NTPsec

Backup/Meinberg

Report generated: Thu Apr 3 03:33:00 2025 UTC
Start Time: Wed Apr 2 03:33:00 2025 UTC
End Time: Thu Apr 3 03:33:00 2025 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 -595.045 -101.606 -58.036 -3.620 55.075 75.613 286.069 113.111 177.219 47.012 -3.428 µs -3.352 53.08
Local Clock Frequency Offset -174.042 -155.991 -143.341 164.886 437.469 532.730 772.324 580.810 688.721 179.050 166.750 ppb -0.06325 2.67

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 15.736 17.923 20.735 36.453 98.174 198.419 255.907 77.439 180.496 28.524 42.620 µs 3.966 22.55

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 7.149 7.855 10.041 18.104 66.456 111.940 124.838 56.415 104.085 18.335 22.639 ppb 3.564 16.37

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 -595.045 -101.606 -58.036 -3.620 55.075 75.613 286.069 113.111 177.219 47.012 -3.428 µs -3.352 53.08

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 -174.042 -155.991 -143.341 164.886 437.469 532.730 772.324 580.810 688.721 179.050 166.750 ppb -0.06325 2.67
Temp /dev/sda 40.000 40.000 40.000 41.000 42.000 42.000 42.000 2.000 2.000 0.669 41.160 °C
Temp /dev/sdb 51.000 51.000 51.000 53.000 54.000 55.000 56.000 3.000 4.000 1.029 52.645 °C
Temp /dev/sdc 51.000 51.000 51.000 53.000 53.000 53.000 54.000 2.000 2.000 0.836 52.557 °C
Temp /dev/sdd 57.000 57.000 57.000 59.000 60.000 60.000 60.000 3.000 3.000 0.854 58.753 °C
Temp /dev/sde 40.000 40.000 40.000 41.000 42.000 42.000 42.000 2.000 2.000 0.653 41.052 °C
Temp /dev/sdf 51.000 51.000 51.000 52.000 53.000 53.000 53.000 2.000 2.000 0.723 52.188 °C
Temp LM0 25.500 25.750 25.750 26.500 28.000 30.500 34.500 2.250 4.750 0.890 26.704 °C
Temp LM1 37.000 37.000 37.000 38.000 39.000 39.500 39.500 2.000 2.500 0.623 38.071 °C
Temp LM10 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM11 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM12 40.000 40.000 40.000 41.000 42.000 42.000 42.000 2.000 2.000 0.669 41.160 °C
Temp LM13 27.800 27.800 27.800 27.800 27.800 27.800 27.800 0.000 0.000 0.000 27.800 °C
Temp LM14 29.800 29.800 29.800 29.800 29.800 29.800 29.800 0.000 0.000 0.000 29.800 °C
Temp LM15 27.000 27.000 27.250 28.000 29.250 29.750 31.250 2.000 2.750 0.646 28.070 °C
Temp LM16 51.000 51.000 51.000 52.000 53.000 54.000 54.000 2.000 3.000 0.751 52.279 °C
Temp LM17 55.500 55.500 55.500 57.500 59.000 59.000 59.500 3.500 3.500 0.842 57.214 °C
Temp LM18 57.000 57.000 57.000 59.000 60.000 60.000 60.000 3.000 3.000 0.875 58.843 °C
Temp LM19 51.000 51.000 51.000 53.000 54.000 55.000 56.000 3.000 4.000 1.059 52.718 °C
Temp LM2 40.000 40.000 40.000 41.000 42.000 42.000 42.000 2.000 2.000 0.659 41.070 °C
Temp LM20 24.000 24.000 24.000 26.000 27.000 34.000 58.000 3.000 10.000 2.694 25.920 °C
Temp LM21 23.000 24.000 24.000 26.000 27.000 34.000 49.000 3.000 10.000 2.229 25.707 °C
Temp LM22 21.000 22.000 22.000 24.000 25.000 32.000 58.000 3.000 10.000 2.711 24.017 °C
Temp LM23 21.000 22.000 23.000 25.000 26.000 33.000 57.000 3.000 11.000 2.839 24.829 °C
Temp LM24 22.000 22.000 23.000 24.000 26.000 33.000 50.000 3.000 11.000 2.351 24.679 °C
Temp LM3 29.000 29.000 29.000 30.000 31.000 32.000 33.000 2.000 3.000 0.793 30.226 °C
Temp LM4 28.500 28.500 29.000 29.500 31.000 31.000 31.500 2.000 2.500 0.650 29.749 °C
Temp LM5 24.000 24.000 24.000 24.000 24.000 24.000 24.000 0.000 0.000 0.000 24.000 °C
Temp LM6 24.000 24.000 24.000 25.000 26.500 33.500 59.500 2.500 9.500 2.781 25.333 °C
Temp LM7 55.000 55.000 55.000 57.000 59.000 59.000 59.000 4.000 4.000 0.902 56.927 °C
Temp LM8 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM9 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp ZONE0 23.000 24.000 24.000 25.000 27.000 34.000 59.000 3.000 10.000 2.801 25.592 °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 55.500 55.500 56.000 57.500 59.000 59.000 59.500 3.000 3.500 0.829 57.220 °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) -963.665 -902.944 -761.697 63.783 361.598 415.060 450.850 1,123.295 1,318.004 292.296 -1.926 µs -1.581 5.267

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 -746.587 -680.750 -593.481 97.924 628.416 740.540 782.289 1,221.897 1,421.290 333.414 49.391 µs -0.1298 2.758

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 -585.576 -124.190 -77.146 -5.790 58.949 99.952 21,495.209 136.095 224.142 946.606 41.647 µs 21.18 471

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 -397.839 -146.350 -76.099 13.917 90.670 305.153 631.533 166.769 451.503 75.246 15.557 µs 1.818 24.16

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.



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) 1.418 4.219 6.491 15.847 50.342 100.214 318.426 43.851 95.995 23.410 21.127 µs 6.607 65.35

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 3.300 4.929 6.835 17.903 47.693 128.084 197.173 40.858 123.155 19.873 22.278 µs 4.539 32.02

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.



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 0.000 5.256 7.951 23.218 61.726 163.783 15,152.366 53.775 158.527 1,121.008 120.639 µs 12.21 152.9

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 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 3.666 5.710 9.131 79.903 151.159 187.986 255.317 142.028 182.276 47.484 76.270 µs 0.3064 2.511

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 -174.042 -155.991 -143.341 164.886 437.469 532.730 772.324 580.810 688.721 179.050 166.750 ppb -0.06325 2.67
Local Clock Time Offset -595.045 -101.606 -58.036 -3.620 55.075 75.613 286.069 113.111 177.219 47.012 -3.428 µs -3.352 53.08
Local RMS Frequency Jitter 7.149 7.855 10.041 18.104 66.456 111.940 124.838 56.415 104.085 18.335 22.639 ppb 3.564 16.37
Local RMS Time Jitter 15.736 17.923 20.735 36.453 98.174 198.419 255.907 77.439 180.496 28.524 42.620 µs 3.966 22.55
Server Jitter 2001:470:e815::8 (spidey.rellim.com) 1.418 4.219 6.491 15.847 50.342 100.214 318.426 43.851 95.995 23.410 21.127 µs 6.607 65.35
Server Jitter 204.17.205.1 3.300 4.929 6.835 17.903 47.693 128.084 197.173 40.858 123.155 19.873 22.278 µs 4.539 32.02
Server Jitter 204.17.205.24 0.000 5.256 7.951 23.218 61.726 163.783 15,152.366 53.775 158.527 1,121.008 120.639 µs 12.21 152.9
Server Jitter 204.17.205.27 3.666 5.710 9.131 79.903 151.159 187.986 255.317 142.028 182.276 47.484 76.270 µs 0.3064 2.511
Server Offset 2001:470:e815::8 (spidey.rellim.com) -963.665 -902.944 -761.697 63.783 361.598 415.060 450.850 1,123.295 1,318.004 292.296 -1.926 µs -1.581 5.267
Server Offset 204.17.205.1 -746.587 -680.750 -593.481 97.924 628.416 740.540 782.289 1,221.897 1,421.290 333.414 49.391 µs -0.1298 2.758
Server Offset 204.17.205.24 -585.576 -124.190 -77.146 -5.790 58.949 99.952 21,495.209 136.095 224.142 946.606 41.647 µs 21.18 471
Server Offset 204.17.205.27 -397.839 -146.350 -76.099 13.917 90.670 305.153 631.533 166.769 451.503 75.246 15.557 µs 1.818 24.16
Temp /dev/sda 40.000 40.000 40.000 41.000 42.000 42.000 42.000 2.000 2.000 0.669 41.160 °C
Temp /dev/sdb 51.000 51.000 51.000 53.000 54.000 55.000 56.000 3.000 4.000 1.029 52.645 °C
Temp /dev/sdc 51.000 51.000 51.000 53.000 53.000 53.000 54.000 2.000 2.000 0.836 52.557 °C
Temp /dev/sdd 57.000 57.000 57.000 59.000 60.000 60.000 60.000 3.000 3.000 0.854 58.753 °C
Temp /dev/sde 40.000 40.000 40.000 41.000 42.000 42.000 42.000 2.000 2.000 0.653 41.052 °C
Temp /dev/sdf 51.000 51.000 51.000 52.000 53.000 53.000 53.000 2.000 2.000 0.723 52.188 °C
Temp LM0 25.500 25.750 25.750 26.500 28.000 30.500 34.500 2.250 4.750 0.890 26.704 °C
Temp LM1 37.000 37.000 37.000 38.000 39.000 39.500 39.500 2.000 2.500 0.623 38.071 °C
Temp LM10 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM11 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM12 40.000 40.000 40.000 41.000 42.000 42.000 42.000 2.000 2.000 0.669 41.160 °C
Temp LM13 27.800 27.800 27.800 27.800 27.800 27.800 27.800 0.000 0.000 0.000 27.800 °C
Temp LM14 29.800 29.800 29.800 29.800 29.800 29.800 29.800 0.000 0.000 0.000 29.800 °C
Temp LM15 27.000 27.000 27.250 28.000 29.250 29.750 31.250 2.000 2.750 0.646 28.070 °C
Temp LM16 51.000 51.000 51.000 52.000 53.000 54.000 54.000 2.000 3.000 0.751 52.279 °C
Temp LM17 55.500 55.500 55.500 57.500 59.000 59.000 59.500 3.500 3.500 0.842 57.214 °C
Temp LM18 57.000 57.000 57.000 59.000 60.000 60.000 60.000 3.000 3.000 0.875 58.843 °C
Temp LM19 51.000 51.000 51.000 53.000 54.000 55.000 56.000 3.000 4.000 1.059 52.718 °C
Temp LM2 40.000 40.000 40.000 41.000 42.000 42.000 42.000 2.000 2.000 0.659 41.070 °C
Temp LM20 24.000 24.000 24.000 26.000 27.000 34.000 58.000 3.000 10.000 2.694 25.920 °C
Temp LM21 23.000 24.000 24.000 26.000 27.000 34.000 49.000 3.000 10.000 2.229 25.707 °C
Temp LM22 21.000 22.000 22.000 24.000 25.000 32.000 58.000 3.000 10.000 2.711 24.017 °C
Temp LM23 21.000 22.000 23.000 25.000 26.000 33.000 57.000 3.000 11.000 2.839 24.829 °C
Temp LM24 22.000 22.000 23.000 24.000 26.000 33.000 50.000 3.000 11.000 2.351 24.679 °C
Temp LM3 29.000 29.000 29.000 30.000 31.000 32.000 33.000 2.000 3.000 0.793 30.226 °C
Temp LM4 28.500 28.500 29.000 29.500 31.000 31.000 31.500 2.000 2.500 0.650 29.749 °C
Temp LM5 24.000 24.000 24.000 24.000 24.000 24.000 24.000 0.000 0.000 0.000 24.000 °C
Temp LM6 24.000 24.000 24.000 25.000 26.500 33.500 59.500 2.500 9.500 2.781 25.333 °C
Temp LM7 55.000 55.000 55.000 57.000 59.000 59.000 59.000 4.000 4.000 0.902 56.927 °C
Temp LM8 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM9 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp ZONE0 23.000 24.000 24.000 25.000 27.000 34.000 59.000 3.000 10.000 2.801 25.592 °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 55.500 55.500 56.000 57.500 59.000 59.000 59.500 3.000 3.500 0.829 57.220 °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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