NTPsec

sam.ljay.org.uk

Report generated: Wed Sep 9 02:00:01 2026 UTC
Start Time: Mon Sep 7 17:00:01 2026 UTC
End Time: Wed Sep 9 02:00:01 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 -48.986 -37.628 -23.979 -0.764 16.397 29.899 47.919 40.376 67.527 12.084 -1.665 µs -5.267 15.88
Local Clock Frequency Offset 13.469 13.472 13.495 13.607 13.663 13.673 13.677 0.168 0.201 0.053 13.590 ppm 1.652e+07 4.208e+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 0.227 0.317 1.265 10.197 17.997 21.618 24.282 16.732 21.301 5.003 9.862 µs 3.828 9.077

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 0.049 0.176 0.643 1.237 1.450 1.717 1.061 1.401 0.318 0.673 ppb 5.042 13.05

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 -48.986 -37.628 -23.979 -0.764 16.397 29.899 47.919 40.376 67.527 12.084 -1.665 µs -5.267 15.88

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 13.469 13.472 13.495 13.607 13.663 13.673 13.677 0.168 0.201 0.053 13.590 ppm 1.652e+07 4.208e+09
Temp LM0 44.000 44.000 44.000 45.000 46.000 46.000 46.000 2.000 2.000 0.424 45.035 °C
Temp LM1 22.000 23.000 23.000 25.000 27.000 30.000 32.000 4.000 7.000 1.377 25.453 °C
Temp LM2 36.000 36.000 36.000 37.000 37.000 39.000 39.000 1.000 3.000 0.556 36.662 °C
Temp LM3 36.000 36.000 36.000 37.000 38.000 39.000 40.000 2.000 3.000 0.614 37.327 °C
Temp LM4 36.000 36.000 36.000 37.000 37.000 38.000 39.000 1.000 2.000 0.542 36.607 °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 40.000 41.000 3.000 6.000 1.167 36.390 °C
Temp LM8 33.000 34.000 35.000 36.000 38.000 40.000 41.000 3.000 6.000 1.175 36.385 °C
Temp LM9 32.000 32.000 33.000 34.000 35.000 37.000 38.000 2.000 5.000 0.837 34.179 °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 41.000 42.000 3.000 7.000 1.148 36.401 °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 7.000 7.000 9.000 10.000 11.000 11.000 3.000 4.000 0.998 8.609 nSat 466.6 3737
TDOP 0.520 0.580 0.620 0.910 1.460 2.020 3.060 0.840 1.440 0.292 0.962 21.1 90.62

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) -710.457 -680.680 -663.602 -623.362 -586.563 -567.425 -536.356 77.039 113.254 23.638 -624.048 ms -2.065e+04 5.682e+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) -48.987 -37.629 -23.980 -0.765 16.398 29.900 47.920 40.378 67.529 12.085 -1.665 µs -5.267 15.88

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 -30.023 -2.937 225.276 438.912 511.316 540.781 567.368 286.040 543.718 96.760 419.299 µs 44.38 165.7

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 -469.559 -394.881 -230.208 8.489 84.815 114.011 151.616 315.023 508.892 90.724 -6.424 µs -7 30.18

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) 47.801 220.166 413.267 697.316 872.186 913.039 939.567 458.919 692.873 143.675 678.416 µs 61.59 263.2

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 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 -405.684 -389.786 -293.001 35.593 107.012 128.013 146.342 400.013 517.799 103.982 13.991 µs -5.752 22.86

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) 0.881 2.661 4.845 12.660 27.357 35.054 48.964 22.512 32.393 6.901 13.897 ms 5.129 15.91

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) 0.148 0.307 0.600 9.932 27.724 38.190 59.687 27.124 37.883 9.030 11.087 µs 1.742 5.852

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 14.367 17.990 23.802 56.891 368.013 915.401 4,434.868 344.211 897.411 409.753 134.316 µs 7.318 77.51

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 0.014 0.019 0.024 0.061 0.327 1.199 2.131 0.303 1.180 0.183 0.097 ms 6.327 63.42

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) 0.012 0.015 0.020 0.056 0.337 3.326 3.494 0.318 3.311 0.361 0.120 ms 5.656 51.22

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 0.020 0.055 0.359 0.476 6.986 0.338 0.461 0.339 0.109 ms 15.42 311.2

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 13.469 13.472 13.495 13.607 13.663 13.673 13.677 0.168 0.201 0.053 13.590 ppm 1.652e+07 4.208e+09
Local Clock Time Offset -48.986 -37.628 -23.979 -0.764 16.397 29.899 47.919 40.376 67.527 12.084 -1.665 µs -5.267 15.88
Local RMS Frequency Jitter 0.026 0.049 0.176 0.643 1.237 1.450 1.717 1.061 1.401 0.318 0.673 ppb 5.042 13.05
Local RMS Time Jitter 0.227 0.317 1.265 10.197 17.997 21.618 24.282 16.732 21.301 5.003 9.862 µs 3.828 9.077
Refclock Offset 127.127.28.0 SHM(0) -710.457 -680.680 -663.602 -623.362 -586.563 -567.425 -536.356 77.039 113.254 23.638 -624.048 ms -2.065e+04 5.682e+05
Refclock Offset 127.127.28.1 SHM(1) -48.987 -37.629 -23.980 -0.765 16.398 29.900 47.920 40.378 67.529 12.085 -1.665 µs -5.267 15.88
Refclock RMS Jitter 127.127.28.0 SHM(0) 0.881 2.661 4.845 12.660 27.357 35.054 48.964 22.512 32.393 6.901 13.897 ms 5.129 15.91
Refclock RMS Jitter 127.127.28.1 SHM(1) 0.148 0.307 0.600 9.932 27.724 38.190 59.687 27.124 37.883 9.030 11.087 µs 1.742 5.852
Server Jitter 139.143.5.31 14.367 17.990 23.802 56.891 368.013 915.401 4,434.868 344.211 897.411 409.753 134.316 µs 7.318 77.51
Server Jitter 193.67.79.202 0.014 0.019 0.024 0.061 0.327 1.199 2.131 0.303 1.180 0.183 0.097 ms 6.327 63.42
Server Jitter 2001:8b0:0:23::205 (ntp2.aa.net.uk) 0.012 0.015 0.020 0.056 0.337 3.326 3.494 0.318 3.311 0.361 0.120 ms 5.656 51.22
Server Jitter 81.187.26.174 0.006 0.016 0.020 0.055 0.359 0.476 6.986 0.338 0.461 0.339 0.109 ms 15.42 311.2
Server Offset 139.143.5.31 -30.023 -2.937 225.276 438.912 511.316 540.781 567.368 286.040 543.718 96.760 419.299 µs 44.38 165.7
Server Offset 193.67.79.202 -469.559 -394.881 -230.208 8.489 84.815 114.011 151.616 315.023 508.892 90.724 -6.424 µs -7 30.18
Server Offset 2001:8b0:0:23::205 (ntp2.aa.net.uk) 47.801 220.166 413.267 697.316 872.186 913.039 939.567 458.919 692.873 143.675 678.416 µs 61.59 263.2
Server Offset 81.187.26.174 -405.684 -389.786 -293.001 35.593 107.012 128.013 146.342 400.013 517.799 103.982 13.991 µs -5.752 22.86
TDOP 0.520 0.580 0.620 0.910 1.460 2.020 3.060 0.840 1.440 0.292 0.962 21.1 90.62
Temp LM0 44.000 44.000 44.000 45.000 46.000 46.000 46.000 2.000 2.000 0.424 45.035 °C
Temp LM1 22.000 23.000 23.000 25.000 27.000 30.000 32.000 4.000 7.000 1.377 25.453 °C
Temp LM2 36.000 36.000 36.000 37.000 37.000 39.000 39.000 1.000 3.000 0.556 36.662 °C
Temp LM3 36.000 36.000 36.000 37.000 38.000 39.000 40.000 2.000 3.000 0.614 37.327 °C
Temp LM4 36.000 36.000 36.000 37.000 37.000 38.000 39.000 1.000 2.000 0.542 36.607 °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 40.000 41.000 3.000 6.000 1.167 36.390 °C
Temp LM8 33.000 34.000 35.000 36.000 38.000 40.000 41.000 3.000 6.000 1.175 36.385 °C
Temp LM9 32.000 32.000 33.000 34.000 35.000 37.000 38.000 2.000 5.000 0.837 34.179 °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 41.000 42.000 3.000 7.000 1.148 36.401 °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 7.000 7.000 9.000 10.000 11.000 11.000 3.000 4.000 0.998 8.609 nSat 466.6 3737
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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