nanog mailing list archives

Re: anyone running GPS clocks in Southeastern Georgia?


From: Owen DeLong <owen () delong com>
Date: Fri, 21 Jan 2011 15:01:10 -0800


On Jan 21, 2011, at 1:45 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.

Loss of lock is a non-issue.

However, the tests they are doing do not necessarily cause loss
of lock. Sometimes, instead, they give you a wrong enough time
to insure that your navigational fix is off by, well, enough to
guarantee that you don't hit what you're aiming at.

Owen



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