[ntp:questions] Tighter regulation?

Charles Swiger 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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