[ntp:questions] Speed of ntp convergence

Martin Burnicki martin.burnicki at meinberg.de
Thu Nov 6 09:46:27 UTC 2008


David Woolley wrote:
> Nicola Berndt wrote:
> 
>> 
>> What really bothers me is that ntp is totally capable of telling me its
>> offset (and so how wrong the time /being served/ is) but not capable of
> 
> Careful.  The theory behind ntpd is that, in normal operation, offset
> consists only of measurement error, not of real clock error.  The
> problem with ntpd is that, after startup, or rapid temperature changes,
> that assumption isn't valid, and offset contains a large component of
> real error.  Worse, it is obvious to a human observer, even without
> hindsight, that that is the case.

Some time ago I have made some tests comparing the system time disciplined
by NTP against the time of a built-in GPS PCI card. The results showed the
offset reported by ntpd did very well match the offset measured against the
GPS card.

I think the current development of NTP goes into a direction which may cover
some special scenarions well, but matches less and less the requirements of
"normal" users.

Martin
-- 
Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont
Germany




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