[ntp:questions] Tighter regulation?
cswiger at mac.com
Fri May 24 06:00:53 UTC 2013
On May 23, 2013, at 10:02 PM, "Mischanko, Edward T" <Edward.Mischanko at arcelormittal.com> wrote:
> It takes too long to figure out it needs a more aggressive correction.
> If I leave maxpoll at the default of 1024 seconds, my clock drifts outside
> of 5 milliseconds consistently.
Measured by what? If you have a better source of time available, sync ntpd using that.
More importantly, ntpd should be entirely able to compensate for a steady drift of ~50 ppm;
are you saying that not only do you have a long-term drift, but short-term instability
which varies by ~50+ ppm hour-by-hour?
> Too much assumption is made that everyone will have the perfect computer and
> the perfect network when configuring these various filters. What works on
> the blackboard does not always work in reality.
Oddly enough, my ~25 year experience with ntpd suggests a great deal of practical
experience has gone into creating a timekeeping solution that avoids chasing short-term
transients in favor of stable long-term behavior.
However, it's certainly OK if someone decides that some other software provides a better
solution for their particular circumstances….
> My computer has a -19 precision but it can't keep time inside 1 millisecond with default
> Settings; go figure.
Precision of -19 suggests commonly available commodity hardware. Keeping time to around 1ms
should be reasonably doable with a decent network connection, at least 4 reasonable peers
or timesources to query, temperature-controlled systems, and an OS with sane timekeeping;
VMs need not apply regardless of OS.
It might help to setup a subnet local peering of ~4 or so machines, in addition to the
remote timesources or a GPS/ACTS/WWVB or similar stratum-1 source.
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