[ntp:questions] client configuration: it's sufficient 3 servers ?

Richard B. Gilbert rgilbert88 at comcast.net
Fri May 24 16:05:26 UTC 2013

On 5/24/2013 5:56 AM, David Lord wrote:
> Riccardo Castellani wrote:
>> If I have 3 internal NTP servers, what do you think if my clients have
>> all these 3 servers in their configuration ?
>> According to '5.3.2. Why should I have more than one clock?' in
>> 'http://www.ntp.org/ntpfaq/NTP-s-algo-real.htm#Q-NTP-ALGO
>> I read 2 servers, it's worst case, but also 3...
> My four pool servers each have 5 x internet sources
> (= 20 different internet sources) and 2 x local peers,
> there are also local sources with MSF and GPS.
> There is an explanation of the selection algorithm in
> the ntpd documentation as to why having only 2 and 3
> sources can give problems. That sets 4 as minimum and
> 5 for safety.
> I've had internet outages where half the sources have
> become unreachable.
> David

The internet is far from the best source of time!  A lot of time is
spent trying to make sense of all the noise!

A gadget whose name I can't remember will lock onto three earth 
satellites and give you time to plus/minus 50 nano seconds.  Very few
people need to slice time that fine!

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