[ntp:questions] Looking for a NTP stratum 2 appliance

Paul tik-tok at bodosom.net
Sat May 27 05:32:20 UTC 2017

On Fri, May 26, 2017 at 10:33 PM, Harlan Stenn <stenn at ntp.org> wrote:

> NIST doesn't control GPS.  That's done by USNO and the USAF.

This is true(ish)* but irrelevant.  NIST defines traceability to NIST and
GPS can be a component of UTC(NIST) traceability.

More importantly the premise of this issue is incorrect (if it has been
properly presented).  If I have an S2 clock peering both with a GPS
disciplined S1 clock and a NIST clock via NTP then "apparent" errors
("drift") are measurements of network instability not variance from
UTC(NIST).  E.g. this line:

 time-d.nist.gov .NIST.           1 u   35  512    7   48.037    1.714

does not mean this clock has a 1.7ms offset and 2.1ms of jitter with
respect to UTC(NIST).

Since NIST specs the NTP error O(50ms) due to network issues it's
insufficient for the stated need in any case.

*NIST publishes the delta and the two groups work to maintain constrained
offset between UTC(NIST) and UTC(USNO) so they can be considered equivalent
instances of UTC in the US.

More information about the questions mailing list