[ntp:questions] Magice Server Numbers: 4,5,7,9

Danny Mayer mayer at ntp.org
Fri Sep 16 17:50:03 UTC 2011


What I said about marauding gangs of clock cliques still holds. Also the
last time I looked at the code the number 10 applied when you specified
pool and would only take the number of servers already specified plus
the number of pool servers needs to get to 10 if there were that many.


On 9/16/2011 10:12 AM, David L. Mills wrote:
> Danny,
> We would not be having this discussion if folks read "how NTP works" in
> the online documentation. The maximum number of selectable candidates is
> not limited to ten. Ten is the high water mark for the number of
> preemptable candidates mobilized by the manycast and pool modes.
> Dave
> Danny Mayer wrote:
>> On 9/16/2011 2:24 AM, unruh wrote:
>>>> 6.  Seven clocks allow for the failure of three.
>>>> Etc, etc. . . .
>>> The only answer is to have at least 10000000000001 clocks although that
>>> is also not foolproof:-) 
>> Actually no. If you get too many reference clocks they will start to
>> gang up against each other and it becomes impossibly complex to try and
>> decide which set to use. As the number of clocks increase the number of
>> gangs will likely increase. That's why the reference implementation
>> limits the number of reference clocks to 10.
>> Danny
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