NTPsec

sam.ljay.org.uk

Report generated: Thu Oct 16 18:00:02 2025 UTC
Start Time: Wed Oct 15 09:00:01 2025 UTC
End Time: Thu Oct 16 18:00:01 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 -49.596 -27.082 -16.884 1.064 28.318 40.305 66.553 45.202 67.387 13.085 3.646 µs -2.007 6.198
Local Clock Frequency Offset 12.519 12.522 12.528 12.790 12.949 12.956 12.959 0.421 0.434 0.129 12.785 ppm 9.424e+05 9.241e+07

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 0.262 0.321 0.400 8.532 16.516 19.276 21.775 16.116 18.955 5.040 8.336 µs 2.316 5.071

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 0.048 0.060 0.112 0.625 1.640 2.139 2.644 1.528 2.079 0.448 0.698 ppb 2.889 8.55

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 -49.596 -27.082 -16.884 1.064 28.318 40.305 66.553 45.202 67.387 13.085 3.646 µs -2.007 6.198

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 12.519 12.522 12.528 12.790 12.949 12.956 12.959 0.421 0.434 0.129 12.785 ppm 9.424e+05 9.241e+07
Temp LM0 38.000 38.000 38.000 39.000 40.000 40.000 40.000 2.000 2.000 0.684 39.146 °C
Temp LM1 17.000 17.000 17.000 20.000 22.000 23.000 25.000 5.000 6.000 1.403 19.698 °C
Temp LM2 31.000 31.000 31.000 32.000 33.000 33.000 35.000 2.000 2.000 0.534 31.997 °C
Temp LM3 31.000 31.000 31.000 32.000 33.000 34.000 35.000 2.000 3.000 0.698 32.360 °C
Temp LM4 30.000 30.000 30.000 32.000 32.000 32.000 34.000 2.000 2.000 0.733 31.491 °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 28.000 28.000 29.000 31.000 33.000 34.000 35.000 4.000 6.000 1.133 30.831 °C
Temp LM8 28.000 28.000 29.000 31.000 33.000 34.000 35.000 4.000 6.000 1.143 30.811 °C
Temp LM9 27.000 27.000 28.000 29.000 31.000 32.000 33.000 3.000 5.000 1.128 29.297 °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 28.000 29.000 29.000 31.000 32.000 33.000 35.000 3.000 4.000 1.112 30.778 °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 0.929 8.611 nSat 589.1 5074
TDOP 0.560 0.560 0.630 0.920 1.560 2.960 4.640 0.930 2.400 0.408 1.018 11.3 63.2

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) -699.711 -676.137 -660.377 -617.724 -581.098 -561.275 -515.472 79.279 114.862 24.515 -618.144 ms -1.809e+04 4.764e+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) -49.597 -27.083 -16.885 1.065 28.319 40.306 66.554 45.204 67.389 13.086 3.646 µs -2.007 6.198

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 -0.138 -0.097 0.050 0.333 1.556 2.509 2.751 1.506 2.606 0.443 0.426 ms 3.438 15.09

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 -507.182 -424.843 -346.351 -11.185 165.218 222.764 251.732 511.569 647.607 122.503 -21.944 µs -6.532 22.95

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) 66.557 221.503 381.068 625.451 859.740 949.786 1,035.397 478.672 728.283 152.896 619.587 µs 37.45 143.9

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 -563.821 -528.041 -405.861 -136.992 -12.566 75.039 117.020 393.295 603.080 101.802 -147.668 µs -23.8 97.3

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) 1.464 3.290 5.217 12.528 26.920 34.698 64.317 21.703 31.408 6.798 13.839 ms 5.377 17.47

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) 0.119 0.234 0.401 8.188 27.400 35.637 62.131 26.999 35.403 9.001 9.661 µs 1.378 4.921

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 0.011 0.017 0.024 0.117 2.785 3.795 6.899 2.760 3.778 1.010 0.698 ms 1.051 6.445

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 0.009 0.017 0.024 0.068 0.401 20.046 31.428 0.377 20.029 2.668 0.400 ms 6.645 73.91

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) 0.010 0.015 0.020 0.061 0.357 1.669 20.053 0.337 1.654 1.856 0.279 ms 7.25 80.14

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 0.018 0.025 0.061 0.409 33.099 33.192 0.384 33.081 4.062 0.718 ms 3.988 33.88

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 12.519 12.522 12.528 12.790 12.949 12.956 12.959 0.421 0.434 0.129 12.785 ppm 9.424e+05 9.241e+07
Local Clock Time Offset -49.596 -27.082 -16.884 1.064 28.318 40.305 66.553 45.202 67.387 13.085 3.646 µs -2.007 6.198
Local RMS Frequency Jitter 0.048 0.060 0.112 0.625 1.640 2.139 2.644 1.528 2.079 0.448 0.698 ppb 2.889 8.55
Local RMS Time Jitter 0.262 0.321 0.400 8.532 16.516 19.276 21.775 16.116 18.955 5.040 8.336 µs 2.316 5.071
Refclock Offset 127.127.28.0 SHM(0) -699.711 -676.137 -660.377 -617.724 -581.098 -561.275 -515.472 79.279 114.862 24.515 -618.144 ms -1.809e+04 4.764e+05
Refclock Offset 127.127.28.1 SHM(1) -49.597 -27.083 -16.885 1.065 28.319 40.306 66.554 45.204 67.389 13.086 3.646 µs -2.007 6.198
Refclock RMS Jitter 127.127.28.0 SHM(0) 1.464 3.290 5.217 12.528 26.920 34.698 64.317 21.703 31.408 6.798 13.839 ms 5.377 17.47
Refclock RMS Jitter 127.127.28.1 SHM(1) 0.119 0.234 0.401 8.188 27.400 35.637 62.131 26.999 35.403 9.001 9.661 µs 1.378 4.921
Server Jitter 139.143.5.31 0.011 0.017 0.024 0.117 2.785 3.795 6.899 2.760 3.778 1.010 0.698 ms 1.051 6.445
Server Jitter 193.67.79.202 0.009 0.017 0.024 0.068 0.401 20.046 31.428 0.377 20.029 2.668 0.400 ms 6.645 73.91
Server Jitter 2001:8b0:0:23::205 (ntp2.aa.net.uk) 0.010 0.015 0.020 0.061 0.357 1.669 20.053 0.337 1.654 1.856 0.279 ms 7.25 80.14
Server Jitter 81.187.26.174 0.010 0.018 0.025 0.061 0.409 33.099 33.192 0.384 33.081 4.062 0.718 ms 3.988 33.88
Server Offset 139.143.5.31 -0.138 -0.097 0.050 0.333 1.556 2.509 2.751 1.506 2.606 0.443 0.426 ms 3.438 15.09
Server Offset 193.67.79.202 -507.182 -424.843 -346.351 -11.185 165.218 222.764 251.732 511.569 647.607 122.503 -21.944 µs -6.532 22.95
Server Offset 2001:8b0:0:23::205 (ntp2.aa.net.uk) 66.557 221.503 381.068 625.451 859.740 949.786 1,035.397 478.672 728.283 152.896 619.587 µs 37.45 143.9
Server Offset 81.187.26.174 -563.821 -528.041 -405.861 -136.992 -12.566 75.039 117.020 393.295 603.080 101.802 -147.668 µs -23.8 97.3
TDOP 0.560 0.560 0.630 0.920 1.560 2.960 4.640 0.930 2.400 0.408 1.018 11.3 63.2
Temp LM0 38.000 38.000 38.000 39.000 40.000 40.000 40.000 2.000 2.000 0.684 39.146 °C
Temp LM1 17.000 17.000 17.000 20.000 22.000 23.000 25.000 5.000 6.000 1.403 19.698 °C
Temp LM2 31.000 31.000 31.000 32.000 33.000 33.000 35.000 2.000 2.000 0.534 31.997 °C
Temp LM3 31.000 31.000 31.000 32.000 33.000 34.000 35.000 2.000 3.000 0.698 32.360 °C
Temp LM4 30.000 30.000 30.000 32.000 32.000 32.000 34.000 2.000 2.000 0.733 31.491 °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 28.000 28.000 29.000 31.000 33.000 34.000 35.000 4.000 6.000 1.133 30.831 °C
Temp LM8 28.000 28.000 29.000 31.000 33.000 34.000 35.000 4.000 6.000 1.143 30.811 °C
Temp LM9 27.000 27.000 28.000 29.000 31.000 32.000 33.000 3.000 5.000 1.128 29.297 °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 28.000 29.000 29.000 31.000 32.000 33.000 35.000 3.000 4.000 1.112 30.778 °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 0.929 8.611 nSat 589.1 5074
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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