[ntp:questions] GPS receivers were severely disrupted on 06 Dec 2006

Ryan Malayter malayter at gmail.com
Thu Apr 5 20:36:31 UTC 2007

On Apr 5, 9:35 am, j... at specsol.spam.sux.com wrote:
> Computer clocks drifting is going to be the least of the worries
> if there is ever an extended and wide spread GPS outage.

I would imagine there are some truly critical applications out there
that rely on accurate time from NTP. And any critical application that
relies on GPS should have an adequate backup in case of GPS failure.

Airplanes/ships have intertial and radio navigation aids to backup
GPS. Car owners should have (or can easily acquire) paper maps to back
up their GPS. Surveyors have old-style mechanical devices to back up

So GPS-disciplined stratum-1 NTP servers most likely have a failover
arrangement with a non-GPS time soruce (such as USNO, NIST, WWV(B),
DFC77, whatever) as a backup, right? But it appears at least some
don't: ntpq reports that my organization's ISP has stratum-1 servers
with GPS sources only. So they would, I think, start reporting
'unsynchronized' to clients in the event of a long GPS outage.

More information about the questions mailing list