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RE: Re-Updated Draft Liaison to Q6/15
Adrian
You indicate
"There is NO REQUIREMENT in any of this WSON work for
any measurement of impairments. The only person to say there
is a requirement is you. Everyone else keeps repeating that there
is no requirement to measure impairments. The only requirement
is to distribute information about impairments however it has been
obtained, and to consider how to use the information during path
computation"
This statement is incorrect.
The substance of my email indicated that there is an IMPLIED REQUIREMENT
for ROADMs to make some form of measurement and it is not appropriate
for CCAMP to write protocol standards that imply ROADM data plane
related requirements.
Or if this is not the case and it is not necessary for ROADMs to make
any measurements, then can we agree that the following text is added to
the Introduction and Scope of all relevant GMPLS for WSON with optical
impairments IDs.
" GMPLS for WSON with Optical Impairments only applies to the case where
ROADMs, OXC, or any other optical network nodes do not make any
measurements related to optical link impairments"
Regards
Don
-----Original Message-----
From: Adrian Farrel [mailto:adrian@olddog.co.uk]
Sent: Wednesday, March 11, 2009 7:10 PM
To: O'Connor, Don; ccamp@ops.ietf.org
Subject: Re: Re-Updated Draft Liaison to Q6/15
Hi Don,
> The draft liaison text below
Not draft any more. The liaison has been sent.
> does not ask Q6/15's views on how the optical link impairment
> data should be acquired such that the wavelength routing
> assignment achieves satisfactory results.
Right.
The liaison explicitly says
"It is not within the scope of CCAMP to determine how impairments are
gathered."
Nor is it our business to request anyone to make standards for this
purpose.
If the standards do not exist and are needed, I am sure people will make
contributions to Q6/5 accordingly.
> Some potential options are
>
> 1) ROADM / OXC measure impairments in service - At present there
> are no ITU SG 15 standards for this
>
> 2) ROADM / OXC estimate link impairment based on measuring
> some link parameters - At present there are no ITU SG 15 standards
> for this
>
> 3) Link impairments are measured out of service with some test
> equipment - then you do not need any CCAMP ROADM protocols
> - the measurement results can be directly exported from the test
> equipment to the PCE
I have no idea what you mean by a CCAMP ROADM protocol.
Of course, it is possible to export information into the PCE's TED by
any
means. This is fundamental to RFC 4655.
You may be considering that all path computaiton in a WSON is
centralised,
but please note that if the path computation is fully distributed, a
convenient mechanism may be to use a routing protocol to distribute this
information (just as we do for TE metric which is a static configured
parameter).
> 4) Link impairments are estimated without making any measurements
> - we do not need any CCAMP ROADM protocols
This is just as above.
Don, it is OK if you do not want to use GMPLS in your WSON.
> The draft text in the liaison below appears to assume that ITU SG 15
> already has standards in place to support control plane based
wavelength
> routing and assignment based on optical impairments, and all that is
> necessary is for SG 15 Q6 to provide CCAMP with some guidance on how
to
> use these standards. I do not [think] this is the case, particularly
for
> the
> case of 1) or 2) above.
Hmmm. You sound less than sure it is the case for 3) and 4).
But no matter. The whole reason for talking to Q6/15 is to let them tell
us
what the state of affairs is. I am sure Q6/15 are perfectly capable of
telling us what can be achieved using their in force Recommendations.
> Let me make an analogy. Today there are no IETF MPLS OAM standards for
> PM measurement. It would not be good for ITU to go off and generate
some
> standards that would require MPLS LSR to perform some PM measurements.
Poor analogy on two fronts.
1. Generating requirements is a very good thing. It is the construction
of solutions that would be worrying.
2. There is NO REQUIREMENT in any of this WSON work for
any measurement of impairments. The only person to say there
is a requirement is you. Everyone else keeps repeating that there
is no requirement to measure impairments. The only requirement
is to distribute information about impairments however it has been
obtained, and to consider how to use the information during path
computation.
> To move the process forward, I will propose the following update
> to the draft liaison text below
As I said in my previous two emails (and this one) the liaison has
already
gone.
> "We would appreciate Q6/15's view on the following issues:
> - What optical link impairments are suitable for consideration in this
> type of network,
OK. We have that already.
> - How should these impairments be measured, estimated, or
> otherwise determined
Why? It is not our business.
If you want an answer to this question, you have to go to Q6/15 direct,
not
through CCAMP.
Since "configured" is always an answer to your question, there is
already a
role for CCAMP protocols to distribute the configured information.
> - In addition to optical link impairments, should other impairments be
> considered such as those introduced by ROADM / OXC, Optical
> Amplifiers, etc
I think we are considering the OLS when we say "optical link", aren't
we?
It may be that we should also consider nodal impairments (at ROADMs and
PXCs) and that would be a very interesting question to put to Q6/15
during
the meeting.
But, as Kireeti commented...
| While I'd like to see this broader, what we deal with primarily in
| GMPLS is link parameters. So I'm okay with this (as a start).
We should note that the IGPs do now have the capability to exchange node
capabilities, so this would not be hard to factor into GMPLS.
> - What rules should we use for these impairments to achieve
> a reasonable approximation of how they are accumulated
> along a path?
> That is, CCAMP is looking for the rules by which the end-
> to-end impairments of a path may be determined from a
> knowledge of parameters of the path and impairments on
> the path segments.
OK. We have that already.
> - What are the generic encodings and ranges of values for
> the impairment parameters?
OK. We have that already.
> - Which existing Recommendations can be applied
OK. We have that already.
> - Will it be necessary for ITU SG 15 Q6 to generate any new
> Recommendations or Amendments to existing Recommendations
> to support this application?
That is also a fine question to bring up in the meeting.
I suspect that in answer to the previous question we will be told of any
lacunae.
Cheers,
Adrian