NTPsec

Backup/Meinberg

Report generated: Wed Apr 2 15:43:00 2025 UTC
Start Time: Wed Mar 26 15:43:00 2025 UTC
End Time: Wed Apr 2 15:43:00 2025 UTC
Report Period: 7.0 days

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 -720.980 -251.382 -77.575 -1.537 73.419 261.521 917.453 150.994 512.903 77.311 -1.425 µs 0.1372 31.36
Local Clock Frequency Offset -711.700 -208.435 -104.919 337.265 695.084 912.674 1,689.438 800.003 1,121.109 246.120 323.511 ppb -0.08283 3.966

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 14.954 19.096 22.787 39.259 163.968 310.069 453.109 141.181 290.973 53.138 55.374 µs 3.48 16.77

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 5.761 8.951 10.911 20.065 115.980 203.078 318.934 105.069 194.127 37.912 32.614 ppb 3.376 16.03

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 -720.980 -251.382 -77.575 -1.537 73.419 261.521 917.453 150.994 512.903 77.311 -1.425 µs 0.1372 31.36

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 -711.700 -208.435 -104.919 337.265 695.084 912.674 1,689.438 800.003 1,121.109 246.120 323.511 ppb -0.08283 3.966
Temp /dev/sda 40.000 40.000 40.000 42.000 43.000 45.000 45.000 3.000 5.000 0.953 41.863 °C
Temp /dev/sdb 50.000 51.000 51.000 53.000 59.000 60.000 60.000 8.000 9.000 2.119 52.985 °C
Temp /dev/sdc 51.000 51.000 51.000 53.000 56.000 56.000 56.000 5.000 5.000 0.999 52.973 °C
Temp /dev/sdd 57.000 57.000 57.000 59.000 67.000 69.000 69.000 10.000 12.000 2.630 59.912 °C
Temp /dev/sde 40.000 40.000 40.000 42.000 45.000 46.000 47.000 5.000 6.000 1.297 41.887 °C
Temp /dev/sdf 51.000 51.000 51.000 53.000 59.000 62.000 62.000 8.000 11.000 2.297 53.455 °C
Temp LM0 25.000 25.250 25.750 27.000 28.500 30.750 35.250 2.750 5.500 0.972 27.084 °C
Temp LM1 36.000 36.500 37.000 38.000 39.500 39.500 40.000 2.500 3.000 0.710 38.252 °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 42.000 43.000 45.000 45.000 3.000 5.000 0.954 41.862 °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 26.250 26.500 27.000 28.250 29.500 31.250 32.250 2.500 4.750 0.843 28.384 °C
Temp LM16 51.000 51.000 51.000 53.000 59.000 62.000 62.000 8.000 11.000 2.305 53.552 °C
Temp LM17 55.500 56.000 56.000 58.000 60.000 61.500 63.000 4.000 5.500 1.168 58.036 °C
Temp LM18 57.000 57.000 57.000 59.000 67.000 69.000 69.000 10.000 12.000 2.637 60.005 °C
Temp LM19 50.000 51.000 51.000 53.000 59.000 60.000 60.000 8.000 9.000 2.139 53.043 °C
Temp LM2 40.000 40.000 40.000 42.000 45.000 46.000 47.000 5.000 6.000 1.303 41.887 °C
Temp LM20 23.000 24.000 24.000 26.000 29.000 31.000 60.000 5.000 7.000 2.114 26.431 °C
Temp LM21 23.000 24.000 24.000 26.000 28.000 30.000 60.000 4.000 6.000 1.986 26.288 °C
Temp LM22 21.000 22.000 22.000 24.000 26.000 29.000 56.000 4.000 7.000 1.968 24.192 °C
Temp LM23 21.000 22.000 23.000 25.000 27.000 30.000 56.000 4.000 8.000 2.150 25.073 °C
Temp LM24 22.000 22.000 23.000 25.000 27.000 30.000 55.000 4.000 8.000 1.902 25.160 °C
Temp LM3 29.000 29.000 29.000 31.000 32.000 32.000 34.000 3.000 3.000 0.826 30.730 °C
Temp LM4 27.500 28.500 28.500 30.000 31.000 32.000 32.500 2.500 3.500 0.754 30.056 °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 23.500 23.500 24.000 25.500 28.000 30.000 58.500 4.000 6.500 2.035 25.888 °C
Temp LM7 55.000 55.000 56.000 58.000 60.000 61.000 63.000 4.000 6.000 1.231 57.776 °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 26.000 28.000 31.000 60.000 4.000 7.000 2.113 26.124 °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 56.000 56.000 58.000 60.000 61.500 63.000 4.000 5.500 1.165 58.038 °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) -2.957 -2.051 -0.826 0.077 1.205 3.147 4.222 2.032 5.198 0.681 0.062 ms 1.54 13.19

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 -2.700 -2.124 -0.798 0.052 0.769 2.507 4.009 1.566 4.631 0.645 0.054 ms 0.7348 11.25

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 -0.505 -0.110 -0.075 -0.006 0.056 0.092 34.857 0.131 0.201 0.605 0.004 ms 57.18 3295

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 -4.931 -3.804 -0.769 0.013 0.953 2.349 3.199 1.722 6.153 0.742 -0.011 ms -1.912 17.89

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 4.097 6.222 17.303 93.909 203.545 524.607 87.687 199.448 38.830 28.888 µs 5.128 41.39

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 2.540 4.873 7.197 19.171 95.915 214.088 592.160 88.718 209.215 40.079 30.846 µs 5.172 43.08

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 0.005 0.008 0.025 0.062 0.092 16.680 0.054 0.087 0.288 0.034 ms 57.37 3310

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 11.331 25.497 94.813 174.134 279.155 740.744 148.637 267.824 52.646 98.237 µs 2.493 21.42

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 -711.700 -208.435 -104.919 337.265 695.084 912.674 1,689.438 800.003 1,121.109 246.120 323.511 ppb -0.08283 3.966
Local Clock Time Offset -720.980 -251.382 -77.575 -1.537 73.419 261.521 917.453 150.994 512.903 77.311 -1.425 µs 0.1372 31.36
Local RMS Frequency Jitter 5.761 8.951 10.911 20.065 115.980 203.078 318.934 105.069 194.127 37.912 32.614 ppb 3.376 16.03
Local RMS Time Jitter 14.954 19.096 22.787 39.259 163.968 310.069 453.109 141.181 290.973 53.138 55.374 µs 3.48 16.77
Server Jitter 2001:470:e815::8 (spidey.rellim.com) 1.418 4.097 6.222 17.303 93.909 203.545 524.607 87.687 199.448 38.830 28.888 µs 5.128 41.39
Server Jitter 204.17.205.1 2.540 4.873 7.197 19.171 95.915 214.088 592.160 88.718 209.215 40.079 30.846 µs 5.172 43.08
Server Jitter 204.17.205.24 0.000 0.005 0.008 0.025 0.062 0.092 16.680 0.054 0.087 0.288 0.034 ms 57.37 3310
Server Jitter 204.17.205.27 3.666 11.331 25.497 94.813 174.134 279.155 740.744 148.637 267.824 52.646 98.237 µs 2.493 21.42
Server Offset 2001:470:e815::8 (spidey.rellim.com) -2.957 -2.051 -0.826 0.077 1.205 3.147 4.222 2.032 5.198 0.681 0.062 ms 1.54 13.19
Server Offset 204.17.205.1 -2.700 -2.124 -0.798 0.052 0.769 2.507 4.009 1.566 4.631 0.645 0.054 ms 0.7348 11.25
Server Offset 204.17.205.24 -0.505 -0.110 -0.075 -0.006 0.056 0.092 34.857 0.131 0.201 0.605 0.004 ms 57.18 3295
Server Offset 204.17.205.27 -4.931 -3.804 -0.769 0.013 0.953 2.349 3.199 1.722 6.153 0.742 -0.011 ms -1.912 17.89
Temp /dev/sda 40.000 40.000 40.000 42.000 43.000 45.000 45.000 3.000 5.000 0.953 41.863 °C
Temp /dev/sdb 50.000 51.000 51.000 53.000 59.000 60.000 60.000 8.000 9.000 2.119 52.985 °C
Temp /dev/sdc 51.000 51.000 51.000 53.000 56.000 56.000 56.000 5.000 5.000 0.999 52.973 °C
Temp /dev/sdd 57.000 57.000 57.000 59.000 67.000 69.000 69.000 10.000 12.000 2.630 59.912 °C
Temp /dev/sde 40.000 40.000 40.000 42.000 45.000 46.000 47.000 5.000 6.000 1.297 41.887 °C
Temp /dev/sdf 51.000 51.000 51.000 53.000 59.000 62.000 62.000 8.000 11.000 2.297 53.455 °C
Temp LM0 25.000 25.250 25.750 27.000 28.500 30.750 35.250 2.750 5.500 0.972 27.084 °C
Temp LM1 36.000 36.500 37.000 38.000 39.500 39.500 40.000 2.500 3.000 0.710 38.252 °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 42.000 43.000 45.000 45.000 3.000 5.000 0.954 41.862 °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 26.250 26.500 27.000 28.250 29.500 31.250 32.250 2.500 4.750 0.843 28.384 °C
Temp LM16 51.000 51.000 51.000 53.000 59.000 62.000 62.000 8.000 11.000 2.305 53.552 °C
Temp LM17 55.500 56.000 56.000 58.000 60.000 61.500 63.000 4.000 5.500 1.168 58.036 °C
Temp LM18 57.000 57.000 57.000 59.000 67.000 69.000 69.000 10.000 12.000 2.637 60.005 °C
Temp LM19 50.000 51.000 51.000 53.000 59.000 60.000 60.000 8.000 9.000 2.139 53.043 °C
Temp LM2 40.000 40.000 40.000 42.000 45.000 46.000 47.000 5.000 6.000 1.303 41.887 °C
Temp LM20 23.000 24.000 24.000 26.000 29.000 31.000 60.000 5.000 7.000 2.114 26.431 °C
Temp LM21 23.000 24.000 24.000 26.000 28.000 30.000 60.000 4.000 6.000 1.986 26.288 °C
Temp LM22 21.000 22.000 22.000 24.000 26.000 29.000 56.000 4.000 7.000 1.968 24.192 °C
Temp LM23 21.000 22.000 23.000 25.000 27.000 30.000 56.000 4.000 8.000 2.150 25.073 °C
Temp LM24 22.000 22.000 23.000 25.000 27.000 30.000 55.000 4.000 8.000 1.902 25.160 °C
Temp LM3 29.000 29.000 29.000 31.000 32.000 32.000 34.000 3.000 3.000 0.826 30.730 °C
Temp LM4 27.500 28.500 28.500 30.000 31.000 32.000 32.500 2.500 3.500 0.754 30.056 °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 23.500 23.500 24.000 25.500 28.000 30.000 58.500 4.000 6.500 2.035 25.888 °C
Temp LM7 55.000 55.000 56.000 58.000 60.000 61.000 63.000 4.000 6.000 1.231 57.776 °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 26.000 28.000 31.000 60.000 4.000 7.000 2.113 26.124 °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 56.000 56.000 58.000 60.000 61.500 63.000 4.000 5.500 1.165 58.038 °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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