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Re: [CCAMP] draft-ietf-ccamp-gmpls-g-694-lambda-labels and unique resource identification
Jonas,
A very good question! In the common/general setup case I think it
won't matter. But there are cases where it may:
- In GMPLS we have a precedent of being able to use the label to
represent a specific physical resource, be it a time slot, frequency or
even port. If we assume that this is a function worth preserving (and I
believe it is, at least with today's equipment) than it is
desirable/required to be able to use GMPLS to control a specific laser.
Even a tunable one. With the current definition, this isn't possible.
- The more practical/import case is graceful restart. In certain
restart cases, the restarting node may need to match particular node
resources (e.g., tunable lasers) against a particular frequency to
ensure no data loss and the restarting node may no longer have the
information to do the matching. In all other cases that I know about,
GMPLS allows for sufficient information for a node to reconstruct this
mapping.
- MP to CP handover may also need to identify specific node resources
(e.g., tunable lasers).
I believe these are the primary cases.
I hope this helps,
Lou
On 11/2/2009 5:35 AM, Jonas Mårtensson wrote:
> Lou,
>
> Maybe this is a silly question but if all lasers in the system are tunable, why does it matter which one is used? Can't the node decide this locally?
>
> Regards,
> Jonas
>
>> -----Original Message-----
>> From: ccamp-bounces at ietf.org [mailto:ccamp-bounces at ietf.org]
>> On Behalf Of Lou Berger
>> Sent: den 30 oktober 2009 14:02
>> To: Richard Rabbat
>> Cc: ccamp at ietf.org
>> Subject: Re: [CCAMP]
>> draft-ietf-ccamp-gmpls-g-694-lambda-labels and unique
>> resource identification
>>
>> Richard,
>>
>> Okay let me try again with a specific case. If I have an rro
>> or ero that identifies the label (lambda) per your document,
>> how does a node know which laser the label corresponds to
>> when all lasers in the system are tunable?
>>
>> Thanks,
>> Lou
>>
>> On 10/29/2009 2:22 PM, Richard Rabbat wrote:
>>> sorry for the lag.
>>> do you want to describe your use-case further in terms of what you
>>> can't do and your proposed change?
>>> thanks,
>>> Richard.
>>>
>>> On Thu, Oct 15, 2009 at 8:53 AM, Lou Berger <lberger at labn.net
>>> <mailto:lberger at labn.net>> wrote:
>>>
>>> Authors,
>>> Have you given any additional thought on the
>> repesentation of
>>> tunable
>>> lasers (and unique resource identification) beyond what
>> is currently in
>>> the draft? The current text is:
>>> If the node has a tunable wavelength transponder, the tuning
>>> wavelength is considered as a part of wavelength switching
>>> operation.
>>>
>>> In the past, labels used for TE LSPs always represented
>> a specific
>>> resource that is uniquely identifiable by the node that
>> allocates the
>>> label and resource. Such unique identification is
>> important/required
>>> for certan restart and other corner cases. Your current
>> definition works
>>> fine for fixed lasers that can only be mapped to a
>> single fiber. But,
>>> the defined global label will not uniquely identify a
>> resource on a node
>>> when (a) tunable lasers are used, or (b) when a node
>> supports multiple
>>> fixed lasers that can be (optically) switched to a
>> particular output
>>> interface.
>>>
>>> What are your thoughts on how to provide such link-scoped unique
>>> resource identification in the context of your draft?
>>>
>>> I don't think it'll be too difficult to address this
>> critical point, and
>>> see a couple of straightforward solutions if you'd like
>> to discuss
>>> off-line.
>>>
>>> Much thanks,
>>> Lou
>>>
>>>
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>>>
>>>
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>
>
>
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