NTPsec

b-ntpsec-120-hour-stats

Report generated: Tue Jun 25 00:43:15 2019 UTC
Start Time: Thu Jun 20 00:41:16 2019 UTC
End Time: Tue Jun 25 00:41:16 2019 UTC
Report published: Mon Jun 24 17:49:40 2019 PDT
Report Period: 5.0 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 -21.804 -1.516 -0.808 0.017 0.758 1.204 10.989 1.566 2.720 0.568 0.000 µs -6.141 84.67
Local Clock Frequency Offset -7.477 -6.375 -6.218 -5.841 -5.784 -5.774 -5.754 0.435 0.601 0.161 -5.924 ppm -5.372e+04 2.03e+06

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 0.148 0.256 0.309 0.534 1.043 1.610 9.202 0.734 1.354 0.335 0.601 µs 9.033 98.28

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 0.000 1.687 2.008 3.354 6.366 10.830 88.390 4.358 9.143 2.337 3.784 ppb 11.08 187

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 -21.804 -1.516 -0.808 0.017 0.758 1.204 10.989 1.566 2.720 0.568 0.000 µs -6.141 84.67

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 -7.477 -6.375 -6.218 -5.841 -5.784 -5.774 -5.754 0.435 0.601 0.161 -5.924 ppm -5.372e+04 2.03e+06
Temp ZONE0 38.090 53.154 54.230 59.072 62.300 63.376 64.990 8.070 10.222 2.920 58.727 °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 6.000 7.000 7.000 10.000 12.000 12.000 12.000 5.000 5.000 1.366 9.672 nSat 242.7 1587
TDOP 0.490 0.550 0.600 0.790 1.340 1.740 2.470 0.740 1.190 0.244 0.860 25.17 100.6

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 162.213.2.253

peer offset 162.213.2.253 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 162.213.2.253 -2.593 -2.417 -2.130 -1.451 -0.904 -0.560 38.284 1.225 1.857 2.219 -1.311 ms 5.256 159.1

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

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

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

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



Server Offset 169.229.128.134

peer offset 169.229.128.134 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 169.229.128.134 -2.340 -2.188 -1.983 -1.408 -0.794 5.711 114.950 1.189 7.899 5.012 -0.985 ms 11.12 256.2

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 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 -2.675 -2.424 -2.229 -1.535 -0.944 3.948 42.105 1.285 6.372 1.977 -1.374 ms 3.29 154.9

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 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 -445.949 -13.596 35.016 101.173 216.896 279.600 394.151 181.880 293.196 59.563 112.509 µs 3.399 13.36

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 -735.700 -30.474 10.776 173.283 360.901 406.050 1,420.238 350.125 436.524 123.517 178.437 µs 1.562 5.805

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 192.168.1.41

peer offset 192.168.1.41 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 192.168.1.41 -177.146 -0.076 0.002 0.104 0.387 0.495 13.965 0.385 0.571 6.406 -0.073 ms -31.5 872.6

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 76.14.161.109

peer offset 76.14.161.109 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 76.14.161.109 -67.996 -61.426 -55.069 -4.775 6.149 41.830 79.411 61.218 103.256 18.735 -9.747 ms -9.01 31.34

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) -493.164 -431.219 -417.344 -373.267 -327.540 -314.590 -255.577 89.805 116.629 27.513 -373.142 ms -3132 4.624e+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) -21.805 -1.518 -0.810 0.018 0.759 1.205 10.990 1.569 2.723 0.571 -0.000 µs -6.268 87.42

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 162.213.2.253

peer jitter 162.213.2.253 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 162.213.2.253 0.000 0.188 0.254 0.617 13.520 87.828 130.557 13.266 87.640 14.420 4.588 ms 3.417 25.8

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 169.229.128.134

peer jitter 169.229.128.134 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 169.229.128.134 0.000 0.160 0.240 0.617 12.107 112.009 150.463 11.867 111.850 16.923 5.214 ms 3.407 25.7

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 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 0.180 0.237 0.672 12.338 106.246 136.288 12.101 106.066 16.375 5.391 ms 3.034 21.26

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 0.000 0.024 0.050 0.159 8.656 8.989 115.870 8.607 8.965 4.153 1.349 ms 9.404 201.9

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 0.023 0.045 0.171 8.646 9.601 57.348 8.602 9.578 4.691 1.471 ms 6.486 79.56

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 192.168.1.41

peer jitter 192.168.1.41 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 192.168.1.41 0.000 0.056 0.092 0.500 8.700 74.871 189.813 8.608 74.816 9.769 2.702 ms 5.462 62.74

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 76.14.161.109

peer jitter 76.14.161.109 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 76.14.161.109 0.000 0.775 1.342 12.288 56.562 102.593 139.282 55.220 101.818 20.563 18.828 ms 1.892 8.393

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 4.745 6.431 12.601 26.551 36.246 80.531 20.120 31.501 6.509 14.076 ms 6.597 24.05

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 0.179 0.250 0.557 1.345 2.169 18.237 1.095 1.990 0.493 0.662 µs 8.109 114.4

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.



Summary


Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Frequency Offset -7.477 -6.375 -6.218 -5.841 -5.784 -5.774 -5.754 0.435 0.601 0.161 -5.924 ppm -5.372e+04 2.03e+06
Local Clock Time Offset -21.804 -1.516 -0.808 0.017 0.758 1.204 10.989 1.566 2.720 0.568 0.000 µs -6.141 84.67
Local RMS Frequency Jitter 0.000 1.687 2.008 3.354 6.366 10.830 88.390 4.358 9.143 2.337 3.784 ppb 11.08 187
Local RMS Time Jitter 0.148 0.256 0.309 0.534 1.043 1.610 9.202 0.734 1.354 0.335 0.601 µs 9.033 98.28
Server Jitter 162.213.2.253 0.000 0.188 0.254 0.617 13.520 87.828 130.557 13.266 87.640 14.420 4.588 ms 3.417 25.8
Server Jitter 169.229.128.134 0.000 0.160 0.240 0.617 12.107 112.009 150.463 11.867 111.850 16.923 5.214 ms 3.407 25.7
Server Jitter 169.229.128.142 0.000 0.180 0.237 0.672 12.338 106.246 136.288 12.101 106.066 16.375 5.391 ms 3.034 21.26
Server Jitter 192.168.1.10 0.000 0.024 0.050 0.159 8.656 8.989 115.870 8.607 8.965 4.153 1.349 ms 9.404 201.9
Server Jitter 192.168.1.12 0.000 0.023 0.045 0.171 8.646 9.601 57.348 8.602 9.578 4.691 1.471 ms 6.486 79.56
Server Jitter 192.168.1.41 0.000 0.056 0.092 0.500 8.700 74.871 189.813 8.608 74.816 9.769 2.702 ms 5.462 62.74
Server Jitter 76.14.161.109 0.000 0.775 1.342 12.288 56.562 102.593 139.282 55.220 101.818 20.563 18.828 ms 1.892 8.393
Server Jitter SHM(0) 0.000 4.745 6.431 12.601 26.551 36.246 80.531 20.120 31.501 6.509 14.076 ms 6.597 24.05
Server Jitter SHM(1) 0.000 0.179 0.250 0.557 1.345 2.169 18.237 1.095 1.990 0.493 0.662 µs 8.109 114.4
Server Offset 162.213.2.253 -2.593 -2.417 -2.130 -1.451 -0.904 -0.560 38.284 1.225 1.857 2.219 -1.311 ms 5.256 159.1
Server Offset 169.229.128.134 -2.340 -2.188 -1.983 -1.408 -0.794 5.711 114.950 1.189 7.899 5.012 -0.985 ms 11.12 256.2
Server Offset 169.229.128.142 -2.675 -2.424 -2.229 -1.535 -0.944 3.948 42.105 1.285 6.372 1.977 -1.374 ms 3.29 154.9
Server Offset 192.168.1.10 -445.949 -13.596 35.016 101.173 216.896 279.600 394.151 181.880 293.196 59.563 112.509 µs 3.399 13.36
Server Offset 192.168.1.12 -735.700 -30.474 10.776 173.283 360.901 406.050 1,420.238 350.125 436.524 123.517 178.437 µs 1.562 5.805
Server Offset 192.168.1.41 -177.146 -0.076 0.002 0.104 0.387 0.495 13.965 0.385 0.571 6.406 -0.073 ms -31.5 872.6
Server Offset 76.14.161.109 -67.996 -61.426 -55.069 -4.775 6.149 41.830 79.411 61.218 103.256 18.735 -9.747 ms -9.01 31.34
Server Offset SHM(0) -493.164 -431.219 -417.344 -373.267 -327.540 -314.590 -255.577 89.805 116.629 27.513 -373.142 ms -3132 4.624e+04
Server Offset SHM(1) -21.805 -1.518 -0.810 0.018 0.759 1.205 10.990 1.569 2.723 0.571 -0.000 µs -6.268 87.42
TDOP 0.490 0.550 0.600 0.790 1.340 1.740 2.470 0.740 1.190 0.244 0.860 25.17 100.6
Temp ZONE0 38.090 53.154 54.230 59.072 62.300 63.376 64.990 8.070 10.222 2.920 58.727 °C
nSats 6.000 7.000 7.000 10.000 12.000 12.000 12.000 5.000 5.000 1.366 9.672 nSat 242.7 1587
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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