Dave Hart wrote:
I would agree if you said "perceived wander with measurement-induced error". In other words, while turning the slew knob faster reduces your offsets faster, doing so risks following measurement noise rather than the underlying trend.
That was my point. Unruh's main issue is that, on modern LANs, the dominant low frequency error is in the local clock, rather than the measurements.
You do not understand NTP's clock filter. As each new sample is pushed in, only one of the prior 8 samples is used for the moment, but each sample has 8 chances to be that favorite. That is not equivalent to "throwing away 7 out of 8 readings" on my planet.
It's more complicated. I don't think the current version ages the samples, so, for a concrete example, if you have a downwards sawtooth, in delay, of period 16, you will get all the first 16, the last of these will be repeated 8 times. When it drops out of the filter, one will be on the 8th entry in the sawtooth, so you will get another run of 9 different samples, so it will "throw away" 7 in 16 on the long term average. I think, if you increase the sawtooth period, it will be 7 in n. Obviously, these are contrived cases. I think the filter will take out more like 7 in 8 for gaussian input, but the expected input pattern isn't actually gaussian, either.
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