NTPsec

A-ntpsec-3-hour-stats

Report generated: Thu Jul 18 03:02:59 2019 UTC
Start Time: Thu Jul 18 00:02:58 2019 UTC
End Time: Thu Jul 18 03:02:58 2019 UTC
Report published: Wed Jul 17 20:03:08 2019 PDT
Report Period: 0.1 days

Local Clock Time/Frequency Offsets

local offset plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Time Offset -1,327.000 -882.000 -757.000 -400.000 -81.000 3.000 130.000 676.000 885.000 210.156 -400.843 ns -33.63 129.2
Local Clock Frequency Offset -760.803 -760.315 -757.645 -720.825 -681.625 -677.963 -677.261 76.020 82.352 24.920 -720.912 ppb -2.69e+04 8.077e+05

The time and frequency offsets between the ntpd calculated time and the local system clock. Showing frequency offset (red, in parts per million, scale on right) and the time offset (blue, in μs, scale on left). Quick changes in time offset will lead to larger frequency offsets.

These are fields 3 (time) and 4 (frequency) from the loopstats log file.



Local RMS Time Jitter

local jitter plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local RMS Time Jitter 81.000 90.000 107.000 170.000 279.000 348.000 485.000 172.000 258.000 52.741 177.604 ns 21.75 84.98

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 41.000 52.000 122.000 204.000 229.000 270.000 152.000 188.000 44.002 123.920 10e-12 11.76 35.82

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 -1,327.000 -882.000 -757.000 -400.000 -81.000 3.000 130.000 676.000 885.000 210.156 -400.843 ns -33.63 129.2

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 -760.803 -760.315 -757.645 -720.825 -681.625 -677.963 -677.261 76.020 82.352 24.920 -720.912 ppb -2.69e+04 8.077e+05
Temp ZONE0 60.148 60.148 60.686 61.224 61.224 62.300 62.300 0.538 2.152 0.335 61.031 °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 7.000 8.000 9.000 10.000 12.000 12.000 12.000 3.000 4.000 0.951 9.989 nSat 886.5 8709
TDOP 0.490 0.490 0.580 0.710 1.170 1.200 1.520 0.590 0.710 0.193 0.811 42.67 175.6

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 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 -1.933 -1.933 -1.811 -1.428 -1.061 -1.060 -1.060 0.750 0.872 0.210 -1.417 ms -488.9 3980

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 -21.709 35.455 94.004 126.604 148.579 156.093 91.149 170.288 27.887 87.137 µs 14.48 42.39

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 -46.497 26.206 80.230 127.211 165.642 235.237 239.916 85.412 209.031 28.357 125.441 µs 49.27 206.6

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 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 72.881 621.797 968.443 979.371 979.371 895.562 1,028.214 263.284 580.990 µs 4.651 9.988

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 -1.522 -1.522 -1.488 -0.946 -0.748 -0.687 -0.687 0.741 0.835 0.206 -1.007 ms -222.7 1438

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 -1.388 -1.388 -1.304 -0.932 -0.680 -0.591 -0.591 0.624 0.797 0.199 -0.970 ms -219.4 1393

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 -4.070 -3.554 -3.035 -2.916 -2.916 1.035 1.329 0.270 -3.578 ms -2943 4.258e+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 -65.127 -62.745 -55.475 -49.988 -48.545 -46.642 12.757 16.581 3.658 -55.761 ms -4335 7.124e+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) -1,328.000 -883.000 -758.000 -401.000 -82.000 4.000 131.000 676.000 887.000 210.206 -401.787 ns -33.74 129.7

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 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 0.231 0.463 8.382 8.451 8.451 8.151 8.246 2.089 1.197 ms 1.361 5.573

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 0.034 0.080 0.457 8.232 8.738 12.639 8.151 8.704 2.641 1.630 ms 0.8243 3.733

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 0.006 0.007 0.047 0.374 9.218 10.773 57.197 9.172 10.765 5.348 2.120 ms 5.237 57.28

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 0.184 0.184 0.190 0.594 12.354 12.356 12.356 12.164 12.172 3.991 2.853 ms 0.3533 1.913

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 0.127 0.127 0.191 0.486 8.746 8.770 8.770 8.555 8.643 3.268 2.254 ms 0.3613 1.849

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 0.155 0.155 0.155 0.502 8.886 8.958 8.958 8.730 8.803 2.714 1.838 ms 0.8038 3.236

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 0.275 0.275 0.285 0.485 9.095 9.132 9.132 8.810 8.857 3.744 2.709 ms 0.1837 1.396

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) 0.159 0.376 0.539 1.391 3.478 5.767 11.380 2.939 5.391 1.061 1.653 ms 4.077 18.58

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) 38.000 55.000 73.000 167.000 385.000 501.000 935.000 312.000 446.000 97.481 189.299 ns 5.435 21.96

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 -760.315 -757.645 -720.825 -681.625 -677.963 -677.261 76.020 82.352 24.920 -720.912 ppb -2.69e+04 8.077e+05
Local Clock Time Offset -1,327.000 -882.000 -757.000 -400.000 -81.000 3.000 130.000 676.000 885.000 210.156 -400.843 ns -33.63 129.2
Local RMS Frequency Jitter 38.000 41.000 52.000 122.000 204.000 229.000 270.000 152.000 188.000 44.002 123.920 10e-12 11.76 35.82
Local RMS Time Jitter 81.000 90.000 107.000 170.000 279.000 348.000 485.000 172.000 258.000 52.741 177.604 ns 21.75 84.98
Server Jitter 169.229.128.142 0.205 0.205 0.231 0.463 8.382 8.451 8.451 8.151 8.246 2.089 1.197 ms 1.361 5.573
Server Jitter 192.168.1.11 0.022 0.034 0.080 0.457 8.232 8.738 12.639 8.151 8.704 2.641 1.630 ms 0.8243 3.733
Server Jitter 192.168.1.12 0.006 0.007 0.047 0.374 9.218 10.773 57.197 9.172 10.765 5.348 2.120 ms 5.237 57.28
Server Jitter 199.102.46.72 0.184 0.184 0.190 0.594 12.354 12.356 12.356 12.164 12.172 3.991 2.853 ms 0.3533 1.913
Server Jitter 216.218.192.202 0.127 0.127 0.191 0.486 8.746 8.770 8.770 8.555 8.643 3.268 2.254 ms 0.3613 1.849
Server Jitter 216.218.254.202 0.155 0.155 0.155 0.502 8.886 8.958 8.958 8.730 8.803 2.714 1.838 ms 0.8038 3.236
Server Jitter 63.145.169.3 0.275 0.275 0.285 0.485 9.095 9.132 9.132 8.810 8.857 3.744 2.709 ms 0.1837 1.396
Server Jitter SHM(0) 0.159 0.376 0.539 1.391 3.478 5.767 11.380 2.939 5.391 1.061 1.653 ms 4.077 18.58
Server Jitter SHM(1) 38.000 55.000 73.000 167.000 385.000 501.000 935.000 312.000 446.000 97.481 189.299 ns 5.435 21.96
Server Offset 169.229.128.142 -1.933 -1.933 -1.811 -1.428 -1.061 -1.060 -1.060 0.750 0.872 0.210 -1.417 ms -488.9 3980
Server Offset 192.168.1.11 -44.056 -21.709 35.455 94.004 126.604 148.579 156.093 91.149 170.288 27.887 87.137 µs 14.48 42.39
Server Offset 192.168.1.12 -46.497 26.206 80.230 127.211 165.642 235.237 239.916 85.412 209.031 28.357 125.441 µs 49.27 206.6
Server Offset 199.102.46.72 -48.843 -48.843 72.881 621.797 968.443 979.371 979.371 895.562 1,028.214 263.284 580.990 µs 4.651 9.988
Server Offset 216.218.192.202 -1.522 -1.522 -1.488 -0.946 -0.748 -0.687 -0.687 0.741 0.835 0.206 -1.007 ms -222.7 1438
Server Offset 216.218.254.202 -1.388 -1.388 -1.304 -0.932 -0.680 -0.591 -0.591 0.624 0.797 0.199 -0.970 ms -219.4 1393
Server Offset 63.145.169.3 -4.245 -4.245 -4.070 -3.554 -3.035 -2.916 -2.916 1.035 1.329 0.270 -3.578 ms -2943 4.258e+04
Server Offset SHM(0) -71.556 -65.127 -62.745 -55.475 -49.988 -48.545 -46.642 12.757 16.581 3.658 -55.761 ms -4335 7.124e+04
Server Offset SHM(1) -1,328.000 -883.000 -758.000 -401.000 -82.000 4.000 131.000 676.000 887.000 210.206 -401.787 ns -33.74 129.7
TDOP 0.490 0.490 0.580 0.710 1.170 1.200 1.520 0.590 0.710 0.193 0.811 42.67 175.6
Temp ZONE0 60.148 60.148 60.686 61.224 61.224 62.300 62.300 0.538 2.152 0.335 61.031 °C
nSats 7.000 8.000 9.000 10.000 12.000 12.000 12.000 3.000 4.000 0.951 9.989 nSat 886.5 8709
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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