[ntp:questions] client configuration: it's sufficient 3 servers ?
snews at lordynet.org
Fri May 24 16:44:48 UTC 2013
Richard B. Gilbert wrote:
> 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
>>> 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.
> 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!
A bit like my GPS receiver that mostly gives offset << 0.010 ms
currently 0.001 ms.
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