NTPsec

time.achjoj.info

Report generated: Tue Oct 20 04:33:02 2026 UTC
Start Time: Mon Oct 19 02:09:02 2026 UTC
End Time: Tue Oct 20 04:33:02 2026 UTC
Report Period: 1.1 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 -1,074.146 -922.101 -723.344 -175.354 786.046 945.947 1,255.839 1,509.390 1,868.048 452.944 -112.895 µs -5.166 11.93
Local Clock Frequency Offset 18.821 18.822 18.829 18.870 18.886 18.887 18.887 0.057 0.065 0.0170 18.866 ppm 1.373e+09 1.526e+12

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 185.195 190.673 207.618 301.001 481.540 538.919 544.167 273.922 348.246 85.151 311.017 µs 27.36 102.3

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 0.497 0.512 0.563 0.994 1.908 2.097 2.112 1.345 1.585 0.436 1.090 ppb 8.522 24.82

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 -1,074.146 -922.101 -723.344 -175.354 786.046 945.947 1,255.839 1,509.390 1,868.048 452.944 -112.895 µs -5.166 11.93

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 18.821 18.822 18.829 18.870 18.886 18.887 18.887 0.057 0.065 0.0170 18.866 ppm 1.373e+09 1.526e+12
Temp /dev/sdb 30.000 30.000 30.000 30.000 32.000 32.000 32.000 2.000 2.000 0.482 30.127 °C
Temp LM0 10.000 11.000 11.000 13.000 15.000 15.000 15.000 4.000 4.000 1.196 12.723 °C
Temp LM1 9.000 10.000 10.000 12.000 14.000 15.000 15.000 4.000 5.000 1.186 11.939 °C
Temp LM2 47.000 47.000 47.000 48.000 49.000 50.000 50.000 2.000 3.000 0.795 48.274 °C
Temp LM3 16.500 17.500 17.500 19.000 19.500 20.500 20.500 2.000 3.000 0.769 18.839 °C
Temp LM4 16.500 17.500 17.500 19.000 20.500 20.500 21.000 3.000 3.000 0.812 18.904 °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 4.000 5.000 5.000 8.000 10.000 11.000 12.000 5.000 6.000 1.351 7.707 nSat 118.2 625.4
TDOP 0.590 0.620 0.740 1.110 2.490 4.180 13.290 1.750 3.560 0.889 1.301 9.988 124.7

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 150.254.190.51

peer offset 150.254.190.51 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 150.254.190.51 -3.986 -3.986 0.295 1.136 2.065 2.520 2.520 1.770 6.506 0.840 1.150 ms -2.554 19.51

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 153.19.250.123

peer offset 153.19.250.123 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 153.19.250.123 -1.839 -1.839 -1.127 -0.204 1.179 1.484 1.484 2.307 3.323 0.664 -0.185 ms -5.756 14.46

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 193.110.137.171

peer offset 193.110.137.171 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 193.110.137.171 -1.529 -1.529 -0.903 -0.090 0.877 3.877 3.877 1.779 5.407 0.771 0.011 ms -1.838 10.07

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 194.146.251.100

peer offset 194.146.251.100 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 194.146.251.100 -1.587 -1.587 -1.091 -0.137 1.266 2.562 2.562 2.356 4.148 0.782 -0.117 ms -3.976 9.41

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 194.146.251.101

peer offset 194.146.251.101 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 194.146.251.101 -2.132 -2.132 -0.902 -0.054 1.092 1.445 1.445 1.993 3.577 0.638 -0.048 ms -4.578 12.59

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 194.29.130.252

peer offset 194.29.130.252 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 194.29.130.252 -0.984 -0.984 -0.630 0.019 1.449 1.789 1.789 2.079 2.772 0.670 0.144 ms -2.046 4.343

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 195.187.245.55

peer offset 195.187.245.55 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 195.187.245.55 -1.470 -1.470 -1.353 -0.260 0.532 0.785 0.785 1.885 2.255 0.565 -0.312 ms -8.606 23.8

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 213.135.57.60

peer offset 213.135.57.60 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 213.135.57.60 -2.257 -2.257 -1.371 -0.013 1.085 2.401 2.401 2.456 4.658 0.749 -0.038 ms -4.109 11.82

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 150.254.190.51

peer jitter 150.254.190.51 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 150.254.190.51 0.302 0.302 0.370 1.076 7.749 7.862 7.862 7.379 7.561 2.087 1.988 ms 1.7 5.035

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 153.19.250.123

peer jitter 153.19.250.123 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 153.19.250.123 0.344 0.344 0.422 1.092 3.454 4.399 4.399 3.032 4.055 0.904 1.336 ms 3.071 9.233

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 193.110.137.171

peer jitter 193.110.137.171 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 193.110.137.171 0.428 0.428 0.468 1.186 2.316 4.003 4.003 1.848 3.575 0.634 1.277 ms 5.768 21.17

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 194.146.251.100

peer jitter 194.146.251.100 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 194.146.251.100 0.210 0.210 0.364 0.902 1.997 3.402 3.402 1.633 3.192 0.600 1.024 ms 3.714 12.07

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 194.146.251.101

peer jitter 194.146.251.101 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 194.146.251.101 0.232 0.232 0.359 0.872 1.365 2.536 2.536 1.006 2.304 0.360 0.893 ms 9.138 35.03

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 194.29.130.252

peer jitter 194.29.130.252 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 194.29.130.252 0.247 0.247 0.313 1.383 2.139 2.326 2.326 1.826 2.079 0.598 1.192 ms 3.879 8.344

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 195.187.245.55

peer jitter 195.187.245.55 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 195.187.245.55 0.249 0.249 0.297 0.881 2.429 2.546 2.546 2.131 2.297 0.646 1.077 ms 3.104 7.662

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 213.135.57.60

peer jitter 213.135.57.60 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 213.135.57.60 0.242 0.242 0.303 0.847 1.962 2.449 2.449 1.660 2.206 0.504 0.899 ms 3.681 9.885

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 18.821 18.822 18.829 18.870 18.886 18.887 18.887 0.057 0.065 0.0170 18.866 ppm 1.373e+09 1.526e+12
Local Clock Time Offset -1,074.146 -922.101 -723.344 -175.354 786.046 945.947 1,255.839 1,509.390 1,868.048 452.944 -112.895 µs -5.166 11.93
Local RMS Frequency Jitter 0.497 0.512 0.563 0.994 1.908 2.097 2.112 1.345 1.585 0.436 1.090 ppb 8.522 24.82
Local RMS Time Jitter 185.195 190.673 207.618 301.001 481.540 538.919 544.167 273.922 348.246 85.151 311.017 µs 27.36 102.3
Server Jitter 150.254.190.51 0.302 0.302 0.370 1.076 7.749 7.862 7.862 7.379 7.561 2.087 1.988 ms 1.7 5.035
Server Jitter 153.19.250.123 0.344 0.344 0.422 1.092 3.454 4.399 4.399 3.032 4.055 0.904 1.336 ms 3.071 9.233
Server Jitter 193.110.137.171 0.428 0.428 0.468 1.186 2.316 4.003 4.003 1.848 3.575 0.634 1.277 ms 5.768 21.17
Server Jitter 194.146.251.100 0.210 0.210 0.364 0.902 1.997 3.402 3.402 1.633 3.192 0.600 1.024 ms 3.714 12.07
Server Jitter 194.146.251.101 0.232 0.232 0.359 0.872 1.365 2.536 2.536 1.006 2.304 0.360 0.893 ms 9.138 35.03
Server Jitter 194.29.130.252 0.247 0.247 0.313 1.383 2.139 2.326 2.326 1.826 2.079 0.598 1.192 ms 3.879 8.344
Server Jitter 195.187.245.55 0.249 0.249 0.297 0.881 2.429 2.546 2.546 2.131 2.297 0.646 1.077 ms 3.104 7.662
Server Jitter 213.135.57.60 0.242 0.242 0.303 0.847 1.962 2.449 2.449 1.660 2.206 0.504 0.899 ms 3.681 9.885
Server Offset 150.254.190.51 -3.986 -3.986 0.295 1.136 2.065 2.520 2.520 1.770 6.506 0.840 1.150 ms -2.554 19.51
Server Offset 153.19.250.123 -1.839 -1.839 -1.127 -0.204 1.179 1.484 1.484 2.307 3.323 0.664 -0.185 ms -5.756 14.46
Server Offset 193.110.137.171 -1.529 -1.529 -0.903 -0.090 0.877 3.877 3.877 1.779 5.407 0.771 0.011 ms -1.838 10.07
Server Offset 194.146.251.100 -1.587 -1.587 -1.091 -0.137 1.266 2.562 2.562 2.356 4.148 0.782 -0.117 ms -3.976 9.41
Server Offset 194.146.251.101 -2.132 -2.132 -0.902 -0.054 1.092 1.445 1.445 1.993 3.577 0.638 -0.048 ms -4.578 12.59
Server Offset 194.29.130.252 -0.984 -0.984 -0.630 0.019 1.449 1.789 1.789 2.079 2.772 0.670 0.144 ms -2.046 4.343
Server Offset 195.187.245.55 -1.470 -1.470 -1.353 -0.260 0.532 0.785 0.785 1.885 2.255 0.565 -0.312 ms -8.606 23.8
Server Offset 213.135.57.60 -2.257 -2.257 -1.371 -0.013 1.085 2.401 2.401 2.456 4.658 0.749 -0.038 ms -4.109 11.82
TDOP 0.590 0.620 0.740 1.110 2.490 4.180 13.290 1.750 3.560 0.889 1.301 9.988 124.7
Temp /dev/sdb 30.000 30.000 30.000 30.000 32.000 32.000 32.000 2.000 2.000 0.482 30.127 °C
Temp LM0 10.000 11.000 11.000 13.000 15.000 15.000 15.000 4.000 4.000 1.196 12.723 °C
Temp LM1 9.000 10.000 10.000 12.000 14.000 15.000 15.000 4.000 5.000 1.186 11.939 °C
Temp LM2 47.000 47.000 47.000 48.000 49.000 50.000 50.000 2.000 3.000 0.795 48.274 °C
Temp LM3 16.500 17.500 17.500 19.000 19.500 20.500 20.500 2.000 3.000 0.769 18.839 °C
Temp LM4 16.500 17.500 17.500 19.000 20.500 20.500 21.000 3.000 3.000 0.812 18.904 °C
nSats 4.000 5.000 5.000 8.000 10.000 11.000 12.000 5.000 6.000 1.351 7.707 nSat 118.2 625.4
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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