NTPsec

sam.ljay.org.uk

Report generated: Tue Sep 16 14:00:02 2025 UTC
Start Time: Mon Sep 15 05:00:01 2025 UTC
End Time: Tue Sep 16 14:00:01 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 -39.755 -27.483 -15.567 1.776 17.589 28.013 37.389 33.156 55.496 9.603 1.351 µs -3.438 11.13
Local Clock Frequency Offset 13.233 13.236 13.240 13.329 13.370 13.378 13.386 0.130 0.142 0.042 13.316 ppm 3.162e+07 9.997e+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 0.374 0.475 0.605 5.406 15.034 17.521 22.974 14.429 17.046 5.012 6.305 µs 1.294 3.008

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 0.064 0.109 0.496 1.031 1.193 1.362 0.922 1.129 0.291 0.515 ppb 3.127 7.262

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 -39.755 -27.483 -15.567 1.776 17.589 28.013 37.389 33.156 55.496 9.603 1.351 µs -3.438 11.13

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 13.233 13.236 13.240 13.329 13.370 13.378 13.386 0.130 0.142 0.042 13.316 ppm 3.162e+07 9.997e+09
Temp LM0 42.000 42.000 42.000 42.000 43.000 43.000 43.000 1.000 1.000 0.495 42.428 °C
Temp LM1 21.000 21.000 21.000 23.000 25.000 26.000 29.000 4.000 5.000 1.137 23.018 °C
Temp LM2 34.000 35.000 35.000 35.000 35.000 36.000 38.000 0.000 1.000 0.274 35.053 °C
Temp LM3 35.000 35.000 35.000 35.000 36.000 36.000 38.000 1.000 1.000 0.507 35.365 °C
Temp LM4 34.000 34.000 34.000 34.000 35.000 35.000 37.000 1.000 1.000 0.437 34.209 °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 31.000 32.000 33.000 34.000 35.000 36.000 38.000 2.000 4.000 0.875 33.899 °C
Temp LM8 31.000 32.000 33.000 34.000 35.000 36.000 38.000 2.000 4.000 0.880 33.882 °C
Temp LM9 29.000 30.000 30.000 32.000 33.000 34.000 34.000 3.000 4.000 0.881 31.650 °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 32.000 32.000 33.000 34.000 35.000 36.000 38.000 2.000 4.000 0.858 33.872 °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 8.000 10.000 11.000 11.000 3.000 5.000 0.990 8.553 nSat 469.4 3769
TDOP 0.550 0.580 0.630 0.900 1.420 1.750 2.060 0.790 1.170 0.246 0.932 31.03 124.4

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) -693.053 -665.340 -644.756 -607.505 -573.878 -561.152 -536.980 70.878 104.189 21.604 -608.412 ms -2.489e+04 7.283e+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) -39.756 -27.484 -15.568 1.777 17.590 28.014 37.390 33.158 55.498 9.603 1.351 µs -3.438 11.13

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 69.996 214.219 341.622 611.926 690.448 798.267 877.692 348.826 584.048 98.587 596.338 µs 141.7 769

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 -312.180 -193.370 12.026 261.904 352.275 456.095 502.458 340.249 649.465 101.383 249.953 µs 5.146 14.94

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) -0.209 -0.087 -0.003 0.508 1.613 1.696 1.737 1.616 1.783 0.448 0.652 ms 2.076 5.105

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 -306.421 -261.907 -166.682 168.495 239.163 359.875 438.409 405.845 621.782 112.104 141.865 µs -1.208 5.97

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) 1.490 3.061 4.561 11.558 24.627 32.425 48.133 20.066 29.364 6.223 12.691 ms 5.405 17.64

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) 0.155 0.247 0.369 2.876 24.216 32.755 52.767 23.847 32.508 8.333 7.410 µs 0.9659 3.806

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 0.008 0.013 0.021 0.063 0.695 1.666 40.173 0.674 1.652 1.887 0.243 ms 17.32 368.8

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.



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 0.006 0.014 0.020 0.062 0.373 1.400 4.048 0.352 1.386 0.249 0.114 ms 8.538 124.1

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) 8.730 10.570 17.685 57.838 331.820 438.597 1,054.675 314.135 428.027 97.797 85.793 µs 3.438 24.05

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 0.010 0.016 0.021 0.062 0.386 3.949 20.148 0.365 3.934 1.496 0.239 ms 8.504 106.6

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 13.233 13.236 13.240 13.329 13.370 13.378 13.386 0.130 0.142 0.042 13.316 ppm 3.162e+07 9.997e+09
Local Clock Time Offset -39.755 -27.483 -15.567 1.776 17.589 28.013 37.389 33.156 55.496 9.603 1.351 µs -3.438 11.13
Local RMS Frequency Jitter 0.039 0.064 0.109 0.496 1.031 1.193 1.362 0.922 1.129 0.291 0.515 ppb 3.127 7.262
Local RMS Time Jitter 0.374 0.475 0.605 5.406 15.034 17.521 22.974 14.429 17.046 5.012 6.305 µs 1.294 3.008
Refclock Offset 127.127.28.0 SHM(0) -693.053 -665.340 -644.756 -607.505 -573.878 -561.152 -536.980 70.878 104.189 21.604 -608.412 ms -2.489e+04 7.283e+05
Refclock Offset 127.127.28.1 SHM(1) -39.756 -27.484 -15.568 1.777 17.590 28.014 37.390 33.158 55.498 9.603 1.351 µs -3.438 11.13
Refclock RMS Jitter 127.127.28.0 SHM(0) 1.490 3.061 4.561 11.558 24.627 32.425 48.133 20.066 29.364 6.223 12.691 ms 5.405 17.64
Refclock RMS Jitter 127.127.28.1 SHM(1) 0.155 0.247 0.369 2.876 24.216 32.755 52.767 23.847 32.508 8.333 7.410 µs 0.9659 3.806
Server Jitter 139.143.5.31 0.008 0.013 0.021 0.063 0.695 1.666 40.173 0.674 1.652 1.887 0.243 ms 17.32 368.8
Server Jitter 193.67.79.202 0.006 0.014 0.020 0.062 0.373 1.400 4.048 0.352 1.386 0.249 0.114 ms 8.538 124.1
Server Jitter 2001:8b0:0:23::205 (ntp2.aa.net.uk) 8.730 10.570 17.685 57.838 331.820 438.597 1,054.675 314.135 428.027 97.797 85.793 µs 3.438 24.05
Server Jitter 81.187.26.174 0.010 0.016 0.021 0.062 0.386 3.949 20.148 0.365 3.934 1.496 0.239 ms 8.504 106.6
Server Offset 139.143.5.31 69.996 214.219 341.622 611.926 690.448 798.267 877.692 348.826 584.048 98.587 596.338 µs 141.7 769
Server Offset 193.67.79.202 -312.180 -193.370 12.026 261.904 352.275 456.095 502.458 340.249 649.465 101.383 249.953 µs 5.146 14.94
Server Offset 2001:8b0:0:23::205 (ntp2.aa.net.uk) -0.209 -0.087 -0.003 0.508 1.613 1.696 1.737 1.616 1.783 0.448 0.652 ms 2.076 5.105
Server Offset 81.187.26.174 -306.421 -261.907 -166.682 168.495 239.163 359.875 438.409 405.845 621.782 112.104 141.865 µs -1.208 5.97
TDOP 0.550 0.580 0.630 0.900 1.420 1.750 2.060 0.790 1.170 0.246 0.932 31.03 124.4
Temp LM0 42.000 42.000 42.000 42.000 43.000 43.000 43.000 1.000 1.000 0.495 42.428 °C
Temp LM1 21.000 21.000 21.000 23.000 25.000 26.000 29.000 4.000 5.000 1.137 23.018 °C
Temp LM2 34.000 35.000 35.000 35.000 35.000 36.000 38.000 0.000 1.000 0.274 35.053 °C
Temp LM3 35.000 35.000 35.000 35.000 36.000 36.000 38.000 1.000 1.000 0.507 35.365 °C
Temp LM4 34.000 34.000 34.000 34.000 35.000 35.000 37.000 1.000 1.000 0.437 34.209 °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 31.000 32.000 33.000 34.000 35.000 36.000 38.000 2.000 4.000 0.875 33.899 °C
Temp LM8 31.000 32.000 33.000 34.000 35.000 36.000 38.000 2.000 4.000 0.880 33.882 °C
Temp LM9 29.000 30.000 30.000 32.000 33.000 34.000 34.000 3.000 4.000 0.881 31.650 °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 32.000 32.000 33.000 34.000 35.000 36.000 38.000 2.000 4.000 0.858 33.872 °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 8.000 10.000 11.000 11.000 3.000 5.000 0.990 8.553 nSat 469.4 3769
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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