NTPsec

A-ntpsec-5-day-stats

Report generated: Thu Jul 18 02:16:06 2019 UTC
Start Time: Sat Jul 13 02:15:17 2019 UTC
End Time: Thu Jul 18 02:15:17 2019 UTC
Report published: Wed Jul 17 19:18:22 2019 PDT
Report Period: 5.0 days
Warning: plots clipped

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 -2,356.000 -942.000 -694.000 13.000 700.000 992.000 2,676.000 1,394.000 1,934.000 453.979 7.538 ns -3.899 9.607
Local Clock Frequency Offset -1.190 -1.155 -1.052 -0.778 -0.628 -0.617 -0.614 0.424 0.538 0.131 -0.805 ppm -383.7 2902

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 62.000 91.000 107.000 165.000 278.000 361.000 1,350.000 171.000 270.000 61.004 176.045 ns 16.19 112

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 17.000 28.000 37.000 111.000 299.000 586.000 3,302.000 262.000 558.000 121.030 132.548 10e-12 7.949 136.7

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 -2,356.000 -942.000 -694.000 13.000 700.000 992.000 2,676.000 1,394.000 1,934.000 453.979 7.538 ns -3.899 9.607

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 -1.190 -1.155 -1.052 -0.778 -0.628 -0.617 -0.614 0.424 0.538 0.131 -0.805 ppm -383.7 2902
Temp ZONE0 59.072 59.072 60.148 61.224 63.914 64.990 65.528 3.766 5.918 1.328 61.623 °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 2.000 6.000 7.000 10.000 12.000 12.000 12.000 5.000 6.000 1.487 9.626 nSat 180.2 1076
TDOP 0.000 0.560 0.600 0.800 1.430 1.770 3.030 0.830 1.210 0.267 0.881 20.99 86.61

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 169.229.128.142

peer offset 169.229.128.142 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 169.229.128.142 -6.133 -2.111 -1.945 -1.501 -1.168 -1.002 -0.675 0.777 1.109 0.278 -1.524 ms -295.8 2198

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 -230.435 -65.370 -17.915 45.149 111.909 163.187 311.991 129.824 228.557 42.004 46.628 µs 0.3837 5.812

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 192.168.1.12

peer offset 192.168.1.12 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 192.168.1.12 -42,506.984 -2.792 70.089 130.348 171.171 211.612 9,051.117 101.082 214.404 539.417 122.152 µs -77.35 6194

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 199.102.46.72

peer offset 199.102.46.72 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 199.102.46.72 -3.751 -2.859 -0.124 0.597 0.910 1.034 1.309 1.035 3.893 0.706 0.438 ms -5.006 24.41

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 216.218.192.202

peer offset 216.218.192.202 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 216.218.192.202 -5.886 -1.612 -1.461 -1.007 -0.702 -0.557 -0.295 0.759 1.055 0.283 -1.039 ms -121.6 815.4

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 -1.803 -1.518 -1.376 -0.937 -0.613 -0.459 -0.306 0.763 1.059 0.231 -0.957 ms -152.6 874.6

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

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

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

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



Server Offset 63.145.169.3

peer offset 63.145.169.3 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 63.145.169.3 -7.934 -4.240 -4.050 -3.573 -3.242 -3.095 -2.736 0.808 1.146 0.289 -3.602 ms -2498 3.449e+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) -82.897 -66.328 -63.366 -54.901 -48.384 -45.518 -42.010 14.982 20.810 4.717 -55.364 ms -2104 2.73e+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) -2,357.000 -943.000 -695.000 14.000 701.000 995.000 2,677.000 1,396.000 1,938.000 455.198 7.748 ns -3.889 9.596

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 169.229.128.142

peer jitter 169.229.128.142 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 169.229.128.142 0.000 0.158 0.228 0.502 8.796 11.690 15.599 8.568 11.532 3.200 2.205 ms 0.6604 2.925

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 0.000 0.020 0.046 0.175 8.665 9.132 59.836 8.619 9.112 3.321 1.427 ms 4.759 78.88

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 192.168.1.12

peer jitter 192.168.1.12 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 192.168.1.12 0.000 0.022 0.054 0.519 8.728 56.279 131.631 8.674 56.257 6.601 2.373 ms 5.407 60.28

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.



Server Jitter 199.102.46.72

peer jitter 199.102.46.72 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 199.102.46.72 0.000 0.160 0.240 0.531 8.878 12.278 19.034 8.637 12.118 3.382 2.397 ms 0.7069 3.336

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 216.218.192.202

peer jitter 216.218.192.202 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 216.218.192.202 0.000 0.169 0.230 0.506 8.845 12.142 117.601 8.616 11.973 4.896 2.307 ms 10.06 220.4

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 0.000 0.172 0.236 0.514 8.866 10.622 190.809 8.630 10.450 6.350 2.464 ms 19.18 571

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 63.145.169.3

peer jitter 63.145.169.3 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 63.145.169.3 0.000 0.174 0.237 0.503 8.896 17.037 80.135 8.659 16.863 4.719 2.367 ms 5.909 92.51

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 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) 0.000 0.365 0.530 1.354 3.575 6.030 19.456 3.045 5.665 1.107 1.637 ms 3.996 20.05

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter SHM(1)

peer jitter SHM(1) plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter SHM(1) 0.000 58.000 79.000 166.000 372.000 538.000 2,822.000 293.000 480.000 101.485 188.732 ns 6.059 44.78

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 -1.190 -1.155 -1.052 -0.778 -0.628 -0.617 -0.614 0.424 0.538 0.131 -0.805 ppm -383.7 2902
Local Clock Time Offset -2,356.000 -942.000 -694.000 13.000 700.000 992.000 2,676.000 1,394.000 1,934.000 453.979 7.538 ns -3.899 9.607
Local RMS Frequency Jitter 17.000 28.000 37.000 111.000 299.000 586.000 3,302.000 262.000 558.000 121.030 132.548 10e-12 7.949 136.7
Local RMS Time Jitter 62.000 91.000 107.000 165.000 278.000 361.000 1,350.000 171.000 270.000 61.004 176.045 ns 16.19 112
Server Jitter 169.229.128.142 0.000 0.158 0.228 0.502 8.796 11.690 15.599 8.568 11.532 3.200 2.205 ms 0.6604 2.925
Server Jitter 192.168.1.11 0.000 0.020 0.046 0.175 8.665 9.132 59.836 8.619 9.112 3.321 1.427 ms 4.759 78.88
Server Jitter 192.168.1.12 0.000 0.022 0.054 0.519 8.728 56.279 131.631 8.674 56.257 6.601 2.373 ms 5.407 60.28
Server Jitter 199.102.46.72 0.000 0.160 0.240 0.531 8.878 12.278 19.034 8.637 12.118 3.382 2.397 ms 0.7069 3.336
Server Jitter 216.218.192.202 0.000 0.169 0.230 0.506 8.845 12.142 117.601 8.616 11.973 4.896 2.307 ms 10.06 220.4
Server Jitter 216.218.254.202 0.000 0.172 0.236 0.514 8.866 10.622 190.809 8.630 10.450 6.350 2.464 ms 19.18 571
Server Jitter 63.145.169.3 0.000 0.174 0.237 0.503 8.896 17.037 80.135 8.659 16.863 4.719 2.367 ms 5.909 92.51
Server Jitter SHM(0) 0.000 0.365 0.530 1.354 3.575 6.030 19.456 3.045 5.665 1.107 1.637 ms 3.996 20.05
Server Jitter SHM(1) 0.000 58.000 79.000 166.000 372.000 538.000 2,822.000 293.000 480.000 101.485 188.732 ns 6.059 44.78
Server Offset 169.229.128.142 -6.133 -2.111 -1.945 -1.501 -1.168 -1.002 -0.675 0.777 1.109 0.278 -1.524 ms -295.8 2198
Server Offset 192.168.1.11 -230.435 -65.370 -17.915 45.149 111.909 163.187 311.991 129.824 228.557 42.004 46.628 µs 0.3837 5.812
Server Offset 192.168.1.12 -42,506.984 -2.792 70.089 130.348 171.171 211.612 9,051.117 101.082 214.404 539.417 122.152 µs -77.35 6194
Server Offset 199.102.46.72 -3.751 -2.859 -0.124 0.597 0.910 1.034 1.309 1.035 3.893 0.706 0.438 ms -5.006 24.41
Server Offset 216.218.192.202 -5.886 -1.612 -1.461 -1.007 -0.702 -0.557 -0.295 0.759 1.055 0.283 -1.039 ms -121.6 815.4
Server Offset 216.218.254.202 -1.803 -1.518 -1.376 -0.937 -0.613 -0.459 -0.306 0.763 1.059 0.231 -0.957 ms -152.6 874.6
Server Offset 63.145.169.3 -7.934 -4.240 -4.050 -3.573 -3.242 -3.095 -2.736 0.808 1.146 0.289 -3.602 ms -2498 3.449e+04
Server Offset SHM(0) -82.897 -66.328 -63.366 -54.901 -48.384 -45.518 -42.010 14.982 20.810 4.717 -55.364 ms -2104 2.73e+04
Server Offset SHM(1) -2,357.000 -943.000 -695.000 14.000 701.000 995.000 2,677.000 1,396.000 1,938.000 455.198 7.748 ns -3.889 9.596
TDOP 0.000 0.560 0.600 0.800 1.430 1.770 3.030 0.830 1.210 0.267 0.881 20.99 86.61
Temp ZONE0 59.072 59.072 60.148 61.224 63.914 64.990 65.528 3.766 5.918 1.328 61.623 °C
nSats 2.000 6.000 7.000 10.000 12.000 12.000 12.000 5.000 6.000 1.487 9.626 nSat 180.2 1076
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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