NTPsec

ntp1.wiktel.com

Report generated: Sat Dec 9 05:45:03 2023 UTC
Start Time: Sat Dec 2 05:45:01 2023 UTC
End Time: Sat Dec 9 05:45:01 2023 UTC
Report Period: 7.0 days

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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 -11.674 -3.778 -3.100 -0.435 3.886 4.642 11.712 6.986 8.420 2.372 0.002 µs -3.638 8.303
Local Clock Frequency Offset 17.400 17.432 17.449 17.522 17.712 17.767 18.723 0.262 0.335 0.102 17.549 ppm 5.009e+06 8.57e+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 0.203 0.357 0.444 0.647 0.967 1.550 3.574 0.523 1.193 0.212 0.677 µs 20.74 110.1

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 0.193 0.355 0.459 1.036 1.789 2.105 5.394 1.330 1.750 0.467 1.060 ppb 7.805 37.15

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 -11.674 -3.778 -3.100 -0.435 3.886 4.642 11.712 6.986 8.420 2.372 0.002 µs -3.638 8.303

The clock offsets of the local clock as a histogram.

The Local Clock Offset is field 3 from the loopstats 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 128.101.101.101

peer offset 128.101.101.101 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 128.101.101.101 -455.353 -199.373 -39.468 68.204 136.332 191.745 328.672 175.800 391.118 63.376 61.023 µs -2.414 16.15

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 128.138.141.177

peer offset 128.138.141.177 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 128.138.141.177 -316.312 -55.611 163.120 287.227 589.674 759.963 972.023 426.554 815.574 140.665 318.041 µs 6.333 20.93

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 2001:470:0:2c8::2 (clock.nyc.he.net)

peer offset 2001:470:0:2c8::2 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2001:470:0:2c8::2 (clock.nyc.he.net) -1,794.976 -951.624 -759.004 -490.727 -112.442 38.001 377.840 646.562 989.625 214.153 -461.777 µs -41.25 169.7

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 209.87.233.54

peer offset 209.87.233.54 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 209.87.233.54 -15.650 -5.171 -2.101 1.324 4.079 5.430 9.292 6.180 10.601 2.010 1.171 ms -2.484 11.89

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 2602:fd53:11e:123::2 (time2.mbix.ca)

peer offset 2602:fd53:11e:123::2 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2602:fd53:11e:123::2 (time2.mbix.ca) -35.456 -0.159 -0.104 0.004 0.133 0.249 3.092 0.237 0.408 0.789 -0.004 ms -48.16 2168

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 2606:4700:f1::1 (time.cloudflare.com)

peer offset 2606:4700:f1::1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2606:4700:f1::1 (time.cloudflare.com) 1.073 1.293 1.338 1.476 1.802 2.014 2.300 0.464 0.721 0.146 1.506 ms 838.3 8121

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 2607:f128:1:3::dd1 (dns1.steadfast.net)

peer offset 2607:f128:1:3::dd1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2607:f128:1:3::dd1 (dns1.steadfast.net) 33.792 133.665 151.361 192.742 233.007 247.937 280.537 81.646 114.272 24.643 192.870 µs 338.5 2451

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 2607:f388::123:1 (ntp1.doit.wisc.edu)

peer offset 2607:f388::123:1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2607:f388::123:1 (ntp1.doit.wisc.edu) -13.023 -12.999 -12.978 -12.941 -12.908 -12.892 -12.857 0.070 0.107 0.021 -12.941 ms -2.192e+08 1.321e+11

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 PPS(0)

peer offset PPS(0) plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset PPS(0) -11.675 -3.779 -3.101 -0.436 3.887 4.643 11.713 6.988 8.422 2.373 0.002 µs -3.638 8.302

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 128.101.101.101

peer jitter 128.101.101.101 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 128.101.101.101 4.399 8.034 10.626 22.862 68.652 172.669 434.962 58.026 164.635 31.125 29.940 µs 6.086 55.93

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 128.138.141.177

peer jitter 128.138.141.177 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 128.138.141.177 0.000 0.282 0.368 0.608 0.858 0.962 6.119 0.490 0.681 0.196 0.612 ms 26.98 453.6

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 2001:470:0:2c8::2 (clock.nyc.he.net)

peer jitter 2001:470:0:2c8::2 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2001:470:0:2c8::2 (clock.nyc.he.net) 3.948 8.348 11.212 22.163 64.532 183.280 2,067.878 53.320 174.932 74.700 32.109 µs 19.39 504.7

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 209.87.233.54

peer jitter 209.87.233.54 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 209.87.233.54 1.306 2.932 5.228 12.224 28.965 39.484 119.885 23.736 36.552 8.200 13.829 ms 5.767 45.31

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 2602:fd53:11e:123::2 (time2.mbix.ca)

peer jitter 2602:fd53:11e:123::2 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2602:fd53:11e:123::2 (time2.mbix.ca) 0.005 0.008 0.010 0.021 0.041 0.063 35.288 0.031 0.055 0.909 0.061 ms 28.94 1053

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 2606:4700:f1::1 (time.cloudflare.com)

peer jitter 2606:4700:f1::1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2606:4700:f1::1 (time.cloudflare.com) 0.005 0.009 0.012 0.027 0.162 2.184 5.225 0.150 2.175 0.357 0.086 ms 6.205 70.15

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 2607:f128:1:3::dd1 (dns1.steadfast.net)

peer jitter 2607:f128:1:3::dd1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2607:f128:1:3::dd1 (dns1.steadfast.net) 8.442 13.771 17.440 33.903 88.809 854.837 2,753.733 71.369 841.066 136.882 55.164 µs 8.559 124.8

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 2607:f388::123:1 (ntp1.doit.wisc.edu)

peer jitter 2607:f388::123:1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2607:f388::123:1 (ntp1.doit.wisc.edu) 0.017 0.026 0.040 0.096 3.102 4.897 5.584 3.063 4.872 0.975 0.417 ms 1.459 8.035

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 PPS(0)

peer jitter PPS(0) plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter PPS(0) 0.081 0.238 0.345 0.694 1.480 2.039 11.410 1.135 1.801 0.401 0.782 µs 6.686 45.88

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 17.400 17.432 17.449 17.522 17.712 17.767 18.723 0.262 0.335 0.102 17.549 ppm 5.009e+06 8.57e+08
Local Clock Time Offset -11.674 -3.778 -3.100 -0.435 3.886 4.642 11.712 6.986 8.420 2.372 0.002 µs -3.638 8.303
Local RMS Frequency Jitter 0.193 0.355 0.459 1.036 1.789 2.105 5.394 1.330 1.750 0.467 1.060 ppb 7.805 37.15
Local RMS Time Jitter 0.203 0.357 0.444 0.647 0.967 1.550 3.574 0.523 1.193 0.212 0.677 µs 20.74 110.1
Server Jitter 128.101.101.101 4.399 8.034 10.626 22.862 68.652 172.669 434.962 58.026 164.635 31.125 29.940 µs 6.086 55.93
Server Jitter 128.138.141.177 0.000 0.282 0.368 0.608 0.858 0.962 6.119 0.490 0.681 0.196 0.612 ms 26.98 453.6
Server Jitter 2001:470:0:2c8::2 (clock.nyc.he.net) 3.948 8.348 11.212 22.163 64.532 183.280 2,067.878 53.320 174.932 74.700 32.109 µs 19.39 504.7
Server Jitter 209.87.233.54 1.306 2.932 5.228 12.224 28.965 39.484 119.885 23.736 36.552 8.200 13.829 ms 5.767 45.31
Server Jitter 2602:fd53:11e:123::2 (time2.mbix.ca) 0.005 0.008 0.010 0.021 0.041 0.063 35.288 0.031 0.055 0.909 0.061 ms 28.94 1053
Server Jitter 2606:4700:f1::1 (time.cloudflare.com) 0.005 0.009 0.012 0.027 0.162 2.184 5.225 0.150 2.175 0.357 0.086 ms 6.205 70.15
Server Jitter 2607:f128:1:3::dd1 (dns1.steadfast.net) 8.442 13.771 17.440 33.903 88.809 854.837 2,753.733 71.369 841.066 136.882 55.164 µs 8.559 124.8
Server Jitter 2607:f388::123:1 (ntp1.doit.wisc.edu) 0.017 0.026 0.040 0.096 3.102 4.897 5.584 3.063 4.872 0.975 0.417 ms 1.459 8.035
Server Jitter PPS(0) 0.081 0.238 0.345 0.694 1.480 2.039 11.410 1.135 1.801 0.401 0.782 µs 6.686 45.88
Server Offset 128.101.101.101 -455.353 -199.373 -39.468 68.204 136.332 191.745 328.672 175.800 391.118 63.376 61.023 µs -2.414 16.15
Server Offset 128.138.141.177 -316.312 -55.611 163.120 287.227 589.674 759.963 972.023 426.554 815.574 140.665 318.041 µs 6.333 20.93
Server Offset 2001:470:0:2c8::2 (clock.nyc.he.net) -1,794.976 -951.624 -759.004 -490.727 -112.442 38.001 377.840 646.562 989.625 214.153 -461.777 µs -41.25 169.7
Server Offset 209.87.233.54 -15.650 -5.171 -2.101 1.324 4.079 5.430 9.292 6.180 10.601 2.010 1.171 ms -2.484 11.89
Server Offset 2602:fd53:11e:123::2 (time2.mbix.ca) -35.456 -0.159 -0.104 0.004 0.133 0.249 3.092 0.237 0.408 0.789 -0.004 ms -48.16 2168
Server Offset 2606:4700:f1::1 (time.cloudflare.com) 1.073 1.293 1.338 1.476 1.802 2.014 2.300 0.464 0.721 0.146 1.506 ms 838.3 8121
Server Offset 2607:f128:1:3::dd1 (dns1.steadfast.net) 33.792 133.665 151.361 192.742 233.007 247.937 280.537 81.646 114.272 24.643 192.870 µs 338.5 2451
Server Offset 2607:f388::123:1 (ntp1.doit.wisc.edu) -13.023 -12.999 -12.978 -12.941 -12.908 -12.892 -12.857 0.070 0.107 0.021 -12.941 ms -2.192e+08 1.321e+11
Server Offset PPS(0) -11.675 -3.779 -3.101 -0.436 3.887 4.643 11.713 6.988 8.422 2.373 0.002 µs -3.638 8.302
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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