[ntp:questions] Keeping NTP Honest
Richard B. Gilbert
rgilbert88 at comcast.net
Wed Jul 15 19:26:23 UTC 2009
Evandro Menezes wrote:
> On Jul 15, 6:22 am, "Richard B. Gilbert" <rgilber... at comcast.net>
>> There is no problem unless you insist on shutting down your system
> That's not the only case. In the real world, ambient temperature
> changes frequently even in air-conditioned environments, system load
> affect its internal temperature, network load affects packet jitter,
> etc. And all this also affects a system's peers, compounding the
> issue of NTP's slow reaction time.
> It seems to me that NTP can only work well with a PPS source. For the
> rest of us, it seems to work only in conditions similar to
> Delaware. :-)
>> The subject line seems poorly worded. There is no question of honesty
>> or dishonesty in the usual sense of those words.
> But I'm sure that you've come across these words as an idiom, haven't
> you? ;-)
A lot depends on your requirements. If you need time to the nearest
microsecond, you will pay dearly! The nearest millisecond is somewhat
cheaper. Ten or twenty milliseconds can be easily achieved using NTP
over the internet. A GPS timing receiver in conjunction with NTPD can
keep you within one or two hundred microseconds. The PPS output is good
to 50 or 100 nanoseconds; the problem is to get that timing into your
computer without degradation.
One thing you could try would be to put your clock in a thermostatically
controlled oven. I'm not talking about something you could bake a pizza
in, but rather something that will keep 140 degrees F +/- half a degree.
If that doesn't "float your boat", you could try Rubideum or Cesium
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