Peter, > that differ by few microsecond
Really you normalize only single digit microseconds ??? What if link delay changes in milliseconds scale ? Do you want to compute new topology every few milliseconds ? Out of curiosity as this is not a secret - What are your default min delay normalization timers (if user does not overwrite with their own). Likewise how Junos or Arista normalizes it today ? Thx, R. On Wed, Mar 3, 2021 at 7:41 PM Peter Psenak <[email protected]> wrote: > Tony, > > On 03/03/2021 19:14, Tony Li wrote: > > > > Peter, > > > >>> There are several link types in use that exhibit variable delay: > satellite links (e.g., Starlink), microwave links, and ancient link layers > that deliver reliability through retransmission. > >>> Any of these (and probably a lot more) can create a noticeable and > measurable difference in TWAMP. That would be reflected in an FA metric > change. If you imagine a situation with multiiple parallel paths with > nearly identical delays, you can easily imagine an oscillatory scenario. > IMHO, this is an outstanding concern with FA. > >> yes, and that is what I referred to as "delay normalization", which can > avoid that oscillation. > > > > > > It can also negate the benefits of the feature. One might well imagine > that Starlink would want to follow a min-delay path for optimality. If the > delay variations are “normalized” out of existence, then the benefits are > lost. The whole point is to track the dynamics. > > for all practical purposes that we use it for, the two values of min > delay that differ by few microsecond can be treated as same without any > loss of functionality. So it's about the required normalization interval > - something that can be controlled by the user. > > thanks, > Peter > > > > > > > > >>> Please note that I’m NOT recommending that we back away. Rather, we > should seek to solve the long-standing issue of oscillatory routing. > >> > >> not that I disagree. History tells us that the generic case of > oscillation which is caused by the traffic itself is a hard problem to > solve. > > > > > > Any oscillation is difficult to solve. Positive feedback certainly can > exacerbate the problem. But solving hard problems is why we are here. > > > > Yours in control theory, > > Tony > > > > > > > >
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