Lesser comments on Updated Draft Liaiosn to Q6/15
"Adrian Farrel" <adrian@olddog.co.uk> Tue, 10 March 2009 17:20 UTC
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Reply-To: Adrian Farrel <adrian@olddog.co.uk>
From: Adrian Farrel <adrian@olddog.co.uk>
To: ccamp@ops.ietf.org
Cc: Malcolm Betts <betts01@nortel.com>, Greg Bernstein <gregb@grotto-networking.com>
Subject: Lesser comments on Updated Draft Liaiosn to Q6/15
Date: Tue, 10 Mar 2009 17:20:47 -0000
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Thanks Malcolm and Greg, > Deployment scenario 3 "Concern for "basic" impairments" my > recollection is that we were considering network scenarios in > which we could allocate sufficient margin so that a "simple" > computation of the accumulation could be used and still have > a high probability that the optical path would be viable and > would not perturb any existing paths. Thanks. Yes. "Basic" probably conveys that I was struggling for the right term! Greg suggested "Networks in which approximate impairment estimation is sufficient", and I will merge this with what you suggested (as in this case more may be more!). > Deployment scenario 4 "Concern for "advanced" impairments" > again my recollection is that in this scenario a full computation > of the accumulation of impairments including the impact on > existing paths is required. This significantly increases the scope > of information required and the compute time. Well, let's not get into the compute time :-) But you're right, again I was fishing for words, so I will merge what you said with what Greg supplied. > One final concern: > "With this in mind, CCAMP is looking to Q6/15 to work as a partner in > establishing: > - .... > - the rules by which such impairments are accumulated along a path > ...." > > This implies that we will standardize an aspect of path computation i.e. > the method of computing the accumulation of impairments. If the path > computation is performed in a single PCE then it is only necessary to > standardize the collection of the impairments, if it is distributed > across multiple PCEs it may be preferable to only expose a "figure of > merit" for the portion of the path that has been computed vs. > standardization of the method of computation. This should be discussed > with the experts from Q6. I think you are inferring a little more than was intended. In the PCE working group they talk of "objective functions". For example, they may say "minimize cost" and mean that the cost of a path is computed by accumulating cost in a particular way. But that does not specify a mechanism for computing the least cost path - only the way that the cost of a path is evaluated. So, it was my intent here to make the same statement. That is, that 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. I will add this clarifying text. And note that yes, this should be discussed with Q6. That's why we are meeting them :-) Thanks, Adrian
- Lesser comments on Updated Draft Liaiosn to Q6/15 Adrian Farrel