[ntp:questions] NTP makes a time jump

Rob nomail at example.com
Mon Jul 8 15:37:53 UTC 2013

karpekin at gmail.com <karpekin at gmail.com> wrote:
> Hello,
> Thanks for the answers!
> The reason of such a configuration is simple. Our equipment is a mission-critical set of devices that shall be running without NTP server available. Some drift away from a true time is tolerable. However, all devices must be synched with each other, to a max of 50ms. That's why I have as a fallback - "if no NTP server available, give devices at least your wrong timestamp and get all synched with it". 
> The 3 sec drift I set just to emulate the behavior of our "floating NTP island" for example after 2 years of no upsync. And the fact the time made a jump as soon as true server appeared, makes all the devices to jump, but not at the same time due to polling rates, causing all the devices to loose synch for at least max polling time. The ideal behavior I would like to reach is that the server will start to correct the time, slowly coming to the "real" NTP time.

In what kind of environment can there be a requirement of 50ms time
synchronization, but a sufficiently sloppy monitoring to allow two years
without external sync?

Would it be possible within your budget and installation environment
to have another time reference, e.g. a receiver for a time signal or a
GPS receiver?

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