[ntp:questions] ntpd wedged again

Richard B. Gilbert rgilbert88 at comcast.net
Wed Feb 15 01:55:12 UTC 2012


On 2/14/2012 1:43 AM, David J Taylor wrote:
> "A C" <agcarver+ntp at acarver.net> wrote in message
> news:4F398579.9060201 at acarver.net...
> []
>> I'm not sure it's a good idea either but I would really like to
>> understand why a refclock clamps the polling interval at such a low
>> value when nearly every bit of documentation says we should be kind to
>> NTP servers and make sure the polling period is allowed to reach 1024.
>
> If you look back in the archives of this newsgroup you will find that I
> asked David Mills a similar question, and he gave an answer. I'm not
> sure that I completely understood the answer, though.
>
> I now have lines like the following in my ntp.conf file for my stratum-1
> PCs:
>
> server 0.uk.pool.ntp.org minpoll 10
> server 1.uk.pool.ntp.org minpoll 10
> server 0.nl.pool.ntp.org minpoll 10
>
> As I have three PCs peered fed from different GPS receivers I'm hoping
> that the Internet servers are never needed. <G>
>
> Cheers,
> David

The problem with THREE GPS receivers, or just about any other clock, is 
that it it can too easily degenerate to the two server case.  It is well 
known that "a man with two clocks can never be certain what time it is."

Four, five, and seven are the magic numbers for a robust configuration.
Most sites will settle for four.  The very paranoid or the very rich 
might go for seven.




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