[ntp:questions] frequency adjusting only

Unruh unruh-spam at physics.ubc.ca
Tue Apr 22 16:04:15 UTC 2008


m.louvel at gmail.com (maxime louvel) writes:

>On Tue, Apr 22, 2008 at 2:42 PM, Steve Kostecke <kostecke at ntp.org> wrote:

>> On 2008-04-22, maxime louvel <m.louvel at gmail.com> wrote:
>>
>> > My goal is to achieve a synchronisation between the nodes (not
>> > with the public NTP server) within 50 usec.
>>
>> You may want to explore other synchronization options such as IRIG,
>> distributed PPS, or a distributed 10MHz clock.


>Thanks I'm gonna look at some other synchronisation solution.

>>
>>
>> >I don't care if the synchronisation to the public NTP is accurate
>> >around half a second.
>>
>> You're displaying a common misconception about NTP.
>>
>> The goal of NTP is not explictly to synchronize clocks to "the one
>> true time". Rather, NTP synchronizes clocks to a common time base. A
>> "better" time base, and a "better" distribution method, allows tighter
>> synchronization between nodes.
>>
>> It so happens that UTC (via GPS or HF Radio or UDP) is a ubiquitous,
>> stable, and relatively inexpensive time base. A side effect of using UTC
>> as your time base is that your clocks are synchronized to the correct
>> time.


>Sorry I haven't express myself correctly. What I meant is that I want an
>accuracy of 50 usec within my subnet and I want my whole subnet to be
>synchronised to UTC with an accuracy of 1 second or less if possible.


He is saying that ntp is designed to do the former, and if you include an
external reference you get the latter for free. How badly overloaded are
your switches?


>>
>>
>> --
>> Steve Kostecke <kostecke at ntp.org>
>> NTP Public Services Project - http://support.ntp.org/
>>
>> _______________________________________________
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>> https://lists.ntp.org/mailman/listinfo/questions
>>



>-- 
>Maxime Louvel
>0044 7964 5555 80
>43 Allen road
>Whitemore reans
>WV60AW Wolverhampton
>United Kingdom




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