[ntp:questions] Controlling the combine algorithm

David Woolley david at ex.djwhome.demon.invalid
Mon Jul 4 23:05:48 UTC 2011


Bottom quoting out of character:

I believe that this refers to the following article, in which the writer 
wants the "best" (by which he means something like lowest offset) 6 out 
of 15 servers to contribute to the final time correction.

I may have been responsible for wrongly suggesting maxclock, but not 
having it documented doesn't help in that respect.

 > Subject: Selection and Clustering of candidates
> Mischanko, Edward T wrote:
>> I choose to poll 15 servers on my network for time synchronization.  NTP
>> is selecting over 10 servers and clustering them.  Some of the servers
>> NTP selects have offsets that are higher than the majority; in other
>> words, they do not have the correct time.  Why are they being selected?
>> Why are so many being selected when I really want the best 5 or 6.
>> 
>> # Miscellaneous stuff
>> tinker allan 7
>> tos minclock 4 minsane 3
>> #
>> driftfile "C:\Program Files\NTP\etc\ntp.drift"
>> #
>> enable stats
>> statsdir "C:\Program Files\NTP\etc\"     # directory for statistics
>> files
>> statistics loopstats
>> filegen loopstats file loopstats type day link enable
>> #
>> #    Need to set up time sources...
>> #
>> #
>> server 000.000.102.1 minpoll 4 maxpoll 10
>> server 000.000.106.1 minpoll 4 maxpoll 10
>> server 000.000.109.1 minpoll 4 maxpoll 10
>> server 000.000.110.1 minpoll 4 maxpoll 10
>> server 000.000.112.1 minpoll 4 maxpoll 10
>> server 000.000.120.1 minpoll 4 maxpoll 10
>> server 000.000.121.1 minpoll 4 maxpoll 10
>> server 000.000.122.1 minpoll 4 maxpoll 10
>> server 000.000.123.1 minpoll 4 maxpoll 10
>> server 000.000.124.1 minpoll 4 maxpoll 10
>> server 000.000.125.1 minpoll 4 maxpoll 10
>> server 000.000.126.1 minpoll 4 maxpoll 10
>> server 000.000.129.1 minpoll 4 maxpoll 10
>> server 000.000.131.1 minpoll 4 maxpoll 10
>> server 000.000.134.1 minpoll 4 maxpoll 10




David L. Mills wrote:
> Steve,
> 
> There is something wrong with the nomenclature in your message. By 
> definition, the number of survivors is the number remaining after the 
> cluster algorithm has completedd. This number is three by default, but 
> can be changed using the minclock option. To reduce the numb er of 
> survivors below three is generally a bad idea, but as I said, the option 
> is available.
> 
> I don't understand what you mean by "it doesn't work". The maxclock 
> option does not do what you want. It is intended for automatic 
> configuration, where it specifies the maximum number of servers 
> remaining after the preempt phase. For configured associations, this 
> number is irrelevant.
> 
> Dave
> 
> Steve Kostecke wrote:
> 
>> On 2011-07-02, David L. Mills <mills at udel.edu> wrote:
>>
>>  
>>
>>> The combine algorithm operates on the survivors of the cluster 
>>> algorithm, as described on the "How NTP Works" page. The number of 
>>> survivors can be set using the minclock option. I'm not sure why you 
>>> want to do this, but the option is there.
>>>   
>>
>> Dave,
>>
>> I've been having a discussion with someone who wishes to configure a
>> large number of unicast time servers and restrict the number of
>> survivors to a number below the default. He was attempting to accomplish
>> this using maxclock option, but it did not work.
>>
>> Thanks,
>>
>>  
>>




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