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
_______________________________________________
Lsr mailing list
[email protected]
https://www.ietf.org/mailman/listinfo/lsr
