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doc: update FAQ on improving accuracy

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Miroslav Lichvar 2023-12-05 13:54:44 +01:00
parent 89aa8fa342
commit 598b893e1d
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doc/faq.adoc
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@ -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.