Hi Young. If I understand correctly, your actual requirement is to find a "threshold criteria" to request a route that is "healthy enough" for the PCC. So why have you chosen the BER which more relative to a digital client layer? Why not considering a more optical criteria, like OSNR for instance?
Have a good week-end, Julien -----Original Message----- From: Young Lee [mailto:[email protected]] Hi Julien, The reason why we put the BER threshold in the PCEP request is to "approximate" if the optical path in consideration would be "healthy" enough from the BER perspective. Please note that we have defined two different computation types of IA-PCE functions in the IA-WSON framework draft: (i) approximate approach; (ii) candidate approach. Approximate approach is a quick way of estimating the affects of impairment while the candidate approach is to give a list of acceptable paths with more thorough data/model. The BER can be estimated in various ways given the availability of other impairment parameters. In any IA-RWA (approximate) type computation where we are given impairment parameters to estimate the affects of impairments, we must use some threshold criteria to accept/reject paths. The BER parameter was our first attempt at providing some control over this criterion. Best Regards, Young -----Original Message----- From: [email protected] [mailto:[email protected]] Hi Young. This is a try to resume our discussion started during the SF meeting. Indeed, I still don't get the rationale behind adding the BER as a requirement for PCEP request. First, I wonder what your intend is when requesting a BER threshold at computation time while you can't really know it before LSP provisioning. Obviously, what we look for is a low BER, but the way I see using BER in routing would be to request a 2nd route *after* a poor BER measurement on a firstly established LSP. Then, considering what you called a "BER estimation", I don't clearly see how you intend to estimate (or model?) it. The BER associated to an LSP is highly dependent on so many parameters: link DGD at measurement time, performance of the FEC used for the to-be-provisioned LSP , possible cross-talk and thus impact of potential adjacent channels... Furthermore, I don't really understand why focusing on the measurable BER range while a typical PMD (in)accuracy may just move us between an acceptable route and an unacceptable one, the latter being the very 1st problem we should try to solve. Finally, I don't get the use of such feature. Even if we could, why would I request a 10^(-6) maximum BER? I don't see any room for anything else than "the best one", so do we really need something else? I tend to see BER as a varying quality feed*back*, not as an indicator that we can accurately target at routing time. I completely agree that PCEP must support optical requirements, but my concern is to understand actual needs before loading the protocol. Therefore, I look forward to reading some clarification on those issues. Best regards, Julien _______________________________________________ Pce mailing list [email protected] https://www.ietf.org/mailman/listinfo/pce
