[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?
>
> Thanks
>
> Chip
>
>
<snip>
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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