[ntp:questions] Re: minpoll and maxpoll

Richard B. Gilbert rgilbert88 at comcast.net
Tue Dec 21 21:16:40 UTC 2004


srui at fe.up.pt wrote:

>Dear NTP mailing list users,
>
>I am running a NTP server on an mobile network without regular Internet access
>and I use a GPS (which is always available) to correct the system clock through
>NTP. Sometimes the system has to be shutdown and the hardware clock just isn't
>good enough to keep time between power cycles. In a normal situation with a big
>clock skew the NTP daemon crashes, so I was told that using a low value for
>minpoll would solve this and it would be the correct equivalent to a forced
>initial correction. Is this true? What solutions do I have for this? 
>
>Sergio Rui Silva
>
>Citando "Richard B. Gilbert" <rgilbert88 at comcast.net>:
>
>  
>
>>Helmut Wollmersdorfer wrote:
>>
>>    
>>
>>>Yesterday I specified
>>>
>>>  minpoll 6 maxpoll 8
>>>
>>>for my local references, but no explicit values for the remote, public 
>>>timeservers in /etc/ntp.conf.
>>>
>>>Now, 11 hours after restart, the actual values for poll in
>>>
>>>  ntpq -p
>>>
>>>show no value higher than 256.
>>>
>>>As I remember poll went very fast to 1024 without any minpoll or 
>>>maxpoll in the config.
>>>
>>>As I do not want to produce to much traffic on public servers, shall I 
>>>specify something like
>>>
>>>  minpoll 8 maxpoll 10
>>>
>>>for them?
>>>
>>>Helmut Wollmersdorfer
>>>      
>>>
>>You should not specify either minpoll or maxpoll without very good 
>>reason!  Minpoll defaults to 6 and maxpoll to 10 giving a range from 64 
>>seconds to 1024 seconds.  The daemon will adjust the polling interval 
>>within this range as needed.  The longer polling intervals are needed to 
>>let the code "fine tune" your clock.
>>_______________________________________________
>>questions mailing list
>>questions at lists.ntp.isc.org
>>https://lists.ntp.isc.org/mailman/listinfo/questions
>>
>>    
>>
>
>
>
>
>----- Finalizar mensagem reenviada -----
>
>
>
>  
>
If you start ntpd with the -g option it will make a single "step" 
correction if needed.  If the error is really large (> 600 seconds) it's 
best to set the clock by hand from your wrist watch or cellular phone 
before starting ntpd.

Setting minpoll or maxpoll will not affect the behavior of ntpd when it 
is started with a large error in the local clock; without the - g option 
the daemon will crash if the error exceeds the panic threshold. 

In general, setting either minpoll or maxpoll is not a good idea.



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