[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

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).

More information about the questions mailing list