[ntp:questions] What should the poll be for the shared memory driver (type 28)?

Steve Kostecke kostecke at ntp.org
Mon Jun 17 16:36:49 UTC 2013

On 2013-06-17, David Taylor <david-taylor at blueyonder.co.uk.invalid> wrote:

> another document I've seen suggests setting:
>    server minpoll 1 prefer
> and yet in the ntpq -p billboard the poll is shown as 8 seconds. 
> Loopstats are reported at 8 second intervals, and the poll interval is 
> shown as 3 (i.e. 8 seconds).

grepping the source tree is very informative...

According to ./ntpd/ntp_peer.c:

 * It is an error to set minpoll less than NTP_MINPOLL or to
 * set maxpoll greater than NTP_MAXPOLL. However, minpoll is
 * clamped not greater than NTP_MAXPOLL and maxpoll is clamped
 * not less than NTP_MINPOLL without complaint. Finally,
 * minpoll is clamped not greater than maxpoll.

And in ./include/ntp.h we find:

:#define NTP_MINPOLL     3       /* log2 min poll interval (8 s) */

Steve Kostecke <kostecke at ntp.org>
NTP Public Services Project - http://support.ntp.org/

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