NTPsec

sam.ljay.org.uk

Report generated: Sat Jul 12 05:00:02 2025 UTC
Start Time: Thu Jul 10 20:00:02 2025 UTC
End Time: Sat Jul 12 05:00:02 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 -96.491 -68.312 -32.590 -1.965 24.861 39.760 63.954 57.451 108.072 18.509 -2.275 µs -5.733 19.67
Local Clock Frequency Offset 13.478 13.482 13.494 13.601 13.732 13.767 13.778 0.238 0.285 0.071 13.599 ppm 7.004e+06 1.34e+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 0.325 0.715 2.324 10.212 18.096 20.953 24.089 15.772 20.238 4.533 10.398 µs 6.136 16.07

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 0.256 0.314 0.378 0.809 1.768 3.987 4.480 1.390 3.673 0.632 0.948 ppb 4.615 21.81

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 -96.491 -68.312 -32.590 -1.965 24.861 39.760 63.954 57.451 108.072 18.509 -2.275 µs -5.733 19.67

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 13.478 13.482 13.494 13.601 13.732 13.767 13.778 0.238 0.285 0.071 13.599 ppm 7.004e+06 1.34e+09
Temp LM0 43.000 43.000 43.000 44.000 45.000 46.000 46.000 2.000 3.000 0.674 44.237 °C
Temp LM1 22.000 23.000 23.000 25.000 27.000 29.000 32.000 4.000 6.000 1.289 25.250 °C
Temp LM2 36.000 37.000 37.000 38.000 39.000 40.000 40.000 2.000 3.000 0.677 37.657 °C
Temp LM3 37.000 37.000 37.000 38.000 39.000 40.000 40.000 2.000 3.000 0.608 37.922 °C
Temp LM4 36.000 36.000 36.000 37.000 38.000 39.000 39.000 2.000 3.000 0.691 36.659 °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 34.000 34.000 35.000 36.000 38.000 39.000 41.000 3.000 5.000 1.108 36.293 °C
Temp LM8 34.000 34.000 35.000 36.000 38.000 39.000 41.000 3.000 5.000 1.106 36.295 °C
Temp LM9 31.000 32.000 32.000 34.000 35.000 37.000 38.000 3.000 5.000 0.845 33.576 °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 39.000 41.000 3.000 5.000 1.132 36.265 °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 1.009 8.621 nSat 452 3585
TDOP 0.540 0.560 0.610 0.900 1.540 2.300 2.420 0.930 1.740 0.316 0.967 16.5 63.42

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) -717.539 -705.648 -687.766 -642.049 -600.687 -587.044 -558.564 87.079 118.604 26.152 -642.664 ms -1.68e+04 4.317e+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) -96.492 -68.313 -32.591 -1.966 24.862 39.761 63.955 57.453 108.074 18.509 -2.276 µs -5.733 19.67

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 -84.028 -28.973 252.186 366.211 443.061 503.646 542.099 190.875 532.619 81.433 357.422 µs 46.31 176.8

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 -392.061 -319.290 -110.481 98.023 175.971 213.515 287.598 286.452 532.805 90.313 82.650 µs -2.918 12.96

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 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) -80.530 -0.056 281.041 396.173 494.412 570.448 638.690 213.371 570.504 85.127 386.812 µs 53.41 218.7

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 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 -547.605 -519.583 -370.434 -104.684 -21.227 79.697 172.685 349.207 599.280 100.348 -120.213 µs -19.29 80.14

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) 0.998 2.280 4.093 12.012 26.108 33.935 55.916 22.015 31.654 6.708 13.194 ms 4.945 16

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) 0.151 0.403 1.162 11.051 29.236 40.064 68.759 28.074 39.661 8.752 12.607 µs 2.641 8.743

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 0.012 0.016 0.020 0.052 0.229 1.001 3.066 0.209 0.985 0.216 0.088 ms 9.193 123

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 12.628 16.811 24.605 57.831 234.931 448.247 483.791 210.326 431.436 75.118 78.228 µs 3.387 15.14

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 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) 0.014 0.017 0.023 0.054 0.184 0.511 11.121 0.161 0.494 0.877 0.141 ms 9.25 117.8

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 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 0.014 0.018 0.024 0.059 0.306 0.444 20.708 0.282 0.426 0.948 0.126 ms 18.26 397.5

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 13.478 13.482 13.494 13.601 13.732 13.767 13.778 0.238 0.285 0.071 13.599 ppm 7.004e+06 1.34e+09
Local Clock Time Offset -96.491 -68.312 -32.590 -1.965 24.861 39.760 63.954 57.451 108.072 18.509 -2.275 µs -5.733 19.67
Local RMS Frequency Jitter 0.256 0.314 0.378 0.809 1.768 3.987 4.480 1.390 3.673 0.632 0.948 ppb 4.615 21.81
Local RMS Time Jitter 0.325 0.715 2.324 10.212 18.096 20.953 24.089 15.772 20.238 4.533 10.398 µs 6.136 16.07
Refclock Offset 127.127.28.0 SHM(0) -717.539 -705.648 -687.766 -642.049 -600.687 -587.044 -558.564 87.079 118.604 26.152 -642.664 ms -1.68e+04 4.317e+05
Refclock Offset 127.127.28.1 SHM(1) -96.492 -68.313 -32.591 -1.966 24.862 39.761 63.955 57.453 108.074 18.509 -2.276 µs -5.733 19.67
Refclock RMS Jitter 127.127.28.0 SHM(0) 0.998 2.280 4.093 12.012 26.108 33.935 55.916 22.015 31.654 6.708 13.194 ms 4.945 16
Refclock RMS Jitter 127.127.28.1 SHM(1) 0.151 0.403 1.162 11.051 29.236 40.064 68.759 28.074 39.661 8.752 12.607 µs 2.641 8.743
Server Jitter 139.143.5.31 0.012 0.016 0.020 0.052 0.229 1.001 3.066 0.209 0.985 0.216 0.088 ms 9.193 123
Server Jitter 193.67.79.202 12.628 16.811 24.605 57.831 234.931 448.247 483.791 210.326 431.436 75.118 78.228 µs 3.387 15.14
Server Jitter 2001:8b0:0:23::205 (ntp2.aa.net.uk) 0.014 0.017 0.023 0.054 0.184 0.511 11.121 0.161 0.494 0.877 0.141 ms 9.25 117.8
Server Jitter 81.187.26.174 0.014 0.018 0.024 0.059 0.306 0.444 20.708 0.282 0.426 0.948 0.126 ms 18.26 397.5
Server Offset 139.143.5.31 -84.028 -28.973 252.186 366.211 443.061 503.646 542.099 190.875 532.619 81.433 357.422 µs 46.31 176.8
Server Offset 193.67.79.202 -392.061 -319.290 -110.481 98.023 175.971 213.515 287.598 286.452 532.805 90.313 82.650 µs -2.918 12.96
Server Offset 2001:8b0:0:23::205 (ntp2.aa.net.uk) -80.530 -0.056 281.041 396.173 494.412 570.448 638.690 213.371 570.504 85.127 386.812 µs 53.41 218.7
Server Offset 81.187.26.174 -547.605 -519.583 -370.434 -104.684 -21.227 79.697 172.685 349.207 599.280 100.348 -120.213 µs -19.29 80.14
TDOP 0.540 0.560 0.610 0.900 1.540 2.300 2.420 0.930 1.740 0.316 0.967 16.5 63.42
Temp LM0 43.000 43.000 43.000 44.000 45.000 46.000 46.000 2.000 3.000 0.674 44.237 °C
Temp LM1 22.000 23.000 23.000 25.000 27.000 29.000 32.000 4.000 6.000 1.289 25.250 °C
Temp LM2 36.000 37.000 37.000 38.000 39.000 40.000 40.000 2.000 3.000 0.677 37.657 °C
Temp LM3 37.000 37.000 37.000 38.000 39.000 40.000 40.000 2.000 3.000 0.608 37.922 °C
Temp LM4 36.000 36.000 36.000 37.000 38.000 39.000 39.000 2.000 3.000 0.691 36.659 °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 34.000 34.000 35.000 36.000 38.000 39.000 41.000 3.000 5.000 1.108 36.293 °C
Temp LM8 34.000 34.000 35.000 36.000 38.000 39.000 41.000 3.000 5.000 1.106 36.295 °C
Temp LM9 31.000 32.000 32.000 34.000 35.000 37.000 38.000 3.000 5.000 0.845 33.576 °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 39.000 41.000 3.000 5.000 1.132 36.265 °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 1.009 8.621 nSat 452 3585
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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