DWS/chrony
1
0
Fork 0
mirror of https://gitlab.com/chrony/chrony.git synced 2025-12-07 07:45:06 -05:00
Code Issues Packages Projects Releases Wiki Activity

ntp: add maxdelayquant option

Browse Source 
Add a new test for maximum delay using a long-term estimate of a
p-quantile of the peer delay. If enabled, it replaces the
maxdelaydevratio test. It's main advantage is that it is not sensitive
to outliers corrupting the minimum delay.

As it can take a large number of samples for the estimate to reach the
expected value and adapt to a new value after a network change, the
option is recommended only for local networks with very short polling
intervals.
This commit is contained in:
Miroslav Lichvar
2022-07-21 15:16:47 +02:00
parent 851c823b42
commit 070b4f69d0
12 changed files with 94 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
doc/chrony.conf.adoc
View File

@@ -151,6 +151,20 @@ If a measurement has a ratio of the increase in the round-trip delay from the
minimum delay amongst the previous measurements to the standard deviation of
the previous measurements that is greater than the specified ratio, it will be
rejected. The default is 10.0.
*maxdelayquant* _p_:::
This option disables the *maxdelaydevratio* test and specifies the maximum
acceptable delay as a quantile of the round-trip delay instead of a function of
the minimum delay amongst the buffered measurements. If a measurement has a
round-trip delay that is greater than a long-term estimate of the _p_-quantile,
it will be rejected.
+
The specified _p_ value should be between 0.05 and 0.95. For example,
*maxdelayquant 0.2* would indicate that only measurements with the lowest 20
percent of round-trip delays should be accepted. Note that it can take many
measurements for the estimated quantile to reach the expected value. This
option is intended for synchronisation in mostly static local networks with
very short polling intervals and possibly combined with the *filter* option.
By default, this test is disabled in favour of the *maxdelaydevratio* test.
*mindelay* _delay_:::
This option specifies a fixed minimum round-trip delay to be used instead of
the minimum amongst the previous measurements. This can be useful in networks
@@ -2070,8 +2084,8 @@ from the example line above):
. Stratum of remote computer. [2]
. RFC 5905 tests 1 through 3 (1=pass, 0=fail) [111]
. RFC 5905 tests 5 through 7 (1=pass, 0=fail) [111]
. Tests for maximum delay, maximum delay ratio and maximum delay dev ratio,
against defined parameters, and a test for synchronisation loop (1=pass,
. Results of the *maxdelay*, *maxdelayratio*, and *maxdelaydevratio* (or
*maxdelayquant*) tests, and a test for synchronisation loop (1=pass,
0=fail). The first test from these four also checks the server precision,
response time, and whether an interleaved response is acceptable for
synchronisation. [1111]

3
doc/chronyc.adoc
View File

@@ -699,7 +699,8 @@ packets sent to the source is more variable than the delay of packets sent
from the source back.
*NTP tests*:::
Results of RFC 5905 tests 1 through 3, 5 through 7, and tests for maximum
delay, delay ratio, delay dev ratio, and synchronisation loop.
delay, delay ratio, delay dev ratio (or delay quantile), and synchronisation
loop.
*Interleaved*:::
This shows if the response was in the interleaved mode.
*Authenticated*:::