[ntp:questions] how long does it take ntpd to sync up

Chris Albertson albertson.chris at gmail.com
Sat Aug 27 20:33:04 UTC 2011


On Sat, Aug 27, 2011 at 12:33 PM, unruh <unruh at wormhole.physics.ubc.ca>wrote:

>
> Ah yes, but why a) would you want to only adjust it that way, an b) why
> not do a fit and figure outexactly what the rate of the clock is and how
> far out it is, and correct that, rather then simply


I said the time required to set the clock's speed to within one second per
day if you can detect only one second error is one day.   This exactly
matches what you propose above.

Your fist step is "figure outexactly what the rate of the clock is"   How
can you measure the clock's rate to a precision of one second per day unless
you wait one day or can read the time to less than than one second?     So
my 24 hour estimate of the time required to wait uses your method and
assumes you do it perfectly, without error.

Yes NTP will "jump" the clock if the error is over 125 mS but in this
context 125Ms error is  "way huge".  It is at least two orders of magnitude
over what NTP can do even in a very simple setup.  Jumping like that would
only happen after along a period of being disconnected from a reference
clock.

-- 

Chris Albertson
Redondo Beach, California



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