NTPsec

sam.ljay.org.uk

Report generated: Thu Apr 2 22:00:01 2020 UTC
Start Time: Wed Apr 1 22:00:01 2020 UTC
End Time: Thu Apr 2 22:00:01 2020 UTC
Report Period: 1.0 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 -580.938 -42.859 -14.100 -1.524 14.621 21.686 594.663 28.721 64.545 20.412 -0.858 µs -2.558 476.5
Local Clock Frequency Offset 10.638 10.647 10.672 10.834 10.909 11.429 12.241 0.237 0.782 0.139 10.820 ppm 4.582e+05 3.534e+07

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 2.651 3.934 5.647 10.224 16.030 69.473 441.291 10.383 65.539 20.414 12.267 µs 11.49 173.2

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 0.511 0.761 1.066 1.938 3.500 26.518 412.418 2.434 25.757 16.131 3.324 ppb 14.39 290.4

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 -580.938 -42.859 -14.100 -1.524 14.621 21.686 594.663 28.721 64.545 20.412 -0.858 µs -2.558 476.5

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 10.638 10.647 10.672 10.834 10.909 11.429 12.241 0.237 0.782 0.139 10.820 ppm 4.582e+05 3.534e+07
Temp LM0 40.000 40.000 40.000 41.000 41.000 41.000 41.000 1.000 1.000 0.500 40.516 °C
Temp LM1 19.000 19.000 20.000 21.000 22.000 22.000 23.000 2.000 3.000 0.773 20.612 °C
Temp LM2 34.000 34.000 34.000 35.000 35.000 35.000 35.000 1.000 1.000 0.477 34.651 °C
Temp LM3 34.000 34.000 34.000 35.000 36.000 36.000 36.000 2.000 2.000 0.528 34.862 °C
Temp LM4 33.000 33.000 33.000 34.000 34.000 35.000 35.000 1.000 2.000 0.368 33.886 °C
Temp LM5 27.800 27.800 27.800 27.800 27.800 27.800 27.800 0.000 0.000 0.000 27.800 °C
Temp LM6 29.800 29.800 29.800 29.800 29.800 29.800 29.800 0.000 0.000 0.000 29.800 °C
Temp LM7 29.000 30.000 30.000 32.000 33.000 33.000 34.000 3.000 3.000 0.817 31.758 °C
Temp LM8 29.000 30.000 30.000 32.000 33.000 33.000 34.000 3.000 3.000 0.815 31.751 °C
Temp LM9 27.000 27.000 28.000 29.000 31.000 32.000 32.000 3.000 5.000 1.057 29.426 °C
Temp ZONE0 29.800 29.800 29.800 29.800 29.800 29.800 29.800 0.000 0.000 0.000 29.800 °C
Temp ZONE1 30.000 30.000 30.000 32.000 33.000 34.000 34.000 3.000 4.000 0.867 31.858 °C
Temp ZONE2 27.800 27.800 27.800 27.800 27.800 27.800 27.800 0.000 0.000 0.000 27.800 °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.



Local GPS

local gps plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
nSats 3.000 3.000 3.000 6.000 8.000 9.000 10.000 5.000 6.000 1.410 6.062 nSat 45.47 182.3
TDOP 0.000 0.000 0.000 1.300 3.750 7.640 18.820 3.750 7.640 1.505 1.642 6.308 64.59

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. TDOP ranges from 1 to greater than 20. 1 denotes the highest possible confidence level. 2 to 5 is good. Greater than 20 means there will be significant inaccuracy and error.



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.



Refclock Offset 127.127.28.0 SHM(0)

peer offset 127.127.28.0 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Refclock Offset 127.127.28.0 SHM(0) -101.151 -86.347 -66.654 -11.474 60.061 103.871 133.862 126.715 190.218 37.922 -9.461 ms -5.176 12.76

The offset of a local refclock in seconds. This is useful to see how the measured offset is behaving.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local serial GPS 200 ms; local PPS 20µs.

Clock Offset is field 5 in the peerstats log file.



Refclock Offset 127.127.28.1 SHM(1)

peer offset 127.127.28.1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Refclock Offset 127.127.28.1 SHM(1) -101.820 -40.758 -14.083 -1.524 14.622 21.687 594.664 28.705 62.445 17.270 -0.647 µs 11.5 447.9

The offset of a local refclock in seconds. This is useful to see how the measured offset is behaving.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local serial GPS 200 ms; local PPS 20µs.

Clock Offset is field 5 in the peerstats log file.



Server Offset 193.67.79.202

peer offset 193.67.79.202 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 193.67.79.202 -853.256 -847.035 -781.879 -632.617 -475.179 -428.844 -402.122 306.700 418.191 92.818 -628.961 µs -493.6 4024

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 2001:440:1880:1000::20

peer offset 2001:440:1880:1000::20 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2001:440:1880:1000::20 -851.748 -838.772 -788.604 -644.070 -486.173 -372.099 -332.548 302.431 466.673 95.075 -641.594 µs -488.1 3959

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 2001:8b0:0:23::205 (ntp2.aa.net.uk)

peer offset 2001:8b0:0:23::205 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2001:8b0:0:23::205 (ntp2.aa.net.uk) -728.868 -688.577 -592.307 -333.099 -175.467 49.188 247.309 416.840 737.765 133.568 -348.628 µs -57.94 253.4

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 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.



Refclock RMS Jitter 127.127.28.0 SHM(0)

peer jitter 127.127.28.0 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Refclock RMS Jitter 127.127.28.0 SHM(0) 0.000 2.555 3.449 8.276 21.259 30.257 51.258 17.810 27.702 5.932 9.803 ms 3.958 14.73

The RMS Jitter of a local refclock. 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.



Refclock RMS Jitter 127.127.28.1 SHM(1)

peer jitter 127.127.28.1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Refclock RMS Jitter 127.127.28.1 SHM(1) 0.119 1.742 3.144 9.656 20.426 28.964 361.624 17.282 27.222 12.694 11.011 µs 18.32 437.7

The RMS Jitter of a local refclock. 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 193.67.79.202

peer jitter 193.67.79.202 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 193.67.79.202 0.040 0.061 0.080 0.348 0.903 2.770 3.110 0.823 2.709 0.453 0.429 ms 3.517 19.22

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 2001:440:1880:1000::20

peer jitter 2001:440:1880:1000::20 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2001:440:1880:1000::20 0.039 0.053 0.074 0.320 2.143 6.680 24.948 2.069 6.627 2.167 0.682 ms 7.353 83.08

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 2001:8b0:0:23::205 (ntp2.aa.net.uk)

peer jitter 2001:8b0:0:23::205 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2001:8b0:0:23::205 (ntp2.aa.net.uk) 0.056 0.063 0.078 0.366 0.843 1.176 2.114 0.765 1.113 0.291 0.403 ms 2.803 12.64

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 10.638 10.647 10.672 10.834 10.909 11.429 12.241 0.237 0.782 0.139 10.820 ppm 4.582e+05 3.534e+07
Local Clock Time Offset -580.938 -42.859 -14.100 -1.524 14.621 21.686 594.663 28.721 64.545 20.412 -0.858 µs -2.558 476.5
Local RMS Frequency Jitter 0.511 0.761 1.066 1.938 3.500 26.518 412.418 2.434 25.757 16.131 3.324 ppb 14.39 290.4
Local RMS Time Jitter 2.651 3.934 5.647 10.224 16.030 69.473 441.291 10.383 65.539 20.414 12.267 µs 11.49 173.2
Refclock Offset 127.127.28.0 SHM(0) -101.151 -86.347 -66.654 -11.474 60.061 103.871 133.862 126.715 190.218 37.922 -9.461 ms -5.176 12.76
Refclock Offset 127.127.28.1 SHM(1) -101.820 -40.758 -14.083 -1.524 14.622 21.687 594.664 28.705 62.445 17.270 -0.647 µs 11.5 447.9
Refclock RMS Jitter 127.127.28.0 SHM(0) 0.000 2.555 3.449 8.276 21.259 30.257 51.258 17.810 27.702 5.932 9.803 ms 3.958 14.73
Refclock RMS Jitter 127.127.28.1 SHM(1) 0.119 1.742 3.144 9.656 20.426 28.964 361.624 17.282 27.222 12.694 11.011 µs 18.32 437.7
Server Jitter 193.67.79.202 0.040 0.061 0.080 0.348 0.903 2.770 3.110 0.823 2.709 0.453 0.429 ms 3.517 19.22
Server Jitter 2001:440:1880:1000::20 0.039 0.053 0.074 0.320 2.143 6.680 24.948 2.069 6.627 2.167 0.682 ms 7.353 83.08
Server Jitter 2001:8b0:0:23::205 (ntp2.aa.net.uk) 0.056 0.063 0.078 0.366 0.843 1.176 2.114 0.765 1.113 0.291 0.403 ms 2.803 12.64
Server Offset 193.67.79.202 -853.256 -847.035 -781.879 -632.617 -475.179 -428.844 -402.122 306.700 418.191 92.818 -628.961 µs -493.6 4024
Server Offset 2001:440:1880:1000::20 -851.748 -838.772 -788.604 -644.070 -486.173 -372.099 -332.548 302.431 466.673 95.075 -641.594 µs -488.1 3959
Server Offset 2001:8b0:0:23::205 (ntp2.aa.net.uk) -728.868 -688.577 -592.307 -333.099 -175.467 49.188 247.309 416.840 737.765 133.568 -348.628 µs -57.94 253.4
TDOP 0.000 0.000 0.000 1.300 3.750 7.640 18.820 3.750 7.640 1.505 1.642 6.308 64.59
Temp LM0 40.000 40.000 40.000 41.000 41.000 41.000 41.000 1.000 1.000 0.500 40.516 °C
Temp LM1 19.000 19.000 20.000 21.000 22.000 22.000 23.000 2.000 3.000 0.773 20.612 °C
Temp LM2 34.000 34.000 34.000 35.000 35.000 35.000 35.000 1.000 1.000 0.477 34.651 °C
Temp LM3 34.000 34.000 34.000 35.000 36.000 36.000 36.000 2.000 2.000 0.528 34.862 °C
Temp LM4 33.000 33.000 33.000 34.000 34.000 35.000 35.000 1.000 2.000 0.368 33.886 °C
Temp LM5 27.800 27.800 27.800 27.800 27.800 27.800 27.800 0.000 0.000 0.000 27.800 °C
Temp LM6 29.800 29.800 29.800 29.800 29.800 29.800 29.800 0.000 0.000 0.000 29.800 °C
Temp LM7 29.000 30.000 30.000 32.000 33.000 33.000 34.000 3.000 3.000 0.817 31.758 °C
Temp LM8 29.000 30.000 30.000 32.000 33.000 33.000 34.000 3.000 3.000 0.815 31.751 °C
Temp LM9 27.000 27.000 28.000 29.000 31.000 32.000 32.000 3.000 5.000 1.057 29.426 °C
Temp ZONE0 29.800 29.800 29.800 29.800 29.800 29.800 29.800 0.000 0.000 0.000 29.800 °C
Temp ZONE1 30.000 30.000 30.000 32.000 33.000 34.000 34.000 3.000 4.000 0.867 31.858 °C
Temp ZONE2 27.800 27.800 27.800 27.800 27.800 27.800 27.800 0.000 0.000 0.000 27.800 °C
nSats 3.000 3.000 3.000 6.000 8.000 9.000 10.000 5.000 6.000 1.410 6.062 nSat 45.47 182.3
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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