shiba - see inline for some additional hints:
Shiba, Sidney wrote:Adrian, Dimitri, Thanks for reviewing these I-D. Wavelength continuity constraint does require the use of semanticfullabel whether it is spectral or index.=> see my reply to adrian on this specific pointI 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 pathThe 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[Sidney]What I've meant here was that it was not necessary to update any document when new wavelengths are inventoried. In the case of indexing approach, it would require the wavelength indexing document to be updated with implementation impacts.In the case, the nominal value is used, there is no need for documentation update.
ok - what you mean here is that you are going to make use of the already defined C-Type 2 - what about the specific encoding of the value space ?
=> now i have a more specific question before being light-up how do you know the frequency that you can support ?[Sidney] Some new technologies integrate optical switch and mux/demux capabilities, which allows the equipment to know the spectrum it supports.
indeed - but the question is what does happen if the "detected" values (during initialization) do not match the nominal values ? you don't initialize then ?
if these differ from the nominal values how are you going to deal with these discrepancies ?[Sidney] These new technologies uses the nominal value as reference. We can say that a lightpath wavelength is identified by its nominal value. If the equipment is drifting from this nominal value, it is considered as a failure.
ok - but if the deviation is such you have overlap - how the control plane is going to be able to detect such failure ?
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 ?)[Sidney] The wavelength is WDM specific as much as the SUKLM label encodingis for SONET. The wavelegth/frequency nominal value is used to identify the facilities to cross-connect.
there is an equivalence but there is also a major difference, the structure is invariant independently of the state of the network, with spectral value space you may have labels that become unavailable due to non-local usage of wavelength in the network
hence, there is also no real coupling to the data plane more than knowing the type of interface and some generic capabilities
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, - dimitri.
-----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.orgSubject: Re: comments ondraft-shiba-ccamp-gmpls-lambda-labels-00.txtDimitri,Thanks for your work reviewing these recent I-Ds. It is really valuableand 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 labelWithout being too picky, I think all labels are semanticful otherwise, wewould not know what resource they refered to.So the point reduces to whether the scope of the semantics are link-localor wider.so, the comparison from this perspective with TDM labels isdifficult toparse, 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 wereenthusiastic abouttransparent 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 requirementsfor 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 interactionsbetween wavelengths this knowledge is at the end of littlepracticalusage; (introduces implicit ordering)- indexed values: the # of the wavelength: it does notprovide for afuture proof label space for inst. in case new frequenciesare insertedin the grid (introduces explicit ordering)- diff. values e.g. freq spacing starting from a referencevalue: pausesthe question of the reference value and does suffer from the former issue (introduces implicit ordering) - the solution available today - cumbersome in some control planeoperations (e.g. label set translation) and not easy totroubleshoot butindependent of any physical consideration (spectral), scale to anynumber of wavelength per fiber, does not introduce anyordering, themost 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-lambda-labels -00.txt> ..