NTPsec

c-ntpsec-14-day-stats

Report generated: Thu Sep 24 21:58:16 2020 UTC
Start Time: Thu Sep 10 21:58:06 2020 UTC
End Time: Thu Sep 24 21:58:06 2020 UTC
Report published: Thu Sep 24 14:58:49 2020 PDT
Report Period: 14.0 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 -1,302.000 -609.000 -438.000 -9.000 488.000 701.000 2,621.000 926.000 1,310.000 282.172 3.222 ns -3.674 9.259
Local Clock Frequency Offset -5.209 -5.204 -5.189 -5.109 -5.066 -5.062 -5.059 0.123 0.141 0.040 -5.117 ppm -2.21e+06 2.879e+08

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 55.000 88.000 104.000 155.000 231.000 274.000 433.000 127.000 186.000 39.467 159.528 ns 38.08 155.1

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 15.000 28.000 34.000 60.000 116.000 160.000 624.000 82.000 132.000 28.851 66.031 10e-12 9.08 58.81

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 -1,302.000 -609.000 -438.000 -9.000 488.000 701.000 2,621.000 926.000 1,310.000 282.172 3.222 ns -3.674 9.259

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 -5.209 -5.204 -5.189 -5.109 -5.066 -5.062 -5.059 0.123 0.141 0.040 -5.117 ppm -2.21e+06 2.879e+08
Temp ZONE0 59.072 59.610 60.148 61.224 63.376 63.914 64.452 3.228 4.304 1.059 61.463 °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 1.136 9.362 nSat 400.9 3061
TDOP 0.490 0.540 0.610 0.810 1.420 1.610 2.460 0.810 1.070 0.247 0.879 25.77 101.9

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 104.131.155.175

peer offset 104.131.155.175 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 104.131.155.175 0.526 0.983 1.328 2.032 3.035 10.846 61.837 1.707 9.863 3.826 2.429 ms 11.02 145.7

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 162.159.200.1

peer offset 162.159.200.1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 162.159.200.1 -2.344 -0.394 0.739 1.548 2.735 51.490 252.833 1.996 51.884 9.982 2.684 ms 11.71 236.7

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 173.11.101.155

peer offset 173.11.101.155 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 173.11.101.155 -21.733 -1.322 -0.587 0.233 1.300 51.517 314.894 1.887 52.839 11.908 1.518 ms 11.04 224.7

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 178.62.68.79

peer offset 178.62.68.79 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 178.62.68.79 -6.535 1.247 2.301 3.962 5.994 51.348 254.826 3.693 50.101 10.485 5.235 ms 11.1 188.6

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

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

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

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



Server Offset 192.168.1.10

peer offset 192.168.1.10 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 192.168.1.10 -110.472 -19.869 -0.487 45.581 109.305 130.773 231.039 109.792 150.642 33.086 48.773 µs 1.854 5.483

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 204.123.2.5

peer offset 204.123.2.5 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 204.123.2.5 -6.440 1.778 2.039 2.427 3.045 26.232 96.353 1.006 24.454 5.462 3.022 ms 9.399 113.5

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 2405:fc00:0:1::123

peer offset 2405:fc00:0:1::123 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2405:fc00:0:1::123 -53.597 2.255 3.156 4.000 4.947 58.491 315.359 1.791 56.236 12.042 5.219 ms 11.8 228

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) -75.229 -67.223 -63.715 -54.924 -46.505 -43.899 -39.719 17.210 23.324 5.221 -54.987 ms -1568 1.849e+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) -1,303.000 -610.000 -439.000 -10.000 489.000 702.000 2,622.000 928.000 1,312.000 282.933 3.194 ns -3.676 9.25

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 104.131.155.175

peer jitter 104.131.155.175 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 104.131.155.175 0.000 0.272 0.494 2.032 45.356 137.434 456.714 44.862 137.162 31.410 9.426 ms 6.371 79.02

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 162.159.200.1

peer jitter 162.159.200.1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 162.159.200.1 0.111 0.234 0.365 1.967 34.290 82.374 474.181 33.926 82.141 24.528 7.579 ms 8.279 127.2

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 173.11.101.155

peer jitter 173.11.101.155 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 173.11.101.155 0.000 0.419 0.673 2.410 33.293 98.083 407.774 32.620 97.664 25.137 8.444 ms 6.868 89.44

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 178.62.68.79

peer jitter 178.62.68.79 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 178.62.68.79 0.152 0.259 0.384 1.904 38.672 87.254 380.467 38.289 86.996 24.955 8.094 ms 6.206 76.54

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 192.168.1.10

peer jitter 192.168.1.10 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 192.168.1.10 0.011 0.030 0.047 0.138 8.690 9.179 30.040 8.643 9.149 2.707 1.240 ms 0.6066 4.624

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 204.123.2.5

peer jitter 204.123.2.5 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 204.123.2.5 0.103 0.235 0.371 2.031 39.858 94.695 419.028 39.487 94.461 28.675 8.519 ms 6.698 81.93

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 2405:fc00:0:1::123

peer jitter 2405:fc00:0:1::123 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2405:fc00:0:1::123 0.000 0.300 0.544 5.132 47.049 190.877 430.808 46.505 190.577 30.132 13.217 ms 4.698 46.02

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 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) 0.042 0.218 0.343 0.970 3.198 5.838 11.211 2.855 5.621 1.033 1.256 ms 3.365 15.17

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 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) 22.000 63.000 88.000 198.000 454.000 597.000 1,570.000 366.000 534.000 116.687 224.902 ns 4.944 16.91

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.



Summary


Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Frequency Offset -5.209 -5.204 -5.189 -5.109 -5.066 -5.062 -5.059 0.123 0.141 0.040 -5.117 ppm -2.21e+06 2.879e+08
Local Clock Time Offset -1,302.000 -609.000 -438.000 -9.000 488.000 701.000 2,621.000 926.000 1,310.000 282.172 3.222 ns -3.674 9.259
Local RMS Frequency Jitter 15.000 28.000 34.000 60.000 116.000 160.000 624.000 82.000 132.000 28.851 66.031 10e-12 9.08 58.81
Local RMS Time Jitter 55.000 88.000 104.000 155.000 231.000 274.000 433.000 127.000 186.000 39.467 159.528 ns 38.08 155.1
Server Jitter 104.131.155.175 0.000 0.272 0.494 2.032 45.356 137.434 456.714 44.862 137.162 31.410 9.426 ms 6.371 79.02
Server Jitter 162.159.200.1 0.111 0.234 0.365 1.967 34.290 82.374 474.181 33.926 82.141 24.528 7.579 ms 8.279 127.2
Server Jitter 173.11.101.155 0.000 0.419 0.673 2.410 33.293 98.083 407.774 32.620 97.664 25.137 8.444 ms 6.868 89.44
Server Jitter 178.62.68.79 0.152 0.259 0.384 1.904 38.672 87.254 380.467 38.289 86.996 24.955 8.094 ms 6.206 76.54
Server Jitter 192.168.1.10 0.011 0.030 0.047 0.138 8.690 9.179 30.040 8.643 9.149 2.707 1.240 ms 0.6066 4.624
Server Jitter 204.123.2.5 0.103 0.235 0.371 2.031 39.858 94.695 419.028 39.487 94.461 28.675 8.519 ms 6.698 81.93
Server Jitter 2405:fc00:0:1::123 0.000 0.300 0.544 5.132 47.049 190.877 430.808 46.505 190.577 30.132 13.217 ms 4.698 46.02
Server Jitter SHM(0) 0.042 0.218 0.343 0.970 3.198 5.838 11.211 2.855 5.621 1.033 1.256 ms 3.365 15.17
Server Jitter SHM(1) 22.000 63.000 88.000 198.000 454.000 597.000 1,570.000 366.000 534.000 116.687 224.902 ns 4.944 16.91
Server Offset 104.131.155.175 0.526 0.983 1.328 2.032 3.035 10.846 61.837 1.707 9.863 3.826 2.429 ms 11.02 145.7
Server Offset 162.159.200.1 -2.344 -0.394 0.739 1.548 2.735 51.490 252.833 1.996 51.884 9.982 2.684 ms 11.71 236.7
Server Offset 173.11.101.155 -21.733 -1.322 -0.587 0.233 1.300 51.517 314.894 1.887 52.839 11.908 1.518 ms 11.04 224.7
Server Offset 178.62.68.79 -6.535 1.247 2.301 3.962 5.994 51.348 254.826 3.693 50.101 10.485 5.235 ms 11.1 188.6
Server Offset 192.168.1.10 -110.472 -19.869 -0.487 45.581 109.305 130.773 231.039 109.792 150.642 33.086 48.773 µs 1.854 5.483
Server Offset 204.123.2.5 -6.440 1.778 2.039 2.427 3.045 26.232 96.353 1.006 24.454 5.462 3.022 ms 9.399 113.5
Server Offset 2405:fc00:0:1::123 -53.597 2.255 3.156 4.000 4.947 58.491 315.359 1.791 56.236 12.042 5.219 ms 11.8 228
Server Offset SHM(0) -75.229 -67.223 -63.715 -54.924 -46.505 -43.899 -39.719 17.210 23.324 5.221 -54.987 ms -1568 1.849e+04
Server Offset SHM(1) -1,303.000 -610.000 -439.000 -10.000 489.000 702.000 2,622.000 928.000 1,312.000 282.933 3.194 ns -3.676 9.25
TDOP 0.490 0.540 0.610 0.810 1.420 1.610 2.460 0.810 1.070 0.247 0.879 25.77 101.9
Temp ZONE0 59.072 59.610 60.148 61.224 63.376 63.914 64.452 3.228 4.304 1.059 61.463 °C
nSats 6.000 7.000 7.000 9.000 11.000 12.000 12.000 4.000 5.000 1.136 9.362 nSat 400.9 3061
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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