NTPsec

sam.ljay.org.uk

Report generated: Tue Sep 15 00:00:02 2026 UTC
Start Time: Sun Sep 13 15:00:02 2026 UTC
End Time: Tue Sep 15 00:00:02 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 -43.909 -33.359 -21.197 2.028 20.067 29.699 52.146 41.264 63.058 12.158 1.164 µs -3.777 11.03
Local Clock Frequency Offset 13.609 13.611 13.620 13.684 13.800 13.808 13.815 0.180 0.197 0.059 13.690 ppm 1.221e+07 2.811e+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 0.286 0.441 1.456 10.611 17.837 20.804 24.678 16.381 20.363 4.767 10.331 µs 4.944 12.04

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 0.063 0.156 0.701 1.167 1.346 1.778 1.011 1.283 0.296 0.684 ppb 6.277 16.57

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 -43.909 -33.359 -21.197 2.028 20.067 29.699 52.146 41.264 63.058 12.158 1.164 µs -3.777 11.03

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 13.609 13.611 13.620 13.684 13.800 13.808 13.815 0.180 0.197 0.059 13.690 ppm 1.221e+07 2.811e+09
Temp LM0 45.000 45.000 45.000 45.000 46.000 46.000 46.000 1.000 1.000 0.488 45.390 °C
Temp LM1 23.000 23.000 24.000 26.000 27.000 30.000 31.000 3.000 7.000 1.237 25.622 °C
Temp LM2 36.000 36.000 36.000 37.000 38.000 39.000 40.000 2.000 3.000 0.585 36.899 °C
Temp LM3 37.000 37.000 37.000 38.000 38.000 40.000 40.000 1.000 3.000 0.567 37.620 °C
Temp LM4 36.000 36.000 36.000 37.000 38.000 39.000 40.000 2.000 3.000 0.566 36.932 °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 34.000 34.000 35.000 37.000 38.000 40.000 42.000 3.000 6.000 1.086 36.552 °C
Temp LM8 34.000 34.000 35.000 37.000 38.000 40.000 42.000 3.000 6.000 1.081 36.554 °C
Temp LM9 32.000 33.000 33.000 34.000 35.000 38.000 39.000 2.000 5.000 0.884 34.222 °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 40.000 41.000 3.000 6.000 1.049 36.499 °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 6.000 7.000 9.000 10.000 11.000 11.000 3.000 5.000 1.025 8.692 nSat 440 3455
TDOP 0.540 0.570 0.620 0.920 1.440 1.910 5.530 0.820 1.340 0.356 0.964 16.19 139.2

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) -695.932 -681.370 -666.508 -625.225 -588.877 -570.279 -527.963 77.631 111.091 23.105 -626.037 ms -2.226e+04 6.278e+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) -43.910 -33.360 -21.198 2.029 20.068 29.700 52.147 41.266 63.060 12.159 1.164 µs -3.777 11.03

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 -69.335 16.727 118.020 433.085 512.380 547.466 578.840 394.360 530.739 106.459 410.940 µs 29.63 97.72

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 -477.422 -403.610 -239.700 12.589 102.758 125.291 164.715 342.458 528.901 97.855 -3.586 µs -6.681 28.08

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) -0.150 -0.034 0.207 0.710 1.143 1.275 1.300 0.937 1.309 0.277 0.682 ms 7.182 18.38

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 -407.844 -380.742 -288.327 36.331 107.583 131.281 144.818 395.910 512.023 102.442 12.688 µs -5.755 22.84

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) 1.201 2.877 5.038 12.576 27.646 36.588 52.657 22.608 33.711 7.013 13.945 ms 5.136 16.75

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) 0.145 0.465 0.777 10.719 28.830 37.469 55.555 28.053 37.004 8.804 11.788 µs 2.041 6.258

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 13.688 15.888 24.422 60.287 390.954 751.199 1,478.381 366.532 735.311 138.070 104.293 µs 3.698 27.66

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 14.658 16.775 24.322 57.156 321.561 460.023 492.966 297.239 443.248 85.752 84.684 µs 2.856 11.33

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) 7.719 12.816 20.111 60.549 392.337 455.456 1,863.747 372.226 442.640 171.311 103.985 µs 5.706 55.73

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 11.309 15.891 24.115 62.939 357.836 431.633 504.793 333.721 415.742 89.051 88.705 µs 2.642 9.697

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 13.609 13.611 13.620 13.684 13.800 13.808 13.815 0.180 0.197 0.059 13.690 ppm 1.221e+07 2.811e+09
Local Clock Time Offset -43.909 -33.359 -21.197 2.028 20.067 29.699 52.146 41.264 63.058 12.158 1.164 µs -3.777 11.03
Local RMS Frequency Jitter 0.032 0.063 0.156 0.701 1.167 1.346 1.778 1.011 1.283 0.296 0.684 ppb 6.277 16.57
Local RMS Time Jitter 0.286 0.441 1.456 10.611 17.837 20.804 24.678 16.381 20.363 4.767 10.331 µs 4.944 12.04
Refclock Offset 127.127.28.0 SHM(0) -695.932 -681.370 -666.508 -625.225 -588.877 -570.279 -527.963 77.631 111.091 23.105 -626.037 ms -2.226e+04 6.278e+05
Refclock Offset 127.127.28.1 SHM(1) -43.910 -33.360 -21.198 2.029 20.068 29.700 52.147 41.266 63.060 12.159 1.164 µs -3.777 11.03
Refclock RMS Jitter 127.127.28.0 SHM(0) 1.201 2.877 5.038 12.576 27.646 36.588 52.657 22.608 33.711 7.013 13.945 ms 5.136 16.75
Refclock RMS Jitter 127.127.28.1 SHM(1) 0.145 0.465 0.777 10.719 28.830 37.469 55.555 28.053 37.004 8.804 11.788 µs 2.041 6.258
Server Jitter 139.143.5.31 13.688 15.888 24.422 60.287 390.954 751.199 1,478.381 366.532 735.311 138.070 104.293 µs 3.698 27.66
Server Jitter 193.67.79.202 14.658 16.775 24.322 57.156 321.561 460.023 492.966 297.239 443.248 85.752 84.684 µs 2.856 11.33
Server Jitter 2001:8b0:0:23::205 (ntp2.aa.net.uk) 7.719 12.816 20.111 60.549 392.337 455.456 1,863.747 372.226 442.640 171.311 103.985 µs 5.706 55.73
Server Jitter 81.187.26.174 11.309 15.891 24.115 62.939 357.836 431.633 504.793 333.721 415.742 89.051 88.705 µs 2.642 9.697
Server Offset 139.143.5.31 -69.335 16.727 118.020 433.085 512.380 547.466 578.840 394.360 530.739 106.459 410.940 µs 29.63 97.72
Server Offset 193.67.79.202 -477.422 -403.610 -239.700 12.589 102.758 125.291 164.715 342.458 528.901 97.855 -3.586 µs -6.681 28.08
Server Offset 2001:8b0:0:23::205 (ntp2.aa.net.uk) -0.150 -0.034 0.207 0.710 1.143 1.275 1.300 0.937 1.309 0.277 0.682 ms 7.182 18.38
Server Offset 81.187.26.174 -407.844 -380.742 -288.327 36.331 107.583 131.281 144.818 395.910 512.023 102.442 12.688 µs -5.755 22.84
TDOP 0.540 0.570 0.620 0.920 1.440 1.910 5.530 0.820 1.340 0.356 0.964 16.19 139.2
Temp LM0 45.000 45.000 45.000 45.000 46.000 46.000 46.000 1.000 1.000 0.488 45.390 °C
Temp LM1 23.000 23.000 24.000 26.000 27.000 30.000 31.000 3.000 7.000 1.237 25.622 °C
Temp LM2 36.000 36.000 36.000 37.000 38.000 39.000 40.000 2.000 3.000 0.585 36.899 °C
Temp LM3 37.000 37.000 37.000 38.000 38.000 40.000 40.000 1.000 3.000 0.567 37.620 °C
Temp LM4 36.000 36.000 36.000 37.000 38.000 39.000 40.000 2.000 3.000 0.566 36.932 °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 34.000 34.000 35.000 37.000 38.000 40.000 42.000 3.000 6.000 1.086 36.552 °C
Temp LM8 34.000 34.000 35.000 37.000 38.000 40.000 42.000 3.000 6.000 1.081 36.554 °C
Temp LM9 32.000 33.000 33.000 34.000 35.000 38.000 39.000 2.000 5.000 0.884 34.222 °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 40.000 41.000 3.000 6.000 1.049 36.499 °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 6.000 7.000 9.000 10.000 11.000 11.000 3.000 5.000 1.025 8.692 nSat 440 3455
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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