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Re: comments on draft-shiba-ccamp-gmpls-lambda-labels-00.txt

shiba

Shiba, Sidney wrote:


Adrian, Dimitri,

Thanks for reviewing these I-D.

Wavelength continuity constraint does require the use of semanticful
label whether it is spectral or index. 

=> see my reply to adrian on this specific point
I agree with Dimitri that the wavelength indexing requires document updating each time a new spectrum is introduced. 

=> indeed and in addition it requires updating the already signaled path


The use of spectral label provides self maintainance, i.e., no need to
update any document and the use of the nominal value provides a common semantic ground.
=> what do you mean by self-maintenance - would you provide a bit more detail
=> now i have a more specific question before being light-up how do you know the frequency that you can support ? if these differ from the nominal values how are you going to deal with these discrepancies ? this said i am not necessarily sure that having to maintain the data plane specifics as part of the control plane is really helping operations (is this method not just duplicating complexity ?) 


I'm not sure if the draft needs to be updated before the face-to-face
meeting or after all comments are collected. Please advise.
=> suggest to keep discussion on - document update can be performed at a later stage 


Thanks,

Sidney



-----Original Message-----
From: owner-ccamp@ops.ietf.org [mailto:owner-ccamp@ops.ietf.org]On
Behalf Of Adrian Farrel
Sent: Thursday, October 27, 2005 4:45 AM
To: dpapadimitriou@psg.com; dimitri.papadimitriou@alcatel.be;
ccamp@ops.ietf.org
Subject: Re: comments on draft-shiba-ccamp-gmpls-lambda-labels-00.txt


Dimitri,
Thanks for your work reviewing these recent I-Ds. It is really valuable 
and I'd welcome other people doing similar reviews.



there is a specific point to be clarified in this document:

semanticless vs semanticful label (even here there is a distinction
between spectral vs indexes i.e. using the wavelength index)

domain-wide vs link local significant label
Without being too picky, I think all labels are semanticful otherwise, we 
would not know what resource they refered to.
So the point reduces to whether the scope of the semantics are link-local 
or wider.
so, the comparison from this perspective with TDM labels is 

difficult to


parse, the latter is semanticful but link local

now, i don't specifically see what has changed the late 90's, early
y2k's, to have a change in the wavelength label definition;
This is the question I would like to get to the bottom of. In other words: 
do we need this function?

It seems to me that the question being asked is this:

  If I want to compute a path that has some form of wavelength
  constraints, what information do I need access to?

Another question might be:

  If I want to signal a path with wavelength constraints what
  information do I need to include in the signaling message?


I'd suggest that when we started on GMPLS, we were enthusiastic about
transparent optical networks, but we were not properly focusing wavelength constraints because lambda-switching PXCs didn't take off. Therefore we didn't examine the requirements for wavelength constraints in routing and signaling. The authors of this I-D are claiming new hardware requirements 
for the same function.



there are
several solution possible

- absolute values: the freq. of the wavelength: difficult to adopt
because referenced values are nominal and knowing all interactions
between wavelengths this knowledge is at the end of little practical
usage; (introduces implicit ordering)

- indexed values: the # of the wavelength: it does not provide for a
future proof label space for inst. in case new frequencies 

are inserted


in the grid (introduces explicit ordering)
- diff. values e.g. freq spacing starting from a reference 

value: pauses


the question of the reference value and does suffer from the former
issue (introduces implicit ordering)

- the solution available today - cumbersome in some control plane
operations (e.g. label set translation) and not easy to 

troubleshoot but


independent of any physical consideration (spectral), scale to any
number of wavelength per fiber, does not introduce any ordering, the
most flexible (since allowing each system to maintain its specific
control operations) and the less constraining since maintaining the
control plane operations independent of any data plane specifics




<http://www.ietf.org/internet-drafts/draft-shiba-ccamp-gmpls-l


ambda-labels
-00.txt>

.