NTPsec

A-ntpsec-12-hour-stats

Report generated: Thu Jul 18 02:04:49 2019 UTC
Start Time: Wed Jul 17 14:04:44 2019 UTC
End Time: Thu Jul 18 02:04:44 2019 UTC
Report published: Wed Jul 17 19:05:13 2019 PDT
Report Period: 0.5 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 -801.000 -590.000 -162.000 226.000 377.000 611.000 816.000 1,178.000 251.065 -165.594 ns -9.786 28.82
Local Clock Frequency Offset -737.900 -734.619 -719.269 -632.034 -615.143 -614.548 -614.197 104.126 120.071 33.550 -645.299 ppb -8346 1.702e+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 75.000 93.000 112.000 183.000 264.000 318.000 485.000 152.000 225.000 47.514 185.071 ns 33.64 133.4

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 19.000 27.000 33.000 55.000 157.000 203.000 270.000 124.000 176.000 39.768 70.168 10e-12 4.344 14.13

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 -801.000 -590.000 -162.000 226.000 377.000 611.000 816.000 1,178.000 251.065 -165.594 ns -9.786 28.82

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 -737.900 -734.619 -719.269 -632.034 -615.143 -614.548 -614.197 104.126 120.071 33.550 -645.299 ppb -8346 1.702e+05
Temp ZONE0 59.072 59.072 59.072 60.148 61.224 61.224 61.224 2.152 2.152 0.548 60.071 °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 9.000 11.000 12.000 12.000 4.000 5.000 1.266 9.077 nSat 253.6 1682
TDOP 0.490 0.580 0.600 0.850 1.510 1.760 2.430 0.910 1.180 0.273 0.917 21.33 80.41

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 -2.049 -1.980 -1.933 -1.495 -1.177 -1.060 -0.988 0.756 0.920 0.216 -1.487 ms -517.3 4284

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 -169.804 -51.022 22.896 87.355 136.933 176.438 253.958 114.037 227.460 39.447 82.891 µs 3.341 13.09

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 32.142 74.859 125.469 165.073 184.386 239.916 90.214 152.244 26.642 124.591 µs 59.92 260.7

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 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 -149.798 -69.778 149.220 613.910 921.856 976.560 1,061.819 772.636 1,046.338 228.017 593.457 µs 8.2 20.92

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 -1.488 -1.423 -0.994 -0.753 -0.687 -0.682 0.671 0.802 0.190 -1.019 ms -277.3 1901

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 -1.518 -1.499 -1.337 -0.944 -0.647 -0.482 -0.378 0.690 1.017 0.216 -0.957 ms -177.2 1058

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 -4.164 -4.070 -3.943 -3.550 -3.247 -2.916 -2.736 0.697 1.154 0.221 -3.561 ms -5092 8.818e+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) -70.272 -62.972 -59.808 -52.809 -47.062 -45.125 -42.413 12.746 17.847 3.923 -52.984 ms -3096 4.555e+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 -802.000 -591.000 -163.000 227.000 378.000 612.000 818.000 1,180.000 251.696 -166.039 ns -9.782 28.78

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 0.107 0.112 0.188 0.458 8.753 8.909 8.962 8.564 8.796 2.770 1.730 ms 0.6663 2.847

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 0.034 0.066 0.512 8.667 8.985 10.922 8.601 8.951 2.566 1.652 ms 0.9479 3.753

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 0.019 0.058 0.497 8.896 56.705 57.197 8.838 56.686 6.980 2.449 ms 4.285 35.89

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 0.138 0.172 0.272 0.501 8.836 12.354 12.356 8.564 12.182 3.578 2.759 ms 0.3658 1.786

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 0.130 0.210 0.444 8.663 8.867 10.213 8.453 8.736 3.128 2.067 ms 0.3878 2.004

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 0.218 0.488 8.777 8.968 8.998 8.559 8.813 3.135 2.130 ms 0.3875 1.958

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 0.144 0.167 0.243 0.437 8.919 31.495 31.672 8.676 31.328 4.802 2.608 ms 1.939 14.07

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 0.365 0.529 1.342 3.452 5.533 13.731 2.923 5.168 1.037 1.584 ms 4.192 20.76

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) 37.000 57.000 80.000 177.000 354.000 469.000 935.000 274.000 412.000 86.037 192.151 ns 6.946 25.19

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 -737.900 -734.619 -719.269 -632.034 -615.143 -614.548 -614.197 104.126 120.071 33.550 -645.299 ppb -8346 1.702e+05
Local Clock Time Offset -1,327.000 -801.000 -590.000 -162.000 226.000 377.000 611.000 816.000 1,178.000 251.065 -165.594 ns -9.786 28.82
Local RMS Frequency Jitter 19.000 27.000 33.000 55.000 157.000 203.000 270.000 124.000 176.000 39.768 70.168 10e-12 4.344 14.13
Local RMS Time Jitter 75.000 93.000 112.000 183.000 264.000 318.000 485.000 152.000 225.000 47.514 185.071 ns 33.64 133.4
Server Jitter 169.229.128.142 0.107 0.112 0.188 0.458 8.753 8.909 8.962 8.564 8.796 2.770 1.730 ms 0.6663 2.847
Server Jitter 192.168.1.11 0.014 0.034 0.066 0.512 8.667 8.985 10.922 8.601 8.951 2.566 1.652 ms 0.9479 3.753
Server Jitter 192.168.1.12 0.006 0.019 0.058 0.497 8.896 56.705 57.197 8.838 56.686 6.980 2.449 ms 4.285 35.89
Server Jitter 199.102.46.72 0.138 0.172 0.272 0.501 8.836 12.354 12.356 8.564 12.182 3.578 2.759 ms 0.3658 1.786
Server Jitter 216.218.192.202 0.127 0.130 0.210 0.444 8.663 8.867 10.213 8.453 8.736 3.128 2.067 ms 0.3878 2.004
Server Jitter 216.218.254.202 0.155 0.155 0.218 0.488 8.777 8.968 8.998 8.559 8.813 3.135 2.130 ms 0.3875 1.958
Server Jitter 63.145.169.3 0.144 0.167 0.243 0.437 8.919 31.495 31.672 8.676 31.328 4.802 2.608 ms 1.939 14.07
Server Jitter SHM(0) 0.159 0.365 0.529 1.342 3.452 5.533 13.731 2.923 5.168 1.037 1.584 ms 4.192 20.76
Server Jitter SHM(1) 37.000 57.000 80.000 177.000 354.000 469.000 935.000 274.000 412.000 86.037 192.151 ns 6.946 25.19
Server Offset 169.229.128.142 -2.049 -1.980 -1.933 -1.495 -1.177 -1.060 -0.988 0.756 0.920 0.216 -1.487 ms -517.3 4284
Server Offset 192.168.1.11 -169.804 -51.022 22.896 87.355 136.933 176.438 253.958 114.037 227.460 39.447 82.891 µs 3.341 13.09
Server Offset 192.168.1.12 -46.497 32.142 74.859 125.469 165.073 184.386 239.916 90.214 152.244 26.642 124.591 µs 59.92 260.7
Server Offset 199.102.46.72 -149.798 -69.778 149.220 613.910 921.856 976.560 1,061.819 772.636 1,046.338 228.017 593.457 µs 8.2 20.92
Server Offset 216.218.192.202 -1.522 -1.488 -1.423 -0.994 -0.753 -0.687 -0.682 0.671 0.802 0.190 -1.019 ms -277.3 1901
Server Offset 216.218.254.202 -1.518 -1.499 -1.337 -0.944 -0.647 -0.482 -0.378 0.690 1.017 0.216 -0.957 ms -177.2 1058
Server Offset 63.145.169.3 -4.164 -4.070 -3.943 -3.550 -3.247 -2.916 -2.736 0.697 1.154 0.221 -3.561 ms -5092 8.818e+04
Server Offset SHM(0) -70.272 -62.972 -59.808 -52.809 -47.062 -45.125 -42.413 12.746 17.847 3.923 -52.984 ms -3096 4.555e+04
Server Offset SHM(1) -1,328.000 -802.000 -591.000 -163.000 227.000 378.000 612.000 818.000 1,180.000 251.696 -166.039 ns -9.782 28.78
TDOP 0.490 0.580 0.600 0.850 1.510 1.760 2.430 0.910 1.180 0.273 0.917 21.33 80.41
Temp ZONE0 59.072 59.072 59.072 60.148 61.224 61.224 61.224 2.152 2.152 0.548 60.071 °C
nSats 6.000 7.000 7.000 9.000 11.000 12.000 12.000 4.000 5.000 1.266 9.077 nSat 253.6 1682
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.



This page autogenerated by ntpviz, part of the NTPsec project
html 5    Valid CSS!