Hi, Tony, > On May 21, 2026, at 1:40 AM, Tony Li <[email protected]> wrote: > > > Hi Robert, > >>> as the traffic demand matrix is not a constant from one day to the next. >> >> Hmmm that is a pretty bold statement and intuitively hard to argue with. > > > Well, Carlos did ask that we be rigorous.
More than rigor, I was arguing for complete and comprehensive. Rather than precision in each measurement, I was arguing for inclusion of all constitutive power contributors. > It’s quite clear that the traffic demand is not 100% identical from day to > day. The question then is does it change enough to matter > > If one wants to be rigorous, one needs to ensure that the traffic matrix > between the power save case and the non-power save case is within a delta so > small that it doesn’t affect LSP placement. [Fond memories of delta-epsilon > proofs come to mind.] This argument can be shifted to say that there’s a potential of penny-wise-pound-foolish in non considering deltas. > > >> However maybe you and some of the folks on the list recall Cariden and their >> tool to build traffic demands in days, weeks and months of the number of >> tier 1 ISPs. Well the outcome of that was contrary and they found the >> traffic demand patterns to actually be pretty consistent in a given time >> deltas. >> >> That in turn allowed them to achieve traffic engineering of the relatively >> large global backbones by only adjusting the link metrics and the proven >> claim was that it was as good (say - 10%) as compared to the outcome of >> RSVP-TE. > > > I am not arguing that such a delta does not exist. Certainly it does, > however if one wants to make a true apples-to-apples comparison, the delta > must be shown to be small enough to not affect the result. > > >> I am mentioning it here as a potential alternative view on how to shift >> traffic between selected paths without the need to run full RSVP-TE in the >> network. Obviously this would rather fall into a controller driven bucket of >> solutions. > > > Let’s not repeat the debate of centralized vs. distributed yet again, please. > It only generates heat and no light. Another shift in perspective is to maximize system-level savings — without debating centralized vs. distributed vs. hybrid in the abstract. Best, Carlos. > > Cheers, > Tony > >
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