NTPsec

Backup/Meinberg

Report generated: Thu Jul 3 05:33:00 2025 UTC
Start Time: Wed Jul 2 05:33:00 2025 UTC
End Time: Thu Jul 3 05:33:00 2025 UTC
Report Period: 1.0 days
Warning: plots clipped

Daily stats   Weekly stats  

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 -16.533 -15.277 -14.160 -4.521 17.503 22.491 34.448 31.663 37.768 10.368 -1.707 µs 0.7525 2.694
Local Clock Frequency Offset 6.206 6.206 6.208 6.402 6.585 6.607 6.615 0.377 0.401 0.124 6.390 ppm -0.0305 1.66

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 0.357 0.422 0.495 0.728 1.252 2.849 3.779 0.757 2.427 0.400 0.813 µs 3.958 21.85

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 0.071 0.091 0.139 0.593 1.049 1.203 1.624 0.910 1.112 0.284 0.574 ppb 0.2581 2.778

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 -16.533 -15.277 -14.160 -4.521 17.503 22.491 34.448 31.663 37.768 10.368 -1.707 µs 0.7525 2.694

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 6.206 6.206 6.208 6.402 6.585 6.607 6.615 0.377 0.401 0.124 6.390 ppm -0.0305 1.66
Temp /dev/sda 47.000 47.000 47.000 48.000 49.000 49.000 49.000 2.000 2.000 0.758 47.976 °C
Temp /dev/sdb 57.000 57.000 57.000 59.000 59.000 60.000 60.000 2.000 3.000 0.651 58.502 °C
Temp /dev/sdc 58.000 58.000 58.000 60.000 60.000 61.000 61.000 2.000 3.000 0.609 59.819 °C
Temp /dev/sdd 64.000 64.000 64.000 65.000 66.000 66.000 67.000 2.000 2.000 0.810 65.226 °C
Temp /dev/sdf 58.000 58.000 58.000 59.000 60.000 60.000 60.000 2.000 2.000 0.776 59.063 °C
Temp LM0 31.500 31.500 31.500 32.750 33.500 33.750 34.750 2.000 2.250 0.703 32.548 °C
Temp LM1 43.500 43.500 43.500 44.500 45.500 46.000 46.000 2.000 2.500 0.711 44.742 °C
Temp LM10 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM11 47.000 47.000 47.000 48.000 49.000 49.000 49.000 2.000 2.000 0.760 47.979 °C
Temp LM12 27.800 27.800 27.800 27.800 27.800 27.800 27.800 0.000 0.000 0.000 27.800 °C
Temp LM13 29.800 29.800 29.800 29.800 29.800 29.800 29.800 0.000 0.000 0.000 29.800 °C
Temp LM14 32.750 32.750 32.750 34.000 34.750 35.000 35.000 2.000 2.250 0.717 33.843 °C
Temp LM15 58.000 58.000 58.000 59.000 60.000 60.000 61.000 2.000 2.000 0.759 59.220 °C
Temp LM16 63.500 63.500 63.500 65.000 65.500 66.000 66.000 2.000 2.500 0.635 64.613 °C
Temp LM17 64.000 64.000 64.000 66.000 66.000 66.000 67.000 2.000 2.000 0.672 65.411 °C
Temp LM18 58.000 58.000 58.000 59.000 60.000 60.000 60.000 2.000 2.000 0.643 58.679 °C
Temp LM19 30.000 30.000 31.000 32.000 33.000 34.000 38.000 2.000 4.000 0.958 32.073 °C
Temp LM2 35.000 36.000 36.000 37.000 37.000 38.000 38.000 1.000 2.000 0.540 36.519 °C
Temp LM20 29.000 30.000 30.000 31.000 33.000 34.000 38.000 3.000 4.000 1.055 31.544 °C
Temp LM21 27.000 27.000 28.000 29.000 31.000 31.000 35.000 3.000 4.000 0.982 29.122 °C
Temp LM22 29.000 30.000 30.000 32.000 33.000 34.000 38.000 3.000 4.000 0.984 31.683 °C
Temp LM23 28.000 29.000 29.000 31.000 32.000 33.000 36.000 3.000 4.000 1.037 30.770 °C
Temp LM3 34.000 34.000 34.500 35.500 37.000 37.000 37.000 2.500 3.000 0.876 35.526 °C
Temp LM4 24.000 24.000 24.000 24.000 24.000 24.000 24.000 0.000 0.000 0.000 24.000 °C
Temp LM5 30.500 30.500 30.500 30.500 30.500 30.500 30.500 0.000 0.000 0.000 30.500 °C
Temp LM6 63.000 63.000 63.000 65.000 65.000 65.000 66.000 2.000 2.000 0.717 64.415 °C
Temp LM7 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM8 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM9 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp ZONE0 30.000 30.000 30.000 32.000 33.000 34.000 37.000 3.000 4.000 0.885 31.756 °C
Temp ZONE1 27.800 27.800 27.800 27.800 27.800 27.800 27.800 0.000 0.000 0.000 27.800 °C
Temp ZONE2 63.500 63.500 63.500 65.000 65.500 65.500 66.000 2.000 2.000 0.626 64.611 °C
Temp ZONE3 29.800 29.800 29.800 29.800 29.800 29.800 29.800 0.000 0.000 0.000 29.800 °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.



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 2001:470:e815::8 (spidey.rellim.com)

peer offset 2001:470:e815::8 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2001:470:e815::8 (spidey.rellim.com) -160.606 -146.096 -116.522 45.274 156.782 168.459 178.748 273.304 314.555 83.140 26.489 µs -0.2781 2.132

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 204.17.205.1

peer offset 204.17.205.1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 204.17.205.1 -322.242 -310.156 -264.991 76.371 585.243 695.322 726.592 850.234 1,005.478 238.602 83.225 µs 0.5137 3.078

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 204.17.205.24

peer offset 204.17.205.24 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 204.17.205.24 -68.268 -35.311 -13.199 47.212 80.714 90.994 104.544 93.913 126.305 27.960 41.953 µs -0.7554 3.537

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 204.17.205.27

peer offset 204.17.205.27 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 204.17.205.27 -46.660 -17.649 6.355 45.149 84.241 108.739 128.898 77.886 126.388 22.946 45.017 µs -0.1129 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 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) -16.534 -15.278 -14.161 -4.522 17.504 22.492 34.449 31.665 37.770 10.368 -1.707 µs 0.7525 2.694

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 2001:470:e815::8 (spidey.rellim.com)

peer jitter 2001:470:e815::8 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2001:470:e815::8 (spidey.rellim.com) 2.159 3.273 4.784 14.131 68.933 82.484 102.570 64.149 79.211 19.615 21.845 µs 1.625 5.026

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 204.17.205.1

peer jitter 204.17.205.1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 204.17.205.1 2.317 3.771 4.856 10.966 23.654 29.565 38.312 18.798 25.794 5.826 12.039 µs 1.015 3.947

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 204.17.205.24

peer jitter 204.17.205.24 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 204.17.205.24 3.229 4.028 5.967 23.882 86.513 120.051 139.773 80.546 116.023 23.996 30.010 µs 2.089 7.788

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 204.17.205.27

peer jitter 204.17.205.27 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 204.17.205.27 1.815 2.727 4.624 10.265 43.764 117.104 167.034 39.140 114.377 19.715 16.151 µs 4.002 21.36

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) 0.252 0.358 0.501 1.651 4.877 12.088 20.009 4.376 11.730 1.998 2.140 µs 3.923 25.85

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 6.206 6.206 6.208 6.402 6.585 6.607 6.615 0.377 0.401 0.124 6.390 ppm -0.0305 1.66
Local Clock Time Offset -16.533 -15.277 -14.160 -4.521 17.503 22.491 34.448 31.663 37.768 10.368 -1.707 µs 0.7525 2.694
Local RMS Frequency Jitter 0.071 0.091 0.139 0.593 1.049 1.203 1.624 0.910 1.112 0.284 0.574 ppb 0.2581 2.778
Local RMS Time Jitter 0.357 0.422 0.495 0.728 1.252 2.849 3.779 0.757 2.427 0.400 0.813 µs 3.958 21.85
Server Jitter 2001:470:e815::8 (spidey.rellim.com) 2.159 3.273 4.784 14.131 68.933 82.484 102.570 64.149 79.211 19.615 21.845 µs 1.625 5.026
Server Jitter 204.17.205.1 2.317 3.771 4.856 10.966 23.654 29.565 38.312 18.798 25.794 5.826 12.039 µs 1.015 3.947
Server Jitter 204.17.205.24 3.229 4.028 5.967 23.882 86.513 120.051 139.773 80.546 116.023 23.996 30.010 µs 2.089 7.788
Server Jitter 204.17.205.27 1.815 2.727 4.624 10.265 43.764 117.104 167.034 39.140 114.377 19.715 16.151 µs 4.002 21.36
Server Jitter SHM(0) 0.252 0.358 0.501 1.651 4.877 12.088 20.009 4.376 11.730 1.998 2.140 µs 3.923 25.85
Server Offset 2001:470:e815::8 (spidey.rellim.com) -160.606 -146.096 -116.522 45.274 156.782 168.459 178.748 273.304 314.555 83.140 26.489 µs -0.2781 2.132
Server Offset 204.17.205.1 -322.242 -310.156 -264.991 76.371 585.243 695.322 726.592 850.234 1,005.478 238.602 83.225 µs 0.5137 3.078
Server Offset 204.17.205.24 -68.268 -35.311 -13.199 47.212 80.714 90.994 104.544 93.913 126.305 27.960 41.953 µs -0.7554 3.537
Server Offset 204.17.205.27 -46.660 -17.649 6.355 45.149 84.241 108.739 128.898 77.886 126.388 22.946 45.017 µs -0.1129 4.343
Server Offset SHM(0) -16.534 -15.278 -14.161 -4.522 17.504 22.492 34.449 31.665 37.770 10.368 -1.707 µs 0.7525 2.694
Temp /dev/sda 47.000 47.000 47.000 48.000 49.000 49.000 49.000 2.000 2.000 0.758 47.976 °C
Temp /dev/sdb 57.000 57.000 57.000 59.000 59.000 60.000 60.000 2.000 3.000 0.651 58.502 °C
Temp /dev/sdc 58.000 58.000 58.000 60.000 60.000 61.000 61.000 2.000 3.000 0.609 59.819 °C
Temp /dev/sdd 64.000 64.000 64.000 65.000 66.000 66.000 67.000 2.000 2.000 0.810 65.226 °C
Temp /dev/sdf 58.000 58.000 58.000 59.000 60.000 60.000 60.000 2.000 2.000 0.776 59.063 °C
Temp LM0 31.500 31.500 31.500 32.750 33.500 33.750 34.750 2.000 2.250 0.703 32.548 °C
Temp LM1 43.500 43.500 43.500 44.500 45.500 46.000 46.000 2.000 2.500 0.711 44.742 °C
Temp LM10 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM11 47.000 47.000 47.000 48.000 49.000 49.000 49.000 2.000 2.000 0.760 47.979 °C
Temp LM12 27.800 27.800 27.800 27.800 27.800 27.800 27.800 0.000 0.000 0.000 27.800 °C
Temp LM13 29.800 29.800 29.800 29.800 29.800 29.800 29.800 0.000 0.000 0.000 29.800 °C
Temp LM14 32.750 32.750 32.750 34.000 34.750 35.000 35.000 2.000 2.250 0.717 33.843 °C
Temp LM15 58.000 58.000 58.000 59.000 60.000 60.000 61.000 2.000 2.000 0.759 59.220 °C
Temp LM16 63.500 63.500 63.500 65.000 65.500 66.000 66.000 2.000 2.500 0.635 64.613 °C
Temp LM17 64.000 64.000 64.000 66.000 66.000 66.000 67.000 2.000 2.000 0.672 65.411 °C
Temp LM18 58.000 58.000 58.000 59.000 60.000 60.000 60.000 2.000 2.000 0.643 58.679 °C
Temp LM19 30.000 30.000 31.000 32.000 33.000 34.000 38.000 2.000 4.000 0.958 32.073 °C
Temp LM2 35.000 36.000 36.000 37.000 37.000 38.000 38.000 1.000 2.000 0.540 36.519 °C
Temp LM20 29.000 30.000 30.000 31.000 33.000 34.000 38.000 3.000 4.000 1.055 31.544 °C
Temp LM21 27.000 27.000 28.000 29.000 31.000 31.000 35.000 3.000 4.000 0.982 29.122 °C
Temp LM22 29.000 30.000 30.000 32.000 33.000 34.000 38.000 3.000 4.000 0.984 31.683 °C
Temp LM23 28.000 29.000 29.000 31.000 32.000 33.000 36.000 3.000 4.000 1.037 30.770 °C
Temp LM3 34.000 34.000 34.500 35.500 37.000 37.000 37.000 2.500 3.000 0.876 35.526 °C
Temp LM4 24.000 24.000 24.000 24.000 24.000 24.000 24.000 0.000 0.000 0.000 24.000 °C
Temp LM5 30.500 30.500 30.500 30.500 30.500 30.500 30.500 0.000 0.000 0.000 30.500 °C
Temp LM6 63.000 63.000 63.000 65.000 65.000 65.000 66.000 2.000 2.000 0.717 64.415 °C
Temp LM7 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM8 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp LM9 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C
Temp ZONE0 30.000 30.000 30.000 32.000 33.000 34.000 37.000 3.000 4.000 0.885 31.756 °C
Temp ZONE1 27.800 27.800 27.800 27.800 27.800 27.800 27.800 0.000 0.000 0.000 27.800 °C
Temp ZONE2 63.500 63.500 63.500 65.000 65.500 65.500 66.000 2.000 2.000 0.626 64.611 °C
Temp ZONE3 29.800 29.800 29.800 29.800 29.800 29.800 29.800 0.000 0.000 0.000 29.800 °C
Summary as CSV file


This server:

CPU: Quad core Intel Xeon E3-1241 v3
Kernel: config.gz
Motherboard: Supermicro X10SAE
OS: Gentoo stable
GPS; Meinberg GPS180PEX
GPS/PPS server: gpsd
NTP server: NTPsec
ntp.conf: current
ntp.log: current

Notes:

Notes:
03:20Z 20 Dec 2018 Change poll from 8s to 4s.  4s seems best.
01:30Z 20 Dec 2018 Change poll from 2s to 8s.
23:00Z 20 Dec 2018 Change poll from 4s to 2s.
22:00Z 20 Dec 2018 Change poll from 64s to 4s.
21:40  19 Dec 2018 -- just started

Poll:
64s   SHM(0) offset StdDev 34.5 us, jitter 5.3 us
8s    8s better jitter than 4s, but worse offset than 4s
4s    SHM(0) offset mean 0 ns StdDev 481 ns, jitter 449 ns StdDev 250 ns
      better than 2s, almost unstable
2s

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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