[ntp:questions] Query about NTP accuracy

smithmikek at googlemail.com smithmikek at googlemail.com
Tue Jun 2 05:56:42 UTC 2009


On Jun 1, 10:00 pm, David Woolley
<da... at ex.djwhome.demon.co.uk.invalid> wrote:
> Mike K Smith wrote:
>
> > I thought a falseticker's dispersion had to have no overlap with the
> > other clocks - like this:
>
> You can have cliques of false tickers.
Yes, but we are discussing whether or not two truechimers will always
outvote one falseticker.
In the case below, will server 3 be treated as a falseticker because
its offset lies outside the dispersion interval of the other two
servers even though there is some intersection between its dispersion
and that of server 2.
1
          |--------+--------|
2
              |----------+----------|
3                              |------------+------------|

>
>
>
> > 1
> >           |--------+--------|
> > 2
> >               |----------+----------|
> > 3                                          |------------+------------|
>
> > Surely in this case either 1 or 2 would be selected and 3 flagged as
> > falseticker.
>
> Both 1 and 2 would be selected, although only one of them would be used
> to determine the stratum and downstream quality parameters.  Both will
> be used to estimate the time.
I mean selected as the system peer, sorry for the imprecise language.
So in this case two truechimers would definitely outvote one
flseticker.

Brian Utterback I would hugely appreciate your comment on this. I want
to see if I have correctly understood the point you were making.

Mike




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