From: Miroslav Lichvar Date: Tue, 5 Dec 2023 12:54:44 +0000 (+0100) Subject: doc: update FAQ on improving accuracy X-Git-Tag: 4.5~1 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=598b893e1d0a9a8ac362080e3497ac14e9b64c7d;p=thirdparty%2Fchrony.git doc: update FAQ on improving accuracy --- diff --git a/doc/faq.adoc b/doc/faq.adoc index 32210c74..06eaabcd 100644 --- a/doc/faq.adoc +++ b/doc/faq.adoc @@ -381,7 +381,7 @@ outliers corrupting the minimum delay. For example: server ntp.local minpoll -7 maxpoll -7 filter 31 maxdelayquant 0.3 xleave ---- -As an experimental feature added in version 4.2, `chronyd` supports an NTPv4 +Since version 4.2, `chronyd` supports an NTPv4 extension field containing an additional timestamp to enable frequency transfer and significantly improve stability of synchronisation. It can be enabled by the `extfield F323` option. For example: @@ -390,6 +390,18 @@ the `extfield F323` option. For example: server ntp.local minpoll 0 maxpoll 0 xleave extfield F323 ---- +Since version 4.5, `chronyd` can apply corrections from PTP one-step end-to-end +transparent clocks (e.g. network switches) to significantly improve accuracy of +synchronisation in local networks. It requires the PTP transport to be enabled +by the `ptpport` directive, HW timestamping, and the `extfield F324` option. +For example: + +---- +server ntp.local minpoll -4 maxpoll -4 xleave extfield F323 extfield F324 port 319 +ptpport 319 +hwtimestamp eth0 minpoll -4 +---- + === Does `chronyd` have an ntpdate mode? Yes. With the `-q` option `chronyd` will set the system clock once and exit.