[ntp:questions] Tighter regulation?

Mischanko, Edward T Edward.Mischanko at arcelormittal.com
Sat May 25 09:29:22 UTC 2013

> -----Original Message-----
> From: Charles Swiger [mailto:cswiger at mac.com]
> Sent: Friday, May 24, 2013 1:01 AM
> To: Mischanko, Edward T
> Cc: questions at lists.ntp.org
> Subject: Re: [ntp:questions] Tighter regulation?
> 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.
[Mischanko, Edward T] 

Measured by the best time sources I have available.  I am saying that my
 clock will drift to 5 milliseconds at maxpoll 10 and polling does not
 decrease to a level that will bring my clock back to an offset of +/- 1

> 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.
[Mischanko, Edward T] 

I your 25 year experience have you ever thought they may be a better way to
 achieve the same goals?  Or, have you ever looked at your goals and asked
 yourself what are the primary goals and what are secondary goals?  I am
 suggesting that clock offset is primary to clock jitter.

> 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.
[Mischanko, Edward T] 

I have common PC running Windows XP with 10 peers on my side of a corporate
> 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 time sources 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 time sources or a GPS/ACTS/WWVB or similar stratum-1 source.
> Regards,
> --
> -Chuck

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