NTPsec

ntpsec-72-hour-stats

Report generated: Thu Jul 18 02:09:47 2019 UTC
Start Time: Mon Jul 15 02:09:20 2019 UTC
End Time: Thu Jul 18 02:09:20 2019 UTC
Report published: Wed Jul 17 19:11:13 2019 PDT
Report Period: 3.0 days

Local Clock Time/Frequency Offsets

local offset plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Time Offset -1.327 -0.883 -0.691 0.007 0.725 1.021 1.682 1.416 1.904 0.446 0.010 µs -3.757 8.674
Local Clock Frequency Offset -1.071 -1.068 -1.042 -0.768 -0.620 -0.616 -0.614 0.421 0.453 0.132 -0.798 ppm -368.5 2749

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 66.000 92.000 109.000 171.000 280.000 360.000 603.000 171.000 268.000 55.583 180.921 ns 19.56 74.96

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 30.000 37.000 109.000 275.000 486.000 1,087.000 238.000 456.000 92.883 127.228 10e-12 4.049 23.9

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 -0.883 -0.691 0.007 0.725 1.021 1.682 1.416 1.904 0.446 0.010 µs -3.757 8.674

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 -1.071 -1.068 -1.042 -0.768 -0.620 -0.616 -0.614 0.421 0.453 0.132 -0.798 ppm -368.5 2749
Temp ZONE0 59.072 59.072 59.610 61.224 63.914 64.452 64.452 4.304 5.380 1.367 61.535 °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 5.000 6.000 7.000 10.000 12.000 12.000 12.000 5.000 6.000 1.518 9.596 nSat 166.6 970.7
TDOP 0.490 0.550 0.600 0.810 1.470 1.840 3.030 0.870 1.290 0.279 0.886 18.97 80.16

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 -2.237 -2.111 -1.948 -1.514 -1.187 -1.037 -0.820 0.761 1.074 0.228 -1.529 ms -482.2 3908

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 -230.435 -76.067 -20.688 48.252 120.559 165.573 253.958 141.247 241.640 44.794 50.761 µs 0.1635 5.398

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 -193.371 -17.763 55.837 129.111 170.152 224.024 392.722 114.315 241.787 37.704 124.471 µs 17.73 59.68

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 -3.286 -2.958 -2.525 0.595 0.924 1.052 1.242 3.449 4.010 0.862 0.356 ms -4.979 20.43

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 -1.650 -1.611 -1.440 -1.000 -0.708 -0.570 -0.428 0.732 1.042 0.220 -1.027 ms -200.6 1247

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 -1.803 -1.516 -1.357 -0.937 -0.597 -0.445 -0.306 0.760 1.071 0.231 -0.949 ms -148.9 847.2

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 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 -4.321 -4.169 -4.011 -3.559 -3.223 -3.081 -2.736 0.788 1.089 0.229 -3.577 ms -4663 7.848e+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) -82.897 -66.027 -63.183 -54.720 -48.169 -45.786 -42.010 15.015 20.241 4.735 -55.176 ms -2064 2.661e+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 -0.884 -0.692 0.008 0.726 1.022 1.683 1.418 1.906 0.447 0.010 µs -3.758 8.671

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 0.144 0.220 0.484 8.791 10.373 14.811 8.571 10.229 3.071 2.044 ms 0.6446 2.853

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 0.012 0.028 0.060 0.202 8.665 9.305 59.836 8.605 9.277 3.661 1.489 ms 5.673 86.54

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 0.035 0.074 0.533 8.729 18.301 65.429 8.655 18.266 5.685 2.237 ms 5.304 53.91

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 0.113 0.162 0.242 0.526 8.928 13.945 19.034 8.686 13.783 3.477 2.384 ms 0.736 3.681

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 0.160 0.230 0.492 8.819 12.493 57.825 8.589 12.333 4.141 2.166 ms 4.884 67.13

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 0.107 0.168 0.227 0.528 8.886 10.545 190.809 8.658 10.377 7.609 2.644 ms 17.81 444

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 0.112 0.175 0.234 0.480 8.892 12.292 31.672 8.658 12.117 3.656 2.134 ms 1.769 13.5

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) 0.041 0.372 0.541 1.380 3.614 5.997 16.859 3.073 5.624 1.108 1.657 ms 4.032 19.95

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) 27.000 60.000 82.000 172.000 373.000 517.000 1,246.000 291.000 457.000 95.609 193.196 ns 5.819 22.74

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.



Summary


Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Frequency Offset -1.071 -1.068 -1.042 -0.768 -0.620 -0.616 -0.614 0.421 0.453 0.132 -0.798 ppm -368.5 2749
Local Clock Time Offset -1.327 -0.883 -0.691 0.007 0.725 1.021 1.682 1.416 1.904 0.446 0.010 µs -3.757 8.674
Local RMS Frequency Jitter 19.000 30.000 37.000 109.000 275.000 486.000 1,087.000 238.000 456.000 92.883 127.228 10e-12 4.049 23.9
Local RMS Time Jitter 66.000 92.000 109.000 171.000 280.000 360.000 603.000 171.000 268.000 55.583 180.921 ns 19.56 74.96
Server Jitter 169.229.128.142 0.107 0.144 0.220 0.484 8.791 10.373 14.811 8.571 10.229 3.071 2.044 ms 0.6446 2.853
Server Jitter 192.168.1.11 0.012 0.028 0.060 0.202 8.665 9.305 59.836 8.605 9.277 3.661 1.489 ms 5.673 86.54
Server Jitter 192.168.1.12 0.006 0.035 0.074 0.533 8.729 18.301 65.429 8.655 18.266 5.685 2.237 ms 5.304 53.91
Server Jitter 199.102.46.72 0.113 0.162 0.242 0.526 8.928 13.945 19.034 8.686 13.783 3.477 2.384 ms 0.736 3.681
Server Jitter 216.218.192.202 0.127 0.160 0.230 0.492 8.819 12.493 57.825 8.589 12.333 4.141 2.166 ms 4.884 67.13
Server Jitter 216.218.254.202 0.107 0.168 0.227 0.528 8.886 10.545 190.809 8.658 10.377 7.609 2.644 ms 17.81 444
Server Jitter 63.145.169.3 0.112 0.175 0.234 0.480 8.892 12.292 31.672 8.658 12.117 3.656 2.134 ms 1.769 13.5
Server Jitter SHM(0) 0.041 0.372 0.541 1.380 3.614 5.997 16.859 3.073 5.624 1.108 1.657 ms 4.032 19.95
Server Jitter SHM(1) 27.000 60.000 82.000 172.000 373.000 517.000 1,246.000 291.000 457.000 95.609 193.196 ns 5.819 22.74
Server Offset 169.229.128.142 -2.237 -2.111 -1.948 -1.514 -1.187 -1.037 -0.820 0.761 1.074 0.228 -1.529 ms -482.2 3908
Server Offset 192.168.1.11 -230.435 -76.067 -20.688 48.252 120.559 165.573 253.958 141.247 241.640 44.794 50.761 µs 0.1635 5.398
Server Offset 192.168.1.12 -193.371 -17.763 55.837 129.111 170.152 224.024 392.722 114.315 241.787 37.704 124.471 µs 17.73 59.68
Server Offset 199.102.46.72 -3.286 -2.958 -2.525 0.595 0.924 1.052 1.242 3.449 4.010 0.862 0.356 ms -4.979 20.43
Server Offset 216.218.192.202 -1.650 -1.611 -1.440 -1.000 -0.708 -0.570 -0.428 0.732 1.042 0.220 -1.027 ms -200.6 1247
Server Offset 216.218.254.202 -1.803 -1.516 -1.357 -0.937 -0.597 -0.445 -0.306 0.760 1.071 0.231 -0.949 ms -148.9 847.2
Server Offset 63.145.169.3 -4.321 -4.169 -4.011 -3.559 -3.223 -3.081 -2.736 0.788 1.089 0.229 -3.577 ms -4663 7.848e+04
Server Offset SHM(0) -82.897 -66.027 -63.183 -54.720 -48.169 -45.786 -42.010 15.015 20.241 4.735 -55.176 ms -2064 2.661e+04
Server Offset SHM(1) -1.328 -0.884 -0.692 0.008 0.726 1.022 1.683 1.418 1.906 0.447 0.010 µs -3.758 8.671
TDOP 0.490 0.550 0.600 0.810 1.470 1.840 3.030 0.870 1.290 0.279 0.886 18.97 80.16
Temp ZONE0 59.072 59.072 59.610 61.224 63.914 64.452 64.452 4.304 5.380 1.367 61.535 °C
nSats 5.000 6.000 7.000 10.000 12.000 12.000 12.000 5.000 6.000 1.518 9.596 nSat 166.6 970.7
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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