NTPsec

A-ntpsec-1-hour-stats

Report generated: Mon Sep 16 02:02:08 2019 UTC
Start Time: Mon Sep 16 01:01:39 2019 UTC
End Time: Mon Sep 16 02:02:07 2019 UTC
Report published: Sun Sep 15 19:02:15 2019 PDT
Report Period: 0.0 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 -1.111 -1.070 -0.885 -0.459 -0.132 0.037 0.162 0.753 1.107 0.229 -0.468 µs -37.55 147.2
Local Clock Frequency Offset -983.307 -982.788 -979.446 -960.129 -949.982 -948.868 -948.578 29.464 33.920 9.382 -962.153 ppb -1.111e+06 1.151e+08

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 104.000 111.000 125.000 179.000 276.000 325.000 331.000 151.000 214.000 44.936 188.107 ns 42.74 178.2

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 60.000 71.000 126.000 265.000 318.000 321.000 194.000 258.000 60.319 145.051 10e-12 7.97 24.5

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 -1.111 -1.070 -0.885 -0.459 -0.132 0.037 0.162 0.753 1.107 0.229 -0.468 µs -37.55 147.2

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 -982.788 -979.446 -960.129 -949.982 -948.868 -948.578 29.464 33.920 9.382 -962.153 ppb -1.111e+06 1.151e+08
Temp ZONE0 63.376 63.376 63.376 64.452 64.452 64.452 64.452 1.076 1.076 0.420 64.075 °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 10.000 10.000 11.000 11.000 12.000 12.000 12.000 1.000 2.000 0.493 11.300 nSat 1.058e+04 2.333e+05
TDOP 0.690 0.690 0.700 0.810 0.850 1.100 1.100 0.150 0.410 0.067 0.793 1289 1.43e+04

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 1.163 1.163 1.163 2.383 2.741 2.741 2.741 1.578 1.578 0.543 2.157 ms 34.73 127.2

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

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

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

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



Server Offset 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 178.62.68.79 863.306 863.306 863.306 863.306 863.306 863.306 863.306 0.000 0.000 0.000 863.306 µs nan nan

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 19.053 19.053 60.116 99.010 162.659 198.854 198.854 102.543 179.801 32.063 101.080 µs 16.88 56.77

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 3.322 3.322 3.322 3.799 4.273 4.273 4.273 0.951 0.951 0.265 3.757 ms 2337 3.137e+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 1.309 1.309 1.309 1.870 2.700 2.700 2.700 1.391 1.391 0.344 1.918 ms 110.3 579.7

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 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 2.164 2.164 2.164 2.582 2.897 2.897 2.897 0.733 0.733 0.260 2.502 ms 663.5 5939

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 1.585 2.485 2.612 2.612 2.612 1.028 1.028 0.272 2.393 ms 494.2 3989

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 -68.514 -63.538 -59.779 -56.214 -54.898 -52.976 7.324 13.616 2.500 -59.831 ms -1.557e+04 3.902e+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) -1.112 -1.071 -0.886 -0.460 -0.133 0.038 0.163 0.753 1.109 0.229 -0.469 µs -37.65 147.7

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 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 0.826 0.826 0.826 2.626 15.832 15.832 15.832 15.005 15.005 5.336 5.019 ms 1.063 2.457

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 4.355 4.355 4.355 4.355 4.355 4.355 4.355 0.000 0.000 0.000 4.355 ms nan nan

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 0.014 0.037 0.165 8.750 11.075 11.075 8.713 11.061 2.970 1.630 ms 0.5259 3.181

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 0.890 0.890 0.890 5.923 11.765 11.765 11.765 10.875 10.875 3.873 5.688 ms 1.742 3.257

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 0.935 0.935 0.935 2.048 13.905 13.905 13.905 12.970 12.970 4.251 4.338 ms 1.232 2.904

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 0.315 4.167 11.511 11.511 11.511 11.196 11.196 3.761 5.440 ms 1.834 3.851

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 0.648 0.648 0.648 1.616 9.595 9.595 9.595 8.947 8.947 2.934 3.187 ms 1.324 3.038

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) 0.254 0.472 0.642 1.573 4.341 7.966 14.155 3.699 7.494 1.461 2.029 ms 3.545 15.79

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) 67.000 76.000 98.000 181.000 364.000 522.000 619.000 266.000 446.000 89.095 200.162 ns 7.19 25.55

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 -982.788 -979.446 -960.129 -949.982 -948.868 -948.578 29.464 33.920 9.382 -962.153 ppb -1.111e+06 1.151e+08
Local Clock Time Offset -1.111 -1.070 -0.885 -0.459 -0.132 0.037 0.162 0.753 1.107 0.229 -0.468 µs -37.55 147.2
Local RMS Frequency Jitter 57.000 60.000 71.000 126.000 265.000 318.000 321.000 194.000 258.000 60.319 145.051 10e-12 7.97 24.5
Local RMS Time Jitter 104.000 111.000 125.000 179.000 276.000 325.000 331.000 151.000 214.000 44.936 188.107 ns 42.74 178.2
Server Jitter 104.131.155.175 0.826 0.826 0.826 2.626 15.832 15.832 15.832 15.005 15.005 5.336 5.019 ms 1.063 2.457
Server Jitter 178.62.68.79 4.355 4.355 4.355 4.355 4.355 4.355 4.355 0.000 0.000 0.000 4.355 ms nan nan
Server Jitter 192.168.1.11 0.014 0.014 0.037 0.165 8.750 11.075 11.075 8.713 11.061 2.970 1.630 ms 0.5259 3.181
Server Jitter 203.123.48.219 0.890 0.890 0.890 5.923 11.765 11.765 11.765 10.875 10.875 3.873 5.688 ms 1.742 3.257
Server Jitter 204.17.205.24 0.935 0.935 0.935 2.048 13.905 13.905 13.905 12.970 12.970 4.251 4.338 ms 1.232 2.904
Server Jitter 216.218.254.202 0.315 0.315 0.315 4.167 11.511 11.511 11.511 11.196 11.196 3.761 5.440 ms 1.834 3.851
Server Jitter 66.220.9.122 0.648 0.648 0.648 1.616 9.595 9.595 9.595 8.947 8.947 2.934 3.187 ms 1.324 3.038
Server Jitter SHM(0) 0.254 0.472 0.642 1.573 4.341 7.966 14.155 3.699 7.494 1.461 2.029 ms 3.545 15.79
Server Jitter SHM(1) 67.000 76.000 98.000 181.000 364.000 522.000 619.000 266.000 446.000 89.095 200.162 ns 7.19 25.55
Server Offset 104.131.155.175 1.163 1.163 1.163 2.383 2.741 2.741 2.741 1.578 1.578 0.543 2.157 ms 34.73 127.2
Server Offset 178.62.68.79 863.306 863.306 863.306 863.306 863.306 863.306 863.306 0.000 0.000 0.000 863.306 µs nan nan
Server Offset 192.168.1.11 19.053 19.053 60.116 99.010 162.659 198.854 198.854 102.543 179.801 32.063 101.080 µs 16.88 56.77
Server Offset 203.123.48.219 3.322 3.322 3.322 3.799 4.273 4.273 4.273 0.951 0.951 0.265 3.757 ms 2337 3.137e+04
Server Offset 204.17.205.24 1.309 1.309 1.309 1.870 2.700 2.700 2.700 1.391 1.391 0.344 1.918 ms 110.3 579.7
Server Offset 216.218.254.202 2.164 2.164 2.164 2.582 2.897 2.897 2.897 0.733 0.733 0.260 2.502 ms 663.5 5939
Server Offset 66.220.9.122 1.585 1.585 1.585 2.485 2.612 2.612 2.612 1.028 1.028 0.272 2.393 ms 494.2 3989
Server Offset SHM(0) -74.698 -68.514 -63.538 -59.779 -56.214 -54.898 -52.976 7.324 13.616 2.500 -59.831 ms -1.557e+04 3.902e+05
Server Offset SHM(1) -1.112 -1.071 -0.886 -0.460 -0.133 0.038 0.163 0.753 1.109 0.229 -0.469 µs -37.65 147.7
TDOP 0.690 0.690 0.700 0.810 0.850 1.100 1.100 0.150 0.410 0.067 0.793 1289 1.43e+04
Temp ZONE0 63.376 63.376 63.376 64.452 64.452 64.452 64.452 1.076 1.076 0.420 64.075 °C
nSats 10.000 10.000 11.000 11.000 12.000 12.000 12.000 1.000 2.000 0.493 11.300 nSat 1.058e+04 2.333e+05
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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