NTPsec

itchy

Report generated: Mon Jan 30 17:15:02 2023 UTC
Start Time: Sun Jan 29 17:15:02 2023 UTC
End Time: Mon Jan 30 17:15:02 2023 UTC
Report Period: 1.0 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 -301.923 -301.923 -222.186 9.662 246.405 371.521 371.521 468.591 673.444 139.185 14.848 µs -3.271 7.662
Local Clock Frequency Offset 67.061 67.061 67.062 67.118 67.134 67.153 67.153 0.073 0.092 0.023 67.110 ppm 2.483e+10 7.244e+13

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 69.584 69.584 76.051 104.487 144.680 153.713 153.713 68.629 84.129 19.673 103.705 µs 91.18 452.4

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 3.820 3.820 4.350 7.852 11.474 14.448 14.448 7.124 10.628 2.150 7.888 ppb 27.59 103.4

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 -301.923 -301.923 -222.186 9.662 246.405 371.521 371.521 468.591 673.444 139.185 14.848 µs -3.271 7.662

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 192.12.19.20

peer offset 192.12.19.20 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 192.12.19.20 -168.729 -168.729 -155.975 41.182 363.750 416.096 416.096 519.725 584.825 140.929 76.436 µs -0.9492 3.002

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 204.34.198.40

peer offset 204.34.198.40 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 204.34.198.40 -14.576 -14.576 -14.527 -14.222 -13.945 -13.870 -13.870 0.582 0.706 0.160 -14.244 ms -7.28e+05 6.551e+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 2600:3c03::f03c:91ff:fe0c:601c (scratchy.podsix.net)

peer offset 2600:3c03::f03c:91ff:fe0c:601c plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2600:3c03::f03c:91ff:fe0c:601c (scratchy.podsix.net) -3.623 -3.623 -3.325 -1.514 -0.499 -0.345 -0.345 2.826 3.278 0.723 -1.541 ms -40.87 168.6

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 2610:20:6f96:96::4 (time-d-b.nist.gov)

peer offset 2610:20:6f96:96::4 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2610:20:6f96:96::4 (time-d-b.nist.gov) 4.169 4.169 20.532 279.892 538.304 635.738 635.738 517.772 631.569 144.778 287.571 µs 4.16 10.56

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 192.12.19.20

peer jitter 192.12.19.20 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 192.12.19.20 61.141 61.141 77.246 154.144 262.267 338.371 338.371 185.021 277.230 62.458 165.156 µs 9.918 29.88

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.



Server Jitter 204.34.198.40

peer jitter 204.34.198.40 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 204.34.198.40 76.965 76.965 86.502 138.553 295.485 378.893 378.893 208.983 301.928 67.941 163.227 µs 8.137 25.9

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 2600:3c03::f03c:91ff:fe0c:601c (scratchy.podsix.net)

peer jitter 2600:3c03::f03c:91ff:fe0c:601c plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2600:3c03::f03c:91ff:fe0c:601c (scratchy.podsix.net) 0.049 0.049 0.072 0.234 1.051 1.192 1.192 0.979 1.143 0.302 0.370 ms 1.728 4.238

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 2610:20:6f96:96::4 (time-d-b.nist.gov)

peer jitter 2610:20:6f96:96::4 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2610:20:6f96:96::4 (time-d-b.nist.gov) 50.048 50.048 52.971 90.894 272.141 342.520 342.520 219.170 292.472 70.363 122.474 µs 3.941 11.32

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 67.061 67.061 67.062 67.118 67.134 67.153 67.153 0.073 0.092 0.023 67.110 ppm 2.483e+10 7.244e+13
Local Clock Time Offset -301.923 -301.923 -222.186 9.662 246.405 371.521 371.521 468.591 673.444 139.185 14.848 µs -3.271 7.662
Local RMS Frequency Jitter 3.820 3.820 4.350 7.852 11.474 14.448 14.448 7.124 10.628 2.150 7.888 ppb 27.59 103.4
Local RMS Time Jitter 69.584 69.584 76.051 104.487 144.680 153.713 153.713 68.629 84.129 19.673 103.705 µs 91.18 452.4
Server Jitter 192.12.19.20 61.141 61.141 77.246 154.144 262.267 338.371 338.371 185.021 277.230 62.458 165.156 µs 9.918 29.88
Server Jitter 204.34.198.40 76.965 76.965 86.502 138.553 295.485 378.893 378.893 208.983 301.928 67.941 163.227 µs 8.137 25.9
Server Jitter 2600:3c03::f03c:91ff:fe0c:601c (scratchy.podsix.net) 0.049 0.049 0.072 0.234 1.051 1.192 1.192 0.979 1.143 0.302 0.370 ms 1.728 4.238
Server Jitter 2610:20:6f96:96::4 (time-d-b.nist.gov) 50.048 50.048 52.971 90.894 272.141 342.520 342.520 219.170 292.472 70.363 122.474 µs 3.941 11.32
Server Offset 192.12.19.20 -168.729 -168.729 -155.975 41.182 363.750 416.096 416.096 519.725 584.825 140.929 76.436 µs -0.9492 3.002
Server Offset 204.34.198.40 -14.576 -14.576 -14.527 -14.222 -13.945 -13.870 -13.870 0.582 0.706 0.160 -14.244 ms -7.28e+05 6.551e+07
Server Offset 2600:3c03::f03c:91ff:fe0c:601c (scratchy.podsix.net) -3.623 -3.623 -3.325 -1.514 -0.499 -0.345 -0.345 2.826 3.278 0.723 -1.541 ms -40.87 168.6
Server Offset 2610:20:6f96:96::4 (time-d-b.nist.gov) 4.169 4.169 20.532 279.892 538.304 635.738 635.738 517.772 631.569 144.778 287.571 µs 4.16 10.56
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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