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Re: New draft on wavelength switched optical networks

Hi Snigdho, good points and questions.  See comments below.

Regards

Greg B.

Bardalai, Snigdho wrote:

Hi Greg,

I believe your ID has presented some of the key points regarding wavelength routing.

I think we are still missing a few other issues that may have to be considered.
1. Constraints related to the configuration of the ROADM switching elements. For
   example, transponders could be pre-wired to a specific port on the ROADM, and hence
   restricting the wavelengths that could be routed to that transponder.
--> Yes. We touched on this only a bit but this is very important. There is a new draft (July 9, 2007) by Wataru. Imajuku, "Routing Extensions to Support Network Elements with Switching Constraint", draft-imajuku-ccamp-rtg-switching-constraint-02.txt. Which also hits some of these issues. But this is an area that needs further requirements analysis. 
It seems like we have at least:
(a) Internal switching topology constraints. Such as you can't get to that port from this port. Illustrated in Wataru's draft. (b) "Colored" interface related constraints where specific lambdas ingressing on a port will egress on a fixed port (not configurable). Like what you mention above. 
(c) Wavelength converter based constraints such as we mention in our draft.
(d) ... Others? Or a better taxonomy than the above?

2. When considering wavelength routing it may be important to consider
if regeneration of the signal is required.
--> This kind of work was started by John Strand and Angela Chiu in RFC4054 on optical impairments related to routing. Now since the publication the ITU-T has made a lot of progress in defining and characterizing various optical impairments so the time maybe about right to related some of this data plane work to the control plane. We originally were looking at this then saw some other gaps that needed filling. 
Also, it may be equally important to
   be able to specify, if and where reqeneration would be required during signaling
   (assuming an external entity such as a PCE can determine where the regeneration can
   be done).
--> Yes. We need regeneration capability information with our topology information which affects routing. Don't know that we'd need extensions to signaling, since once you've specified in the ERO to go through a regenerator element then you're done. At least for the fixed regenerators and those implicit in OEO switches.
It would be of much interest to me to learn what is your (and others) opinion on these 
issues.

Regards,
Snigdho

-----Original Message-----
From: owner-ccamp@ops.ietf.org [mailto:owner-ccamp@ops.ietf.org]On
Behalf Of Greg Bernstein
Sent: Wednesday, June 27, 2007 12:39 PM
To: ccamp; pce@ietf.org
Cc: Young Lee
Subject: New draft on wavelength switched optical networks
Hi CCAMPer's and PCEr's, we have just published a new draft on the "Applicability of GMPLS and PCE to Wavelength Switched Optical Networks" http://www.ietf.org/internet-drafts/draft-bernstein-ccamp-wavelength-switched-00.txt .
This draft looks at optical networks that include tunable lasers and ROADM (reconfigurable optical add/drop multiplexers) with no or limited wavelength conversion capability (these components are defined in the draft). These limitations lead to the RWA (routing and wavelength assignment) problem which is a bit more demanding in terms of input information and computation than other constrained path computation problems. In the draft we look at the implications for GMPLS signaling, GMPLS routing, and PCE protocols and suggest some potential extensions to better accommodate this application.
We'd appreciate feedback/collaboration on (a) overall interest in this application, (b) requirements discussions, and (c) solution/extension discussions. 

Cheers

Greg B.



--
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Dr Greg Bernstein, Grotto Networking (510) 573-2237