RE: New draft on wavelength switched optical networks

["Bardalai, Snigdho" <Snigdho.Bardalai@us.fujitsu.com>]

Hi Greg,

Some more comments.....

Snigdho

-----Original Message-----
From: Greg Bernstein [mailto:gregb@grotto-networking.com]
Sent: Saturday, July 14, 2007 10:46 AM
To: Bardalai, Snigdho
Cc: ccamp; Young Lee; pce@ietf.org
Subject: 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?

[Snigdho] With O-E-O wavelength convertors additional constraints wrt to 
          the signal rate (2.5G or 10G) and other attributes related to the
          electrical signal will have to be taken into account.

> 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.

[Snigdho] I tend to agree with your view on this. Could you elaborate on "gaps" ?

> 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.

[Snigdho] I think it is possible to have per wavelength O-E-O regeneration as well.
          Using this mode of operation, the selection of the regeneration site could
          become more flexible. So routing could pick a site that is suitable considering
          the optical impairment parameters whereas signaling could actually require
          a specific type of regeneration module to be existing at the site.

>    
> 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.
>
>   

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