[ntp:questions] how does jitter and round trip time affect the accuracy of the local clock?
Richard B. Gilbert
rgilbert88 at comcast.net
Sun Jun 26 20:15:20 UTC 2011
On 6/26/2011 3:52 PM, chipper wrote:
> If the ntp client needed to be withing .5 milliseconds of the server,how
> could I tell if the jitter and delay were to
> much to support this kind of accuracy?
Try it! If you are using an NTP server on the internet, it's going to
be difficult. You may find that time quality is excellent between 2300
- 0700 local time and very poor for the remaining sixteen hours!
If you have a GPS receiver, LORAN receiver, etc, you can get time of
very high quality. In particular, GPS sends a pulse per second and one
edge of that pulse is accurate to about +/- 50ns. The rest of the GPS
signal tells you which second is being marked by the specified edge,
leading or trailing (I've forgotten which).
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