[ntp:questions] Using ATOM with any system peer

A C agcarver+ntp at acarver.net
Mon Mar 26 21:49:30 UTC 2012

On 3/26/2012 14:18, E-Mail Sent to this address will be added to the 
BlackLists wrote:
> A C wrote:
>> Would it be possible to modify the ATOM driver such that
>>   it will be activated when a system peer is selected
> Doesn't it already do something like that?
> <http://www.eecis.udel.edu/~mills/ntp/html/drivers/driver22.html>
> <BlockQuote>
> This driver is enabled only under one of two conditions
>      (a) a prefer peer other than this driver is among the
>           survivors of the mitigation algorithms
>   or (b) there are no survivors and the minsane option
>           of the tos command is 0.
>   The prefer peer designates another source that can reliably
>     number the seconds when available.
>    However, if no sources are available,
>     the system clock continues to be disciplined
>     by the PPS driver on an indefinite basis.
> </BlockQuote>

It appears that my copy of 4.2.7p259 does not.  I had to restart because 
of the race condition I mentioned in my original email so I went ahead 
and removed all the prefer keywords.  Upon restarting, ntpd has selected 
a system peer but almost immediately marked ATOM as a false ticker ('x' 
tally code) and has ignored it completely even though the offset is 
about 1 ms (drifts dependent on the internet servers) and jitter is 
0.061ms.  When there is a preferred peer, the behavior is completely 
different.  In that case, ATOM is not selected at all until the prefer 
peer has been reached four times and then, if all the offsets look good, 
ATOM is enabled and starts working as expected.

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