NTPsec

Pi/GR-601W

Report generated: Wed Oct 28 15:13:08 2020 UTC
Start Time: Wed Oct 21 15:13:02 2020 UTC
End Time: Wed Oct 28 15:13:02 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 -882.076 -845.931 -700.943 143.575 199.486 213.811 223.620 900.429 1,059.742 282.391 -0.038 µs -5.745 18.88
Local Clock Frequency Offset -3.482 -3.355 -3.178 -2.553 -1.937 -1.726 -1.550 1.241 1.629 0.366 -2.550 ppm -529.1 4407

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 44.117 62.202 79.012 177.229 343.423 364.686 372.305 264.411 302.484 86.145 192.372 µs 5.962 15.31

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 39.105 43.712 59.955 99.207 102.019 105.695 55.495 62.914 18.383 66.444 ppb 26.25 95.36

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 -882.076 -845.931 -700.943 143.575 199.486 213.811 223.620 900.429 1,059.742 282.391 -0.038 µs -5.745 18.88

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 -3.178 -2.553 -1.937 -1.726 -1.550 1.241 1.629 0.366 -2.550 ppm -529.1 4407
Temp ZONE0 47.774 48.312 49.388 53.692 58.534 59.610 60.148 9.146 11.298 2.671 53.624 °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) 182.717 248.185 297.224 662.416 863.999 891.382 925.822 566.775 643.197 187.512 627.071 µs 19.5 61.18

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) 204.368 246.687 301.482 667.836 866.417 896.056 986.908 564.935 649.369 188.396 629.319 µs 19.42 60.86

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) 121.204 214.928 269.234 653.595 856.631 909.579 1,179.710 587.397 694.651 194.152 612.440 µs 16.04 47.75

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 204.17.205.1 184.931 239.659 283.785 658.897 854.916 883.438 949.075 571.131 643.779 192.555 618.851 µs 17.08 51.66

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 204.17.205.24 185.688 248.892 305.401 675.202 878.858 909.362 954.720 573.457 660.470 189.166 638.392 µs 20.1 63.6

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 204.17.205.27 179.586 234.619 281.477 647.949 843.865 870.610 943.581 562.388 635.991 188.327 607.815 µs 17.32 52.61

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 204.17.205.30 221.988 262.431 307.801 667.972 878.741 925.839 984.440 570.940 663.408 191.102 635.036 µs 19.15 60.07

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 -11.186 -8.447 1.703 12.364 16.954 19.962 20.812 28.140 6.466 1.682 ms -2.492 5.723

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) -882.077 -845.932 -700.944 143.576 199.487 213.812 223.621 900.431 1,059.744 282.392 -0.038 µs -5.745 18.88

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) 142.738 159.473 176.462 251.368 390.472 455.879 2,196.914 214.010 296.406 87.773 266.163 µs 22.17 243.2

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 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) 87.931 108.571 147.671 258.374 395.899 465.453 2,285.339 248.228 356.882 103.597 267.066 µs 14.53 150.8

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 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) 37.821 102.363 137.674 261.160 414.286 491.802 583.337 276.612 389.439 86.662 266.338 µs 15.49 49.96

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 74.839 109.974 146.571 264.178 393.987 472.141 590.190 247.416 362.167 79.948 266.827 µs 20.05 67.86

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 72.517 109.169 148.413 257.317 401.874 469.336 2,005.474 253.461 360.167 93.484 265.994 µs 15.98 130.2

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 85.878 109.840 146.845 261.410 391.173 461.249 572.362 244.328 351.409 79.737 264.283 µs 19.63 66.07

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 82.265 109.782 143.962 260.862 395.645 460.872 657.618 251.683 351.090 81.011 265.010 µs 18.81 62.73

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 0.556 0.909 2.353 5.380 7.441 15.047 4.471 6.886 1.421 2.654 ms 4.61 15.72

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 0.004 0.005 0.138 0.797 1.010 1.012 0.792 1.006 0.268 0.253 ms 0.9212 3.319

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 -3.178 -2.553 -1.937 -1.726 -1.550 1.241 1.629 0.366 -2.550 ppm -529.1 4407
Local Clock Time Offset -882.076 -845.931 -700.943 143.575 199.486 213.811 223.620 900.429 1,059.742 282.391 -0.038 µs -5.745 18.88
Local RMS Frequency Jitter 33.941 39.105 43.712 59.955 99.207 102.019 105.695 55.495 62.914 18.383 66.444 ppb 26.25 95.36
Local RMS Time Jitter 44.117 62.202 79.012 177.229 343.423 364.686 372.305 264.411 302.484 86.145 192.372 µs 5.962 15.31
Server Jitter 2001:470:e815::23 (pi3.rellim.com) 142.738 159.473 176.462 251.368 390.472 455.879 2,196.914 214.010 296.406 87.773 266.163 µs 22.17 243.2
Server Jitter 2001:470:e815::25 (pi5.rellim.com) 87.931 108.571 147.671 258.374 395.899 465.453 2,285.339 248.228 356.882 103.597 267.066 µs 14.53 150.8
Server Jitter 2001:470:e815::8 (spidey.rellim.com) 37.821 102.363 137.674 261.160 414.286 491.802 583.337 276.612 389.439 86.662 266.338 µs 15.49 49.96
Server Jitter 204.17.205.1 74.839 109.974 146.571 264.178 393.987 472.141 590.190 247.416 362.167 79.948 266.827 µs 20.05 67.86
Server Jitter 204.17.205.24 72.517 109.169 148.413 257.317 401.874 469.336 2,005.474 253.461 360.167 93.484 265.994 µs 15.98 130.2
Server Jitter 204.17.205.27 85.878 109.840 146.845 261.410 391.173 461.249 572.362 244.328 351.409 79.737 264.283 µs 19.63 66.07
Server Jitter 204.17.205.30 82.265 109.782 143.962 260.862 395.645 460.872 657.618 251.683 351.090 81.011 265.010 µs 18.81 62.73
Server Jitter SHM(0) 0.169 0.556 0.909 2.353 5.380 7.441 15.047 4.471 6.886 1.421 2.654 ms 4.61 15.72
Server Jitter SHM(1) 0.002 0.004 0.005 0.138 0.797 1.010 1.012 0.792 1.006 0.268 0.253 ms 0.9212 3.319
Server Offset 2001:470:e815::23 (pi3.rellim.com) 182.717 248.185 297.224 662.416 863.999 891.382 925.822 566.775 643.197 187.512 627.071 µs 19.5 61.18
Server Offset 2001:470:e815::25 (pi5.rellim.com) 204.368 246.687 301.482 667.836 866.417 896.056 986.908 564.935 649.369 188.396 629.319 µs 19.42 60.86
Server Offset 2001:470:e815::8 (spidey.rellim.com) 121.204 214.928 269.234 653.595 856.631 909.579 1,179.710 587.397 694.651 194.152 612.440 µs 16.04 47.75
Server Offset 204.17.205.1 184.931 239.659 283.785 658.897 854.916 883.438 949.075 571.131 643.779 192.555 618.851 µs 17.08 51.66
Server Offset 204.17.205.24 185.688 248.892 305.401 675.202 878.858 909.362 954.720 573.457 660.470 189.166 638.392 µs 20.1 63.6
Server Offset 204.17.205.27 179.586 234.619 281.477 647.949 843.865 870.610 943.581 562.388 635.991 188.327 607.815 µs 17.32 52.61
Server Offset 204.17.205.30 221.988 262.431 307.801 667.972 878.741 925.839 984.440 570.940 663.408 191.102 635.036 µs 19.15 60.07
Server Offset SHM(0) -17.335 -11.186 -8.447 1.703 12.364 16.954 19.962 20.812 28.140 6.466 1.682 ms -2.492 5.723
Server Offset SHM(1) -882.077 -845.932 -700.944 143.576 199.487 213.812 223.621 900.431 1,059.744 282.392 -0.038 µs -5.745 18.88
Temp ZONE0 47.774 48.312 49.388 53.692 58.534 59.610 60.148 9.146 11.298 2.671 53.624 °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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