NTPsec

A-ntpsec-1-hour-stats

Report generated: Thu Jul 18 03:02:04 2019 UTC
Start Time: Thu Jul 18 02:01:36 2019 UTC
End Time: Thu Jul 18 03:02:04 2019 UTC
Report published: Wed Jul 17 20:02:11 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 -911.000 -800.000 -645.000 -322.000 -51.000 6.000 36.000 594.000 806.000 186.138 -328.455 ns -29.76 110.7
Local Clock Frequency Offset -760.803 -760.712 -760.010 -747.925 -739.456 -738.068 -737.900 20.554 22.644 6.285 -749.358 ppb -1.738e+06 2.09e+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 81.000 87.000 105.000 155.000 211.000 225.000 248.000 106.000 138.000 31.765 156.183 ns 71.96 332

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 38.000 39.000 41.000 103.000 198.000 226.000 238.000 157.000 187.000 45.031 104.870 10e-12 7.089 21.04

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 -911.000 -800.000 -645.000 -322.000 -51.000 6.000 36.000 594.000 806.000 186.138 -328.455 ns -29.76 110.7

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 -760.803 -760.712 -760.010 -747.925 -739.456 -738.068 -737.900 20.554 22.644 6.285 -749.358 ppb -1.738e+06 2.09e+08
Temp ZONE0 60.686 60.686 60.686 61.224 61.762 62.300 62.300 1.076 1.614 0.275 61.260 °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 9.000 10.000 12.000 12.000 12.000 3.000 3.000 1.170 10.217 nSat 485.5 3946
TDOP 0.610 0.610 0.610 1.010 1.190 1.200 1.200 0.580 0.590 0.208 0.928 51.62 211.2

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 -1.796 -1.796 -1.796 -1.536 -1.169 -1.169 -1.169 0.626 0.626 0.157 -1.517 ms -1239 1.352e+04

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

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

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

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



Server Offset 192.168.1.11

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 -44.056 -44.056 36.907 90.352 123.418 156.093 156.093 86.511 200.149 28.619 86.916 µs 12.88 38.08

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 80.230 80.230 95.292 127.496 135.905 150.875 150.875 40.613 70.645 12.817 124.064 µs 678.8 6092

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 -48.843 -48.843 -48.843 572.066 979.371 979.371 979.371 1,028.214 1,028.214 305.015 461.246 µs 1.637 3.387

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 -1.485 -1.485 -1.485 -0.926 -0.748 -0.748 -0.748 0.737 0.737 0.196 -0.983 ms -236.2 1555

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 -1.227 -1.227 -1.227 -0.932 -0.707 -0.707 -0.707 0.520 0.520 0.153 -0.979 ms -427.5 3330

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 -4.245 -4.245 -4.245 -3.633 -3.283 -3.283 -3.283 0.962 0.962 0.273 -3.657 ms -3036 4.441e+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) -71.556 -65.761 -63.290 -55.858 -49.409 -48.387 -47.361 13.882 17.373 4.301 -55.619 ms -2746 3.885e+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) -912.000 -801.000 -646.000 -323.000 -52.000 7.000 37.000 594.000 808.000 186.202 -329.378 ns -29.87 111.2

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 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 0.205 0.205 0.205 0.396 8.451 8.451 8.451 8.246 8.246 3.111 1.821 ms 0.3307 2.047

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 0.022 0.022 0.078 0.697 8.716 12.639 12.639 8.638 12.617 3.410 2.634 ms 0.5165 2.235

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 0.017 0.017 0.045 0.374 8.691 10.773 10.773 8.647 10.756 2.580 1.230 ms 1.021 4.81

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 0.184 0.184 0.184 0.698 8.962 8.962 8.962 8.778 8.778 3.941 3.795 ms 0.2419 1.111

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 0.191 0.191 0.191 0.503 8.746 8.746 8.746 8.555 8.555 3.249 2.607 ms 0.4385 1.883

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 0.302 0.302 0.302 3.362 3.555 3.555 3.555 3.253 3.253 1.544 1.900 ms 0.7053 1.329

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 0.285 0.285 0.285 0.479 8.704 8.704 8.704 8.419 8.419 2.880 1.617 ms 0.6339 2.774

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) 0.195 0.465 0.616 1.524 3.650 6.043 9.287 3.034 5.578 1.127 1.798 ms 4.062 17.28

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 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) 48.000 62.000 81.000 157.000 333.000 459.000 505.000 252.000 397.000 78.816 172.874 ns 6.648 22.4

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 -760.803 -760.712 -760.010 -747.925 -739.456 -738.068 -737.900 20.554 22.644 6.285 -749.358 ppb -1.738e+06 2.09e+08
Local Clock Time Offset -911.000 -800.000 -645.000 -322.000 -51.000 6.000 36.000 594.000 806.000 186.138 -328.455 ns -29.76 110.7
Local RMS Frequency Jitter 38.000 39.000 41.000 103.000 198.000 226.000 238.000 157.000 187.000 45.031 104.870 10e-12 7.089 21.04
Local RMS Time Jitter 81.000 87.000 105.000 155.000 211.000 225.000 248.000 106.000 138.000 31.765 156.183 ns 71.96 332
Server Jitter 169.229.128.142 0.205 0.205 0.205 0.396 8.451 8.451 8.451 8.246 8.246 3.111 1.821 ms 0.3307 2.047
Server Jitter 192.168.1.11 0.022 0.022 0.078 0.697 8.716 12.639 12.639 8.638 12.617 3.410 2.634 ms 0.5165 2.235
Server Jitter 192.168.1.12 0.017 0.017 0.045 0.374 8.691 10.773 10.773 8.647 10.756 2.580 1.230 ms 1.021 4.81
Server Jitter 199.102.46.72 0.184 0.184 0.184 0.698 8.962 8.962 8.962 8.778 8.778 3.941 3.795 ms 0.2419 1.111
Server Jitter 216.218.192.202 0.191 0.191 0.191 0.503 8.746 8.746 8.746 8.555 8.555 3.249 2.607 ms 0.4385 1.883
Server Jitter 216.218.254.202 0.302 0.302 0.302 3.362 3.555 3.555 3.555 3.253 3.253 1.544 1.900 ms 0.7053 1.329
Server Jitter 63.145.169.3 0.285 0.285 0.285 0.479 8.704 8.704 8.704 8.419 8.419 2.880 1.617 ms 0.6339 2.774
Server Jitter SHM(0) 0.195 0.465 0.616 1.524 3.650 6.043 9.287 3.034 5.578 1.127 1.798 ms 4.062 17.28
Server Jitter SHM(1) 48.000 62.000 81.000 157.000 333.000 459.000 505.000 252.000 397.000 78.816 172.874 ns 6.648 22.4
Server Offset 169.229.128.142 -1.796 -1.796 -1.796 -1.536 -1.169 -1.169 -1.169 0.626 0.626 0.157 -1.517 ms -1239 1.352e+04
Server Offset 192.168.1.11 -44.056 -44.056 36.907 90.352 123.418 156.093 156.093 86.511 200.149 28.619 86.916 µs 12.88 38.08
Server Offset 192.168.1.12 80.230 80.230 95.292 127.496 135.905 150.875 150.875 40.613 70.645 12.817 124.064 µs 678.8 6092
Server Offset 199.102.46.72 -48.843 -48.843 -48.843 572.066 979.371 979.371 979.371 1,028.214 1,028.214 305.015 461.246 µs 1.637 3.387
Server Offset 216.218.192.202 -1.485 -1.485 -1.485 -0.926 -0.748 -0.748 -0.748 0.737 0.737 0.196 -0.983 ms -236.2 1555
Server Offset 216.218.254.202 -1.227 -1.227 -1.227 -0.932 -0.707 -0.707 -0.707 0.520 0.520 0.153 -0.979 ms -427.5 3330
Server Offset 63.145.169.3 -4.245 -4.245 -4.245 -3.633 -3.283 -3.283 -3.283 0.962 0.962 0.273 -3.657 ms -3036 4.441e+04
Server Offset SHM(0) -71.556 -65.761 -63.290 -55.858 -49.409 -48.387 -47.361 13.882 17.373 4.301 -55.619 ms -2746 3.885e+04
Server Offset SHM(1) -912.000 -801.000 -646.000 -323.000 -52.000 7.000 37.000 594.000 808.000 186.202 -329.378 ns -29.87 111.2
TDOP 0.610 0.610 0.610 1.010 1.190 1.200 1.200 0.580 0.590 0.208 0.928 51.62 211.2
Temp ZONE0 60.686 60.686 60.686 61.224 61.762 62.300 62.300 1.076 1.614 0.275 61.260 °C
nSats 9.000 9.000 9.000 10.000 12.000 12.000 12.000 3.000 3.000 1.170 10.217 nSat 485.5 3946
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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