NTPsec

Pi/GR-601W

Report generated: Sat Sep 26 15:13:08 2020 UTC
Start Time: Sat Sep 19 15:13:01 2020 UTC
End Time: Sat Sep 26 15:13:01 2020 UTC
Report Period: 7.0 days

Daily stats   Weekly stats   24 Hour Scatter Plots: ( 1   2   3   )

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 -873.730 -852.631 -705.322 144.294 191.775 204.270 217.310 897.097 1,056.901 280.515 -0.059 µs -5.779 19.14
Local Clock Frequency Offset -3.391 -3.210 -3.038 -2.488 -1.923 -1.778 -1.672 1.114 1.433 0.333 -2.490 ppm -632.8 5577

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 50.052 63.007 74.442 175.158 342.215 363.688 370.295 267.773 300.681 86.231 188.960 µs 5.682 14.5

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 36.109 39.832 43.078 59.582 99.435 102.336 105.449 56.357 62.504 18.623 65.899 ppb 24.55 87.97

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 -873.730 -852.631 -705.322 144.294 191.775 204.270 217.310 897.097 1,056.901 280.515 -0.059 µs -5.779 19.14

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 -3.391 -3.210 -3.038 -2.488 -1.923 -1.778 -1.672 1.114 1.433 0.333 -2.490 ppm -632.8 5577
Temp ZONE0 48.312 49.388 50.464 54.230 57.996 59.072 61.224 7.532 9.684 2.471 54.331 °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::23 (pi3.rellim.com)

peer offset 2001:470:e815::23 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2001:470:e815::23 (pi3.rellim.com) 215.796 244.201 293.746 650.855 872.046 907.073 963.673 578.300 662.872 193.726 621.600 µs 17.08 52.03

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 2001:470:e815::25 (pi5.rellim.com)

peer offset 2001:470:e815::25 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2001:470:e815::25 (pi5.rellim.com) 202.737 246.955 298.306 666.661 869.519 896.303 995.434 571.213 649.348 191.701 629.597 µs 18.36 56.68

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 2001:470: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) 165.686 224.312 275.961 655.937 859.001 916.165 1,031.412 583.040 691.853 193.298 615.345 µs 16.54 49.63

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 204.17.205.1 189.712 237.605 281.578 660.266 859.541 885.679 971.872 577.963 648.074 194.515 620.527 µs 16.66 50.01

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 204.17.205.24 187.204 249.956 302.886 677.019 884.326 911.093 959.921 581.440 661.137 191.649 640.832 µs 19.49 61.17

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 204.17.205.27 177.422 230.870 281.011 656.947 850.090 874.170 944.641 569.079 643.300 189.683 613.369 µs 17.4 52.8

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 204.17.205.30

peer offset 204.17.205.30 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 204.17.205.30 212.568 254.511 300.842 673.359 879.687 924.561 990.408 578.845 670.050 194.112 636.328 µs 18.27 56.43

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 SHM(0)

peer offset SHM(0) plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset SHM(0) -14.960 -8.573 -6.274 1.067 10.833 13.712 17.588 17.107 22.285 5.112 1.367 ms -2.286 5.294

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 SHM(1)

peer offset SHM(1) plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset SHM(1) -873.731 -852.632 -705.323 144.295 191.775 204.271 217.311 897.098 1,056.903 280.515 -0.058 µs -5.779 19.14

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::23 (pi3.rellim.com)

peer jitter 2001:470:e815::23 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2001:470:e815::23 (pi3.rellim.com) 144.986 166.849 182.615 261.571 404.778 467.069 2,150.431 222.163 300.220 117.372 275.225 µs 15.98 198.9

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 2001:470:e815::25 (pi5.rellim.com)

peer jitter 2001:470:e815::25 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2001:470:e815::25 (pi5.rellim.com) 77.155 114.170 146.975 266.381 398.048 470.950 2,517.888 251.073 356.780 105.061 271.350 µs 15.02 165.3

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 2001:470: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) 48.446 105.471 143.336 264.433 406.492 473.795 590.014 263.156 368.324 84.223 267.616 µs 17.15 56.2

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 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 87.690 110.023 146.087 267.362 393.598 468.422 562.098 247.511 358.399 80.386 268.166 µs 19.98 67.22

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 80.325 108.897 148.761 263.004 408.608 482.212 1,814.997 259.847 373.315 95.565 269.617 µs 14.65 96.2

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 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 91.396 112.717 146.247 260.613 395.872 457.947 575.474 249.625 345.230 80.241 264.949 µs 19.39 65.09

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 204.17.205.30

peer jitter 204.17.205.30 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 204.17.205.30 84.253 107.629 144.226 260.213 398.081 467.437 585.095 253.855 359.808 82.611 266.018 µs 17.89 59

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 SHM(0)

peer jitter SHM(0) plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter SHM(0) 0.254 0.561 0.883 2.170 4.971 6.604 10.685 4.088 6.043 1.290 2.452 ms 4.719 15.6

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 SHM(1)

peer jitter SHM(1) plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter SHM(1) 0.002 0.003 0.004 0.135 0.797 1.010 1.021 0.792 1.006 0.267 0.247 ms 0.8938 3.304

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 -3.391 -3.210 -3.038 -2.488 -1.923 -1.778 -1.672 1.114 1.433 0.333 -2.490 ppm -632.8 5577
Local Clock Time Offset -873.730 -852.631 -705.322 144.294 191.775 204.270 217.310 897.097 1,056.901 280.515 -0.059 µs -5.779 19.14
Local RMS Frequency Jitter 36.109 39.832 43.078 59.582 99.435 102.336 105.449 56.357 62.504 18.623 65.899 ppb 24.55 87.97
Local RMS Time Jitter 50.052 63.007 74.442 175.158 342.215 363.688 370.295 267.773 300.681 86.231 188.960 µs 5.682 14.5
Server Jitter 2001:470:e815::23 (pi3.rellim.com) 144.986 166.849 182.615 261.571 404.778 467.069 2,150.431 222.163 300.220 117.372 275.225 µs 15.98 198.9
Server Jitter 2001:470:e815::25 (pi5.rellim.com) 77.155 114.170 146.975 266.381 398.048 470.950 2,517.888 251.073 356.780 105.061 271.350 µs 15.02 165.3
Server Jitter 2001:470:e815::8 (spidey.rellim.com) 48.446 105.471 143.336 264.433 406.492 473.795 590.014 263.156 368.324 84.223 267.616 µs 17.15 56.2
Server Jitter 204.17.205.1 87.690 110.023 146.087 267.362 393.598 468.422 562.098 247.511 358.399 80.386 268.166 µs 19.98 67.22
Server Jitter 204.17.205.24 80.325 108.897 148.761 263.004 408.608 482.212 1,814.997 259.847 373.315 95.565 269.617 µs 14.65 96.2
Server Jitter 204.17.205.27 91.396 112.717 146.247 260.613 395.872 457.947 575.474 249.625 345.230 80.241 264.949 µs 19.39 65.09
Server Jitter 204.17.205.30 84.253 107.629 144.226 260.213 398.081 467.437 585.095 253.855 359.808 82.611 266.018 µs 17.89 59
Server Jitter SHM(0) 0.254 0.561 0.883 2.170 4.971 6.604 10.685 4.088 6.043 1.290 2.452 ms 4.719 15.6
Server Jitter SHM(1) 0.002 0.003 0.004 0.135 0.797 1.010 1.021 0.792 1.006 0.267 0.247 ms 0.8938 3.304
Server Offset 2001:470:e815::23 (pi3.rellim.com) 215.796 244.201 293.746 650.855 872.046 907.073 963.673 578.300 662.872 193.726 621.600 µs 17.08 52.03
Server Offset 2001:470:e815::25 (pi5.rellim.com) 202.737 246.955 298.306 666.661 869.519 896.303 995.434 571.213 649.348 191.701 629.597 µs 18.36 56.68
Server Offset 2001:470:e815::8 (spidey.rellim.com) 165.686 224.312 275.961 655.937 859.001 916.165 1,031.412 583.040 691.853 193.298 615.345 µs 16.54 49.63
Server Offset 204.17.205.1 189.712 237.605 281.578 660.266 859.541 885.679 971.872 577.963 648.074 194.515 620.527 µs 16.66 50.01
Server Offset 204.17.205.24 187.204 249.956 302.886 677.019 884.326 911.093 959.921 581.440 661.137 191.649 640.832 µs 19.49 61.17
Server Offset 204.17.205.27 177.422 230.870 281.011 656.947 850.090 874.170 944.641 569.079 643.300 189.683 613.369 µs 17.4 52.8
Server Offset 204.17.205.30 212.568 254.511 300.842 673.359 879.687 924.561 990.408 578.845 670.050 194.112 636.328 µs 18.27 56.43
Server Offset SHM(0) -14.960 -8.573 -6.274 1.067 10.833 13.712 17.588 17.107 22.285 5.112 1.367 ms -2.286 5.294
Server Offset SHM(1) -873.731 -852.632 -705.323 144.295 191.775 204.271 217.311 897.098 1,056.903 280.515 -0.058 µs -5.779 19.14
Temp ZONE0 48.312 49.388 50.464 54.230 57.996 59.072 61.224 7.532 9.684 2.471 54.331 °C
Summary as CSV file


This server:

Motherboard: Raspberry Pi 2
OS: Gentoo stable
GPS; GR-601W USB
GPS/PPS server: gpsd
NTP server: NTPsec
../ntp.conf

Notes:

22:00 29 Mar 2017 Updated kernel 4.4 to 4.9.17
00:00  3 Feb 2017 Upgraded from Pi B to Pi 2
19:30 15 Oct 2016 UTC precision -10 to -20

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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