NTPsec

tock

Report generated: Sat Jan 25 17:15:44 2020 UTC
Start Time: Sat Jan 18 17:15:43 2020 UTC
End Time: Sat Jan 25 17:15:43 2020 UTC
Report Period: 7.0 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 -1,300.000 -607.000 -331.000 21.000 375.000 568.000 1,179.000 706.000 1,175.000 221.430 20.120 ns -3.714 11.18
Local Clock Frequency Offset -21.811 -21.801 -21.767 -21.670 -21.558 -21.556 -21.556 0.209 0.245 0.063 -21.670 ppm -4.083e+07 1.406e+10

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 74.000 113.000 132.000 189.000 264.000 299.000 410.000 132.000 186.000 40.059 192.531 ns 67.03 307.3

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 16.000 24.000 28.000 41.000 101.000 182.000 350.000 73.000 158.000 29.072 49.750 10e-12 6.292 37.87

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 -1,300.000 -607.000 -331.000 21.000 375.000 568.000 1,179.000 706.000 1,175.000 221.430 20.120 ns -3.714 11.18

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 -21.811 -21.801 -21.767 -21.670 -21.558 -21.556 -21.556 0.209 0.245 0.063 -21.670 ppm -4.083e+07 1.406e+10
Temp ZONE0 49.660 50.634 51.121 52.582 53.556 54.043 55.017 2.435 3.409 0.765 52.474 °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 5.000 5.000 5.000 7.000 8.000 9.000 9.000 3.000 4.000 1.041 6.717 nSat 178.8 1068
TDOP 1.010 1.060 1.170 1.660 4.120 6.550 11.000 2.950 5.490 1.148 2.010 5.972 30.4

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.



Server Offset 10.4.2.51

peer offset 10.4.2.51 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 10.4.2.51 -110.629 -54.366 -49.744 -39.768 17.123 31.363 42.286 66.867 85.729 17.402 -35.420 µs -34.47 118.1

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 10.4.2.53

peer offset 10.4.2.53 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 10.4.2.53 -119.638 -88.837 -82.690 -70.210 -58.351 -53.362 -42.652 24.339 35.475 7.351 -70.350 µs -1213 1.316e+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 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) -1,301.000 -608.000 -332.000 22.000 375.000 569.000 1,180.000 707.000 1,177.000 222.147 20.209 ns -3.713 11.15

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 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) -26.068 -13.683 -9.696 3.197 15.709 19.391 26.438 25.405 33.074 7.773 3.104 ms -2.07 4.874

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 10.4.2.51

peer jitter 10.4.2.51 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 10.4.2.51 2.593 5.212 7.235 21.449 55.577 69.370 101.087 48.342 64.158 14.077 23.102 µs 3.533 11.26

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 10.4.2.53

peer jitter 10.4.2.53 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 10.4.2.53 2.728 5.925 8.357 18.443 32.052 44.938 522.100 23.695 39.013 10.685 19.177 µs 26.01 1136

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) 26.000 73.000 98.000 183.000 353.000 445.000 708.000 255.000 372.000 79.153 198.487 ns 9.087 30.51

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) 0.447 1.311 1.910 4.006 7.727 9.768 16.825 5.816 8.457 1.819 4.327 ms 7.749 25.02

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 -21.811 -21.801 -21.767 -21.670 -21.558 -21.556 -21.556 0.209 0.245 0.063 -21.670 ppm -4.083e+07 1.406e+10
Local Clock Time Offset -1,300.000 -607.000 -331.000 21.000 375.000 568.000 1,179.000 706.000 1,175.000 221.430 20.120 ns -3.714 11.18
Local RMS Frequency Jitter 16.000 24.000 28.000 41.000 101.000 182.000 350.000 73.000 158.000 29.072 49.750 10e-12 6.292 37.87
Local RMS Time Jitter 74.000 113.000 132.000 189.000 264.000 299.000 410.000 132.000 186.000 40.059 192.531 ns 67.03 307.3
Server Jitter 10.4.2.51 2.593 5.212 7.235 21.449 55.577 69.370 101.087 48.342 64.158 14.077 23.102 µs 3.533 11.26
Server Jitter 10.4.2.53 2.728 5.925 8.357 18.443 32.052 44.938 522.100 23.695 39.013 10.685 19.177 µs 26.01 1136
Server Jitter PPS(0) 26.000 73.000 98.000 183.000 353.000 445.000 708.000 255.000 372.000 79.153 198.487 ns 9.087 30.51
Server Jitter SHM(0) 0.447 1.311 1.910 4.006 7.727 9.768 16.825 5.816 8.457 1.819 4.327 ms 7.749 25.02
Server Offset 10.4.2.51 -110.629 -54.366 -49.744 -39.768 17.123 31.363 42.286 66.867 85.729 17.402 -35.420 µs -34.47 118.1
Server Offset 10.4.2.53 -119.638 -88.837 -82.690 -70.210 -58.351 -53.362 -42.652 24.339 35.475 7.351 -70.350 µs -1213 1.316e+04
Server Offset PPS(0) -1,301.000 -608.000 -332.000 22.000 375.000 569.000 1,180.000 707.000 1,177.000 222.147 20.209 ns -3.713 11.15
Server Offset SHM(0) -26.068 -13.683 -9.696 3.197 15.709 19.391 26.438 25.405 33.074 7.773 3.104 ms -2.07 4.874
TDOP 1.010 1.060 1.170 1.660 4.120 6.550 11.000 2.950 5.490 1.148 2.010 5.972 30.4
Temp ZONE0 49.660 50.634 51.121 52.582 53.556 54.043 55.017 2.435 3.409 0.765 52.474 °C
nSats 5.000 5.000 5.000 7.000 8.000 9.000 9.000 3.000 4.000 1.041 6.717 nSat 178.8 1068
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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