NTPsec

Backup/Meinberg

Report generated: Thu Aug 6 20:33:00 2026 UTC
Start Time: Wed Aug 5 20:33:00 2026 UTC
End Time: Thu Aug 6 20:33:00 2026 UTC
Report Period: 1.0 days
Warning: plots clipped

Daily stats   Weekly stats  

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 -110.833 -77.571 -50.511 -3.300 48.243 72.725 101.786 98.754 150.296 28.219 -1.851 µs -0.0247 4.264
Local Clock Frequency Offset 12.583 12.587 12.631 12.880 13.270 13.309 13.320 0.639 0.722 0.218 12.947 ppm 0.2165 1.604

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 10.502 11.306 13.783 33.130 56.324 64.126 69.943 42.541 52.820 12.663 33.669 µs 0.2993 2.51

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 4.254 4.774 7.375 16.053 30.757 37.557 43.118 23.382 32.783 7.254 17.257 ppb 0.7292 3.269

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 -110.833 -77.571 -50.511 -3.300 48.243 72.725 101.786 98.754 150.296 28.219 -1.851 µs -0.0247 4.264

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 12.583 12.587 12.631 12.880 13.270 13.309 13.320 0.639 0.722 0.218 12.947 ppm 0.2165 1.604
Temp /dev/sda 66.000 66.000 67.000 68.000 71.000 71.000 72.000 4.000 5.000 1.596 68.545 °C
Temp /dev/sdb 48.000 48.000 48.000 53.000 55.000 56.000 56.000 7.000 8.000 2.958 51.685 °C
Temp /dev/sdc 60.000 60.000 60.000 60.000 65.000 65.000 65.000 5.000 5.000 2.071 61.741 °C
Temp /dev/sdd 72.000 72.000 72.000 75.000 79.000 79.000 80.000 7.000 7.000 2.361 75.318 °C
Temp /dev/sde 52.000 52.000 52.000 53.000 61.000 61.000 61.000 9.000 9.000 3.278 54.979 °C
Temp /dev/sdf 50.000 50.000 50.000 52.000 58.000 58.000 58.000 8.000 8.000 3.038 53.241 °C
Temp LM0 50.000 50.000 50.000 53.000 58.000 58.000 58.000 8.000 8.000 3.046 53.290 °C
Temp LM1 64.000 64.000 64.000 65.000 69.500 70.000 70.000 5.500 6.000 2.039 66.332 °C
Temp LM10 27.800 27.800 27.800 27.800 27.800 27.800 27.800 0.000 0.000 0.000 27.800 °C
Temp LM11 31.500 31.500 31.750 32.750 35.500 35.750 35.750 3.750 4.250 1.370 33.316 °C
Temp LM12 44.500 44.500 44.500 46.000 46.500 47.000 47.000 2.000 2.500 0.685 45.753 °C
Temp LM13 52.000 52.000 52.000 53.000 61.000 61.000 61.000 9.000 9.000 3.331 55.042 °C
Temp LM14 36.000 36.000 36.000 37.000 38.000 38.000 38.000 2.000 2.000 0.746 36.766 °C
Temp LM15 34.500 34.500 34.500 36.000 37.500 37.500 38.000 3.000 3.000 1.056 36.026 °C
Temp LM16 24.000 24.000 24.000 24.000 24.000 24.000 24.000 0.000 0.000 0.000 24.000 °C
Temp LM17 30.000 30.000 30.500 31.500 34.000 34.500 56.500 3.500 4.500 1.930 31.991 °C
Temp LM18 64.000 64.000 64.000 65.000 69.000 70.000 70.000 5.000 6.000 2.048 66.059 °C
Temp LM19 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM2 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM20 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM21 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM22 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM23 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM24 29.800 29.800 29.800 29.800 29.800 29.800 29.800 0.000 0.000 0.000 29.800 °C
Temp LM3 32.750 32.750 33.000 34.000 36.750 37.000 37.000 3.750 4.250 1.344 34.625 °C
Temp LM4 48.000 48.000 48.000 53.000 55.000 56.000 56.000 7.000 8.000 2.983 51.720 °C
Temp LM5 30.000 30.000 30.000 32.000 34.000 35.000 57.000 4.000 5.000 2.026 32.287 °C
Temp LM6 29.000 29.000 30.000 32.000 34.000 35.000 57.000 4.000 6.000 2.083 32.115 °C
Temp LM7 28.000 28.000 28.000 30.000 32.000 33.000 48.000 4.000 5.000 1.733 30.105 °C
Temp LM8 28.000 29.000 30.000 31.000 34.000 35.000 46.000 4.000 6.000 1.641 31.556 °C
Temp LM9 28.000 29.000 29.000 31.000 33.000 33.000 43.000 4.000 4.000 1.287 30.993 °C
Temp ZONE0 29.000 30.000 30.000 32.000 34.000 35.000 56.000 4.000 5.000 1.972 32.192 °C
Temp ZONE1 27.800 27.800 27.800 27.800 27.800 27.800 27.800 0.000 0.000 0.000 27.800 °C
Temp ZONE2 64.000 64.000 64.000 65.000 69.500 70.000 70.500 5.500 6.000 2.056 66.355 °C
Temp ZONE3 29.800 29.800 29.800 29.800 29.800 29.800 29.800 0.000 0.000 0.000 29.800 °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.



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.



Server Offset 2001:470:e815::8 (spidey.rellim.com)

peer offset 2001:470:e815::8 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2001:470:e815::8 (spidey.rellim.com) -294.891 -257.938 -224.822 -6.943 151.386 193.971 206.775 376.208 451.909 112.031 -11.258 µs -0.2931 2.355

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 204.17.205.1

peer offset 204.17.205.1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 204.17.205.1 -477.199 -425.924 -376.341 -110.847 483.762 526.175 586.565 860.103 952.099 260.836 -41.794 µs 0.6433 2.457

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 204.17.205.24

peer offset 204.17.205.24 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 204.17.205.24 -149.286 -111.677 -66.619 1.811 55.149 96.782 141.226 121.768 208.459 36.931 -0.316 µs -0.4131 4.742

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 204.17.205.27

peer offset 204.17.205.27 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 204.17.205.27 -125.130 -92.723 -64.830 -1.728 59.469 136.648 341.467 124.299 229.371 43.185 0.328 µs 1.752 14.6

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.



Server Jitter 2001:470:e815::8 (spidey.rellim.com)

peer jitter 2001:470:e815::8 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2001:470:e815::8 (spidey.rellim.com) 2.821 4.400 6.911 34.088 94.475 119.455 135.794 87.564 115.055 29.431 40.673 µs 0.7528 2.705

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 204.17.205.1

peer jitter 204.17.205.1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 204.17.205.1 2.960 6.455 10.300 23.244 48.770 65.014 89.001 38.470 58.559 12.601 25.867 µs 1.07 4.659

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 204.17.205.24

peer jitter 204.17.205.24 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 204.17.205.24 2.841 4.020 9.059 24.166 57.681 86.863 102.036 48.622 82.843 15.432 27.575 µs 1.543 6.454

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 204.17.205.27

peer jitter 204.17.205.27 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 204.17.205.27 1.703 7.833 13.435 33.983 121.861 166.018 227.106 108.426 158.185 36.830 47.876 µs 1.73 6.042

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 12.583 12.587 12.631 12.880 13.270 13.309 13.320 0.639 0.722 0.218 12.947 ppm 0.2165 1.604
Local Clock Time Offset -110.833 -77.571 -50.511 -3.300 48.243 72.725 101.786 98.754 150.296 28.219 -1.851 µs -0.0247 4.264
Local RMS Frequency Jitter 4.254 4.774 7.375 16.053 30.757 37.557 43.118 23.382 32.783 7.254 17.257 ppb 0.7292 3.269
Local RMS Time Jitter 10.502 11.306 13.783 33.130 56.324 64.126 69.943 42.541 52.820 12.663 33.669 µs 0.2993 2.51
Server Jitter 2001:470:e815::8 (spidey.rellim.com) 2.821 4.400 6.911 34.088 94.475 119.455 135.794 87.564 115.055 29.431 40.673 µs 0.7528 2.705
Server Jitter 204.17.205.1 2.960 6.455 10.300 23.244 48.770 65.014 89.001 38.470 58.559 12.601 25.867 µs 1.07 4.659
Server Jitter 204.17.205.24 2.841 4.020 9.059 24.166 57.681 86.863 102.036 48.622 82.843 15.432 27.575 µs 1.543 6.454
Server Jitter 204.17.205.27 1.703 7.833 13.435 33.983 121.861 166.018 227.106 108.426 158.185 36.830 47.876 µs 1.73 6.042
Server Offset 2001:470:e815::8 (spidey.rellim.com) -294.891 -257.938 -224.822 -6.943 151.386 193.971 206.775 376.208 451.909 112.031 -11.258 µs -0.2931 2.355
Server Offset 204.17.205.1 -477.199 -425.924 -376.341 -110.847 483.762 526.175 586.565 860.103 952.099 260.836 -41.794 µs 0.6433 2.457
Server Offset 204.17.205.24 -149.286 -111.677 -66.619 1.811 55.149 96.782 141.226 121.768 208.459 36.931 -0.316 µs -0.4131 4.742
Server Offset 204.17.205.27 -125.130 -92.723 -64.830 -1.728 59.469 136.648 341.467 124.299 229.371 43.185 0.328 µs 1.752 14.6
Temp /dev/sda 66.000 66.000 67.000 68.000 71.000 71.000 72.000 4.000 5.000 1.596 68.545 °C
Temp /dev/sdb 48.000 48.000 48.000 53.000 55.000 56.000 56.000 7.000 8.000 2.958 51.685 °C
Temp /dev/sdc 60.000 60.000 60.000 60.000 65.000 65.000 65.000 5.000 5.000 2.071 61.741 °C
Temp /dev/sdd 72.000 72.000 72.000 75.000 79.000 79.000 80.000 7.000 7.000 2.361 75.318 °C
Temp /dev/sde 52.000 52.000 52.000 53.000 61.000 61.000 61.000 9.000 9.000 3.278 54.979 °C
Temp /dev/sdf 50.000 50.000 50.000 52.000 58.000 58.000 58.000 8.000 8.000 3.038 53.241 °C
Temp LM0 50.000 50.000 50.000 53.000 58.000 58.000 58.000 8.000 8.000 3.046 53.290 °C
Temp LM1 64.000 64.000 64.000 65.000 69.500 70.000 70.000 5.500 6.000 2.039 66.332 °C
Temp LM10 27.800 27.800 27.800 27.800 27.800 27.800 27.800 0.000 0.000 0.000 27.800 °C
Temp LM11 31.500 31.500 31.750 32.750 35.500 35.750 35.750 3.750 4.250 1.370 33.316 °C
Temp LM12 44.500 44.500 44.500 46.000 46.500 47.000 47.000 2.000 2.500 0.685 45.753 °C
Temp LM13 52.000 52.000 52.000 53.000 61.000 61.000 61.000 9.000 9.000 3.331 55.042 °C
Temp LM14 36.000 36.000 36.000 37.000 38.000 38.000 38.000 2.000 2.000 0.746 36.766 °C
Temp LM15 34.500 34.500 34.500 36.000 37.500 37.500 38.000 3.000 3.000 1.056 36.026 °C
Temp LM16 24.000 24.000 24.000 24.000 24.000 24.000 24.000 0.000 0.000 0.000 24.000 °C
Temp LM17 30.000 30.000 30.500 31.500 34.000 34.500 56.500 3.500 4.500 1.930 31.991 °C
Temp LM18 64.000 64.000 64.000 65.000 69.000 70.000 70.000 5.000 6.000 2.048 66.059 °C
Temp LM19 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM2 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM20 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM21 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM22 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM23 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM24 29.800 29.800 29.800 29.800 29.800 29.800 29.800 0.000 0.000 0.000 29.800 °C
Temp LM3 32.750 32.750 33.000 34.000 36.750 37.000 37.000 3.750 4.250 1.344 34.625 °C
Temp LM4 48.000 48.000 48.000 53.000 55.000 56.000 56.000 7.000 8.000 2.983 51.720 °C
Temp LM5 30.000 30.000 30.000 32.000 34.000 35.000 57.000 4.000 5.000 2.026 32.287 °C
Temp LM6 29.000 29.000 30.000 32.000 34.000 35.000 57.000 4.000 6.000 2.083 32.115 °C
Temp LM7 28.000 28.000 28.000 30.000 32.000 33.000 48.000 4.000 5.000 1.733 30.105 °C
Temp LM8 28.000 29.000 30.000 31.000 34.000 35.000 46.000 4.000 6.000 1.641 31.556 °C
Temp LM9 28.000 29.000 29.000 31.000 33.000 33.000 43.000 4.000 4.000 1.287 30.993 °C
Temp ZONE0 29.000 30.000 30.000 32.000 34.000 35.000 56.000 4.000 5.000 1.972 32.192 °C
Temp ZONE1 27.800 27.800 27.800 27.800 27.800 27.800 27.800 0.000 0.000 0.000 27.800 °C
Temp ZONE2 64.000 64.000 64.000 65.000 69.500 70.000 70.500 5.500 6.000 2.056 66.355 °C
Temp ZONE3 29.800 29.800 29.800 29.800 29.800 29.800 29.800 0.000 0.000 0.000 29.800 °C
Summary as CSV file


This server:

CPU: Quad core Intel Xeon E3-1241 v3
Kernel: config.gz
Motherboard: Supermicro X10SAE
OS: Gentoo stable
GPS; Meinberg GPS180PEX
GPS/PPS server: gpsd
NTP server: NTPsec
ntp.conf: current
ntp.log: current

Notes:

Notes:
03:20Z 20 Dec 2018 Change poll from 8s to 4s.  4s seems best.
01:30Z 20 Dec 2018 Change poll from 2s to 8s.
23:00Z 20 Dec 2018 Change poll from 4s to 2s.
22:00Z 20 Dec 2018 Change poll from 64s to 4s.
21:40  19 Dec 2018 -- just started

Poll:
64s   SHM(0) offset StdDev 34.5 us, jitter 5.3 us
8s    8s better jitter than 4s, but worse offset than 4s
4s    SHM(0) offset mean 0 ns StdDev 481 ns, jitter 449 ns StdDev 250 ns
      better than 2s, almost unstable
2s

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.
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 FIsher-Pearson moment of skewness. There are other different ways to calculate Skewness Wikipedia describes Skewness best: "The qualitative interpretation of the skew is complicated and unintuitive."
A normal distribution has a skewness of zero.
Kurtosis, Kurt:
The kurtosis of a random variable X is the fourth standardized moment and is a dimension-less ratio. ntpviz uses standard Kurtosis. There are other different ways to calculate 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".
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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