NTPsec

sam.ljay.org.uk

Report generated: Thu Jul 10 02:00:02 2025 UTC
Start Time: Tue Jul 8 17:00:02 2025 UTC
End Time: Thu Jul 10 02:00:02 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 -54.401 -37.373 -26.231 -0.975 21.974 32.295 63.105 48.205 69.668 14.402 -1.217 µs -4.612 12.67
Local Clock Frequency Offset 13.372 13.374 13.394 13.505 13.621 13.636 13.639 0.227 0.262 0.062 13.502 ppm 1.019e+07 2.209e+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 0.348 0.896 2.000 10.135 18.026 20.759 27.754 16.026 19.863 4.632 10.173 µs 5.401 13.89

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 0.085 0.112 0.218 0.729 1.572 1.883 2.242 1.354 1.771 0.378 0.798 ppb 5.476 16.13

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 -54.401 -37.373 -26.231 -0.975 21.974 32.295 63.105 48.205 69.668 14.402 -1.217 µs -4.612 12.67

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 13.372 13.374 13.394 13.505 13.621 13.636 13.639 0.227 0.262 0.062 13.502 ppm 1.019e+07 2.209e+09
Temp LM0 43.000 43.000 43.000 44.000 45.000 45.000 45.000 2.000 2.000 0.484 43.889 °C
Temp LM1 22.000 22.000 23.000 25.000 27.000 28.000 31.000 4.000 6.000 1.334 25.078 °C
Temp LM2 36.000 36.000 37.000 37.000 38.000 39.000 40.000 1.000 3.000 0.564 37.259 °C
Temp LM3 37.000 37.000 37.000 38.000 38.000 39.000 39.000 1.000 2.000 0.528 37.537 °C
Temp LM4 35.000 35.000 36.000 36.000 37.000 38.000 38.000 1.000 3.000 0.511 36.290 °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 34.000 36.000 38.000 38.000 40.000 4.000 4.000 1.115 36.111 °C
Temp LM8 33.000 34.000 34.000 36.000 38.000 38.000 40.000 4.000 4.000 1.106 36.134 °C
Temp LM9 31.000 31.000 32.000 33.000 34.000 36.000 36.000 2.000 5.000 0.895 33.025 °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 33.000 34.000 34.000 36.000 38.000 39.000 40.000 4.000 5.000 1.144 36.063 °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 7.000 7.000 9.000 10.000 11.000 11.000 3.000 4.000 0.977 8.682 nSat 514.4 4250
TDOP 0.550 0.560 0.630 0.910 1.560 2.780 3.550 0.930 2.220 0.384 0.986 11.52 55.1

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) -720.058 -703.425 -688.176 -643.748 -602.872 -590.783 -566.844 85.304 112.642 25.630 -644.369 ms -1.794e+04 4.711e+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) -54.402 -37.374 -26.232 -0.976 21.975 32.296 63.106 48.207 69.670 14.403 -1.217 µs -4.612 12.67

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 -151.820 -27.736 216.295 381.191 490.961 588.999 629.970 274.666 616.735 93.108 373.014 µs 34.24 123.4

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 -261.851 -193.362 -22.546 206.790 302.438 356.629 430.492 324.984 549.991 104.303 182.469 µs 1.125 5.35

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) -127.268 -15.416 67.382 386.037 513.223 583.345 656.926 445.841 598.761 126.551 361.279 µs 10.79 28.4

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 -682.496 -529.163 -307.974 -108.029 10.378 92.739 115.181 318.352 621.902 99.839 -115.485 µs -18.69 79.16

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 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) 1.016 2.322 4.495 12.221 26.810 35.588 53.461 22.315 33.265 6.915 13.559 ms 4.927 15.9

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) 0.123 0.295 0.802 10.524 28.040 38.137 56.585 27.238 37.842 8.507 11.968 µs 2.372 7.449

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 0.016 0.022 0.061 1.558 3.913 9.434 1.536 3.896 0.960 0.307 ms 4.19 40.8

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 0.005 0.014 0.022 0.054 0.369 1.935 18.569 0.347 1.921 1.070 0.189 ms 10.3 167.2

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 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 0.018 0.023 0.060 0.249 1.630 35.770 0.226 1.611 1.744 0.206 ms 15.03 307.1

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 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 7.466 15.325 22.108 60.243 328.456 461.456 1,455.340 306.348 446.131 108.692 89.700 µs 5.256 54.8

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.



Summary


Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Frequency Offset 13.372 13.374 13.394 13.505 13.621 13.636 13.639 0.227 0.262 0.062 13.502 ppm 1.019e+07 2.209e+09
Local Clock Time Offset -54.401 -37.373 -26.231 -0.975 21.974 32.295 63.105 48.205 69.668 14.402 -1.217 µs -4.612 12.67
Local RMS Frequency Jitter 0.085 0.112 0.218 0.729 1.572 1.883 2.242 1.354 1.771 0.378 0.798 ppb 5.476 16.13
Local RMS Time Jitter 0.348 0.896 2.000 10.135 18.026 20.759 27.754 16.026 19.863 4.632 10.173 µs 5.401 13.89
Refclock Offset 127.127.28.0 SHM(0) -720.058 -703.425 -688.176 -643.748 -602.872 -590.783 -566.844 85.304 112.642 25.630 -644.369 ms -1.794e+04 4.711e+05
Refclock Offset 127.127.28.1 SHM(1) -54.402 -37.374 -26.232 -0.976 21.975 32.296 63.106 48.207 69.670 14.403 -1.217 µs -4.612 12.67
Refclock RMS Jitter 127.127.28.0 SHM(0) 1.016 2.322 4.495 12.221 26.810 35.588 53.461 22.315 33.265 6.915 13.559 ms 4.927 15.9
Refclock RMS Jitter 127.127.28.1 SHM(1) 0.123 0.295 0.802 10.524 28.040 38.137 56.585 27.238 37.842 8.507 11.968 µs 2.372 7.449
Server Jitter 139.143.5.31 0.014 0.016 0.022 0.061 1.558 3.913 9.434 1.536 3.896 0.960 0.307 ms 4.19 40.8
Server Jitter 193.67.79.202 0.005 0.014 0.022 0.054 0.369 1.935 18.569 0.347 1.921 1.070 0.189 ms 10.3 167.2
Server Jitter 2001:8b0:0:23::205 (ntp2.aa.net.uk) 0.010 0.018 0.023 0.060 0.249 1.630 35.770 0.226 1.611 1.744 0.206 ms 15.03 307.1
Server Jitter 81.187.26.174 7.466 15.325 22.108 60.243 328.456 461.456 1,455.340 306.348 446.131 108.692 89.700 µs 5.256 54.8
Server Offset 139.143.5.31 -151.820 -27.736 216.295 381.191 490.961 588.999 629.970 274.666 616.735 93.108 373.014 µs 34.24 123.4
Server Offset 193.67.79.202 -261.851 -193.362 -22.546 206.790 302.438 356.629 430.492 324.984 549.991 104.303 182.469 µs 1.125 5.35
Server Offset 2001:8b0:0:23::205 (ntp2.aa.net.uk) -127.268 -15.416 67.382 386.037 513.223 583.345 656.926 445.841 598.761 126.551 361.279 µs 10.79 28.4
Server Offset 81.187.26.174 -682.496 -529.163 -307.974 -108.029 10.378 92.739 115.181 318.352 621.902 99.839 -115.485 µs -18.69 79.16
TDOP 0.550 0.560 0.630 0.910 1.560 2.780 3.550 0.930 2.220 0.384 0.986 11.52 55.1
Temp LM0 43.000 43.000 43.000 44.000 45.000 45.000 45.000 2.000 2.000 0.484 43.889 °C
Temp LM1 22.000 22.000 23.000 25.000 27.000 28.000 31.000 4.000 6.000 1.334 25.078 °C
Temp LM2 36.000 36.000 37.000 37.000 38.000 39.000 40.000 1.000 3.000 0.564 37.259 °C
Temp LM3 37.000 37.000 37.000 38.000 38.000 39.000 39.000 1.000 2.000 0.528 37.537 °C
Temp LM4 35.000 35.000 36.000 36.000 37.000 38.000 38.000 1.000 3.000 0.511 36.290 °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 34.000 36.000 38.000 38.000 40.000 4.000 4.000 1.115 36.111 °C
Temp LM8 33.000 34.000 34.000 36.000 38.000 38.000 40.000 4.000 4.000 1.106 36.134 °C
Temp LM9 31.000 31.000 32.000 33.000 34.000 36.000 36.000 2.000 5.000 0.895 33.025 °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 33.000 34.000 34.000 36.000 38.000 39.000 40.000 4.000 5.000 1.144 36.063 °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 7.000 7.000 9.000 10.000 11.000 11.000 3.000 4.000 0.977 8.682 nSat 514.4 4250
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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