NTPsec

sam.ljay.org.uk

Report generated: Thu Jun 25 15:00:02 2026 UTC
Start Time: Wed Jun 24 06:00:02 2026 UTC
End Time: Thu Jun 25 15:00:02 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 -91.318 -77.764 -50.284 1.632 31.987 45.818 64.677 82.271 123.582 24.330 -1.824 µs -5.44 16.98
Local Clock Frequency Offset 13.668 13.672 13.685 13.930 14.096 14.124 14.131 0.411 0.452 0.136 13.920 ppm 1.043e+06 1.058e+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 0.265 0.322 0.872 10.696 18.329 21.270 24.869 17.457 20.948 5.188 10.336 µs 3.823 8.722

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 0.037 0.093 0.968 3.063 4.716 4.797 2.970 4.679 0.876 1.204 ppb 3.152 11.61

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 -91.318 -77.764 -50.284 1.632 31.987 45.818 64.677 82.271 123.582 24.330 -1.824 µs -5.44 16.98

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 13.668 13.672 13.685 13.930 14.096 14.124 14.131 0.411 0.452 0.136 13.920 ppm 1.043e+06 1.058e+08
Temp LM0 43.000 43.000 43.000 45.000 46.000 46.000 46.000 3.000 3.000 1.114 44.892 °C
Temp LM1 22.000 22.000 23.000 25.000 28.000 29.000 31.000 5.000 7.000 1.380 25.186 °C
Temp LM2 35.000 35.000 36.000 37.000 38.000 39.000 40.000 2.000 4.000 0.957 37.106 °C
Temp LM3 36.000 36.000 36.000 38.000 39.000 39.000 41.000 3.000 3.000 0.988 37.516 °C
Temp LM4 35.000 35.000 35.000 37.000 38.000 38.000 40.000 3.000 3.000 0.973 36.562 °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 33.000 34.000 36.000 38.000 40.000 42.000 4.000 7.000 1.353 36.128 °C
Temp LM8 33.000 33.000 34.000 36.000 38.000 40.000 42.000 4.000 7.000 1.370 36.131 °C
Temp LM9 31.000 32.000 32.000 34.000 36.000 37.000 38.000 4.000 5.000 1.064 33.882 °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 33.000 34.000 36.000 38.000 40.000 42.000 4.000 7.000 1.320 36.053 °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 0.998 8.528 nSat 451.4 3575
TDOP 0.540 0.570 0.620 0.900 1.480 2.060 2.950 0.860 1.490 0.283 0.949 22.06 93.6

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) -688.304 -673.052 -656.768 -623.949 -590.693 -575.671 -551.627 66.074 97.381 20.033 -623.428 ms -3.324e+04 1.071e+06

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) -91.319 -77.765 -50.285 1.633 31.988 45.819 64.678 82.273 123.584 24.330 -1.823 µs -5.439 16.98

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 -201.314 -156.350 -75.150 266.909 436.804 502.686 519.449 511.954 659.036 136.707 248.606 µs 1.822 5.158

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 -521.283 -456.841 -347.118 -14.873 152.439 201.646 312.151 499.557 658.487 126.996 -31.718 µs -7.003 24.07

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) -1.951 -1.605 -1.334 -0.129 0.351 0.446 0.519 1.685 2.051 0.492 -0.233 ms -8.848 28.96

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 -572.369 -541.728 -447.856 -127.304 20.923 73.055 301.994 468.779 614.783 121.294 -140.042 µs -17.88 68.13

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) 1.125 2.193 4.004 11.590 24.341 31.335 50.217 20.337 29.142 6.221 12.597 ms 5.234 16.91

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) 0.167 0.360 0.771 12.094 29.394 38.255 49.456 28.623 37.895 9.043 12.667 µs 2.007 5.421

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 0.016 0.020 0.038 0.158 0.514 21.854 28.346 0.476 21.833 3.072 0.666 ms 4.257 36.87

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 0.013 0.028 0.047 0.213 0.473 9.723 10.677 0.426 9.696 1.138 0.377 ms 5.337 46.17

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) 0.025 0.036 0.053 0.192 0.426 1.667 10.573 0.372 1.632 0.849 0.295 ms 8.009 90.58

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 0.012 0.020 0.030 0.172 1.729 17.475 20.859 1.698 17.455 2.807 0.707 ms 3.057 21.32

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 13.668 13.672 13.685 13.930 14.096 14.124 14.131 0.411 0.452 0.136 13.920 ppm 1.043e+06 1.058e+08
Local Clock Time Offset -91.318 -77.764 -50.284 1.632 31.987 45.818 64.677 82.271 123.582 24.330 -1.824 µs -5.44 16.98
Local RMS Frequency Jitter 0.026 0.037 0.093 0.968 3.063 4.716 4.797 2.970 4.679 0.876 1.204 ppb 3.152 11.61
Local RMS Time Jitter 0.265 0.322 0.872 10.696 18.329 21.270 24.869 17.457 20.948 5.188 10.336 µs 3.823 8.722
Refclock Offset 127.127.28.0 SHM(0) -688.304 -673.052 -656.768 -623.949 -590.693 -575.671 -551.627 66.074 97.381 20.033 -623.428 ms -3.324e+04 1.071e+06
Refclock Offset 127.127.28.1 SHM(1) -91.319 -77.765 -50.285 1.633 31.988 45.819 64.678 82.273 123.584 24.330 -1.823 µs -5.439 16.98
Refclock RMS Jitter 127.127.28.0 SHM(0) 1.125 2.193 4.004 11.590 24.341 31.335 50.217 20.337 29.142 6.221 12.597 ms 5.234 16.91
Refclock RMS Jitter 127.127.28.1 SHM(1) 0.167 0.360 0.771 12.094 29.394 38.255 49.456 28.623 37.895 9.043 12.667 µs 2.007 5.421
Server Jitter 139.143.5.31 0.016 0.020 0.038 0.158 0.514 21.854 28.346 0.476 21.833 3.072 0.666 ms 4.257 36.87
Server Jitter 193.67.79.202 0.013 0.028 0.047 0.213 0.473 9.723 10.677 0.426 9.696 1.138 0.377 ms 5.337 46.17
Server Jitter 2001:8b0:0:23::205 (ntp2.aa.net.uk) 0.025 0.036 0.053 0.192 0.426 1.667 10.573 0.372 1.632 0.849 0.295 ms 8.009 90.58
Server Jitter 81.187.26.174 0.012 0.020 0.030 0.172 1.729 17.475 20.859 1.698 17.455 2.807 0.707 ms 3.057 21.32
Server Offset 139.143.5.31 -201.314 -156.350 -75.150 266.909 436.804 502.686 519.449 511.954 659.036 136.707 248.606 µs 1.822 5.158
Server Offset 193.67.79.202 -521.283 -456.841 -347.118 -14.873 152.439 201.646 312.151 499.557 658.487 126.996 -31.718 µs -7.003 24.07
Server Offset 2001:8b0:0:23::205 (ntp2.aa.net.uk) -1.951 -1.605 -1.334 -0.129 0.351 0.446 0.519 1.685 2.051 0.492 -0.233 ms -8.848 28.96
Server Offset 81.187.26.174 -572.369 -541.728 -447.856 -127.304 20.923 73.055 301.994 468.779 614.783 121.294 -140.042 µs -17.88 68.13
TDOP 0.540 0.570 0.620 0.900 1.480 2.060 2.950 0.860 1.490 0.283 0.949 22.06 93.6
Temp LM0 43.000 43.000 43.000 45.000 46.000 46.000 46.000 3.000 3.000 1.114 44.892 °C
Temp LM1 22.000 22.000 23.000 25.000 28.000 29.000 31.000 5.000 7.000 1.380 25.186 °C
Temp LM2 35.000 35.000 36.000 37.000 38.000 39.000 40.000 2.000 4.000 0.957 37.106 °C
Temp LM3 36.000 36.000 36.000 38.000 39.000 39.000 41.000 3.000 3.000 0.988 37.516 °C
Temp LM4 35.000 35.000 35.000 37.000 38.000 38.000 40.000 3.000 3.000 0.973 36.562 °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 33.000 34.000 36.000 38.000 40.000 42.000 4.000 7.000 1.353 36.128 °C
Temp LM8 33.000 33.000 34.000 36.000 38.000 40.000 42.000 4.000 7.000 1.370 36.131 °C
Temp LM9 31.000 32.000 32.000 34.000 36.000 37.000 38.000 4.000 5.000 1.064 33.882 °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 33.000 34.000 36.000 38.000 40.000 42.000 4.000 7.000 1.320 36.053 °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 0.998 8.528 nSat 451.4 3575
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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