NTPsec

A-ntpsec-3-hour-stats

Report generated: Mon Sep 16 02:02:26 2019 UTC
Start Time: Sun Sep 15 23:02:24 2019 UTC
End Time: Mon Sep 16 02:02:24 2019 UTC
Report published: Sun Sep 15 19:02:35 2019 PDT
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 -1.206 -1.035 -0.858 -0.487 -0.155 0.017 0.307 0.703 1.052 0.222 -0.497 µs -43.64 176.3
Local Clock Frequency Offset -983.307 -980.591 -973.282 -920.883 -855.042 -849.564 -847.137 118.240 131.027 38.665 -918.011 ppb -1.522e+04 3.785e+05

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 96.000 105.000 119.000 174.000 264.000 291.000 331.000 145.000 186.000 42.035 179.759 ns 45.65 191.5

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 57.000 67.000 87.000 169.000 283.000 314.000 329.000 196.000 247.000 60.252 175.574 10e-12 13.1 40.38

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 -1.206 -1.035 -0.858 -0.487 -0.155 0.017 0.307 0.703 1.052 0.222 -0.497 µs -43.64 176.3

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 -983.307 -980.591 -973.282 -920.883 -855.042 -849.564 -847.137 118.240 131.027 38.665 -918.011 ppb -1.522e+04 3.785e+05
Temp ZONE0 62.838 62.838 62.838 63.376 64.452 64.452 64.452 1.614 1.614 0.484 63.717 °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 9.000 9.000 10.000 11.000 12.000 12.000 12.000 2.000 3.000 0.704 11.263 nSat 3421 5.197e+04
TDOP 0.590 0.600 0.620 0.760 1.020 1.230 1.260 0.400 0.630 0.127 0.786 155.8 909.3

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. TDOP ranges from 1 to greater than 20. 1 denotes the highest possible confidence level. 2 to 5 is good. Greater than 20 means there will be significant inaccuracy and error.



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 0.394 0.394 0.888 1.952 2.741 3.364 3.364 1.853 2.970 0.608 2.038 ms 19.64 63.01

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

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

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

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



Server Offset 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 -0.577 -0.577 -0.577 0.863 3.314 3.314 3.314 3.890 3.890 1.434 0.989 ms -0.6612 1.744

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 192.168.1.11

peer offset 192.168.1.11 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 192.168.1.11 -53.598 -29.755 36.885 96.148 145.077 198.530 198.854 108.192 228.285 33.500 92.315 µs 9.915 29.13

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 203.123.48.219

peer offset 203.123.48.219 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 203.123.48.219 2.988 2.988 3.117 3.642 4.022 4.273 4.273 0.906 1.285 0.278 3.638 ms 1809 2.233e+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 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 1.293 1.293 1.309 1.786 2.334 2.700 2.700 1.025 1.407 0.284 1.806 ms 170.9 1018

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 216.218.254.202

peer offset 216.218.254.202 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 216.218.254.202 1.861 1.861 2.131 2.582 3.086 3.151 3.151 0.954 1.290 0.302 2.535 ms 427.8 3333

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 66.220.9.122

peer offset 66.220.9.122 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 66.220.9.122 1.585 1.585 2.139 2.473 2.750 2.767 2.767 0.611 1.182 0.221 2.447 ms 1055 1.091e+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(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) -74.698 -66.210 -62.534 -57.798 -53.300 -51.605 -49.623 9.233 14.604 3.029 -57.865 ms -8184 1.657e+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 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) -1.207 -1.036 -0.859 -0.488 -0.156 0.018 0.308 0.703 1.054 0.222 -0.497 µs -43.76 176.9

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 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 0.700 0.700 0.778 2.474 15.164 15.832 15.832 14.386 15.131 4.085 4.286 ms 1.639 4.577

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 1.682 1.682 1.682 3.175 9.496 9.496 9.496 7.814 7.814 2.249 3.771 ms 3.968 12.2

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 192.168.1.11

peer jitter 192.168.1.11 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 192.168.1.11 0.014 0.017 0.042 0.188 8.729 244.456 245.131 8.687 244.439 24.711 4.308 ms 6.46 65.65

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 203.123.48.219

peer jitter 203.123.48.219 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 203.123.48.219 0.833 0.833 1.224 3.926 13.949 14.064 14.064 12.725 13.231 3.736 5.032 ms 2.144 5.305

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 0.504 0.504 0.508 1.823 12.037 13.905 13.905 11.529 13.401 3.206 3.160 ms 1.962 6.006

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 216.218.254.202

peer jitter 216.218.254.202 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 216.218.254.202 0.315 0.315 0.643 2.132 41.149 41.290 41.290 40.505 40.975 10.631 6.657 ms 1.513 5.816

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 66.220.9.122

peer jitter 66.220.9.122 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 66.220.9.122 0.354 0.354 0.476 3.663 12.445 12.987 12.987 11.969 12.634 4.035 5.126 ms 1.272 2.663

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) 0.222 0.438 0.622 1.463 3.988 7.450 15.045 3.365 7.011 1.313 1.867 ms 3.837 18.6

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 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) 56.000 73.000 91.000 182.000 379.000 510.000 621.000 288.000 437.000 89.928 200.962 ns 6.853 22.86

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.



Summary


Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Frequency Offset -983.307 -980.591 -973.282 -920.883 -855.042 -849.564 -847.137 118.240 131.027 38.665 -918.011 ppb -1.522e+04 3.785e+05
Local Clock Time Offset -1.206 -1.035 -0.858 -0.487 -0.155 0.017 0.307 0.703 1.052 0.222 -0.497 µs -43.64 176.3
Local RMS Frequency Jitter 57.000 67.000 87.000 169.000 283.000 314.000 329.000 196.000 247.000 60.252 175.574 10e-12 13.1 40.38
Local RMS Time Jitter 96.000 105.000 119.000 174.000 264.000 291.000 331.000 145.000 186.000 42.035 179.759 ns 45.65 191.5
Server Jitter 104.131.155.175 0.700 0.700 0.778 2.474 15.164 15.832 15.832 14.386 15.131 4.085 4.286 ms 1.639 4.577
Server Jitter 178.62.68.79 1.682 1.682 1.682 3.175 9.496 9.496 9.496 7.814 7.814 2.249 3.771 ms 3.968 12.2
Server Jitter 192.168.1.11 0.014 0.017 0.042 0.188 8.729 244.456 245.131 8.687 244.439 24.711 4.308 ms 6.46 65.65
Server Jitter 203.123.48.219 0.833 0.833 1.224 3.926 13.949 14.064 14.064 12.725 13.231 3.736 5.032 ms 2.144 5.305
Server Jitter 204.17.205.24 0.504 0.504 0.508 1.823 12.037 13.905 13.905 11.529 13.401 3.206 3.160 ms 1.962 6.006
Server Jitter 216.218.254.202 0.315 0.315 0.643 2.132 41.149 41.290 41.290 40.505 40.975 10.631 6.657 ms 1.513 5.816
Server Jitter 66.220.9.122 0.354 0.354 0.476 3.663 12.445 12.987 12.987 11.969 12.634 4.035 5.126 ms 1.272 2.663
Server Jitter SHM(0) 0.222 0.438 0.622 1.463 3.988 7.450 15.045 3.365 7.011 1.313 1.867 ms 3.837 18.6
Server Jitter SHM(1) 56.000 73.000 91.000 182.000 379.000 510.000 621.000 288.000 437.000 89.928 200.962 ns 6.853 22.86
Server Offset 104.131.155.175 0.394 0.394 0.888 1.952 2.741 3.364 3.364 1.853 2.970 0.608 2.038 ms 19.64 63.01
Server Offset 178.62.68.79 -0.577 -0.577 -0.577 0.863 3.314 3.314 3.314 3.890 3.890 1.434 0.989 ms -0.6612 1.744
Server Offset 192.168.1.11 -53.598 -29.755 36.885 96.148 145.077 198.530 198.854 108.192 228.285 33.500 92.315 µs 9.915 29.13
Server Offset 203.123.48.219 2.988 2.988 3.117 3.642 4.022 4.273 4.273 0.906 1.285 0.278 3.638 ms 1809 2.233e+04
Server Offset 204.17.205.24 1.293 1.293 1.309 1.786 2.334 2.700 2.700 1.025 1.407 0.284 1.806 ms 170.9 1018
Server Offset 216.218.254.202 1.861 1.861 2.131 2.582 3.086 3.151 3.151 0.954 1.290 0.302 2.535 ms 427.8 3333
Server Offset 66.220.9.122 1.585 1.585 2.139 2.473 2.750 2.767 2.767 0.611 1.182 0.221 2.447 ms 1055 1.091e+04
Server Offset SHM(0) -74.698 -66.210 -62.534 -57.798 -53.300 -51.605 -49.623 9.233 14.604 3.029 -57.865 ms -8184 1.657e+05
Server Offset SHM(1) -1.207 -1.036 -0.859 -0.488 -0.156 0.018 0.308 0.703 1.054 0.222 -0.497 µs -43.76 176.9
TDOP 0.590 0.600 0.620 0.760 1.020 1.230 1.260 0.400 0.630 0.127 0.786 155.8 909.3
Temp ZONE0 62.838 62.838 62.838 63.376 64.452 64.452 64.452 1.614 1.614 0.484 63.717 °C
nSats 9.000 9.000 10.000 11.000 12.000 12.000 12.000 2.000 3.000 0.704 11.263 nSat 3421 5.197e+04
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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