NTPsec

C-ntpsec-3-hour-stats

Report generated: Mon Nov 30 05:01:17 2020 UTC
Start Time: Mon Nov 30 02:01:17 2020 UTC
End Time: Mon Nov 30 05:01:17 2020 UTC
Report published: Sun Nov 29 21:01:21 2020 PST
Report Period: 0.1 days

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 -1.490 -0.656 -0.475 0.038 0.665 1.018 1.619 1.140 1.674 0.367 0.073 µs -2.624 7.274
Local Clock Frequency Offset -5.263 -5.263 -5.260 -5.255 -5.251 -5.251 -5.251 0.0085 0.0119 0.0029 -5.256 ppm -6.265e+09 1.155e+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 108.000 124.000 141.000 208.000 333.000 414.000 560.000 192.000 290.000 59.181 215.208 ns 27.83 114.6

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 28.000 33.000 45.000 81.000 136.000 236.000 258.000 91.000 203.000 33.859 85.831 10e-12 9.949 38.55

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 -1.490 -0.656 -0.475 0.038 0.665 1.018 1.619 1.140 1.674 0.367 0.073 µs -2.624 7.274

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 -5.263 -5.263 -5.260 -5.255 -5.251 -5.251 -5.251 0.0085 0.0119 0.0029 -5.256 ppm -6.265e+09 1.155e+13
Temp ZONE0 57.458 57.458 57.996 57.996 58.534 59.072 59.072 0.538 1.614 0.261 58.133 °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.



Local GPS

local gps plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
nSats 7.000 8.000 9.000 10.000 12.000 12.000 12.000 3.000 4.000 1.069 9.828 nSat 575.2 4929
TDOP 0.500 0.510 0.520 0.810 1.100 1.130 1.200 0.580 0.620 0.179 0.797 52.09 220.3

Local GPS. The Time Dilution of Precision (TDOP) is plotted in blue. The number of visible satellites (nSat) is plotted in red.

TDOP is field 3, and nSats is field 4, from the gpsd log file. The gpsd log file is created by the ntploggps program.

TDOP is a dimensionless error factor. Smaller numbers are better. TDOP ranges from 1 (ideal), 2 to 5 (good), to greater than 20 (poor). Some GNSS receivers report TDOP less than one which is theoretically impossible.



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 104.131.155.175

peer offset 104.131.155.175 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 104.131.155.175 1.264 1.264 1.264 1.909 3.324 3.324 3.324 2.060 2.060 0.614 2.059 ms 20.6 71.03

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset 162.159.200.1

peer offset 162.159.200.1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 162.159.200.1 -5.068 -5.068 -4.939 -4.709 -2.272 -2.115 -2.115 2.666 2.954 0.609 -4.578 ms -639.5 5593

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 173.11.101.155

peer offset 173.11.101.155 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 173.11.101.155 -1.585 -1.585 -1.059 0.031 0.812 1.312 1.312 1.871 2.896 0.558 0.006 ms -4.484 12.9

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 178.62.68.79

peer offset 178.62.68.79 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 178.62.68.79 4.769 4.769 5.166 5.774 6.540 7.798 7.798 1.374 3.029 0.498 5.853 ms 1281 1.418e+04

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 192.168.1.10

peer offset 192.168.1.10 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 192.168.1.10 -105.528 -49.045 -32.800 21.455 63.680 86.065 94.249 96.480 135.110 29.157 19.541 µs -1.564 5.839

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 204.123.2.5

peer offset 204.123.2.5 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 204.123.2.5 1.804 1.804 1.804 2.300 3.454 3.454 3.454 1.650 1.650 0.408 2.413 ms 135 759.5

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 2405:fc00:0:1::123

peer offset 2405:fc00:0:1::123 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2405:fc00:0:1::123 4.239 4.239 4.385 4.872 7.448 7.605 7.605 3.063 3.365 0.771 5.047 ms 190 1194

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) -69.247 -68.729 -66.929 -58.739 -51.394 -50.349 -49.043 15.535 18.380 4.865 -58.728 ms -2273 3.023e+04

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) -1.491 -0.657 -0.475 0.039 0.666 1.019 1.620 1.141 1.676 0.368 0.073 µs -2.626 7.268

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 104.131.155.175

peer jitter 104.131.155.175 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 104.131.155.175 0.887 0.887 0.887 1.436 18.740 18.740 18.740 17.853 17.853 7.528 7.163 ms 0.4549 1.482

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 162.159.200.1

peer jitter 162.159.200.1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 162.159.200.1 0.397 0.397 0.442 1.517 13.968 14.155 14.155 13.526 13.758 5.087 5.095 ms 0.6103 1.604

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 173.11.101.155

peer jitter 173.11.101.155 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 173.11.101.155 0.871 0.871 1.200 2.623 11.845 12.896 12.896 10.645 12.024 3.846 5.017 ms 1.6 3.161

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 178.62.68.79

peer jitter 178.62.68.79 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 178.62.68.79 0.216 0.216 0.351 2.947 19.508 19.544 19.544 19.156 19.328 6.240 6.483 ms 0.9675 2.647

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 192.168.1.10

peer jitter 192.168.1.10 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 192.168.1.10 0.019 0.026 0.055 0.172 8.691 8.720 8.731 8.636 8.694 2.549 1.162 ms 0.5648 3.533

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 204.123.2.5

peer jitter 204.123.2.5 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 204.123.2.5 0.860 0.860 0.860 6.891 17.387 17.387 17.387 16.527 16.527 5.746 6.747 ms 0.9915 2.355

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 2405:fc00:0:1::123

peer jitter 2405:fc00:0:1::123 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2405:fc00:0:1::123 0.309 0.309 0.861 10.311 27.392 29.959 29.959 26.531 29.650 9.173 11.062 ms 1.117 2.639

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) 0.168 0.221 0.312 0.956 3.292 5.932 7.580 2.980 5.711 1.042 1.257 ms 3.047 12.75

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) 52.000 89.000 122.000 269.000 659.000 835.000 1,422.000 537.000 746.000 171.000 308.166 ns 4.471 15.97

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 -5.263 -5.263 -5.260 -5.255 -5.251 -5.251 -5.251 0.0085 0.0119 0.0029 -5.256 ppm -6.265e+09 1.155e+13
Local Clock Time Offset -1.490 -0.656 -0.475 0.038 0.665 1.018 1.619 1.140 1.674 0.367 0.073 µs -2.624 7.274
Local RMS Frequency Jitter 28.000 33.000 45.000 81.000 136.000 236.000 258.000 91.000 203.000 33.859 85.831 10e-12 9.949 38.55
Local RMS Time Jitter 108.000 124.000 141.000 208.000 333.000 414.000 560.000 192.000 290.000 59.181 215.208 ns 27.83 114.6
Server Jitter 104.131.155.175 0.887 0.887 0.887 1.436 18.740 18.740 18.740 17.853 17.853 7.528 7.163 ms 0.4549 1.482
Server Jitter 162.159.200.1 0.397 0.397 0.442 1.517 13.968 14.155 14.155 13.526 13.758 5.087 5.095 ms 0.6103 1.604
Server Jitter 173.11.101.155 0.871 0.871 1.200 2.623 11.845 12.896 12.896 10.645 12.024 3.846 5.017 ms 1.6 3.161
Server Jitter 178.62.68.79 0.216 0.216 0.351 2.947 19.508 19.544 19.544 19.156 19.328 6.240 6.483 ms 0.9675 2.647
Server Jitter 192.168.1.10 0.019 0.026 0.055 0.172 8.691 8.720 8.731 8.636 8.694 2.549 1.162 ms 0.5648 3.533
Server Jitter 204.123.2.5 0.860 0.860 0.860 6.891 17.387 17.387 17.387 16.527 16.527 5.746 6.747 ms 0.9915 2.355
Server Jitter 2405:fc00:0:1::123 0.309 0.309 0.861 10.311 27.392 29.959 29.959 26.531 29.650 9.173 11.062 ms 1.117 2.639
Server Jitter SHM(0) 0.168 0.221 0.312 0.956 3.292 5.932 7.580 2.980 5.711 1.042 1.257 ms 3.047 12.75
Server Jitter SHM(1) 52.000 89.000 122.000 269.000 659.000 835.000 1,422.000 537.000 746.000 171.000 308.166 ns 4.471 15.97
Server Offset 104.131.155.175 1.264 1.264 1.264 1.909 3.324 3.324 3.324 2.060 2.060 0.614 2.059 ms 20.6 71.03
Server Offset 162.159.200.1 -5.068 -5.068 -4.939 -4.709 -2.272 -2.115 -2.115 2.666 2.954 0.609 -4.578 ms -639.5 5593
Server Offset 173.11.101.155 -1.585 -1.585 -1.059 0.031 0.812 1.312 1.312 1.871 2.896 0.558 0.006 ms -4.484 12.9
Server Offset 178.62.68.79 4.769 4.769 5.166 5.774 6.540 7.798 7.798 1.374 3.029 0.498 5.853 ms 1281 1.418e+04
Server Offset 192.168.1.10 -105.528 -49.045 -32.800 21.455 63.680 86.065 94.249 96.480 135.110 29.157 19.541 µs -1.564 5.839
Server Offset 204.123.2.5 1.804 1.804 1.804 2.300 3.454 3.454 3.454 1.650 1.650 0.408 2.413 ms 135 759.5
Server Offset 2405:fc00:0:1::123 4.239 4.239 4.385 4.872 7.448 7.605 7.605 3.063 3.365 0.771 5.047 ms 190 1194
Server Offset SHM(0) -69.247 -68.729 -66.929 -58.739 -51.394 -50.349 -49.043 15.535 18.380 4.865 -58.728 ms -2273 3.023e+04
Server Offset SHM(1) -1.491 -0.657 -0.475 0.039 0.666 1.019 1.620 1.141 1.676 0.368 0.073 µs -2.626 7.268
TDOP 0.500 0.510 0.520 0.810 1.100 1.130 1.200 0.580 0.620 0.179 0.797 52.09 220.3
Temp ZONE0 57.458 57.458 57.996 57.996 58.534 59.072 59.072 0.538 1.614 0.261 58.133 °C
nSats 7.000 8.000 9.000 10.000 12.000 12.000 12.000 3.000 4.000 1.069 9.828 nSat 575.2 4929
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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