NTPsec

A-ntpsec-12-hour-stats

Report generated: Mon Oct 19 15:01:31 2020 UTC
Start Time: Mon Oct 19 03:01:30 2020 UTC
End Time: Mon Oct 19 15:01:30 2020 UTC
Report published: Mon Oct 19 08:01:40 2020 PDT
Report Period: 0.5 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 -1.118 -0.783 -0.467 0.369 1.178 1.506 1.865 1.645 2.289 0.499 0.355 µs -0.8847 3.26
Local Clock Frequency Offset -512.451 -512.207 -509.750 -433.121 -276.459 -267.853 -264.816 233.291 244.354 87.757 -410.662 ppb -200 1229

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 240.000 282.000 324.000 469.000 719.000 826.000 972.000 395.000 544.000 120.587 487.896 ns 38.17 154.6

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 57.000 69.000 79.000 125.000 237.000 268.000 304.000 158.000 199.000 50.684 141.171 10e-12 11.8 37.27

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 -1.118 -0.783 -0.467 0.369 1.178 1.506 1.865 1.645 2.289 0.499 0.355 µs -0.8847 3.26

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 -512.451 -512.207 -509.750 -433.121 -276.459 -267.853 -264.816 233.291 244.354 87.757 -410.662 ppb -200 1229
Temp ZONE0 58.534 59.072 59.072 61.224 62.300 62.300 62.300 3.228 3.228 1.204 61.025 °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 12.000 12.000 12.000 5.000 5.000 1.352 9.252 nSat 217.5 1381
TDOP 0.530 0.540 0.600 0.850 1.480 1.730 1.810 0.880 1.190 0.271 0.901 20.69 76.84

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 137.190.2.4

peer offset 137.190.2.4 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 137.190.2.4 1.159 1.163 1.447 1.782 2.296 2.650 2.654 0.849 1.487 0.250 1.784 ms 249.1 1655

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 192.168.1.12

peer offset 192.168.1.12 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 192.168.1.12 30.089 51.738 84.407 136.082 178.258 192.228 226.226 93.851 140.490 29.741 135.152 µs 54.8 231.4

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 216.218.192.202

peer offset 216.218.192.202 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 216.218.192.202 1.783 1.886 2.022 2.398 2.782 2.937 2.994 0.760 1.052 0.222 2.398 ms 972.8 9833

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 216.218.254.202

peer offset 216.218.254.202 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 216.218.254.202 0.891 1.694 1.915 2.368 2.769 3.127 3.128 0.853 1.433 0.286 2.362 ms 403.5 3077

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 73.158.5.1

peer offset 73.158.5.1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 73.158.5.1 -1.604 -1.046 -0.397 0.355 1.053 1.540 2.353 1.450 2.586 0.502 0.299 ms -1.284 6.506

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) -69.301 -57.009 -54.784 -47.397 -42.168 -40.540 -38.329 12.616 16.470 3.843 -47.925 ms -2485 3.403e+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) -1.119 -0.784 -0.468 0.370 1.179 1.507 1.866 1.647 2.291 0.500 0.355 µs -0.8869 3.261

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 137.190.2.4

peer jitter 137.190.2.4 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 137.190.2.4 0.203 0.266 0.345 1.976 9.157 12.554 12.559 8.812 12.289 3.007 2.929 ms 1.325 3.728

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 192.168.1.12

peer jitter 192.168.1.12 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 192.168.1.12 0.021 0.033 0.051 0.170 8.679 11.108 13.293 8.628 11.075 2.673 1.255 ms 0.7572 4.539

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 216.218.192.202

peer jitter 216.218.192.202 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 216.218.192.202 0.186 0.195 0.351 1.665 8.975 11.691 11.841 8.624 11.496 2.868 2.690 ms 1.474 4.273

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 216.218.254.202

peer jitter 216.218.254.202 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 216.218.254.202 0.208 0.234 0.413 1.533 9.616 12.883 13.048 9.203 12.649 3.418 3.063 ms 1.172 3.334

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 73.158.5.1

peer jitter 73.158.5.1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 73.158.5.1 0.591 0.607 0.876 2.033 9.576 14.792 14.909 8.700 14.185 3.068 3.108 ms 2.155 7.043

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) 0.089 0.259 0.393 1.081 3.048 5.579 16.692 2.655 5.320 1.018 1.364 ms 3.783 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 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) 0.104 0.169 0.229 0.448 0.876 1.073 1.568 0.647 0.904 0.196 0.485 µs 8.616 28.16

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 -512.451 -512.207 -509.750 -433.121 -276.459 -267.853 -264.816 233.291 244.354 87.757 -410.662 ppb -200 1229
Local Clock Time Offset -1.118 -0.783 -0.467 0.369 1.178 1.506 1.865 1.645 2.289 0.499 0.355 µs -0.8847 3.26
Local RMS Frequency Jitter 57.000 69.000 79.000 125.000 237.000 268.000 304.000 158.000 199.000 50.684 141.171 10e-12 11.8 37.27
Local RMS Time Jitter 240.000 282.000 324.000 469.000 719.000 826.000 972.000 395.000 544.000 120.587 487.896 ns 38.17 154.6
Server Jitter 137.190.2.4 0.203 0.266 0.345 1.976 9.157 12.554 12.559 8.812 12.289 3.007 2.929 ms 1.325 3.728
Server Jitter 192.168.1.12 0.021 0.033 0.051 0.170 8.679 11.108 13.293 8.628 11.075 2.673 1.255 ms 0.7572 4.539
Server Jitter 216.218.192.202 0.186 0.195 0.351 1.665 8.975 11.691 11.841 8.624 11.496 2.868 2.690 ms 1.474 4.273
Server Jitter 216.218.254.202 0.208 0.234 0.413 1.533 9.616 12.883 13.048 9.203 12.649 3.418 3.063 ms 1.172 3.334
Server Jitter 73.158.5.1 0.591 0.607 0.876 2.033 9.576 14.792 14.909 8.700 14.185 3.068 3.108 ms 2.155 7.043
Server Jitter SHM(0) 0.089 0.259 0.393 1.081 3.048 5.579 16.692 2.655 5.320 1.018 1.364 ms 3.783 21.17
Server Jitter SHM(1) 0.104 0.169 0.229 0.448 0.876 1.073 1.568 0.647 0.904 0.196 0.485 µs 8.616 28.16
Server Offset 137.190.2.4 1.159 1.163 1.447 1.782 2.296 2.650 2.654 0.849 1.487 0.250 1.784 ms 249.1 1655
Server Offset 192.168.1.12 30.089 51.738 84.407 136.082 178.258 192.228 226.226 93.851 140.490 29.741 135.152 µs 54.8 231.4
Server Offset 216.218.192.202 1.783 1.886 2.022 2.398 2.782 2.937 2.994 0.760 1.052 0.222 2.398 ms 972.8 9833
Server Offset 216.218.254.202 0.891 1.694 1.915 2.368 2.769 3.127 3.128 0.853 1.433 0.286 2.362 ms 403.5 3077
Server Offset 73.158.5.1 -1.604 -1.046 -0.397 0.355 1.053 1.540 2.353 1.450 2.586 0.502 0.299 ms -1.284 6.506
Server Offset SHM(0) -69.301 -57.009 -54.784 -47.397 -42.168 -40.540 -38.329 12.616 16.470 3.843 -47.925 ms -2485 3.403e+04
Server Offset SHM(1) -1.119 -0.784 -0.468 0.370 1.179 1.507 1.866 1.647 2.291 0.500 0.355 µs -0.8869 3.261
TDOP 0.530 0.540 0.600 0.850 1.480 1.730 1.810 0.880 1.190 0.271 0.901 20.69 76.84
Temp ZONE0 58.534 59.072 59.072 61.224 62.300 62.300 62.300 3.228 3.228 1.204 61.025 °C
nSats 6.000 7.000 7.000 9.000 12.000 12.000 12.000 5.000 5.000 1.352 9.252 nSat 217.5 1381
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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