NTPsec

A-ntpsec-72-hour-stats

Report generated: Wed Oct 14 19:02:50 2026 UTC
Start Time: Sun Oct 11 19:02:49 2026 UTC
End Time: Wed Oct 14 19:02:49 2026 UTC
Report published: Wed Oct 14 12:03:05 PM 2026 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 -4.976 -1.535 -1.013 0.005 0.986 1.380 2.292 1.999 2.915 0.612 -0.000 µs -0.1904 3.547
Local Clock Frequency Offset 103.302 105.576 107.727 128.998 137.772 140.793 143.936 30.045 35.217 9.776 125.727 ppb -0.4788 2.007

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

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



Local RMS Time Jitter

local jitter plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local RMS Time Jitter 0.310 0.464 0.550 0.798 1.150 1.347 2.662 0.600 0.883 0.188 0.817 µs 0.9037 5.825

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 120.000 174.000 204.000 288.000 399.000 456.000 888.000 195.000 282.000 61.089 293.003 10e-12 0.8188 6.182

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 -4.976 -1.535 -1.013 0.005 0.986 1.380 2.292 1.999 2.915 0.612 -0.000 µs -0.1904 3.547

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 103.302 105.576 107.727 128.998 137.772 140.793 143.936 30.045 35.217 9.776 125.727 ppb -0.4788 2.007
Temp ZONE0 54.768 54.768 54.768 56.382 57.458 57.996 57.996 2.690 3.228 0.812 56.340 °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 8.000 10.000 12.000 13.000 14.000 4.000 6.000 1.266 10.021 nSat 0.4495 3.453
TDOP 0.470 0.500 0.550 0.810 1.190 1.360 2.000 0.640 0.860 0.197 0.833 0.7246 3.805

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. Smaller numbers are better. TDOP ranges from 1 (ideal), 2 to 5 (good), to greater than 20 (poor). Some GNSS receivers report TDOP less than one which is theoretically impossible.



Server Offsets

peer offsets plot

The offset of all refclocks and servers. This can be useful to see if offset changes are happening in a single clock or all clocks together.

Clock Offset is field 5 in the peerstats log file.



Server Offset 162.159.200.123

peer offset 162.159.200.123 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 162.159.200.123 -0.424 1.726 2.451 4.072 4.994 5.614 6.236 2.543 3.889 0.798 3.970 ms -0.8164 4.629

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

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

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

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



Server Offset 169.229.128.134

peer offset 169.229.128.134 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 169.229.128.134 0.867 1.859 2.781 4.268 5.240 5.575 6.433 2.459 3.715 0.817 4.286 ms -0.7501 3.718

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 173.8.172.33

peer offset 173.8.172.33 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 173.8.172.33 -4.001 -2.091 -0.925 1.949 4.453 5.684 6.777 5.378 7.776 1.664 1.907 ms -0.2356 3.072

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 50.116.42.84

peer offset 50.116.42.84 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 50.116.42.84 -0.367 0.605 1.447 3.382 5.312 6.341 6.934 3.864 5.736 1.153 3.364 ms 0.06166 3.311

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 52.10.183.132

peer offset 52.10.183.132 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 52.10.183.132 -0.844 0.545 1.238 3.107 5.352 6.256 7.231 4.114 5.710 1.214 3.211 ms 0.2632 3.369

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 64.142.122.36

peer offset 64.142.122.36 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 64.142.122.36 0.038 1.503 2.140 3.511 4.625 4.830 5.111 2.485 3.327 0.787 3.595 ms -0.6084 3.411

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 66.220.9.122

peer offset 66.220.9.122 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 66.220.9.122 0.478 0.941 2.102 3.708 4.685 5.427 6.386 2.583 4.487 0.867 3.698 ms -0.7895 4.069

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) -135.453 -134.794 -133.837 -130.661 -128.557 -127.951 -126.786 5.280 6.843 1.520 -130.730 ms -0.5881 3.254

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) -4.977 -1.536 -1.014 0.006 0.987 1.381 2.293 2.001 2.917 0.613 -0.000 µs -0.1899 3.54

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

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

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

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



Server Jitters

peer jitters plot

The RMS Jitter of all refclocks and servers. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 162.159.200.123

peer jitter 162.159.200.123 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 162.159.200.123 0.275 0.372 0.540 1.727 10.295 16.241 23.294 9.755 15.868 3.105 2.726 ms 2.952 12.51

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 169.229.128.134

peer jitter 169.229.128.134 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 169.229.128.134 0.156 0.270 0.532 1.639 9.360 17.619 26.495 8.827 17.349 2.991 2.499 ms 3.734 19.76

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 173.8.172.33

peer jitter 173.8.172.33 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 173.8.172.33 0.425 1.024 1.354 2.899 11.560 24.981 72.677 10.206 23.957 5.058 4.193 ms 6.086 57.69

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 50.116.42.84

peer jitter 50.116.42.84 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 50.116.42.84 0.221 0.337 0.656 1.888 11.916 21.573 190.572 11.261 21.237 9.141 3.489 ms 13.75 240

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 52.10.183.132

peer jitter 52.10.183.132 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 52.10.183.132 0.250 0.432 0.705 2.045 10.968 16.693 32.167 10.263 16.261 3.461 3.113 ms 3.463 19.02

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 64.142.122.36

peer jitter 64.142.122.36 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 64.142.122.36 0.198 0.308 0.505 1.640 9.932 15.420 18.189 9.427 15.112 3.114 2.635 ms 2.679 10.08

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 66.220.9.122

peer jitter 66.220.9.122 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 66.220.9.122 0.120 0.322 0.577 1.759 10.856 22.290 63.278 10.280 21.967 5.344 3.035 ms 7.059 66.11

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) 0.028 0.051 0.103 0.444 1.133 1.511 2.239 1.030 1.460 0.321 0.512 ms 1.175 4.841

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter SHM(1)

peer jitter SHM(1) plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter SHM(1) 0.111 0.285 0.393 0.754 1.466 1.886 5.177 1.073 1.601 0.341 0.818 µs 1.345 7.043

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 103.302 105.576 107.727 128.998 137.772 140.793 143.936 30.045 35.217 9.776 125.727 ppb -0.4788 2.007
Local Clock Time Offset -4.976 -1.535 -1.013 0.005 0.986 1.380 2.292 1.999 2.915 0.612 -0.000 µs -0.1904 3.547
Local RMS Frequency Jitter 120.000 174.000 204.000 288.000 399.000 456.000 888.000 195.000 282.000 61.089 293.003 10e-12 0.8188 6.182
Local RMS Time Jitter 0.310 0.464 0.550 0.798 1.150 1.347 2.662 0.600 0.883 0.188 0.817 µs 0.9037 5.825
Server Jitter 162.159.200.123 0.275 0.372 0.540 1.727 10.295 16.241 23.294 9.755 15.868 3.105 2.726 ms 2.952 12.51
Server Jitter 169.229.128.134 0.156 0.270 0.532 1.639 9.360 17.619 26.495 8.827 17.349 2.991 2.499 ms 3.734 19.76
Server Jitter 173.8.172.33 0.425 1.024 1.354 2.899 11.560 24.981 72.677 10.206 23.957 5.058 4.193 ms 6.086 57.69
Server Jitter 50.116.42.84 0.221 0.337 0.656 1.888 11.916 21.573 190.572 11.261 21.237 9.141 3.489 ms 13.75 240
Server Jitter 52.10.183.132 0.250 0.432 0.705 2.045 10.968 16.693 32.167 10.263 16.261 3.461 3.113 ms 3.463 19.02
Server Jitter 64.142.122.36 0.198 0.308 0.505 1.640 9.932 15.420 18.189 9.427 15.112 3.114 2.635 ms 2.679 10.08
Server Jitter 66.220.9.122 0.120 0.322 0.577 1.759 10.856 22.290 63.278 10.280 21.967 5.344 3.035 ms 7.059 66.11
Server Jitter SHM(0) 0.028 0.051 0.103 0.444 1.133 1.511 2.239 1.030 1.460 0.321 0.512 ms 1.175 4.841
Server Jitter SHM(1) 0.111 0.285 0.393 0.754 1.466 1.886 5.177 1.073 1.601 0.341 0.818 µs 1.345 7.043
Server Offset 162.159.200.123 -0.424 1.726 2.451 4.072 4.994 5.614 6.236 2.543 3.889 0.798 3.970 ms -0.8164 4.629
Server Offset 169.229.128.134 0.867 1.859 2.781 4.268 5.240 5.575 6.433 2.459 3.715 0.817 4.286 ms -0.7501 3.718
Server Offset 173.8.172.33 -4.001 -2.091 -0.925 1.949 4.453 5.684 6.777 5.378 7.776 1.664 1.907 ms -0.2356 3.072
Server Offset 50.116.42.84 -0.367 0.605 1.447 3.382 5.312 6.341 6.934 3.864 5.736 1.153 3.364 ms 0.06166 3.311
Server Offset 52.10.183.132 -0.844 0.545 1.238 3.107 5.352 6.256 7.231 4.114 5.710 1.214 3.211 ms 0.2632 3.369
Server Offset 64.142.122.36 0.038 1.503 2.140 3.511 4.625 4.830 5.111 2.485 3.327 0.787 3.595 ms -0.6084 3.411
Server Offset 66.220.9.122 0.478 0.941 2.102 3.708 4.685 5.427 6.386 2.583 4.487 0.867 3.698 ms -0.7895 4.069
Server Offset SHM(0) -135.453 -134.794 -133.837 -130.661 -128.557 -127.951 -126.786 5.280 6.843 1.520 -130.730 ms -0.5881 3.254
Server Offset SHM(1) -4.977 -1.536 -1.014 0.006 0.987 1.381 2.293 2.001 2.917 0.613 -0.000 µs -0.1899 3.54
TDOP 0.470 0.500 0.550 0.810 1.190 1.360 2.000 0.640 0.860 0.197 0.833 0.7246 3.805
Temp ZONE0 54.768 54.768 54.768 56.382 57.458 57.996 57.996 2.690 3.228 0.812 56.340 °C
nSats 6.000 7.000 8.000 10.000 12.000 13.000 14.000 4.000 6.000 1.266 10.021 nSat 0.4495 3.453
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.
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 FIsher-Pearson moment of skewness. There are other different ways to calculate Skewness Wikipedia describes Skewness best: "The qualitative interpretation of the skew is complicated and unintuitive."
A normal distribution has a skewness of zero.
Kurtosis, Kurt:
The kurtosis of a random variable X is the fourth standardized moment and is a dimension-less ratio. ntpviz uses standard Kurtosis. There are other different ways to calculate 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".
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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