NTPsec

sam.ljay.org.uk

Report generated: Wed Oct 15 11:00:03 2025 UTC
Start Time: Tue Oct 7 11:00:02 2025 UTC
End Time: Wed Oct 15 11:00:02 2025 UTC
Report Period: 8.0 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 -50.261 -30.834 -21.072 -1.740 19.017 30.453 54.098 40.089 61.287 11.572 -1.087 µs -4.442 12.45
Local Clock Frequency Offset 12.506 12.527 12.557 12.955 13.315 13.351 13.364 0.758 0.824 0.241 12.950 ppm 1.477e+05 7.811e+06

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 0.240 0.358 0.577 9.896 17.971 21.235 28.196 17.394 20.877 5.558 9.364 µs 2.344 5.116

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 0.077 0.113 0.174 0.651 1.127 1.495 2.139 0.953 1.382 0.301 0.642 ppb 5.327 15.15

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 -50.261 -30.834 -21.072 -1.740 19.017 30.453 54.098 40.089 61.287 11.572 -1.087 µs -4.442 12.45

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 12.506 12.527 12.557 12.955 13.315 13.351 13.364 0.758 0.824 0.241 12.950 ppm 1.477e+05 7.811e+06
Temp LM0 38.000 38.000 38.000 40.000 42.000 42.000 42.000 4.000 4.000 1.371 40.006 °C
Temp LM1 16.000 17.000 18.000 20.000 24.000 25.000 29.000 6.000 8.000 1.841 20.627 °C
Temp LM2 30.000 31.000 31.000 33.000 35.000 35.000 37.000 4.000 4.000 1.185 32.848 °C
Temp LM3 31.000 31.000 32.000 33.000 35.000 36.000 37.000 3.000 5.000 1.273 33.254 °C
Temp LM4 30.000 30.000 30.000 32.000 34.000 34.000 36.000 4.000 4.000 1.302 32.305 °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 27.000 29.000 29.000 32.000 34.000 35.000 38.000 5.000 6.000 1.618 31.742 °C
Temp LM8 27.000 29.000 29.000 32.000 34.000 35.000 38.000 5.000 6.000 1.615 31.748 °C
Temp LM9 25.000 26.000 27.000 29.000 32.000 33.000 36.000 5.000 7.000 1.640 29.267 °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 32.000 34.000 35.000 38.000 5.000 7.000 1.631 31.662 °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 6.000 7.000 9.000 10.000 11.000 11.000 3.000 5.000 0.978 8.541 nSat 485.5 3936
TDOP 0.540 0.580 0.630 0.890 1.490 2.640 4.390 0.860 2.060 0.383 0.978 12.15 69.56

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) -720.101 -683.093 -665.921 -623.525 -584.466 -567.796 -525.597 81.455 115.297 24.804 -623.735 ms -1.795e+04 4.714e+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) -50.262 -30.835 -21.073 -1.741 19.018 30.454 54.099 40.091 61.289 11.573 -1.087 µs -4.442 12.45

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 -153.360 39.463 248.235 432.742 637.769 710.568 1,666.470 389.534 671.105 121.378 430.756 µs 24.31 92.27

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 -490.557 -326.245 -98.458 67.708 293.242 658.912 911.807 391.700 985.157 138.154 78.929 µs -0.4677 8.849

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) -0.826 -0.247 0.080 0.603 1.113 1.477 1.744 1.034 1.725 0.319 0.608 ms 3.22 9.325

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 -554.367 -450.215 -233.497 -43.172 158.604 227.195 399.805 392.101 677.410 120.381 -46.902 µs -7.455 24.27

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) 0.817 2.637 4.602 12.549 27.464 36.195 61.961 22.862 33.558 7.098 13.839 ms 4.835 15.41

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 0.253 0.517 9.826 28.399 37.311 63.589 27.882 37.058 9.243 10.848 µs 1.493 4.823

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 0.000 0.014 0.024 0.078 1.418 3.795 37.603 1.395 3.781 1.820 0.375 ms 12.49 239.1

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 0.000 0.018 0.026 0.071 0.252 0.441 30.925 0.226 0.423 1.317 0.168 ms 17.77 408.9

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) 0.000 0.014 0.023 0.066 0.236 0.446 25.403 0.213 0.432 1.145 0.149 ms 16.88 355

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 0.000 0.017 0.024 0.069 0.315 0.504 39.417 0.291 0.488 1.790 0.209 ms 15.36 319.7

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 12.506 12.527 12.557 12.955 13.315 13.351 13.364 0.758 0.824 0.241 12.950 ppm 1.477e+05 7.811e+06
Local Clock Time Offset -50.261 -30.834 -21.072 -1.740 19.017 30.453 54.098 40.089 61.287 11.572 -1.087 µs -4.442 12.45
Local RMS Frequency Jitter 0.077 0.113 0.174 0.651 1.127 1.495 2.139 0.953 1.382 0.301 0.642 ppb 5.327 15.15
Local RMS Time Jitter 0.240 0.358 0.577 9.896 17.971 21.235 28.196 17.394 20.877 5.558 9.364 µs 2.344 5.116
Refclock Offset 127.127.28.0 SHM(0) -720.101 -683.093 -665.921 -623.525 -584.466 -567.796 -525.597 81.455 115.297 24.804 -623.735 ms -1.795e+04 4.714e+05
Refclock Offset 127.127.28.1 SHM(1) -50.262 -30.835 -21.073 -1.741 19.018 30.454 54.099 40.091 61.289 11.573 -1.087 µs -4.442 12.45
Refclock RMS Jitter 127.127.28.0 SHM(0) 0.817 2.637 4.602 12.549 27.464 36.195 61.961 22.862 33.558 7.098 13.839 ms 4.835 15.41
Refclock RMS Jitter 127.127.28.1 SHM(1) 0.119 0.253 0.517 9.826 28.399 37.311 63.589 27.882 37.058 9.243 10.848 µs 1.493 4.823
Server Jitter 139.143.5.31 0.000 0.014 0.024 0.078 1.418 3.795 37.603 1.395 3.781 1.820 0.375 ms 12.49 239.1
Server Jitter 193.67.79.202 0.000 0.018 0.026 0.071 0.252 0.441 30.925 0.226 0.423 1.317 0.168 ms 17.77 408.9
Server Jitter 2001:8b0:0:23::205 (ntp2.aa.net.uk) 0.000 0.014 0.023 0.066 0.236 0.446 25.403 0.213 0.432 1.145 0.149 ms 16.88 355
Server Jitter 81.187.26.174 0.000 0.017 0.024 0.069 0.315 0.504 39.417 0.291 0.488 1.790 0.209 ms 15.36 319.7
Server Offset 139.143.5.31 -153.360 39.463 248.235 432.742 637.769 710.568 1,666.470 389.534 671.105 121.378 430.756 µs 24.31 92.27
Server Offset 193.67.79.202 -490.557 -326.245 -98.458 67.708 293.242 658.912 911.807 391.700 985.157 138.154 78.929 µs -0.4677 8.849
Server Offset 2001:8b0:0:23::205 (ntp2.aa.net.uk) -0.826 -0.247 0.080 0.603 1.113 1.477 1.744 1.034 1.725 0.319 0.608 ms 3.22 9.325
Server Offset 81.187.26.174 -554.367 -450.215 -233.497 -43.172 158.604 227.195 399.805 392.101 677.410 120.381 -46.902 µs -7.455 24.27
TDOP 0.540 0.580 0.630 0.890 1.490 2.640 4.390 0.860 2.060 0.383 0.978 12.15 69.56
Temp LM0 38.000 38.000 38.000 40.000 42.000 42.000 42.000 4.000 4.000 1.371 40.006 °C
Temp LM1 16.000 17.000 18.000 20.000 24.000 25.000 29.000 6.000 8.000 1.841 20.627 °C
Temp LM2 30.000 31.000 31.000 33.000 35.000 35.000 37.000 4.000 4.000 1.185 32.848 °C
Temp LM3 31.000 31.000 32.000 33.000 35.000 36.000 37.000 3.000 5.000 1.273 33.254 °C
Temp LM4 30.000 30.000 30.000 32.000 34.000 34.000 36.000 4.000 4.000 1.302 32.305 °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 27.000 29.000 29.000 32.000 34.000 35.000 38.000 5.000 6.000 1.618 31.742 °C
Temp LM8 27.000 29.000 29.000 32.000 34.000 35.000 38.000 5.000 6.000 1.615 31.748 °C
Temp LM9 25.000 26.000 27.000 29.000 32.000 33.000 36.000 5.000 7.000 1.640 29.267 °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 32.000 34.000 35.000 38.000 5.000 7.000 1.631 31.662 °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 6.000 7.000 9.000 10.000 11.000 11.000 3.000 5.000 0.978 8.541 nSat 485.5 3936
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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