NTPsec

sam.ljay.org.uk

Report generated: Wed Sep 9 04:00:02 2026 UTC
Start Time: Mon Sep 7 19:00:02 2026 UTC
End Time: Wed Sep 9 04:00:02 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 -48.986 -36.722 -23.979 -1.245 15.738 28.375 47.919 39.717 65.097 11.851 -2.073 µs -5.505 16.54
Local Clock Frequency Offset 13.427 13.435 13.456 13.595 13.647 13.652 13.661 0.191 0.217 0.059 13.576 ppm 1.197e+07 2.738e+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 0.227 0.317 1.075 10.078 17.783 21.379 24.282 16.708 21.062 5.056 9.675 µs 3.506 8.185

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 0.026 0.049 0.176 0.640 1.221 1.450 1.717 1.045 1.401 0.314 0.667 ppb 5.106 13.29

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 -48.986 -36.722 -23.979 -1.245 15.738 28.375 47.919 39.717 65.097 11.851 -2.073 µs -5.505 16.54

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 13.427 13.435 13.456 13.595 13.647 13.652 13.661 0.191 0.217 0.059 13.576 ppm 1.197e+07 2.738e+09
Temp LM0 44.000 44.000 44.000 45.000 46.000 46.000 46.000 2.000 2.000 0.434 44.927 °C
Temp LM1 22.000 23.000 23.000 25.000 27.000 30.000 32.000 4.000 7.000 1.412 25.280 °C
Temp LM2 35.000 36.000 36.000 37.000 37.000 39.000 39.000 1.000 3.000 0.585 36.594 °C
Temp LM3 36.000 36.000 36.000 37.000 38.000 39.000 40.000 2.000 3.000 0.664 37.207 °C
Temp LM4 35.000 36.000 36.000 37.000 37.000 38.000 39.000 1.000 2.000 0.560 36.542 °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 34.000 36.000 38.000 40.000 41.000 4.000 6.000 1.204 36.234 °C
Temp LM8 33.000 34.000 34.000 36.000 38.000 40.000 41.000 4.000 6.000 1.200 36.227 °C
Temp LM9 32.000 32.000 33.000 34.000 35.000 37.000 38.000 2.000 5.000 0.880 34.058 °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 34.000 34.000 35.000 36.000 38.000 41.000 42.000 3.000 7.000 1.166 36.254 °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 11.000 11.000 3.000 5.000 1.014 8.573 nSat 437.2 3432
TDOP 0.520 0.580 0.620 0.920 1.480 2.020 3.060 0.860 1.440 0.296 0.966 20.35 86.18

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) -710.457 -680.041 -662.177 -622.122 -585.541 -567.163 -536.356 76.637 112.879 23.569 -622.769 ms -2.071e+04 5.701e+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) -48.987 -36.723 -23.980 -1.246 15.739 28.376 47.920 39.719 65.099 11.852 -2.073 µs -5.505 16.54

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 -30.023 -2.937 231.517 438.912 511.316 540.524 544.733 279.799 543.461 95.680 420.004 µs 46.42 175.7

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 -469.559 -394.881 -230.208 9.094 89.128 118.965 151.616 319.336 513.846 91.259 -4.535 µs -6.876 29.74

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) 47.801 220.166 426.834 712.967 878.789 932.043 947.339 451.955 711.877 143.451 695.134 µs 67.26 294.8

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 -405.684 -389.786 -281.357 38.212 107.012 136.734 146.342 388.369 526.520 102.277 16.722 µs -5.651 22.79

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 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) 0.881 2.652 4.845 12.655 27.274 34.906 48.964 22.428 32.254 6.860 13.876 ms 5.192 16.21

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) 0.148 0.307 0.593 9.582 27.724 37.685 59.420 27.131 37.378 9.000 10.766 µs 1.614 5.292

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 13.300 17.207 22.661 56.140 368.013 915.401 4,434.868 345.352 898.194 409.420 132.833 µs 7.318 77.63

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 0.014 0.019 0.022 0.060 0.347 1.199 2.131 0.325 1.180 0.184 0.096 ms 6.256 62.45

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) 0.012 0.015 0.020 0.057 0.319 3.326 3.494 0.299 3.311 0.359 0.119 ms 5.703 51.81

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 0.006 0.012 0.019 0.054 0.356 0.476 6.986 0.337 0.465 0.338 0.107 ms 15.5 313.8

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.



Summary


Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Frequency Offset 13.427 13.435 13.456 13.595 13.647 13.652 13.661 0.191 0.217 0.059 13.576 ppm 1.197e+07 2.738e+09
Local Clock Time Offset -48.986 -36.722 -23.979 -1.245 15.738 28.375 47.919 39.717 65.097 11.851 -2.073 µs -5.505 16.54
Local RMS Frequency Jitter 0.026 0.049 0.176 0.640 1.221 1.450 1.717 1.045 1.401 0.314 0.667 ppb 5.106 13.29
Local RMS Time Jitter 0.227 0.317 1.075 10.078 17.783 21.379 24.282 16.708 21.062 5.056 9.675 µs 3.506 8.185
Refclock Offset 127.127.28.0 SHM(0) -710.457 -680.041 -662.177 -622.122 -585.541 -567.163 -536.356 76.637 112.879 23.569 -622.769 ms -2.071e+04 5.701e+05
Refclock Offset 127.127.28.1 SHM(1) -48.987 -36.723 -23.980 -1.246 15.739 28.376 47.920 39.719 65.099 11.852 -2.073 µs -5.505 16.54
Refclock RMS Jitter 127.127.28.0 SHM(0) 0.881 2.652 4.845 12.655 27.274 34.906 48.964 22.428 32.254 6.860 13.876 ms 5.192 16.21
Refclock RMS Jitter 127.127.28.1 SHM(1) 0.148 0.307 0.593 9.582 27.724 37.685 59.420 27.131 37.378 9.000 10.766 µs 1.614 5.292
Server Jitter 139.143.5.31 13.300 17.207 22.661 56.140 368.013 915.401 4,434.868 345.352 898.194 409.420 132.833 µs 7.318 77.63
Server Jitter 193.67.79.202 0.014 0.019 0.022 0.060 0.347 1.199 2.131 0.325 1.180 0.184 0.096 ms 6.256 62.45
Server Jitter 2001:8b0:0:23::205 (ntp2.aa.net.uk) 0.012 0.015 0.020 0.057 0.319 3.326 3.494 0.299 3.311 0.359 0.119 ms 5.703 51.81
Server Jitter 81.187.26.174 0.006 0.012 0.019 0.054 0.356 0.476 6.986 0.337 0.465 0.338 0.107 ms 15.5 313.8
Server Offset 139.143.5.31 -30.023 -2.937 231.517 438.912 511.316 540.524 544.733 279.799 543.461 95.680 420.004 µs 46.42 175.7
Server Offset 193.67.79.202 -469.559 -394.881 -230.208 9.094 89.128 118.965 151.616 319.336 513.846 91.259 -4.535 µs -6.876 29.74
Server Offset 2001:8b0:0:23::205 (ntp2.aa.net.uk) 47.801 220.166 426.834 712.967 878.789 932.043 947.339 451.955 711.877 143.451 695.134 µs 67.26 294.8
Server Offset 81.187.26.174 -405.684 -389.786 -281.357 38.212 107.012 136.734 146.342 388.369 526.520 102.277 16.722 µs -5.651 22.79
TDOP 0.520 0.580 0.620 0.920 1.480 2.020 3.060 0.860 1.440 0.296 0.966 20.35 86.18
Temp LM0 44.000 44.000 44.000 45.000 46.000 46.000 46.000 2.000 2.000 0.434 44.927 °C
Temp LM1 22.000 23.000 23.000 25.000 27.000 30.000 32.000 4.000 7.000 1.412 25.280 °C
Temp LM2 35.000 36.000 36.000 37.000 37.000 39.000 39.000 1.000 3.000 0.585 36.594 °C
Temp LM3 36.000 36.000 36.000 37.000 38.000 39.000 40.000 2.000 3.000 0.664 37.207 °C
Temp LM4 35.000 36.000 36.000 37.000 37.000 38.000 39.000 1.000 2.000 0.560 36.542 °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 34.000 36.000 38.000 40.000 41.000 4.000 6.000 1.204 36.234 °C
Temp LM8 33.000 34.000 34.000 36.000 38.000 40.000 41.000 4.000 6.000 1.200 36.227 °C
Temp LM9 32.000 32.000 33.000 34.000 35.000 37.000 38.000 2.000 5.000 0.880 34.058 °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 34.000 34.000 35.000 36.000 38.000 41.000 42.000 3.000 7.000 1.166 36.254 °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 11.000 11.000 3.000 5.000 1.014 8.573 nSat 437.2 3432
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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