NIST NTP servers
lowen at pari.edu
Wed May 11 18:23:59 UTC 2016
On 05/11/2016 12:05 AM, Joe Klein wrote:
> Is this group aware of the incident with tock.usno.navy.mil &
> tick.usno.navy.mil on November 19. 2012 2107 UTC, when the systems lost 12
> years for the period of one hour, then return?
I remember it like it was only four years ago.... oh, wait....
We have multiple sync sources ourselves, with a Symmetricom (formerly
Datum) SSU2000 setup with a cesium PRS, a rubidium secondary, and an
ovenized quartz for tertiary oscillators. SSU2000 architecture is
separate control and data planes, with time-sync on a different
interface from the LAN-facing NTP NIC. And the control plane is
firewalled off from the main LAN. An Agilent (now Symmetricom) Z3816 is
PC and SBC (RasPi, etc) oscillators are just not accurate enough for
Stratum 1 standards; at best stratum 3 or 4, even when directly
GPS-disciplined (stratum is NOT just a synonym for 'level' as a
particular stratum really has stability, precision, and accuracy
requirements). WWV plus GPS; GPS as you may or may not be aware, is
spoofable and is not as accurate as one might want. Neither is WWV.
Good reference for time-nuts is, well, the 'time-nuts at febo.com' mailing
(We're a radio astronomy observatory; accurate time and frequency
standards are a must here, especially as position accuracy of radio
telescopes approach tens of arcseconds).
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