nanog mailing list archives

Re: anyone running GPS clocks in Southeastern Georgia?


From: Cutler James R <james.cutler () consultant com>
Date: Fri, 21 Jan 2011 16:53:08 -0500


On Jan 21, 2011, at 4:45 PM, Gary Buhrmaster wrote:

NTP isn't going to be the only "ripple".

Most of the "brand name" GPS NTP solutions have a clock
with is more than stable enough to survive without GPS
lock for 45 minutes(*).  Some of the more expensive units with
temperature controlled oscillators have hold times in the
many weeks.  My guess is that the NTP ripples will be
limited to those NTP servers just (or recently) booted
which have not yet achieved a stable clock state.

Gary

(*) This presumes that this test results in loss of signal
   lock, and not intentionally injected false information.

Even if there actually was an "NTP ripple", a properly designed NTP solution should rely on at least three 
geographically diverse sources. Given the ubiquity of the internet this is not difficult to achieve, barring extreme 
circumstances.

James R. Cutler
james.cutler () consultant com






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