[ntp:questions] NTP client configuration

Benjamin CABUT benjamin.cabut at rsacosmos.com
Thu Sep 27 18:59:38 UTC 2012


I don't car in my application to have the correct UTC time.

What I care is that all my computers share exactly the same time.
Our application is not connected to internet.
So only time I can use as a reference is local clock of one computer.

I can realy tell you that my client is not sync some times!
it happen in 2 ways:
-> when I start my computers, it need arround 5 minutes to be sync, it 
is a problem for me
-> when one computer has heavy operation to do, then ntp client desync

and I have offset that can be 2 seconds, and stay like this during 
sereval minutes.
so It realy need a long time to ntp client to detect the big desync.

I do not want to rewrite ntp.
ntpq gives the offset between clock of client and clock of server.

As you say the best way for me is that ntp is working perfectly, but it 
is not the case.
I don't know how to improve this by configuration.

So I was just wondering if I could get the offset in my software to 
solve my problem...


Le 27/09/2012 20:39, unruh a écrit :
> On 2012-09-27, Benjamin CABUT <benjamin.cabut at rsacosmos.com> wrote:
>> Hello,
>> We are using Meindberg NTP client and server.
>> Our configuration is:
>> - 1 Computer under windows that is server
>> server
> Why would you be using a windows machine as your server. Windows is not
> a great platform for time.
> And why in the worl would you have it be using the local refclock. That
> should never be used.  Where in the world is that computer getting its
> time from?
>> broadcast minpoll 4 maxpoll 4 iburst
>> disable auth
>> - several computer under linux + computers under windows, client of this
>> server:
>> server minpoll 4 maxpoll 4 iburst
>> broadcastclient
>> disable auth
>> My problem is the following:
>> Mainly on windows computer, sometime, depending what the computer is
>> doing, there is a big offset between clients and server.
>> ("Big" for me is more than 500ms).
>> I would like to know if it is possible to setup client so as soon as he
>> see offset>500ms, then client do a "fast" synch. (STEP).
> If ntpd sees an offset of 128ms and it believes this is a valid offset,
> it steps.
>> Another way to solve my problem could be for me, to modify the source
>> code of my application in order to get this "offset" information inside
>> my code (C or C++ langage). then I could add this offset to the time of
>> the computer in order to be as much accurate as possible during the time
>> the offset is bigger than 500ms.
> ntpd does its best to get a small offset. What makes yo uthing your C
> program can do better? You have other problems. Worry about them, not
> about rewriting ntpd.
>> Do you have any solution?
>> Regards.
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CABUT Benjamin
CEO - president
RSA Cosmos

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