[ntp:questions] independant time server?

Richard B. Gilbert rgilbert88 at comcast.net
Mon Jan 26 15:53:10 UTC 2009


martin.l.lane at gmail.com wrote:
> I have a network isolated the internet but I need a time server to run
> on this private network.  Are there any standalone time server
> packages out there?  Is there a way to force ntpd to sync with my
> computer clock and then run sending out the time data?  Ntpd will run
> after indicating it can't find a valid source to sync with but then it
> only sends out null data in its response messages for time.  Any
> suggestions?
> 
> Thank you for any help.

Can you afford ~$100 for some hardware?  Can you install a small device 
(bigger than a quarter and smaller than a half dollar) with, perhaps, 
ten feet of cable so that it has an unobstructed view of the sky?

If so, buy a Garmin GPS18-LVC GPS receiver and a 5 Volt DC "wall wart". 
  Connect the two in the intuitively obvious manner and connect the 
serial output of GPS18-LVC to a serial port. . . .

Other hardware will also work but, AFAIK, the Garmin is the cheapest.  I 
use a Motorola Oncore M12+T (Motorola doesn't make them any longer but 
sold the business to something called "SIRF".)

GPS receivers can be either "Timing" or "Navigation".  The receivers 
necessarily output both the time and a 3-D (Latitude, Longitude, 
Elevation) position but the timing receivers are optimized for timing 
and the navigation receivers for navigation.  In particular, the timing 
receivers have a Pulse Per Second (PPS) output that has an "edge" 
(rising or falling) that is accurate to within about 50 nanoseconds.

Yes, you can "force" ntpd to run without an accurate time source but it 
will NOT work very well.  The accurate time sources are not only 
accurate, they are stable!  That stability helps keep your clock both 
accurate and stable.




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