NTPsec

sam.ljay.org.uk

Report generated: Tue Jul 1 17:00:02 2025 UTC
Start Time: Mon Jun 30 08:00:01 2025 UTC
End Time: Tue Jul 1 17:00:01 2025 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 -91.065 -71.902 -46.600 3.629 28.892 39.935 74.585 75.492 111.837 22.393 -1.258 µs -5.323 16.56
Local Clock Frequency Offset 13.441 13.447 13.474 13.718 13.849 13.858 13.869 0.375 0.411 0.120 13.683 ppm 1.455e+06 1.649e+08

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 0.283 0.341 1.029 10.822 17.591 19.979 24.186 16.562 19.638 4.898 10.214 µs 4.24 9.683

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 0.039 0.052 0.214 0.904 2.882 3.951 4.382 2.668 3.899 0.796 1.114 ppb 2.867 9.316

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 -91.065 -71.902 -46.600 3.629 28.892 39.935 74.585 75.492 111.837 22.393 -1.258 µs -5.323 16.56

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 13.441 13.447 13.474 13.718 13.849 13.858 13.869 0.375 0.411 0.120 13.683 ppm 1.455e+06 1.649e+08
Temp LM0 43.000 43.000 43.000 45.000 46.000 46.000 46.000 3.000 3.000 0.941 44.489 °C
Temp LM1 22.000 23.000 24.000 26.000 28.000 29.000 32.000 4.000 6.000 1.373 25.768 °C
Temp LM2 36.000 36.000 36.000 38.000 39.000 39.000 40.000 3.000 3.000 0.867 37.851 °C
Temp LM3 36.000 37.000 37.000 38.000 39.000 40.000 40.000 2.000 3.000 0.797 38.048 °C
Temp LM4 35.000 35.000 36.000 37.000 38.000 38.000 39.000 2.000 3.000 0.798 36.967 °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 33.000 34.000 35.000 37.000 38.000 40.000 42.000 3.000 6.000 1.276 36.720 °C
Temp LM8 33.000 34.000 35.000 37.000 39.000 40.000 42.000 4.000 6.000 1.290 36.741 °C
Temp LM9 31.000 32.000 32.000 34.000 35.000 36.000 38.000 3.000 4.000 0.952 33.831 °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 33.000 34.000 34.000 37.000 39.000 40.000 42.000 5.000 6.000 1.362 36.665 °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 6.000 6.000 7.000 9.000 10.000 10.000 11.000 3.000 4.000 0.945 8.634 nSat 562.3 4772
TDOP 0.550 0.600 0.630 0.910 1.480 1.570 1.670 0.850 0.970 0.234 0.945 38.01 153.8

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) -701.536 -684.974 -672.241 -635.370 -593.992 -579.983 -557.876 78.249 104.991 24.108 -634.319 ms -2.045e+04 5.609e+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) -91.066 -71.903 -46.601 3.630 28.893 39.936 74.586 75.494 111.839 22.394 -1.258 µs -5.323 16.56

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 -79.629 -47.718 150.637 362.148 441.796 490.649 562.449 291.159 538.367 92.369 344.455 µs 26.26 85.27

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 -338.649 -311.996 -206.273 89.526 170.611 220.221 309.709 376.884 532.217 104.687 66.486 µs -3.086 10.79

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) -261.138 -86.569 17.831 349.291 471.429 517.486 612.426 453.598 604.055 122.960 333.694 µs 8.349 21.15

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 -707.024 -533.778 -402.680 -103.859 336.935 441.598 519.945 739.615 975.376 168.407 -92.557 µs -7.482 21.5

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) 0.725 2.449 4.115 12.014 25.678 33.997 60.116 21.563 31.548 6.684 13.156 ms 4.984 16.63

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) 0.175 0.402 0.828 11.205 29.669 38.615 52.430 28.841 38.213 9.209 12.328 µs 1.98 5.886

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 0.012 0.019 0.024 0.058 1.334 28.086 28.180 1.309 28.067 2.957 0.483 ms 5.887 58.25

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 0.012 0.020 0.026 0.059 0.408 2.191 2.766 0.382 2.171 0.392 0.165 ms 2.661 15.83

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) 0.013 0.016 0.022 0.064 0.765 17.299 21.666 0.743 17.283 2.505 0.481 ms 4.336 36.52

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 0.018 0.024 0.066 1.590 26.832 26.953 1.566 26.814 3.088 0.543 ms 5.221 47.62

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 13.441 13.447 13.474 13.718 13.849 13.858 13.869 0.375 0.411 0.120 13.683 ppm 1.455e+06 1.649e+08
Local Clock Time Offset -91.065 -71.902 -46.600 3.629 28.892 39.935 74.585 75.492 111.837 22.393 -1.258 µs -5.323 16.56
Local RMS Frequency Jitter 0.039 0.052 0.214 0.904 2.882 3.951 4.382 2.668 3.899 0.796 1.114 ppb 2.867 9.316
Local RMS Time Jitter 0.283 0.341 1.029 10.822 17.591 19.979 24.186 16.562 19.638 4.898 10.214 µs 4.24 9.683
Refclock Offset 127.127.28.0 SHM(0) -701.536 -684.974 -672.241 -635.370 -593.992 -579.983 -557.876 78.249 104.991 24.108 -634.319 ms -2.045e+04 5.609e+05
Refclock Offset 127.127.28.1 SHM(1) -91.066 -71.903 -46.601 3.630 28.893 39.936 74.586 75.494 111.839 22.394 -1.258 µs -5.323 16.56
Refclock RMS Jitter 127.127.28.0 SHM(0) 0.725 2.449 4.115 12.014 25.678 33.997 60.116 21.563 31.548 6.684 13.156 ms 4.984 16.63
Refclock RMS Jitter 127.127.28.1 SHM(1) 0.175 0.402 0.828 11.205 29.669 38.615 52.430 28.841 38.213 9.209 12.328 µs 1.98 5.886
Server Jitter 139.143.5.31 0.012 0.019 0.024 0.058 1.334 28.086 28.180 1.309 28.067 2.957 0.483 ms 5.887 58.25
Server Jitter 193.67.79.202 0.012 0.020 0.026 0.059 0.408 2.191 2.766 0.382 2.171 0.392 0.165 ms 2.661 15.83
Server Jitter 2001:8b0:0:23::205 (ntp2.aa.net.uk) 0.013 0.016 0.022 0.064 0.765 17.299 21.666 0.743 17.283 2.505 0.481 ms 4.336 36.52
Server Jitter 81.187.26.174 0.011 0.018 0.024 0.066 1.590 26.832 26.953 1.566 26.814 3.088 0.543 ms 5.221 47.62
Server Offset 139.143.5.31 -79.629 -47.718 150.637 362.148 441.796 490.649 562.449 291.159 538.367 92.369 344.455 µs 26.26 85.27
Server Offset 193.67.79.202 -338.649 -311.996 -206.273 89.526 170.611 220.221 309.709 376.884 532.217 104.687 66.486 µs -3.086 10.79
Server Offset 2001:8b0:0:23::205 (ntp2.aa.net.uk) -261.138 -86.569 17.831 349.291 471.429 517.486 612.426 453.598 604.055 122.960 333.694 µs 8.349 21.15
Server Offset 81.187.26.174 -707.024 -533.778 -402.680 -103.859 336.935 441.598 519.945 739.615 975.376 168.407 -92.557 µs -7.482 21.5
TDOP 0.550 0.600 0.630 0.910 1.480 1.570 1.670 0.850 0.970 0.234 0.945 38.01 153.8
Temp LM0 43.000 43.000 43.000 45.000 46.000 46.000 46.000 3.000 3.000 0.941 44.489 °C
Temp LM1 22.000 23.000 24.000 26.000 28.000 29.000 32.000 4.000 6.000 1.373 25.768 °C
Temp LM2 36.000 36.000 36.000 38.000 39.000 39.000 40.000 3.000 3.000 0.867 37.851 °C
Temp LM3 36.000 37.000 37.000 38.000 39.000 40.000 40.000 2.000 3.000 0.797 38.048 °C
Temp LM4 35.000 35.000 36.000 37.000 38.000 38.000 39.000 2.000 3.000 0.798 36.967 °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 33.000 34.000 35.000 37.000 38.000 40.000 42.000 3.000 6.000 1.276 36.720 °C
Temp LM8 33.000 34.000 35.000 37.000 39.000 40.000 42.000 4.000 6.000 1.290 36.741 °C
Temp LM9 31.000 32.000 32.000 34.000 35.000 36.000 38.000 3.000 4.000 0.952 33.831 °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 33.000 34.000 34.000 37.000 39.000 40.000 42.000 5.000 6.000 1.362 36.665 °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 6.000 6.000 7.000 9.000 10.000 10.000 11.000 3.000 4.000 0.945 8.634 nSat 562.3 4772
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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