NTPsec

crane3.services.mbix.ca

Report generated: Wed Sep 16 11:53:02 2026 UTC
Start Time: Tue Sep 15 11:53:01 2026 UTC
End Time: Wed Sep 16 11:53:01 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 -42.359 -23.790 -18.385 -3.327 28.893 40.427 65.104 47.278 64.217 14.320 -0.017 µs -3.075 6.962
Local Clock Frequency Offset 78.520 78.534 78.545 78.612 78.678 78.698 78.735 0.133 0.165 0.042 78.609 ppm 6.63e+09 1.245e+13

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 6.817 9.487 11.780 18.719 26.771 31.035 38.851 14.991 21.548 4.651 18.905 µs 38.31 151.8

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 2.447 3.535 4.346 6.770 9.456 10.828 15.776 5.110 7.293 1.597 6.808 ppb 44.9 185.7

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 -42.359 -23.790 -18.385 -3.327 28.893 40.427 65.104 47.278 64.217 14.320 -0.017 µs -3.075 6.962

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 78.520 78.534 78.545 78.612 78.678 78.698 78.735 0.133 0.165 0.042 78.609 ppm 6.63e+09 1.245e+13
Temp LM0 36.000 37.000 37.000 39.000 40.000 41.000 41.000 3.000 4.000 1.012 39.011 °C
Temp LM1 33.000 34.000 34.000 36.000 37.000 38.000 38.000 3.000 4.000 0.855 35.570 °C
Temp LM10 33.000 33.000 34.000 36.000 37.000 38.000 38.000 3.000 5.000 0.922 35.570 °C
Temp LM2 32.000 33.000 33.000 34.000 36.000 36.000 37.000 3.000 3.000 0.818 34.120 °C
Temp LM3 37.000 37.000 37.000 39.000 40.000 41.000 41.000 3.000 4.000 1.005 38.996 °C
Temp LM4 34.000 34.000 35.000 35.000 36.000 37.000 37.000 1.000 3.000 0.594 35.398 °C
Temp LM5 63.000 63.000 63.000 63.000 64.000 64.000 64.000 1.000 1.000 0.333 63.127 °C
Temp LM6 40.000 41.000 41.000 42.000 43.000 44.000 44.000 2.000 3.000 0.724 42.415 °C
Temp LM7 38.000 39.000 40.000 41.000 42.000 43.000 43.000 2.000 4.000 0.811 40.982 °C
Temp LM8 38.000 39.000 40.000 42.000 43.000 43.000 43.000 3.000 4.000 0.804 41.683 °C
Temp LM9 37.000 37.000 38.000 39.000 40.000 41.000 41.000 2.000 4.000 0.795 39.338 °C
Temp ZONE0 40.000 40.000 41.000 42.000 44.000 45.000 45.000 3.000 5.000 0.766 42.475 °C
Temp ZONE1 37.000 37.000 37.000 39.000 41.000 42.000 42.000 4.000 5.000 1.082 39.162 °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 1.925 1.951 2.001 2.095 2.195 2.225 2.281 0.193 0.273 0.058 2.093 ms 4.426e+04 1.568e+06

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 -134.116 -86.907 -0.058 -0.002 0.036 0.055 0.061 0.094 86.962 11.187 -1.389 ms -14.34 150.7

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) 325.835 330.133 343.646 371.039 408.770 420.734 440.353 65.124 90.601 19.667 372.820 µs 5844 1.059e+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) 1.443 1.458 1.471 1.498 2.074 2.096 2.110 0.603 0.638 0.245 1.633 ms 201.2 1262

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) -1.243 -1.167 -0.842 -0.214 0.270 0.400 0.486 1.112 1.567 0.349 -0.236 ms -10.22 31.1

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) -0.472 -0.450 -0.360 0.981 4.562 6.615 10.211 4.922 7.065 1.599 1.339 ms 1.357 6.997

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) -42.360 -23.791 -18.386 -3.328 28.894 40.428 65.105 47.280 64.219 14.321 -0.017 µs -3.075 6.962

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 0.040 0.043 0.073 0.322 2.561 3.278 3.532 2.488 3.235 0.797 0.657 ms 1.337 4.313

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 0.009 0.013 0.021 0.042 0.422 69.883 79.273 0.400 69.870 9.446 1.660 ms 3.704 31.88

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) 5.020 7.354 10.540 21.621 47.036 94.471 175.432 36.496 87.117 16.002 24.937 µs 6.097 44.51

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) 4.806 7.829 10.743 377.964 574.032 591.049 626.517 563.289 583.220 238.058 280.625 µs 0.4858 1.319

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.



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) 15.763 18.901 22.998 75.499 264.728 647.724 795.568 241.730 628.823 109.384 108.126 µs 3.249 17.16

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) 2.703 4.075 6.486 13.702 21.987 29.609 33.132 15.501 25.534 5.255 13.962 ms 10.09 31.36

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) 0.861 5.357 7.553 17.539 35.273 45.282 68.516 27.720 39.925 8.638 18.913 µs 6.302 20.15

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 78.520 78.534 78.545 78.612 78.678 78.698 78.735 0.133 0.165 0.042 78.609 ppm 6.63e+09 1.245e+13
Local Clock Time Offset -42.359 -23.790 -18.385 -3.327 28.893 40.427 65.104 47.278 64.217 14.320 -0.017 µs -3.075 6.962
Local RMS Frequency Jitter 2.447 3.535 4.346 6.770 9.456 10.828 15.776 5.110 7.293 1.597 6.808 ppb 44.9 185.7
Local RMS Time Jitter 6.817 9.487 11.780 18.719 26.771 31.035 38.851 14.991 21.548 4.651 18.905 µs 38.31 151.8
Server Jitter 132.246.11.227 0.040 0.043 0.073 0.322 2.561 3.278 3.532 2.488 3.235 0.797 0.657 ms 1.337 4.313
Server Jitter 142.3.100.2 0.009 0.013 0.021 0.042 0.422 69.883 79.273 0.400 69.870 9.446 1.660 ms 3.704 31.88
Server Jitter 2600:2600::199 (ntp2.wiktel.com) 5.020 7.354 10.540 21.621 47.036 94.471 175.432 36.496 87.117 16.002 24.937 µs 6.097 44.51
Server Jitter 2602:fde5:2a::13 (ntp3.torix.ca) 4.806 7.829 10.743 377.964 574.032 591.049 626.517 563.289 583.220 238.058 280.625 µs 0.4858 1.319
Server Jitter 2606:4700:f1::1 (time.cloudflare.com) 15.763 18.901 22.998 75.499 264.728 647.724 795.568 241.730 628.823 109.384 108.126 µs 3.249 17.16
Server Jitter 2607:f388::123:1 (ntp1.doit.wisc.edu) 2.703 4.075 6.486 13.702 21.987 29.609 33.132 15.501 25.534 5.255 13.962 ms 10.09 31.36
Server Jitter PPS(0) 0.861 5.357 7.553 17.539 35.273 45.282 68.516 27.720 39.925 8.638 18.913 µs 6.302 20.15
Server Offset 132.246.11.227 1.925 1.951 2.001 2.095 2.195 2.225 2.281 0.193 0.273 0.058 2.093 ms 4.426e+04 1.568e+06
Server Offset 142.3.100.2 -134.116 -86.907 -0.058 -0.002 0.036 0.055 0.061 0.094 86.962 11.187 -1.389 ms -14.34 150.7
Server Offset 2600:2600::199 (ntp2.wiktel.com) 325.835 330.133 343.646 371.039 408.770 420.734 440.353 65.124 90.601 19.667 372.820 µs 5844 1.059e+05
Server Offset 2602:fde5:2a::13 (ntp3.torix.ca) 1.443 1.458 1.471 1.498 2.074 2.096 2.110 0.603 0.638 0.245 1.633 ms 201.2 1262
Server Offset 2606:4700:f1::1 (time.cloudflare.com) -1.243 -1.167 -0.842 -0.214 0.270 0.400 0.486 1.112 1.567 0.349 -0.236 ms -10.22 31.1
Server Offset 2607:f388::123:1 (ntp1.doit.wisc.edu) -0.472 -0.450 -0.360 0.981 4.562 6.615 10.211 4.922 7.065 1.599 1.339 ms 1.357 6.997
Server Offset PPS(0) -42.360 -23.791 -18.386 -3.328 28.894 40.428 65.105 47.280 64.219 14.321 -0.017 µs -3.075 6.962
Temp LM0 36.000 37.000 37.000 39.000 40.000 41.000 41.000 3.000 4.000 1.012 39.011 °C
Temp LM1 33.000 34.000 34.000 36.000 37.000 38.000 38.000 3.000 4.000 0.855 35.570 °C
Temp LM10 33.000 33.000 34.000 36.000 37.000 38.000 38.000 3.000 5.000 0.922 35.570 °C
Temp LM2 32.000 33.000 33.000 34.000 36.000 36.000 37.000 3.000 3.000 0.818 34.120 °C
Temp LM3 37.000 37.000 37.000 39.000 40.000 41.000 41.000 3.000 4.000 1.005 38.996 °C
Temp LM4 34.000 34.000 35.000 35.000 36.000 37.000 37.000 1.000 3.000 0.594 35.398 °C
Temp LM5 63.000 63.000 63.000 63.000 64.000 64.000 64.000 1.000 1.000 0.333 63.127 °C
Temp LM6 40.000 41.000 41.000 42.000 43.000 44.000 44.000 2.000 3.000 0.724 42.415 °C
Temp LM7 38.000 39.000 40.000 41.000 42.000 43.000 43.000 2.000 4.000 0.811 40.982 °C
Temp LM8 38.000 39.000 40.000 42.000 43.000 43.000 43.000 3.000 4.000 0.804 41.683 °C
Temp LM9 37.000 37.000 38.000 39.000 40.000 41.000 41.000 2.000 4.000 0.795 39.338 °C
Temp ZONE0 40.000 40.000 41.000 42.000 44.000 45.000 45.000 3.000 5.000 0.766 42.475 °C
Temp ZONE1 37.000 37.000 37.000 39.000 41.000 42.000 42.000 4.000 5.000 1.082 39.162 °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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