NTPsec

sam.ljay.org.uk

Report generated: Sat Mar 14 21:00:02 2026 UTC
Start Time: Fri Mar 13 12:00:01 2026 UTC
End Time: Sat Mar 14 21:00:01 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 -43.390 -29.816 -17.971 -0.125 27.996 40.877 54.737 45.967 70.693 14.031 1.886 µs -2.673 6.764
Local Clock Frequency Offset 12.596 12.598 12.608 12.855 13.114 13.127 13.131 0.506 0.529 0.153 12.844 ppm 5.751e+05 4.784e+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 0.365 0.525 0.718 6.743 15.755 18.593 24.315 15.037 18.068 5.017 7.203 µs 1.795 4.069

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 0.073 0.092 0.161 0.648 1.655 2.036 2.350 1.494 1.944 0.454 0.738 ppb 3.06 8.35

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 -43.390 -29.816 -17.971 -0.125 27.996 40.877 54.737 45.967 70.693 14.031 1.886 µs -2.673 6.764

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 12.596 12.598 12.608 12.855 13.114 13.127 13.131 0.506 0.529 0.153 12.844 ppm 5.751e+05 4.784e+07
Temp LM0 38.000 38.000 38.000 40.000 41.000 41.000 41.000 3.000 3.000 0.955 39.547 °C
Temp LM1 18.000 18.000 19.000 21.000 23.000 24.000 27.000 4.000 6.000 1.437 20.894 °C
Temp LM2 31.000 31.000 31.000 32.000 34.000 34.000 35.000 3.000 3.000 0.950 32.204 °C
Temp LM3 32.000 32.000 32.000 33.000 34.000 34.000 35.000 2.000 2.000 0.836 32.763 °C
Temp LM4 30.000 30.000 30.000 32.000 33.000 33.000 34.000 3.000 3.000 0.893 31.690 °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 29.000 29.000 30.000 32.000 34.000 34.000 35.000 4.000 5.000 1.192 31.929 °C
Temp LM8 29.000 30.000 30.000 32.000 34.000 34.000 35.000 4.000 4.000 1.168 31.942 °C
Temp LM9 25.000 26.000 26.000 29.000 31.000 32.000 33.000 5.000 6.000 1.466 28.723 °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 29.000 29.000 30.000 32.000 34.000 34.000 36.000 4.000 5.000 1.225 31.809 °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 8.000 10.000 11.000 11.000 3.000 5.000 0.977 8.460 nSat 471.5 3788
TDOP 0.540 0.590 0.630 0.930 1.520 2.200 2.890 0.890 1.610 0.313 0.989 18.6 76.8

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) -691.113 -670.343 -653.053 -613.018 -577.321 -556.867 -529.512 75.731 113.476 22.990 -613.511 ms -2.13e+04 5.922e+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) -43.391 -29.817 -17.972 -0.125 27.997 40.878 54.738 45.969 70.695 14.032 1.886 µs -2.673 6.764

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 -495.375 -451.579 -384.206 -36.558 55.086 143.529 250.441 439.292 595.108 124.640 -67.608 µs -9.953 35.62

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 -708.836 -659.833 -599.080 -238.352 -156.707 -98.950 38.393 442.373 560.883 120.861 -271.050 µs -45.7 204.3

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 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) -2.066 -1.803 -1.245 -0.227 0.317 0.398 0.481 1.562 2.201 0.443 -0.287 ms -10.88 39.16

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 -917.721 -909.844 -836.478 -466.224 -364.203 -225.227 -20.733 472.275 684.617 139.740 -502.149 µs -112 599.7

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 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) 1.517 3.067 4.611 11.363 24.526 31.562 50.873 19.914 28.496 6.166 12.519 ms 5.357 17.36

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) 0.124 0.217 0.377 4.873 25.053 33.530 53.448 24.676 33.313 8.484 8.002 µs 1.175 4.473

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 0.014 0.018 0.026 0.074 0.373 1.128 12.374 0.347 1.110 0.824 0.168 ms 11.37 169.6

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.



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 0.010 0.019 0.028 0.068 0.953 7.337 13.607 0.925 7.318 1.234 0.301 ms 5.141 52.6

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.



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) 0.006 0.013 0.025 0.067 0.333 1.663 6.476 0.308 1.650 0.403 0.136 ms 9.213 129.2

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.



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 0.009 0.021 0.030 0.078 0.409 21.297 29.160 0.379 21.277 2.939 0.435 ms 6.151 62.02

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 12.596 12.598 12.608 12.855 13.114 13.127 13.131 0.506 0.529 0.153 12.844 ppm 5.751e+05 4.784e+07
Local Clock Time Offset -43.390 -29.816 -17.971 -0.125 27.996 40.877 54.737 45.967 70.693 14.031 1.886 µs -2.673 6.764
Local RMS Frequency Jitter 0.073 0.092 0.161 0.648 1.655 2.036 2.350 1.494 1.944 0.454 0.738 ppb 3.06 8.35
Local RMS Time Jitter 0.365 0.525 0.718 6.743 15.755 18.593 24.315 15.037 18.068 5.017 7.203 µs 1.795 4.069
Refclock Offset 127.127.28.0 SHM(0) -691.113 -670.343 -653.053 -613.018 -577.321 -556.867 -529.512 75.731 113.476 22.990 -613.511 ms -2.13e+04 5.922e+05
Refclock Offset 127.127.28.1 SHM(1) -43.391 -29.817 -17.972 -0.125 27.997 40.878 54.738 45.969 70.695 14.032 1.886 µs -2.673 6.764
Refclock RMS Jitter 127.127.28.0 SHM(0) 1.517 3.067 4.611 11.363 24.526 31.562 50.873 19.914 28.496 6.166 12.519 ms 5.357 17.36
Refclock RMS Jitter 127.127.28.1 SHM(1) 0.124 0.217 0.377 4.873 25.053 33.530 53.448 24.676 33.313 8.484 8.002 µs 1.175 4.473
Server Jitter 139.143.5.31 0.014 0.018 0.026 0.074 0.373 1.128 12.374 0.347 1.110 0.824 0.168 ms 11.37 169.6
Server Jitter 193.67.79.202 0.010 0.019 0.028 0.068 0.953 7.337 13.607 0.925 7.318 1.234 0.301 ms 5.141 52.6
Server Jitter 2001:8b0:0:23::205 (ntp2.aa.net.uk) 0.006 0.013 0.025 0.067 0.333 1.663 6.476 0.308 1.650 0.403 0.136 ms 9.213 129.2
Server Jitter 81.187.26.174 0.009 0.021 0.030 0.078 0.409 21.297 29.160 0.379 21.277 2.939 0.435 ms 6.151 62.02
Server Offset 139.143.5.31 -495.375 -451.579 -384.206 -36.558 55.086 143.529 250.441 439.292 595.108 124.640 -67.608 µs -9.953 35.62
Server Offset 193.67.79.202 -708.836 -659.833 -599.080 -238.352 -156.707 -98.950 38.393 442.373 560.883 120.861 -271.050 µs -45.7 204.3
Server Offset 2001:8b0:0:23::205 (ntp2.aa.net.uk) -2.066 -1.803 -1.245 -0.227 0.317 0.398 0.481 1.562 2.201 0.443 -0.287 ms -10.88 39.16
Server Offset 81.187.26.174 -917.721 -909.844 -836.478 -466.224 -364.203 -225.227 -20.733 472.275 684.617 139.740 -502.149 µs -112 599.7
TDOP 0.540 0.590 0.630 0.930 1.520 2.200 2.890 0.890 1.610 0.313 0.989 18.6 76.8
Temp LM0 38.000 38.000 38.000 40.000 41.000 41.000 41.000 3.000 3.000 0.955 39.547 °C
Temp LM1 18.000 18.000 19.000 21.000 23.000 24.000 27.000 4.000 6.000 1.437 20.894 °C
Temp LM2 31.000 31.000 31.000 32.000 34.000 34.000 35.000 3.000 3.000 0.950 32.204 °C
Temp LM3 32.000 32.000 32.000 33.000 34.000 34.000 35.000 2.000 2.000 0.836 32.763 °C
Temp LM4 30.000 30.000 30.000 32.000 33.000 33.000 34.000 3.000 3.000 0.893 31.690 °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 29.000 29.000 30.000 32.000 34.000 34.000 35.000 4.000 5.000 1.192 31.929 °C
Temp LM8 29.000 30.000 30.000 32.000 34.000 34.000 35.000 4.000 4.000 1.168 31.942 °C
Temp LM9 25.000 26.000 26.000 29.000 31.000 32.000 33.000 5.000 6.000 1.466 28.723 °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 29.000 29.000 30.000 32.000 34.000 34.000 36.000 4.000 5.000 1.225 31.809 °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 8.000 10.000 11.000 11.000 3.000 5.000 0.977 8.460 nSat 471.5 3788
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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