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

unruh unruh at wormhole.physics.ubc.ca
Sat Aug 27 21:01:02 UTC 2011


On 2011-08-27, David J Taylor <david-taylor at blueyonder.co.uk.invalid> wrote:
>> I read somewhere that it takes an ntpd 24 hours to truly sync up to a 
>> stratum 2 master.
>>
>> Is this true?
>>
>> Thanks
>>
>> Chip
>
> Chip, it depends on the accuracy you need.  To get within some 
> milliseconds, perhaps a minute or less.  How accurate do you need, and 
> what is your connection to the server(s)?  You may be able to tune NTP to 
> meet your particular needs rather than relying on the out-of-the-box 
> configuration.

See the last two graphs on www.theory.physics.ubc.ca/chrony/chrony.html
which are the response of ntp to a rate change from about215PPM to
168PPM The "halving time" for the offset is about .04 days, which is
about 1 hr. Thus it depends on how far off you clock is. Also this graph
is for the poll interval of 16 sec. ( a gps receiver) For longer poll
intervals the time will be proportionately longer. 






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