NTPsec

sam.ljay.org.uk

Report generated: Sun Feb 1 17:00:02 2026 UTC
Start Time: Sat Jan 31 08:00:02 2026 UTC
End Time: Sun Feb 1 17:00:02 2026 UTC
Report Period: 1.4 days

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Local Clock Time/Frequency Offsets

local offset plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Time Offset -41.875 -30.991 -20.390 1.804 24.205 34.136 45.458 44.595 65.127 12.601 1.377 µs -3.246 8.781
Local Clock Frequency Offset 12.186 12.189 12.202 12.289 12.371 12.376 12.380 0.169 0.187 0.054 12.283 ppm 1.171e+07 2.66e+09

The time and frequency offsets between the ntpd calculated time and the local system clock. Showing frequency offset (red, in parts per million, scale on right) and the time offset (blue, in μs, scale on left). Quick changes in time offset will lead to larger frequency offsets.

These are fields 3 (time) and 4 (frequency) from the loopstats log file.



Local RMS Time Jitter

local jitter plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local RMS Time Jitter 0.326 0.387 0.897 10.672 18.192 20.860 23.398 17.295 20.473 5.105 10.255 µs 3.88 8.806

The RMS Jitter of the local clock offset. In other words, how fast the local clock offset is changing.

Lower is better. An ideal system would be a horizontal line at 0μs.

RMS jitter is field 5 in the loopstats log file.



Local RMS Frequency Jitter

local stability plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local RMS Frequency Jitter 0.032 0.055 0.233 0.722 1.215 1.527 1.722 0.982 1.472 0.313 0.709 ppb 5.989 15.87

The RMS Frequency Jitter (aka wander) of the local clock's frequency. In other words, how fast the local clock changes frequency.

Lower is better. An ideal clock would be a horizontal line at 0ppm.

RMS Frequency Jitter is field 6 in the loopstats log file.



Local Clock Time Offset Histogram

local offset histogram plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Offset -41.875 -30.991 -20.390 1.804 24.205 34.136 45.458 44.595 65.127 12.601 1.377 µs -3.246 8.781

The clock offsets of the local clock as a histogram.

The Local Clock Offset is field 3 from the loopstats log file.



Local Temperatures

local temps plot

Local temperatures. These will be site-specific depending upon what temperature sensors you collect data from. Temperature changes affect the local clock crystal frequency and stability. The math of how temperature changes frequency is complex, and also depends on crystal aging. So there is no easy way to correct for it in software. This is the single most important component of frequency drift.

The Local Temperatures are from field 3 from the tempstats log file.



Local Frequency/Temp

local freq temps plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Frequency Offset 12.186 12.189 12.202 12.289 12.371 12.376 12.380 0.169 0.187 0.054 12.283 ppm 1.171e+07 2.66e+09
Temp LM0 38.000 38.000 38.000 38.000 39.000 39.000 39.000 1.000 1.000 0.496 38.438 °C
Temp LM1 16.000 17.000 17.000 19.000 21.000 22.000 24.000 4.000 5.000 1.339 19.438 °C
Temp LM2 30.000 30.000 31.000 31.000 32.000 32.000 34.000 1.000 2.000 0.556 31.297 °C
Temp LM3 31.000 31.000 31.000 32.000 32.000 32.000 34.000 1.000 1.000 0.330 31.932 °C
Temp LM4 30.000 30.000 30.000 31.000 32.000 32.000 34.000 2.000 2.000 0.568 30.851 °C
Temp LM5 27.800 27.800 27.800 27.800 27.800 27.800 27.800 0.000 0.000 0.000 27.800 °C
Temp LM6 29.800 29.800 29.800 29.800 29.800 29.800 29.800 0.000 0.000 0.000 29.800 °C
Temp LM7 28.000 28.000 29.000 31.000 32.000 33.000 34.000 3.000 5.000 1.103 30.607 °C
Temp LM8 28.000 28.000 29.000 31.000 32.000 33.000 34.000 3.000 5.000 1.101 30.599 °C
Temp LM9 25.000 26.000 26.000 28.000 30.000 31.000 33.000 4.000 5.000 1.081 28.025 °C
Temp ZONE0 29.800 29.800 29.800 29.800 29.800 29.800 29.800 0.000 0.000 0.000 29.800 °C
Temp ZONE1 28.000 28.000 29.000 31.000 32.000 33.000 34.000 3.000 5.000 1.040 30.499 °C
Temp ZONE2 27.800 27.800 27.800 27.800 27.800 27.800 27.800 0.000 0.000 0.000 27.800 °C

The frequency offsets and temperatures. Showing frequency offset (red, in parts per million, scale on right) and the temperatures.

These are field 4 (frequency) from the loopstats log file, and field 3 from the tempstats log file.



Local GPS

local gps plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
nSats 5.000 5.000 7.000 8.000 10.000 10.000 11.000 3.000 5.000 1.012 8.217 nSat 382.5 2876
TDOP 0.520 0.580 0.640 0.950 1.760 2.960 6.500 1.120 2.380 0.499 1.052 10.06 81.95

Local GPS. The Time Dilution of Precision (TDOP) is plotted in blue. The number of visible satellites (nSat) is plotted in red.

TDOP is field 3, and nSats is field 4, from the gpsd log file. The gpsd log file is created by the ntploggps program.

TDOP is a dimensionless error factor. Smaller numbers are better. TDOP ranges from 1 (ideal), 2 to 5 (good), to greater than 20 (poor). Some GNSS receivers report TDOP less than one which is theoretically impossible.



Server Offsets

peer offsets plot

The offset of all refclocks and servers. This can be useful to see if offset changes are happening in a single clock or all clocks together.

Clock Offset is field 5 in the peerstats log file.



Refclock Offset 127.127.28.0 SHM(0)

peer offset 127.127.28.0 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Refclock Offset 127.127.28.0 SHM(0) -697.561 -679.323 -664.342 -626.681 -584.858 -567.832 -552.528 79.483 111.491 23.972 -625.651 ms -1.998e+04 5.437e+05

The offset of a local refclock in seconds. This is useful to see how the measured offset is behaving.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local serial GPS 200 ms; local PPS 20µs.

Clock Offset is field 5 in the peerstats log file.



Refclock Offset 127.127.28.1 SHM(1)

peer offset 127.127.28.1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Refclock Offset 127.127.28.1 SHM(1) -41.876 -30.992 -20.391 1.805 24.206 34.137 45.459 44.597 65.129 12.601 1.377 µs -3.246 8.781

The offset of a local refclock in seconds. This is useful to see how the measured offset is behaving.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local serial GPS 200 ms; local PPS 20µs.

Clock Offset is field 5 in the peerstats log file.



Server Offset 139.143.5.31

peer offset 139.143.5.31 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 139.143.5.31 115.655 135.670 198.613 547.769 631.100 747.568 815.868 432.487 611.898 118.181 520.822 µs 47.96 186.1

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset 193.67.79.202

peer offset 193.67.79.202 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 193.67.79.202 -164.367 -118.246 -43.546 298.126 422.920 514.737 552.615 466.466 632.983 123.098 272.921 µs 3.914 9.383

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset 2001:8b0:0:23::205 (ntp2.aa.net.uk)

peer offset 2001:8b0:0:23::205 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2001:8b0:0:23::205 (ntp2.aa.net.uk) 102.915 177.406 262.293 590.824 719.583 820.984 888.624 457.290 643.578 124.037 571.427 µs 56.37 233

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset 81.187.26.174

peer offset 81.187.26.174 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 81.187.26.174 -276.082 -257.495 -206.465 150.961 249.021 338.597 370.254 455.486 596.092 120.448 123.057 µs -1.661 5.857

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Jitters

peer jitters plot

The RMS Jitter of all refclocks and servers. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Refclock RMS Jitter 127.127.28.0 SHM(0)

peer jitter 127.127.28.0 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Refclock RMS Jitter 127.127.28.0 SHM(0) 1.204 2.415 4.177 12.069 26.218 33.642 50.013 22.041 31.227 6.658 13.151 ms 4.929 15.5

The RMS Jitter of a local refclock. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Refclock RMS Jitter 127.127.28.1 SHM(1)

peer jitter 127.127.28.1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Refclock RMS Jitter 127.127.28.1 SHM(1) 0.119 0.279 0.552 11.000 29.591 38.748 62.630 29.039 38.469 9.319 11.990 µs 1.755 5.269

The RMS Jitter of a local refclock. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 139.143.5.31

peer jitter 139.143.5.31 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 139.143.5.31 0.011 0.017 0.022 0.058 0.450 16.352 33.990 0.427 16.335 3.167 0.573 ms 5.631 61.53

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 193.67.79.202

peer jitter 193.67.79.202 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 193.67.79.202 0.013 0.017 0.025 0.067 0.479 20.048 22.266 0.454 20.031 2.823 0.584 ms 3.576 28.59

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 2001:8b0:0:23::205 (ntp2.aa.net.uk)

peer jitter 2001:8b0:0:23::205 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2001:8b0:0:23::205 (ntp2.aa.net.uk) 0.011 0.016 0.022 0.058 0.400 8.437 51.578 0.377 8.421 3.606 0.427 ms 9.638 138.8

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 81.187.26.174

peer jitter 81.187.26.174 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 81.187.26.174 0.011 0.017 0.024 0.065 0.426 34.517 52.322 0.402 34.500 5.730 1.011 ms 4.005 36.43

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Summary


Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Frequency Offset 12.186 12.189 12.202 12.289 12.371 12.376 12.380 0.169 0.187 0.054 12.283 ppm 1.171e+07 2.66e+09
Local Clock Time Offset -41.875 -30.991 -20.390 1.804 24.205 34.136 45.458 44.595 65.127 12.601 1.377 µs -3.246 8.781
Local RMS Frequency Jitter 0.032 0.055 0.233 0.722 1.215 1.527 1.722 0.982 1.472 0.313 0.709 ppb 5.989 15.87
Local RMS Time Jitter 0.326 0.387 0.897 10.672 18.192 20.860 23.398 17.295 20.473 5.105 10.255 µs 3.88 8.806
Refclock Offset 127.127.28.0 SHM(0) -697.561 -679.323 -664.342 -626.681 -584.858 -567.832 -552.528 79.483 111.491 23.972 -625.651 ms -1.998e+04 5.437e+05
Refclock Offset 127.127.28.1 SHM(1) -41.876 -30.992 -20.391 1.805 24.206 34.137 45.459 44.597 65.129 12.601 1.377 µs -3.246 8.781
Refclock RMS Jitter 127.127.28.0 SHM(0) 1.204 2.415 4.177 12.069 26.218 33.642 50.013 22.041 31.227 6.658 13.151 ms 4.929 15.5
Refclock RMS Jitter 127.127.28.1 SHM(1) 0.119 0.279 0.552 11.000 29.591 38.748 62.630 29.039 38.469 9.319 11.990 µs 1.755 5.269
Server Jitter 139.143.5.31 0.011 0.017 0.022 0.058 0.450 16.352 33.990 0.427 16.335 3.167 0.573 ms 5.631 61.53
Server Jitter 193.67.79.202 0.013 0.017 0.025 0.067 0.479 20.048 22.266 0.454 20.031 2.823 0.584 ms 3.576 28.59
Server Jitter 2001:8b0:0:23::205 (ntp2.aa.net.uk) 0.011 0.016 0.022 0.058 0.400 8.437 51.578 0.377 8.421 3.606 0.427 ms 9.638 138.8
Server Jitter 81.187.26.174 0.011 0.017 0.024 0.065 0.426 34.517 52.322 0.402 34.500 5.730 1.011 ms 4.005 36.43
Server Offset 139.143.5.31 115.655 135.670 198.613 547.769 631.100 747.568 815.868 432.487 611.898 118.181 520.822 µs 47.96 186.1
Server Offset 193.67.79.202 -164.367 -118.246 -43.546 298.126 422.920 514.737 552.615 466.466 632.983 123.098 272.921 µs 3.914 9.383
Server Offset 2001:8b0:0:23::205 (ntp2.aa.net.uk) 102.915 177.406 262.293 590.824 719.583 820.984 888.624 457.290 643.578 124.037 571.427 µs 56.37 233
Server Offset 81.187.26.174 -276.082 -257.495 -206.465 150.961 249.021 338.597 370.254 455.486 596.092 120.448 123.057 µs -1.661 5.857
TDOP 0.520 0.580 0.640 0.950 1.760 2.960 6.500 1.120 2.380 0.499 1.052 10.06 81.95
Temp LM0 38.000 38.000 38.000 38.000 39.000 39.000 39.000 1.000 1.000 0.496 38.438 °C
Temp LM1 16.000 17.000 17.000 19.000 21.000 22.000 24.000 4.000 5.000 1.339 19.438 °C
Temp LM2 30.000 30.000 31.000 31.000 32.000 32.000 34.000 1.000 2.000 0.556 31.297 °C
Temp LM3 31.000 31.000 31.000 32.000 32.000 32.000 34.000 1.000 1.000 0.330 31.932 °C
Temp LM4 30.000 30.000 30.000 31.000 32.000 32.000 34.000 2.000 2.000 0.568 30.851 °C
Temp LM5 27.800 27.800 27.800 27.800 27.800 27.800 27.800 0.000 0.000 0.000 27.800 °C
Temp LM6 29.800 29.800 29.800 29.800 29.800 29.800 29.800 0.000 0.000 0.000 29.800 °C
Temp LM7 28.000 28.000 29.000 31.000 32.000 33.000 34.000 3.000 5.000 1.103 30.607 °C
Temp LM8 28.000 28.000 29.000 31.000 32.000 33.000 34.000 3.000 5.000 1.101 30.599 °C
Temp LM9 25.000 26.000 26.000 28.000 30.000 31.000 33.000 4.000 5.000 1.081 28.025 °C
Temp ZONE0 29.800 29.800 29.800 29.800 29.800 29.800 29.800 0.000 0.000 0.000 29.800 °C
Temp ZONE1 28.000 28.000 29.000 31.000 32.000 33.000 34.000 3.000 5.000 1.040 30.499 °C
Temp ZONE2 27.800 27.800 27.800 27.800 27.800 27.800 27.800 0.000 0.000 0.000 27.800 °C
nSats 5.000 5.000 7.000 8.000 10.000 10.000 11.000 3.000 5.000 1.012 8.217 nSat 382.5 2876
Summary as CSV file


Glossary:

frequency offset:
The difference between the ntpd calculated frequency and the local system clock frequency (usually in parts per million, ppm)
jitter, dispersion:
The short term change in a value. NTP measures Local Time Jitter, Refclock Jitter, and Server Jitter in seconds. Local Frequency Jitter is in ppm or ppb.
kurtosis, Kurt:
The kurtosis of a random variable X is the fourth standardized moment and is a dimension-less ratio. ntpviz uses the Pearson's moment coefficient of kurtosis. A normal distribution has a kurtosis of three. NIST describes a kurtosis over three as "heavy tailed" and one under three as "light tailed".
ms, millisecond:
One thousandth of a second = 0.001 seconds, 1e-3 seconds
mu, mean:
The arithmetic mean: the sum of all the values divided by the number of values. The formula for mu is: "mu = (∑xi) / N". Where xi denotes the data points and N is the number of data points.
ns, nanosecond:
One billionth of a second, also one thousandth of a microsecond, 0.000000001 seconds and 1e-9 seconds.
percentile:
The value below which a given percentage of values fall.
ppb, parts per billion:
Ratio between two values. These following are all the same: 1 ppb, one in one billion, 1/1,000,000,000, 0.000,000,001, 1e-9 and 0.000,000,1%
ppm, parts per million:
Ratio between two values. These following are all the same: 1 ppm, one in one million, 1/1,000,000, 0.000,001, and 0.000,1%
‰, parts per thousand:
Ratio between two values. These following are all the same: 1 ‰. one in one thousand, 1/1,000, 0.001, and 0.1%
refclock:
Reference clock, a local GPS module or other local source of time.
remote clock:
Any clock reached over the network, LAN or WAN. Also called a peer or server.
time offset:
The difference between the ntpd calculated time and the local system clock's time. Also called phase offset.
σ, sigma:
Sigma denotes the standard deviation (SD) and is centered on the arithmetic mean of the data set. The SD is simply the square root of the variance of the data set. Two sigma is simply twice the standard deviation. Three sigma is three times sigma. Smaller is better.
The formula for sigma is: "σ = √[ ∑(xi-mu)^2 / N ]". Where xi denotes the data points and N is the number of data points.
skewness, Skew:
The skewness of a random variable X is the third standardized moment and is a dimension-less ratio. ntpviz uses the Pearson's moment coefficient of skewness. Wikipedia describes it best: "The qualitative interpretation of the skew is complicated and unintuitive."
A normal distribution has a skewness of zero.
upstream clock:
Any server or reference clock used as a source of time.
µs, us, microsecond:
One millionth of a second, also one thousandth of a millisecond, 0.000,001 seconds, and 1e-6 seconds.



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