NTPsec

sam.ljay.org.uk

Report generated: Thu Sep 10 17:00:03 2026 UTC
Start Time: Wed Sep 2 17:00:01 2026 UTC
End Time: Thu Sep 10 17:00:01 2026 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 -64.937 -35.617 -22.566 0.763 18.482 29.925 47.919 41.048 65.542 12.121 -0.121 µs -4.526 13.72
Local Clock Frequency Offset 13.366 13.372 13.403 13.580 13.726 13.761 13.775 0.323 0.389 0.094 13.567 ppm 2.986e+06 4.301e+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 0.227 0.407 1.006 10.165 17.499 20.430 26.983 16.493 20.023 5.025 9.711 µs 3.528 8.059

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 0.071 0.167 0.658 1.229 1.602 2.403 1.062 1.531 0.325 0.664 ppb 4.897 14.47

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 -64.937 -35.617 -22.566 0.763 18.482 29.925 47.919 41.048 65.542 12.121 -0.121 µs -4.526 13.72

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 13.366 13.372 13.403 13.580 13.726 13.761 13.775 0.323 0.389 0.094 13.567 ppm 2.986e+06 4.301e+08
Temp LM0 44.000 44.000 44.000 45.000 46.000 46.000 46.000 2.000 2.000 0.699 45.036 °C
Temp LM1 21.000 23.000 23.000 25.000 27.000 29.000 33.000 4.000 6.000 1.300 25.336 °C
Temp LM2 35.000 35.000 36.000 37.000 38.000 38.000 40.000 2.000 3.000 0.676 36.656 °C
Temp LM3 36.000 36.000 36.000 37.000 38.000 39.000 40.000 2.000 3.000 0.758 37.315 °C
Temp LM4 35.000 35.000 36.000 37.000 38.000 38.000 40.000 2.000 3.000 0.665 36.598 °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 36.000 38.000 39.000 43.000 3.000 5.000 1.182 36.282 °C
Temp LM8 33.000 34.000 35.000 36.000 38.000 39.000 43.000 3.000 5.000 1.185 36.275 °C
Temp LM9 32.000 32.000 33.000 34.000 36.000 37.000 40.000 3.000 5.000 0.943 34.207 °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 35.000 36.000 38.000 39.000 42.000 3.000 5.000 1.150 36.229 °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 0.997 8.570 nSat 460.8 3673
TDOP 0.520 0.580 0.620 0.920 1.460 1.860 4.490 0.840 1.280 0.291 0.966 21.69 99.13

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) -711.342 -678.331 -662.680 -622.232 -583.078 -566.819 -530.809 79.602 111.513 23.762 -622.614 ms -2.021e+04 5.519e+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) -64.938 -35.618 -22.567 0.764 18.483 29.926 47.920 41.050 65.544 12.122 -0.121 µs -4.526 13.72

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 -212.449 16.782 127.966 433.063 509.771 537.349 576.310 381.805 520.567 102.626 410.991 µs 33.76 116.2

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 -473.778 -410.691 -324.529 9.010 98.557 517.461 636.503 423.086 928.152 128.392 -11.774 µs -4.965 19.76

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) -0.611 -0.340 -0.012 0.585 0.889 1.180 1.821 0.901 1.519 0.283 0.547 ms 2.981 8.79

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 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 -479.966 -378.056 -302.030 31.669 109.726 135.514 622.135 411.756 513.570 110.506 5.320 µs -5.785 21.73

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) 0.746 2.724 4.789 12.424 26.811 34.987 63.665 22.022 32.263 6.805 13.682 ms 5.206 16.8

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) 0.122 0.279 0.538 10.200 28.065 36.617 59.687 27.527 36.338 9.050 11.076 µs 1.621 5.117

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 0.007 0.017 0.024 0.060 0.394 1.306 4.797 0.370 1.288 0.291 0.126 ms 7.845 106.3

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 7.851 19.187 25.864 63.189 381.109 758.647 4,695.663 355.245 739.460 251.959 115.826 µs 9.395 145.1

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 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) 0.009 0.015 0.022 0.060 0.368 1.244 3.494 0.346 1.228 0.241 0.112 ms 7.31 86.71

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 0.016 0.022 0.063 0.374 0.580 6.986 0.352 0.563 0.210 0.110 ms 15.26 438.1

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.



Summary


Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Frequency Offset 13.366 13.372 13.403 13.580 13.726 13.761 13.775 0.323 0.389 0.094 13.567 ppm 2.986e+06 4.301e+08
Local Clock Time Offset -64.937 -35.617 -22.566 0.763 18.482 29.925 47.919 41.048 65.542 12.121 -0.121 µs -4.526 13.72
Local RMS Frequency Jitter 0.026 0.071 0.167 0.658 1.229 1.602 2.403 1.062 1.531 0.325 0.664 ppb 4.897 14.47
Local RMS Time Jitter 0.227 0.407 1.006 10.165 17.499 20.430 26.983 16.493 20.023 5.025 9.711 µs 3.528 8.059
Refclock Offset 127.127.28.0 SHM(0) -711.342 -678.331 -662.680 -622.232 -583.078 -566.819 -530.809 79.602 111.513 23.762 -622.614 ms -2.021e+04 5.519e+05
Refclock Offset 127.127.28.1 SHM(1) -64.938 -35.618 -22.567 0.764 18.483 29.926 47.920 41.050 65.544 12.122 -0.121 µs -4.526 13.72
Refclock RMS Jitter 127.127.28.0 SHM(0) 0.746 2.724 4.789 12.424 26.811 34.987 63.665 22.022 32.263 6.805 13.682 ms 5.206 16.8
Refclock RMS Jitter 127.127.28.1 SHM(1) 0.122 0.279 0.538 10.200 28.065 36.617 59.687 27.527 36.338 9.050 11.076 µs 1.621 5.117
Server Jitter 139.143.5.31 0.007 0.017 0.024 0.060 0.394 1.306 4.797 0.370 1.288 0.291 0.126 ms 7.845 106.3
Server Jitter 193.67.79.202 7.851 19.187 25.864 63.189 381.109 758.647 4,695.663 355.245 739.460 251.959 115.826 µs 9.395 145.1
Server Jitter 2001:8b0:0:23::205 (ntp2.aa.net.uk) 0.009 0.015 0.022 0.060 0.368 1.244 3.494 0.346 1.228 0.241 0.112 ms 7.31 86.71
Server Jitter 81.187.26.174 0.006 0.016 0.022 0.063 0.374 0.580 6.986 0.352 0.563 0.210 0.110 ms 15.26 438.1
Server Offset 139.143.5.31 -212.449 16.782 127.966 433.063 509.771 537.349 576.310 381.805 520.567 102.626 410.991 µs 33.76 116.2
Server Offset 193.67.79.202 -473.778 -410.691 -324.529 9.010 98.557 517.461 636.503 423.086 928.152 128.392 -11.774 µs -4.965 19.76
Server Offset 2001:8b0:0:23::205 (ntp2.aa.net.uk) -0.611 -0.340 -0.012 0.585 0.889 1.180 1.821 0.901 1.519 0.283 0.547 ms 2.981 8.79
Server Offset 81.187.26.174 -479.966 -378.056 -302.030 31.669 109.726 135.514 622.135 411.756 513.570 110.506 5.320 µs -5.785 21.73
TDOP 0.520 0.580 0.620 0.920 1.460 1.860 4.490 0.840 1.280 0.291 0.966 21.69 99.13
Temp LM0 44.000 44.000 44.000 45.000 46.000 46.000 46.000 2.000 2.000 0.699 45.036 °C
Temp LM1 21.000 23.000 23.000 25.000 27.000 29.000 33.000 4.000 6.000 1.300 25.336 °C
Temp LM2 35.000 35.000 36.000 37.000 38.000 38.000 40.000 2.000 3.000 0.676 36.656 °C
Temp LM3 36.000 36.000 36.000 37.000 38.000 39.000 40.000 2.000 3.000 0.758 37.315 °C
Temp LM4 35.000 35.000 36.000 37.000 38.000 38.000 40.000 2.000 3.000 0.665 36.598 °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 36.000 38.000 39.000 43.000 3.000 5.000 1.182 36.282 °C
Temp LM8 33.000 34.000 35.000 36.000 38.000 39.000 43.000 3.000 5.000 1.185 36.275 °C
Temp LM9 32.000 32.000 33.000 34.000 36.000 37.000 40.000 3.000 5.000 0.943 34.207 °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 35.000 36.000 38.000 39.000 42.000 3.000 5.000 1.150 36.229 °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 0.997 8.570 nSat 460.8 3673
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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