NTPsec

Pi/GR-601W

Report generated: Sat Oct 31 15:13:07 2020 UTC
Start Time: Sat Oct 24 15:13:01 2020 UTC
End Time: Sat Oct 31 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 -880.289 -848.541 -703.031 141.825 196.317 213.811 223.620 899.348 1,062.352 281.277 -0.084 µs -5.765 19.03
Local Clock Frequency Offset -3.482 -3.355 -3.150 -2.517 -1.888 -1.693 -1.558 1.262 1.662 0.371 -2.516 ppm -495.7 4045

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 45.024 60.364 75.494 176.268 342.974 364.003 372.305 267.480 303.639 86.498 190.453 µs 5.737 14.62

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 33.941 38.451 42.912 59.743 99.308 102.180 106.138 56.396 63.729 18.603 66.096 ppb 24.84 89.11

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 -880.289 -848.541 -703.031 141.825 196.317 213.811 223.620 899.348 1,062.352 281.277 -0.084 µs -5.765 19.03

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 -3.482 -3.355 -3.150 -2.517 -1.888 -1.693 -1.558 1.262 1.662 0.371 -2.516 ppm -495.7 4045
Temp ZONE0 47.774 48.312 49.388 53.692 59.072 59.610 60.148 9.684 11.298 2.825 54.043 °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) 201.796 244.160 290.297 660.604 868.643 896.147 942.190 578.346 651.987 190.529 625.809 µs 18.37 56.72

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) 185.577 246.010 293.127 672.627 870.256 898.291 986.908 577.129 652.281 192.609 630.441 µs 18.15 55.78

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) 24.060 219.421 276.947 653.660 861.531 907.628 1,179.710 584.584 688.207 193.360 614.883 µs 16.49 49.53

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 204.17.205.1 184.931 239.208 282.179 661.361 856.968 887.058 961.846 574.789 647.850 192.862 620.971 µs 17.17 51.89

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 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 204.17.205.24 165.314 254.796 304.470 678.440 882.771 911.962 968.641 578.301 657.166 189.823 639.279 µs 19.97 63.11

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 204.17.205.27 184.089 234.441 274.973 642.931 844.121 871.409 932.738 569.148 636.968 190.938 604.832 µs 16.3 48.76

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 204.17.205.30 221.870 257.126 304.004 669.000 879.955 921.754 976.606 575.951 664.628 190.579 635.814 µs 19.39 61.01

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 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) -17.335 -11.275 -8.457 1.419 12.310 16.954 19.962 20.768 28.229 6.449 1.320 ms -2.681 6.124

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) -880.290 -848.542 -703.032 141.825 196.318 213.812 223.621 899.350 1,062.354 281.278 -0.084 µs -5.765 19.03

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 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) 146.602 161.368 178.555 255.689 404.289 474.079 2,196.914 225.734 312.711 115.688 272.596 µs 16.19 208

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) 88.819 109.859 149.127 263.844 403.079 482.795 2,285.339 253.952 372.936 113.680 272.549 µs 13.5 148.7

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) 69.105 106.564 138.352 261.395 412.526 482.741 698.967 274.174 376.177 86.395 266.612 µs 15.72 51.05

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 74.839 110.224 146.097 264.541 394.783 463.565 586.767 248.686 353.341 80.061 266.958 µs 19.97 67.26

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 80.910 110.134 144.430 258.893 403.200 476.209 1,617.983 258.770 366.075 96.739 267.501 µs 14.66 104.8

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 82.812 109.840 143.099 260.613 394.667 464.861 572.362 251.568 355.021 81.702 264.081 µs 18.13 60.1

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 83.371 107.903 143.540 260.913 399.146 460.680 550.397 255.606 352.777 81.187 265.489 µs 18.78 62.47

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) 0.169 0.528 0.862 2.282 5.218 7.253 15.047 4.356 6.725 1.407 2.561 ms 4.481 16.06

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 0.137 0.797 1.010 1.012 0.792 1.006 0.267 0.250 ms 0.9047 3.306

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 -3.482 -3.355 -3.150 -2.517 -1.888 -1.693 -1.558 1.262 1.662 0.371 -2.516 ppm -495.7 4045
Local Clock Time Offset -880.289 -848.541 -703.031 141.825 196.317 213.811 223.620 899.348 1,062.352 281.277 -0.084 µs -5.765 19.03
Local RMS Frequency Jitter 33.941 38.451 42.912 59.743 99.308 102.180 106.138 56.396 63.729 18.603 66.096 ppb 24.84 89.11
Local RMS Time Jitter 45.024 60.364 75.494 176.268 342.974 364.003 372.305 267.480 303.639 86.498 190.453 µs 5.737 14.62
Server Jitter 2001:470:e815::23 (pi3.rellim.com) 146.602 161.368 178.555 255.689 404.289 474.079 2,196.914 225.734 312.711 115.688 272.596 µs 16.19 208
Server Jitter 2001:470:e815::25 (pi5.rellim.com) 88.819 109.859 149.127 263.844 403.079 482.795 2,285.339 253.952 372.936 113.680 272.549 µs 13.5 148.7
Server Jitter 2001:470:e815::8 (spidey.rellim.com) 69.105 106.564 138.352 261.395 412.526 482.741 698.967 274.174 376.177 86.395 266.612 µs 15.72 51.05
Server Jitter 204.17.205.1 74.839 110.224 146.097 264.541 394.783 463.565 586.767 248.686 353.341 80.061 266.958 µs 19.97 67.26
Server Jitter 204.17.205.24 80.910 110.134 144.430 258.893 403.200 476.209 1,617.983 258.770 366.075 96.739 267.501 µs 14.66 104.8
Server Jitter 204.17.205.27 82.812 109.840 143.099 260.613 394.667 464.861 572.362 251.568 355.021 81.702 264.081 µs 18.13 60.1
Server Jitter 204.17.205.30 83.371 107.903 143.540 260.913 399.146 460.680 550.397 255.606 352.777 81.187 265.489 µs 18.78 62.47
Server Jitter SHM(0) 0.169 0.528 0.862 2.282 5.218 7.253 15.047 4.356 6.725 1.407 2.561 ms 4.481 16.06
Server Jitter SHM(1) 0.002 0.003 0.004 0.137 0.797 1.010 1.012 0.792 1.006 0.267 0.250 ms 0.9047 3.306
Server Offset 2001:470:e815::23 (pi3.rellim.com) 201.796 244.160 290.297 660.604 868.643 896.147 942.190 578.346 651.987 190.529 625.809 µs 18.37 56.72
Server Offset 2001:470:e815::25 (pi5.rellim.com) 185.577 246.010 293.127 672.627 870.256 898.291 986.908 577.129 652.281 192.609 630.441 µs 18.15 55.78
Server Offset 2001:470:e815::8 (spidey.rellim.com) 24.060 219.421 276.947 653.660 861.531 907.628 1,179.710 584.584 688.207 193.360 614.883 µs 16.49 49.53
Server Offset 204.17.205.1 184.931 239.208 282.179 661.361 856.968 887.058 961.846 574.789 647.850 192.862 620.971 µs 17.17 51.89
Server Offset 204.17.205.24 165.314 254.796 304.470 678.440 882.771 911.962 968.641 578.301 657.166 189.823 639.279 µs 19.97 63.11
Server Offset 204.17.205.27 184.089 234.441 274.973 642.931 844.121 871.409 932.738 569.148 636.968 190.938 604.832 µs 16.3 48.76
Server Offset 204.17.205.30 221.870 257.126 304.004 669.000 879.955 921.754 976.606 575.951 664.628 190.579 635.814 µs 19.39 61.01
Server Offset SHM(0) -17.335 -11.275 -8.457 1.419 12.310 16.954 19.962 20.768 28.229 6.449 1.320 ms -2.681 6.124
Server Offset SHM(1) -880.290 -848.542 -703.032 141.825 196.318 213.812 223.621 899.350 1,062.354 281.278 -0.084 µs -5.765 19.03
Temp ZONE0 47.774 48.312 49.388 53.692 59.072 59.610 60.148 9.684 11.298 2.825 54.043 °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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