NTPsec

crane3.services.mbix.ca

Report generated: Mon Aug 24 20:53:01 2026 UTC
Start Time: Sun Aug 23 20:53:01 2026 UTC
End Time: Mon Aug 24 20:53:01 2026 UTC
Report Period: 1.0 days

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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 -45.743 -23.172 -17.449 -2.862 27.273 39.004 65.814 44.722 62.176 13.620 -0.033 µs -3.102 7.158
Local Clock Frequency Offset 78.424 78.452 78.475 78.649 78.707 78.724 78.760 0.233 0.272 0.078 78.622 ppm 1.015e+09 1.02e+12

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 5.462 9.001 11.103 17.746 26.276 30.257 42.978 15.173 21.256 4.647 18.046 µs 33.09 127.6

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 2.359 3.418 4.111 6.369 9.117 10.409 15.062 5.006 6.991 1.555 6.465 ppb 41.34 167.7

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 -45.743 -23.172 -17.449 -2.862 27.273 39.004 65.814 44.722 62.176 13.620 -0.033 µs -3.102 7.158

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 78.424 78.452 78.475 78.649 78.707 78.724 78.760 0.233 0.272 0.078 78.622 ppm 1.015e+09 1.02e+12
Temp LM0 37.000 38.000 39.000 40.000 41.000 41.000 41.000 2.000 3.000 0.798 39.854 °C
Temp LM1 34.000 35.000 35.000 36.000 38.000 39.000 39.000 3.000 4.000 0.904 36.452 °C
Temp LM10 32.000 33.000 34.000 35.000 37.000 38.000 38.000 3.000 5.000 1.009 35.014 °C
Temp LM2 33.000 33.000 33.000 34.000 36.000 36.000 37.000 3.000 3.000 0.792 34.480 °C
Temp LM3 38.000 38.000 39.000 40.000 41.000 41.000 41.000 2.000 3.000 0.765 39.847 °C
Temp LM4 35.000 35.000 36.000 37.000 38.000 38.000 39.000 2.000 3.000 0.826 36.630 °C
Temp LM5 62.000 62.000 62.000 63.000 64.000 64.000 64.000 2.000 2.000 0.594 63.057 °C
Temp LM6 40.000 40.000 40.000 41.000 43.000 44.000 44.000 3.000 4.000 0.921 41.523 °C
Temp LM7 38.000 38.000 39.000 40.000 42.000 43.000 43.000 3.000 5.000 0.887 40.438 °C
Temp LM8 38.000 38.000 39.000 41.000 42.000 43.000 44.000 3.000 5.000 1.021 40.883 °C
Temp LM9 37.000 38.000 38.000 40.000 41.000 43.000 43.000 3.000 5.000 0.977 39.705 °C
Temp ZONE0 40.000 40.000 40.000 42.000 43.000 44.000 45.000 3.000 4.000 0.996 41.683 °C
Temp ZONE1 38.000 38.000 39.000 40.000 41.000 42.000 42.000 2.000 4.000 0.873 39.915 °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 132.246.11.227

peer offset 132.246.11.227 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 132.246.11.227 1.839 2.087 6.644 6.723 7.690 7.763 12.344 1.046 5.676 0.681 6.825 ms 761.4 7116

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 142.3.100.2

peer offset 142.3.100.2 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 142.3.100.2 -55.473 -54.247 -39.094 -1.833 43.649 75.475 86.059 82.743 129.722 25.849 0.676 µs -3.415 8.206

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 2600:2600::199 (ntp2.wiktel.com)

peer offset 2600:2600::199 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2600:2600::199 (ntp2.wiktel.com) 327.595 334.091 346.058 373.301 401.084 411.469 436.232 55.026 77.378 17.370 373.372 µs 8671 1.79e+05

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 2602:fde5:2a::13 (ntp3.torix.ca)

peer offset 2602:fde5:2a::13 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2602:fde5:2a::13 (ntp3.torix.ca) 1.449 1.461 1.476 1.509 2.082 2.096 2.104 0.607 0.635 0.276 1.708 ms 156.6 904.2

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 2606:4700:f1::1 (time.cloudflare.com)

peer offset 2606:4700:f1::1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2606:4700:f1::1 (time.cloudflare.com) -105.227 -60.903 30.366 169.223 401.633 496.210 542.647 371.267 557.113 112.911 180.793 µs 2.687 7.887

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 2607:f388::123:1 (ntp1.doit.wisc.edu)

peer offset 2607:f388::123:1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2607:f388::123:1 (ntp1.doit.wisc.edu) -0.493 -0.429 -0.309 1.219 4.314 6.845 8.152 4.623 7.274 1.571 1.564 ms 1.232 4.988

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 PPS(0)

peer offset PPS(0) plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset PPS(0) -45.744 -23.173 -17.450 -2.863 27.274 39.005 65.815 44.724 62.178 13.621 -0.033 µs -3.103 7.158

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 132.246.11.227

peer jitter 132.246.11.227 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 132.246.11.227 0.000 0.014 0.067 0.412 2.633 6.640 98.853 2.566 6.625 7.613 1.312 ms 8.783 108.9

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 142.3.100.2

peer jitter 142.3.100.2 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 142.3.100.2 0.015 0.018 0.022 0.043 0.107 0.629 8.135 0.085 0.611 0.476 0.083 ms 13.51 229.6

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 2600:2600::199 (ntp2.wiktel.com)

peer jitter 2600:2600::199 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2600:2600::199 (ntp2.wiktel.com) 6.725 7.491 10.166 19.262 36.365 50.553 77.348 26.199 43.062 8.937 21.113 µs 8.486 35

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 2602:fde5:2a::13 (ntp3.torix.ca)

peer jitter 2602:fde5:2a::13 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2602:fde5:2a::13 (ntp3.torix.ca) 5.076 7.930 12.042 379.481 581.754 594.037 607.074 569.712 586.107 240.820 279.362 µs 0.4408 1.287

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 2606:4700:f1::1 (time.cloudflare.com)

peer jitter 2606:4700:f1::1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2606:4700:f1::1 (time.cloudflare.com) 7.111 12.042 15.394 35.209 168.502 286.014 375.307 153.108 273.972 55.581 56.352 µs 2.776 12.34

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 2607:f388::123:1 (ntp1.doit.wisc.edu)

peer jitter 2607:f388::123:1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2607:f388::123:1 (ntp1.doit.wisc.edu) 3.712 4.924 6.594 12.128 22.318 27.147 30.089 15.724 22.222 4.835 12.971 ms 10.64 34.17

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 PPS(0)

peer jitter PPS(0) plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter PPS(0) 2.621 5.213 7.377 16.501 33.526 43.824 72.209 26.149 38.611 8.218 17.989 µs 6.42 21.28

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 78.424 78.452 78.475 78.649 78.707 78.724 78.760 0.233 0.272 0.078 78.622 ppm 1.015e+09 1.02e+12
Local Clock Time Offset -45.743 -23.172 -17.449 -2.862 27.273 39.004 65.814 44.722 62.176 13.620 -0.033 µs -3.102 7.158
Local RMS Frequency Jitter 2.359 3.418 4.111 6.369 9.117 10.409 15.062 5.006 6.991 1.555 6.465 ppb 41.34 167.7
Local RMS Time Jitter 5.462 9.001 11.103 17.746 26.276 30.257 42.978 15.173 21.256 4.647 18.046 µs 33.09 127.6
Server Jitter 132.246.11.227 0.000 0.014 0.067 0.412 2.633 6.640 98.853 2.566 6.625 7.613 1.312 ms 8.783 108.9
Server Jitter 142.3.100.2 0.015 0.018 0.022 0.043 0.107 0.629 8.135 0.085 0.611 0.476 0.083 ms 13.51 229.6
Server Jitter 2600:2600::199 (ntp2.wiktel.com) 6.725 7.491 10.166 19.262 36.365 50.553 77.348 26.199 43.062 8.937 21.113 µs 8.486 35
Server Jitter 2602:fde5:2a::13 (ntp3.torix.ca) 5.076 7.930 12.042 379.481 581.754 594.037 607.074 569.712 586.107 240.820 279.362 µs 0.4408 1.287
Server Jitter 2606:4700:f1::1 (time.cloudflare.com) 7.111 12.042 15.394 35.209 168.502 286.014 375.307 153.108 273.972 55.581 56.352 µs 2.776 12.34
Server Jitter 2607:f388::123:1 (ntp1.doit.wisc.edu) 3.712 4.924 6.594 12.128 22.318 27.147 30.089 15.724 22.222 4.835 12.971 ms 10.64 34.17
Server Jitter PPS(0) 2.621 5.213 7.377 16.501 33.526 43.824 72.209 26.149 38.611 8.218 17.989 µs 6.42 21.28
Server Offset 132.246.11.227 1.839 2.087 6.644 6.723 7.690 7.763 12.344 1.046 5.676 0.681 6.825 ms 761.4 7116
Server Offset 142.3.100.2 -55.473 -54.247 -39.094 -1.833 43.649 75.475 86.059 82.743 129.722 25.849 0.676 µs -3.415 8.206
Server Offset 2600:2600::199 (ntp2.wiktel.com) 327.595 334.091 346.058 373.301 401.084 411.469 436.232 55.026 77.378 17.370 373.372 µs 8671 1.79e+05
Server Offset 2602:fde5:2a::13 (ntp3.torix.ca) 1.449 1.461 1.476 1.509 2.082 2.096 2.104 0.607 0.635 0.276 1.708 ms 156.6 904.2
Server Offset 2606:4700:f1::1 (time.cloudflare.com) -105.227 -60.903 30.366 169.223 401.633 496.210 542.647 371.267 557.113 112.911 180.793 µs 2.687 7.887
Server Offset 2607:f388::123:1 (ntp1.doit.wisc.edu) -0.493 -0.429 -0.309 1.219 4.314 6.845 8.152 4.623 7.274 1.571 1.564 ms 1.232 4.988
Server Offset PPS(0) -45.744 -23.173 -17.450 -2.863 27.274 39.005 65.815 44.724 62.178 13.621 -0.033 µs -3.103 7.158
Temp LM0 37.000 38.000 39.000 40.000 41.000 41.000 41.000 2.000 3.000 0.798 39.854 °C
Temp LM1 34.000 35.000 35.000 36.000 38.000 39.000 39.000 3.000 4.000 0.904 36.452 °C
Temp LM10 32.000 33.000 34.000 35.000 37.000 38.000 38.000 3.000 5.000 1.009 35.014 °C
Temp LM2 33.000 33.000 33.000 34.000 36.000 36.000 37.000 3.000 3.000 0.792 34.480 °C
Temp LM3 38.000 38.000 39.000 40.000 41.000 41.000 41.000 2.000 3.000 0.765 39.847 °C
Temp LM4 35.000 35.000 36.000 37.000 38.000 38.000 39.000 2.000 3.000 0.826 36.630 °C
Temp LM5 62.000 62.000 62.000 63.000 64.000 64.000 64.000 2.000 2.000 0.594 63.057 °C
Temp LM6 40.000 40.000 40.000 41.000 43.000 44.000 44.000 3.000 4.000 0.921 41.523 °C
Temp LM7 38.000 38.000 39.000 40.000 42.000 43.000 43.000 3.000 5.000 0.887 40.438 °C
Temp LM8 38.000 38.000 39.000 41.000 42.000 43.000 44.000 3.000 5.000 1.021 40.883 °C
Temp LM9 37.000 38.000 38.000 40.000 41.000 43.000 43.000 3.000 5.000 0.977 39.705 °C
Temp ZONE0 40.000 40.000 40.000 42.000 43.000 44.000 45.000 3.000 4.000 0.996 41.683 °C
Temp ZONE1 38.000 38.000 39.000 40.000 41.000 42.000 42.000 2.000 4.000 0.873 39.915 °C
Summary as CSV file


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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