Re: [gpsd-dev] Final revisions to the Time Service HOWTO

[Miroslav Lichvar]

On Thu, Nov 21, 2013 at 11:58:29PM -0500, Eric S. Raymond wrote:
> Miroslav Lichvar <address@hidden>:
> So here's what I'm going to do:
> 
>     Both ntpd and chrony use this technique (ntpd also uses a more
>     esoteric form of estimation called a "PLL/FLL hybrid loop").  Both NTP
>     implementations automatically adjust the value of the polling interval
>     to get the best results.  That turns into the N above.
> 
> This preserves the reader's (justified) sense of having gained some
> understanding of drift compensation and saves us from having to
> explain a lot of implementation-specific details about the differences
> in what ntpd and chrony are doing.

Well, I think that could be misleading as PLL/FLL doesn't use linear
fit.

> > With reference clocks, however, the polling interval in ntpd is fixed
> > by default to 64 seconds (minpoll 6 maxpoll 6) and chronyd uses always
> > constant polling interval, 16 seconds by default (poll 4).
> 
> Thanks for being excruciatingly cirrect about this. It's too much detail
> for the HOWTO.

The text explains how the polling interval is adjusted, but normally
with reference clock (i.e. with gpsd) the interval is fixed. I'd suggest
to mention that, so users are not confused when they don't see any
adjustments in the interval.

-- 
Miroslav Lichvar