NTPsec

sam.ljay.org.uk

Report generated: Fri Sep 12 20:00:02 2025 UTC
Start Time: Thu Sep 11 11:00:01 2025 UTC
End Time: Fri Sep 12 20:00:01 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 -39.434 -29.566 -15.458 0.331 17.336 27.780 43.230 32.794 57.346 10.297 0.493 µs -3.717 10.83
Local Clock Frequency Offset 13.430 13.433 13.444 13.535 13.619 13.622 13.626 0.175 0.189 0.055 13.537 ppm 1.458e+07 3.561e+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 0.428 0.497 0.679 6.695 14.528 16.949 20.512 13.849 16.452 4.735 6.790 µs 1.671 3.59

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 0.083 0.123 0.199 0.529 1.089 1.322 1.634 0.890 1.199 0.279 0.569 ppb 4.88 13.4

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 -39.434 -29.566 -15.458 0.331 17.336 27.780 43.230 32.794 57.346 10.297 0.493 µs -3.717 10.83

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 13.430 13.433 13.444 13.535 13.619 13.622 13.626 0.175 0.189 0.055 13.537 ppm 1.458e+07 3.561e+09
Temp LM0 43.000 43.000 43.000 44.000 44.000 44.000 44.000 1.000 1.000 0.489 43.605 °C
Temp LM1 21.000 22.000 22.000 25.000 27.000 27.000 30.000 5.000 5.000 1.340 24.579 °C
Temp LM2 36.000 36.000 36.000 36.000 37.000 37.000 39.000 1.000 1.000 0.508 36.388 °C
Temp LM3 36.000 36.000 36.000 37.000 37.000 38.000 39.000 1.000 2.000 0.585 36.615 °C
Temp LM4 35.000 35.000 35.000 36.000 36.000 36.000 38.000 1.000 1.000 0.519 35.577 °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 33.000 34.000 36.000 37.000 38.000 40.000 3.000 5.000 1.056 35.524 °C
Temp LM8 33.000 33.000 34.000 36.000 37.000 38.000 40.000 3.000 5.000 1.039 35.539 °C
Temp LM9 31.000 31.000 32.000 33.000 34.000 35.000 36.000 2.000 4.000 0.822 33.134 °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 33.000 34.000 35.000 37.000 38.000 39.000 3.000 5.000 1.030 35.499 °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 0.957 8.601 nSat 532.9 4449
TDOP 0.540 0.580 0.640 0.880 1.440 2.500 3.070 0.800 1.920 0.311 0.960 17.94 80.66

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) -690.508 -667.825 -648.241 -609.393 -575.809 -561.723 -535.284 72.432 106.102 22.034 -610.441 ms -2.374e+04 6.838e+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) -39.435 -29.567 -15.459 0.332 17.337 27.781 43.231 32.796 57.348 10.297 0.493 µs -3.717 10.83

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 139.143.5.31 165.393 204.940 307.131 619.564 706.392 808.011 882.922 399.261 603.071 108.990 597.387 µs 101.6 497.5

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 -203.477 -155.331 -88.126 260.248 345.902 467.029 536.821 434.028 622.360 112.627 241.978 µs 2.974 8.196

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) -0.443 -0.170 -0.025 0.716 1.549 1.623 1.693 1.574 1.793 0.430 0.771 ms 2.926 7.142

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 -326.366 -245.591 -193.007 164.524 267.749 358.158 393.870 460.756 603.749 123.898 137.391 µs -1.391 5.184

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) 1.169 3.100 4.778 11.575 25.084 32.539 50.174 20.305 29.439 6.286 12.753 ms 5.33 17.09

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) 0.130 0.250 0.443 4.260 24.115 33.140 48.367 23.672 32.890 8.232 7.715 µs 1.107 4.109

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 0.015 0.021 0.069 1.162 3.626 30.874 1.142 3.611 1.564 0.328 ms 13.46 264.2

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 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 10.455 18.199 21.678 55.998 385.501 469.246 4,260.174 363.823 451.047 298.766 111.273 µs 9.872 136.8

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 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) 8.745 12.644 18.591 54.539 312.919 438.320 3,474.392 294.328 425.676 241.812 96.882 µs 9.704 131.9

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 8.470 16.371 21.583 68.145 382.225 437.781 526.002 360.642 421.410 105.140 106.844 µs 1.9 5.878

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 13.430 13.433 13.444 13.535 13.619 13.622 13.626 0.175 0.189 0.055 13.537 ppm 1.458e+07 3.561e+09
Local Clock Time Offset -39.434 -29.566 -15.458 0.331 17.336 27.780 43.230 32.794 57.346 10.297 0.493 µs -3.717 10.83
Local RMS Frequency Jitter 0.083 0.123 0.199 0.529 1.089 1.322 1.634 0.890 1.199 0.279 0.569 ppb 4.88 13.4
Local RMS Time Jitter 0.428 0.497 0.679 6.695 14.528 16.949 20.512 13.849 16.452 4.735 6.790 µs 1.671 3.59
Refclock Offset 127.127.28.0 SHM(0) -690.508 -667.825 -648.241 -609.393 -575.809 -561.723 -535.284 72.432 106.102 22.034 -610.441 ms -2.374e+04 6.838e+05
Refclock Offset 127.127.28.1 SHM(1) -39.435 -29.567 -15.459 0.332 17.337 27.781 43.231 32.796 57.348 10.297 0.493 µs -3.717 10.83
Refclock RMS Jitter 127.127.28.0 SHM(0) 1.169 3.100 4.778 11.575 25.084 32.539 50.174 20.305 29.439 6.286 12.753 ms 5.33 17.09
Refclock RMS Jitter 127.127.28.1 SHM(1) 0.130 0.250 0.443 4.260 24.115 33.140 48.367 23.672 32.890 8.232 7.715 µs 1.107 4.109
Server Jitter 139.143.5.31 0.012 0.015 0.021 0.069 1.162 3.626 30.874 1.142 3.611 1.564 0.328 ms 13.46 264.2
Server Jitter 193.67.79.202 10.455 18.199 21.678 55.998 385.501 469.246 4,260.174 363.823 451.047 298.766 111.273 µs 9.872 136.8
Server Jitter 2001:8b0:0:23::205 (ntp2.aa.net.uk) 8.745 12.644 18.591 54.539 312.919 438.320 3,474.392 294.328 425.676 241.812 96.882 µs 9.704 131.9
Server Jitter 81.187.26.174 8.470 16.371 21.583 68.145 382.225 437.781 526.002 360.642 421.410 105.140 106.844 µs 1.9 5.878
Server Offset 139.143.5.31 165.393 204.940 307.131 619.564 706.392 808.011 882.922 399.261 603.071 108.990 597.387 µs 101.6 497.5
Server Offset 193.67.79.202 -203.477 -155.331 -88.126 260.248 345.902 467.029 536.821 434.028 622.360 112.627 241.978 µs 2.974 8.196
Server Offset 2001:8b0:0:23::205 (ntp2.aa.net.uk) -0.443 -0.170 -0.025 0.716 1.549 1.623 1.693 1.574 1.793 0.430 0.771 ms 2.926 7.142
Server Offset 81.187.26.174 -326.366 -245.591 -193.007 164.524 267.749 358.158 393.870 460.756 603.749 123.898 137.391 µs -1.391 5.184
TDOP 0.540 0.580 0.640 0.880 1.440 2.500 3.070 0.800 1.920 0.311 0.960 17.94 80.66
Temp LM0 43.000 43.000 43.000 44.000 44.000 44.000 44.000 1.000 1.000 0.489 43.605 °C
Temp LM1 21.000 22.000 22.000 25.000 27.000 27.000 30.000 5.000 5.000 1.340 24.579 °C
Temp LM2 36.000 36.000 36.000 36.000 37.000 37.000 39.000 1.000 1.000 0.508 36.388 °C
Temp LM3 36.000 36.000 36.000 37.000 37.000 38.000 39.000 1.000 2.000 0.585 36.615 °C
Temp LM4 35.000 35.000 35.000 36.000 36.000 36.000 38.000 1.000 1.000 0.519 35.577 °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 33.000 34.000 36.000 37.000 38.000 40.000 3.000 5.000 1.056 35.524 °C
Temp LM8 33.000 33.000 34.000 36.000 37.000 38.000 40.000 3.000 5.000 1.039 35.539 °C
Temp LM9 31.000 31.000 32.000 33.000 34.000 35.000 36.000 2.000 4.000 0.822 33.134 °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 33.000 34.000 35.000 37.000 38.000 39.000 3.000 5.000 1.030 35.499 °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 0.957 8.601 nSat 532.9 4449
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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