[ntp:questions] NTP with GPS and RTC

Harlan Stenn stenn at ntp.org
Sat Apr 27 09:16:08 UTC 2013


unruh writes:
> On 2013-04-26, Harlan Stenn <stenn at ntp.org> wrote:
> > unruh writes:
> >> Define occasionally. Unfortuneately ntpd requires about 5-10 hours to
> >> rediscipline a clock to ultimate accuracy when the connection comes up
> >> again, so if the connection time is shorter than that, chrony (assuming
> >> you run linux or some unix) is a better choice ( faster lock and
> >> discipline time). It also allows you to "trim by hand". Ie, if you can
> >> phone into the device, and find it is say 1 min off, you can tell chrony
> >> to correct that offset by hand.
> >
> > And Bill's statement above also depends on your definition of "better".
> >
> > My understanding is chrony will do an excellent job of tracking the
> > upstream source it is listening to.  That is not necessarily the same as
> > maintaining better system time.
> 
> Sorry, what other definition do you have of "better system time"? All
> anything can do is to use a source and assume that that sourc is a good
> source. 

I haven't looked in a while.  What does chrony do about selecting
between multiple servers?  What about clockhopping?

For some, "better" may mean "My clock frequency is stable and I am
tracking the middle of the clique" as opposed to "I am tighty latched
to the server I am currently listening to."

H


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