continue mode? Also in these two circuit cases (TDM, and optical) do we
have the same danger as in the packet case where looping traffic can greatly
degrade other flows. Was there some general looping concerns already
published for GMPLS with respect to circuits? IB>> There is a profound difference.
I am not talking here about accidental looping, rather about deliberate
looping: if some nodes can perform wavelength conversion while others can not,
then you will want to route the connection to one or several conversion points
and after that get it back on the main path. In other words you will
deliberately request, say, a PCE to produce looped path, and then GMPLS RSVP-TE
to signal looped path, which is completely out of normal paradigm of work for
both PCE and RSVP. --> I thought you were worried about accidental
loops. I didn't even consider what you are talking about
"looping", but would RSVP processing get fouled up? It sure looks
like a loop at the "node" level. Cheers, Igor --snip-- -- ===================================================Dr Greg Bernstein, Grotto Networking (510) 573-2237 |