NTPsec

A-ntpsec-24-hour-stats

Report generated: Tue Apr 20 12:01:55 2021 UTC
Start Time: Mon Apr 19 12:01:54 2021 UTC
End Time: Tue Apr 20 12:01:54 2021 UTC
Report published: Tue Apr 20 05:02:03 2021 PDT
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 -2.107 -1.269 -0.694 0.045 0.646 0.885 1.497 1.340 2.154 0.418 0.018 µs -4.417 13.44
Local Clock Frequency Offset -234.207 -233.902 -230.667 -180.176 -153.427 -152.664 -151.733 77.240 81.238 26.799 -186.079 ppb -525.4 4374

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 199.000 240.000 275.000 453.000 783.000 930.000 1,209.000 508.000 690.000 155.552 479.891 ns 16.21 56.11

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 39.000 51.000 62.000 95.000 150.000 173.000 217.000 88.000 122.000 26.905 99.016 10e-12 28 105.7

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 -2.107 -1.269 -0.694 0.045 0.646 0.885 1.497 1.340 2.154 0.418 0.018 µs -4.417 13.44

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 -234.207 -233.902 -230.667 -180.176 -153.427 -152.664 -151.733 77.240 81.238 26.799 -186.079 ppb -525.4 4374
Temp ZONE0 56.920 56.920 56.920 57.996 59.610 60.148 60.148 2.690 3.228 0.783 58.279 °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 1.386 9.321 nSat 204.5 1268
TDOP 0.540 0.560 0.600 0.850 1.290 1.600 2.020 0.690 1.040 0.221 0.880 37.12 158.2

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 -0.735 0.684 0.853 1.157 1.438 1.517 1.601 0.585 0.833 0.202 1.143 ms 111.5 570.9

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 -217.081 -142.867 -89.784 56.567 156.479 200.773 257.533 246.263 343.640 73.336 48.194 µs -1.513 4.43

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 1.632 1.885 2.102 2.326 2.581 2.723 2.852 0.479 0.838 0.155 2.335 ms 2820 4.023e+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 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 0.779 2.034 2.140 2.337 2.570 2.760 3.542 0.431 0.726 0.188 2.346 ms 1559 1.832e+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 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 -2.373 -2.253 -1.516 -0.260 0.561 0.903 2.862 2.077 3.156 0.666 -0.343 ms -8.253 25.04

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(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) -84.440 -56.383 -54.125 -49.148 -43.888 -42.146 -40.533 10.237 14.237 3.179 -49.022 ms -4478 7.435e+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) -2.108 -1.270 -0.695 0.046 0.647 0.886 1.498 1.342 2.156 0.419 0.018 µs -4.414 13.42

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 0.140 0.161 0.233 1.245 9.328 14.684 15.779 9.095 14.523 3.338 2.787 ms 1.211 4.269

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 0.023 0.043 0.064 0.182 8.662 8.919 12.313 8.597 8.876 2.613 1.417 ms 0.6955 3.675

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 0.158 0.163 0.201 1.200 9.378 12.530 13.250 9.177 12.367 3.172 2.564 ms 1.104 3.684

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 0.103 0.144 0.178 0.937 9.069 17.738 18.046 8.891 17.594 3.569 2.514 ms 1.319 5.946

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 0.697 0.771 1.030 2.558 10.824 18.580 60.867 9.794 17.808 4.883 4.277 ms 5.599 60.28

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) 0.052 0.259 0.381 0.890 2.336 3.956 32.096 1.955 3.697 0.811 1.077 ms 7.211 113.6

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 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) 0.089 0.143 0.191 0.416 0.939 1.371 2.165 0.748 1.228 0.248 0.473 µs 5.1 18.79

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 -234.207 -233.902 -230.667 -180.176 -153.427 -152.664 -151.733 77.240 81.238 26.799 -186.079 ppb -525.4 4374
Local Clock Time Offset -2.107 -1.269 -0.694 0.045 0.646 0.885 1.497 1.340 2.154 0.418 0.018 µs -4.417 13.44
Local RMS Frequency Jitter 39.000 51.000 62.000 95.000 150.000 173.000 217.000 88.000 122.000 26.905 99.016 10e-12 28 105.7
Local RMS Time Jitter 199.000 240.000 275.000 453.000 783.000 930.000 1,209.000 508.000 690.000 155.552 479.891 ns 16.21 56.11
Server Jitter 137.190.2.4 0.140 0.161 0.233 1.245 9.328 14.684 15.779 9.095 14.523 3.338 2.787 ms 1.211 4.269
Server Jitter 192.168.1.12 0.023 0.043 0.064 0.182 8.662 8.919 12.313 8.597 8.876 2.613 1.417 ms 0.6955 3.675
Server Jitter 216.218.192.202 0.158 0.163 0.201 1.200 9.378 12.530 13.250 9.177 12.367 3.172 2.564 ms 1.104 3.684
Server Jitter 216.218.254.202 0.103 0.144 0.178 0.937 9.069 17.738 18.046 8.891 17.594 3.569 2.514 ms 1.319 5.946
Server Jitter 73.158.5.1 0.697 0.771 1.030 2.558 10.824 18.580 60.867 9.794 17.808 4.883 4.277 ms 5.599 60.28
Server Jitter SHM(0) 0.052 0.259 0.381 0.890 2.336 3.956 32.096 1.955 3.697 0.811 1.077 ms 7.211 113.6
Server Jitter SHM(1) 0.089 0.143 0.191 0.416 0.939 1.371 2.165 0.748 1.228 0.248 0.473 µs 5.1 18.79
Server Offset 137.190.2.4 -0.735 0.684 0.853 1.157 1.438 1.517 1.601 0.585 0.833 0.202 1.143 ms 111.5 570.9
Server Offset 192.168.1.12 -217.081 -142.867 -89.784 56.567 156.479 200.773 257.533 246.263 343.640 73.336 48.194 µs -1.513 4.43
Server Offset 216.218.192.202 1.632 1.885 2.102 2.326 2.581 2.723 2.852 0.479 0.838 0.155 2.335 ms 2820 4.023e+04
Server Offset 216.218.254.202 0.779 2.034 2.140 2.337 2.570 2.760 3.542 0.431 0.726 0.188 2.346 ms 1559 1.832e+04
Server Offset 73.158.5.1 -2.373 -2.253 -1.516 -0.260 0.561 0.903 2.862 2.077 3.156 0.666 -0.343 ms -8.253 25.04
Server Offset SHM(0) -84.440 -56.383 -54.125 -49.148 -43.888 -42.146 -40.533 10.237 14.237 3.179 -49.022 ms -4478 7.435e+04
Server Offset SHM(1) -2.108 -1.270 -0.695 0.046 0.647 0.886 1.498 1.342 2.156 0.419 0.018 µs -4.414 13.42
TDOP 0.540 0.560 0.600 0.850 1.290 1.600 2.020 0.690 1.040 0.221 0.880 37.12 158.2
Temp ZONE0 56.920 56.920 56.920 57.996 59.610 60.148 60.148 2.690 3.228 0.783 58.279 °C
nSats 6.000 7.000 7.000 9.000 11.000 12.000 12.000 4.000 5.000 1.386 9.321 nSat 204.5 1268
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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