NTPsec

Backup/Meinberg

Report generated: Fri Nov 6 17:33:00 2026 UTC
Start Time: Thu Nov 5 17:33:00 2026 UTC
End Time: Fri Nov 6 17:33:00 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 -126.461 -98.372 -62.236 -2.160 58.246 97.680 154.626 120.482 196.052 37.039 -2.300 µs 0.1164 4.215
Local Clock Frequency Offset 5.684 5.702 5.761 6.037 6.231 6.377 6.454 0.470 0.675 0.151 6.026 ppm -0.1106 2.43

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 15.581 18.684 25.231 41.484 67.264 75.907 86.470 42.033 57.223 12.697 43.109 µs 0.5549 3.132

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 7.665 8.632 11.038 21.130 38.417 46.095 51.076 27.379 37.463 7.871 22.240 ppb 0.9562 4.186

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 -126.461 -98.372 -62.236 -2.160 58.246 97.680 154.626 120.482 196.052 37.039 -2.300 µs 0.1164 4.215

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 5.684 5.702 5.761 6.037 6.231 6.377 6.454 0.470 0.675 0.151 6.026 ppm -0.1106 2.43
Temp /dev/sda 61.000 61.000 61.000 62.000 64.000 64.000 67.000 3.000 3.000 1.065 62.678 °C
Temp /dev/sdb 44.000 44.000 44.000 45.000 46.000 46.000 46.000 2.000 2.000 0.596 44.958 °C
Temp /dev/sdc 54.000 54.000 54.000 56.000 56.000 56.000 56.000 2.000 2.000 0.904 55.427 °C
Temp /dev/sdd 67.000 68.000 68.000 69.000 70.000 70.000 70.000 2.000 2.000 0.568 68.797 °C
Temp /dev/sde 47.000 47.000 47.000 48.000 49.000 49.000 49.000 2.000 2.000 0.611 47.976 °C
Temp /dev/sdf 45.000 45.000 45.000 46.000 47.000 47.000 47.000 2.000 2.000 0.623 45.990 °C
Temp LM0 26.000 26.000 26.250 27.500 28.500 34.750 36.500 2.250 8.750 1.171 27.517 °C
Temp LM1 38.000 38.500 39.000 39.500 40.500 41.000 41.500 1.500 2.500 0.558 39.694 °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 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °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 27.250 27.250 27.250 28.750 30.000 32.750 33.750 2.750 5.500 0.887 28.753 °C
Temp LM16 45.000 45.000 45.000 46.000 47.000 47.000 47.000 2.000 2.000 0.617 45.983 °C
Temp LM17 57.500 57.500 57.500 59.000 60.000 60.500 61.000 2.500 3.000 0.694 58.848 °C
Temp LM18 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM19 44.000 44.000 44.000 45.000 46.000 46.000 46.000 2.000 2.000 0.591 44.941 °C
Temp LM2 47.000 47.000 47.000 48.000 49.000 49.000 49.000 2.000 2.000 0.617 47.969 °C
Temp LM20 25.000 25.000 25.000 27.000 28.000 54.000 62.000 3.000 29.000 3.634 27.217 °C
Temp LM21 25.000 25.000 25.000 27.000 28.000 51.000 62.000 3.000 26.000 3.301 27.098 °C
Temp LM22 22.000 22.000 23.000 24.000 26.000 45.000 52.000 3.000 23.000 2.999 24.804 °C
Temp LM23 23.000 23.000 24.000 25.000 27.000 46.000 59.000 3.000 23.000 3.102 25.811 °C
Temp LM24 23.000 23.000 23.000 25.000 27.000 50.000 55.000 4.000 27.000 3.064 25.350 °C
Temp LM3 30.000 30.000 30.000 32.000 33.000 35.000 36.000 3.000 5.000 0.822 31.622 °C
Temp LM4 28.000 28.500 28.500 30.500 31.500 32.000 33.000 3.000 3.500 0.986 30.231 °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 25.000 25.000 25.500 26.500 27.500 53.500 59.500 2.000 28.500 3.515 26.802 °C
Temp LM7 57.000 57.000 57.000 59.000 60.000 60.000 61.000 3.000 3.000 0.777 58.654 °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 25.000 25.000 25.000 27.000 28.000 54.000 62.000 3.000 29.000 3.671 27.014 °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 57.500 57.500 57.500 59.000 60.000 60.500 61.000 2.500 3.000 0.704 58.837 °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) -723.118 -666.052 -298.697 30.470 218.321 287.234 324.538 517.018 953.286 190.237 -9.689 µs -1.037 4.474

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 -1.296 -1.243 -0.566 0.051 0.372 0.417 0.476 0.937 1.660 0.329 -0.020 ms -1.213 4.863

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 -197.812 -134.540 -85.874 -6.784 61.668 124.831 233.271 147.542 259.371 47.190 -7.563 µs 0.2455 6.039

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 -281.850 -164.669 -74.353 12.966 94.190 168.256 345.032 168.543 332.925 59.331 13.905 µs -0.008264 7.993

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) 3.268 4.596 7.038 34.938 90.512 108.676 126.739 83.474 104.080 26.780 39.675 µs 0.7443 2.843

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 1.342 5.932 9.741 23.888 63.834 98.583 150.975 54.093 92.651 18.131 28.371 µs 2.239 10.53

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 2.272 3.819 7.415 26.421 78.824 95.195 129.897 71.409 91.376 20.637 31.520 µs 1.426 5.192

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 5.599 9.207 19.038 87.244 155.988 187.396 271.841 136.950 178.189 41.542 87.248 µs 0.2751 3.156

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 5.684 5.702 5.761 6.037 6.231 6.377 6.454 0.470 0.675 0.151 6.026 ppm -0.1106 2.43
Local Clock Time Offset -126.461 -98.372 -62.236 -2.160 58.246 97.680 154.626 120.482 196.052 37.039 -2.300 µs 0.1164 4.215
Local RMS Frequency Jitter 7.665 8.632 11.038 21.130 38.417 46.095 51.076 27.379 37.463 7.871 22.240 ppb 0.9562 4.186
Local RMS Time Jitter 15.581 18.684 25.231 41.484 67.264 75.907 86.470 42.033 57.223 12.697 43.109 µs 0.5549 3.132
Server Jitter 2001:470:e815::8 (spidey.rellim.com) 3.268 4.596 7.038 34.938 90.512 108.676 126.739 83.474 104.080 26.780 39.675 µs 0.7443 2.843
Server Jitter 204.17.205.1 1.342 5.932 9.741 23.888 63.834 98.583 150.975 54.093 92.651 18.131 28.371 µs 2.239 10.53
Server Jitter 204.17.205.24 2.272 3.819 7.415 26.421 78.824 95.195 129.897 71.409 91.376 20.637 31.520 µs 1.426 5.192
Server Jitter 204.17.205.27 5.599 9.207 19.038 87.244 155.988 187.396 271.841 136.950 178.189 41.542 87.248 µs 0.2751 3.156
Server Offset 2001:470:e815::8 (spidey.rellim.com) -723.118 -666.052 -298.697 30.470 218.321 287.234 324.538 517.018 953.286 190.237 -9.689 µs -1.037 4.474
Server Offset 204.17.205.1 -1.296 -1.243 -0.566 0.051 0.372 0.417 0.476 0.937 1.660 0.329 -0.020 ms -1.213 4.863
Server Offset 204.17.205.24 -197.812 -134.540 -85.874 -6.784 61.668 124.831 233.271 147.542 259.371 47.190 -7.563 µs 0.2455 6.039
Server Offset 204.17.205.27 -281.850 -164.669 -74.353 12.966 94.190 168.256 345.032 168.543 332.925 59.331 13.905 µs -0.008264 7.993
Temp /dev/sda 61.000 61.000 61.000 62.000 64.000 64.000 67.000 3.000 3.000 1.065 62.678 °C
Temp /dev/sdb 44.000 44.000 44.000 45.000 46.000 46.000 46.000 2.000 2.000 0.596 44.958 °C
Temp /dev/sdc 54.000 54.000 54.000 56.000 56.000 56.000 56.000 2.000 2.000 0.904 55.427 °C
Temp /dev/sdd 67.000 68.000 68.000 69.000 70.000 70.000 70.000 2.000 2.000 0.568 68.797 °C
Temp /dev/sde 47.000 47.000 47.000 48.000 49.000 49.000 49.000 2.000 2.000 0.611 47.976 °C
Temp /dev/sdf 45.000 45.000 45.000 46.000 47.000 47.000 47.000 2.000 2.000 0.623 45.990 °C
Temp LM0 26.000 26.000 26.250 27.500 28.500 34.750 36.500 2.250 8.750 1.171 27.517 °C
Temp LM1 38.000 38.500 39.000 39.500 40.500 41.000 41.500 1.500 2.500 0.558 39.694 °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 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °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 27.250 27.250 27.250 28.750 30.000 32.750 33.750 2.750 5.500 0.887 28.753 °C
Temp LM16 45.000 45.000 45.000 46.000 47.000 47.000 47.000 2.000 2.000 0.617 45.983 °C
Temp LM17 57.500 57.500 57.500 59.000 60.000 60.500 61.000 2.500 3.000 0.694 58.848 °C
Temp LM18 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM19 44.000 44.000 44.000 45.000 46.000 46.000 46.000 2.000 2.000 0.591 44.941 °C
Temp LM2 47.000 47.000 47.000 48.000 49.000 49.000 49.000 2.000 2.000 0.617 47.969 °C
Temp LM20 25.000 25.000 25.000 27.000 28.000 54.000 62.000 3.000 29.000 3.634 27.217 °C
Temp LM21 25.000 25.000 25.000 27.000 28.000 51.000 62.000 3.000 26.000 3.301 27.098 °C
Temp LM22 22.000 22.000 23.000 24.000 26.000 45.000 52.000 3.000 23.000 2.999 24.804 °C
Temp LM23 23.000 23.000 24.000 25.000 27.000 46.000 59.000 3.000 23.000 3.102 25.811 °C
Temp LM24 23.000 23.000 23.000 25.000 27.000 50.000 55.000 4.000 27.000 3.064 25.350 °C
Temp LM3 30.000 30.000 30.000 32.000 33.000 35.000 36.000 3.000 5.000 0.822 31.622 °C
Temp LM4 28.000 28.500 28.500 30.500 31.500 32.000 33.000 3.000 3.500 0.986 30.231 °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 25.000 25.000 25.500 26.500 27.500 53.500 59.500 2.000 28.500 3.515 26.802 °C
Temp LM7 57.000 57.000 57.000 59.000 60.000 60.000 61.000 3.000 3.000 0.777 58.654 °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 25.000 25.000 25.000 27.000 28.000 54.000 62.000 3.000 29.000 3.671 27.014 °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 57.500 57.500 57.500 59.000 60.000 60.500 61.000 2.500 3.000 0.704 58.837 °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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