NTPsec

A-ntpsec-12-hour-stats

Report generated: Mon Nov 30 04:01:33 2020 UTC
Start Time: Sun Nov 29 16:01:32 2020 UTC
End Time: Mon Nov 30 04:01:32 2020 UTC
Report published: Sun Nov 29 20:01:38 2020 PST
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 -1.505 -1.048 -0.776 -0.070 0.653 1.033 1.475 1.429 2.081 0.442 -0.063 µs -4.821 12.15
Local Clock Frequency Offset -252.762 -252.457 -245.865 -218.033 -179.520 -178.986 -178.513 66.345 73.471 22.700 -209.033 ppb -1094 1.149e+04

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 199.000 247.000 308.000 461.000 692.000 810.000 1,037.000 384.000 563.000 115.175 474.284 ns 40.4 166.1

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 50.000 57.000 66.000 95.000 173.000 212.000 249.000 107.000 155.000 33.151 104.063 10e-12 17.52 64.46

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 -1.505 -1.048 -0.776 -0.070 0.653 1.033 1.475 1.429 2.081 0.442 -0.063 µs -4.821 12.15

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 -252.762 -252.457 -245.865 -218.033 -179.520 -178.986 -178.513 66.345 73.471 22.700 -209.033 ppb -1094 1.149e+04
Temp ZONE0 55.844 55.844 56.382 57.996 59.072 59.072 59.610 2.690 3.228 0.976 57.899 °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 7.000 8.000 8.000 9.000 11.000 12.000 12.000 3.000 4.000 0.999 9.360 nSat 611.7 5346
TDOP 0.500 0.520 0.600 0.800 1.220 1.400 1.730 0.620 0.880 0.200 0.859 46.11 195.5

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 1.070 1.189 1.297 1.629 2.261 3.050 3.403 0.965 1.861 0.328 1.670 ms 82.78 425.8

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 -2.577 13.540 33.902 113.325 160.778 180.531 187.158 126.876 166.991 39.928 107.292 µs 9.436 24.7

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 1.973 2.070 2.175 2.451 4.486 7.177 20.553 2.311 5.107 1.636 2.733 ms 11.19 120.2

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 0.528 1.047 2.016 2.391 4.404 6.700 12.217 2.388 5.653 1.107 2.601 ms 12.1 88.8

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 -2.303 -1.915 -0.937 0.143 1.402 2.919 4.453 2.339 4.833 0.811 0.135 ms -1.8 9.457

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) -66.616 -58.064 -55.354 -49.634 -45.518 -44.293 -42.670 9.836 13.772 2.962 -49.959 ms -5759 1.039e+05

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) -1.506 -1.049 -0.777 -0.071 0.654 1.034 1.476 1.431 2.083 0.443 -0.063 µs -4.821 12.14

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 0.129 0.160 0.264 1.830 18.661 20.341 20.429 18.397 20.181 5.872 5.302 ms 0.7972 2.666

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 0.019 0.028 0.038 0.145 8.633 8.771 9.468 8.595 8.743 2.226 0.938 ms 0.9466 5.256

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 0.148 0.167 0.266 1.719 15.274 22.005 22.054 15.008 21.838 5.493 5.149 ms 0.7872 2.771

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 0.118 0.137 0.219 1.475 21.026 24.815 25.610 20.807 24.677 6.705 5.894 ms 0.7785 2.916

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 0.691 0.748 1.176 4.791 19.788 57.968 75.036 18.612 57.220 10.833 7.932 ms 2.921 16.37

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) 0.046 0.302 0.449 1.183 3.028 5.260 13.644 2.579 4.958 0.958 1.425 ms 4.006 20.44

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) 0.111 0.172 0.225 0.438 0.847 1.067 1.583 0.622 0.895 0.193 0.472 µs 8.556 28.59

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 -252.762 -252.457 -245.865 -218.033 -179.520 -178.986 -178.513 66.345 73.471 22.700 -209.033 ppb -1094 1.149e+04
Local Clock Time Offset -1.505 -1.048 -0.776 -0.070 0.653 1.033 1.475 1.429 2.081 0.442 -0.063 µs -4.821 12.15
Local RMS Frequency Jitter 50.000 57.000 66.000 95.000 173.000 212.000 249.000 107.000 155.000 33.151 104.063 10e-12 17.52 64.46
Local RMS Time Jitter 199.000 247.000 308.000 461.000 692.000 810.000 1,037.000 384.000 563.000 115.175 474.284 ns 40.4 166.1
Server Jitter 137.190.2.4 0.129 0.160 0.264 1.830 18.661 20.341 20.429 18.397 20.181 5.872 5.302 ms 0.7972 2.666
Server Jitter 192.168.1.12 0.019 0.028 0.038 0.145 8.633 8.771 9.468 8.595 8.743 2.226 0.938 ms 0.9466 5.256
Server Jitter 216.218.192.202 0.148 0.167 0.266 1.719 15.274 22.005 22.054 15.008 21.838 5.493 5.149 ms 0.7872 2.771
Server Jitter 216.218.254.202 0.118 0.137 0.219 1.475 21.026 24.815 25.610 20.807 24.677 6.705 5.894 ms 0.7785 2.916
Server Jitter 73.158.5.1 0.691 0.748 1.176 4.791 19.788 57.968 75.036 18.612 57.220 10.833 7.932 ms 2.921 16.37
Server Jitter SHM(0) 0.046 0.302 0.449 1.183 3.028 5.260 13.644 2.579 4.958 0.958 1.425 ms 4.006 20.44
Server Jitter SHM(1) 0.111 0.172 0.225 0.438 0.847 1.067 1.583 0.622 0.895 0.193 0.472 µs 8.556 28.59
Server Offset 137.190.2.4 1.070 1.189 1.297 1.629 2.261 3.050 3.403 0.965 1.861 0.328 1.670 ms 82.78 425.8
Server Offset 192.168.1.12 -2.577 13.540 33.902 113.325 160.778 180.531 187.158 126.876 166.991 39.928 107.292 µs 9.436 24.7
Server Offset 216.218.192.202 1.973 2.070 2.175 2.451 4.486 7.177 20.553 2.311 5.107 1.636 2.733 ms 11.19 120.2
Server Offset 216.218.254.202 0.528 1.047 2.016 2.391 4.404 6.700 12.217 2.388 5.653 1.107 2.601 ms 12.1 88.8
Server Offset 73.158.5.1 -2.303 -1.915 -0.937 0.143 1.402 2.919 4.453 2.339 4.833 0.811 0.135 ms -1.8 9.457
Server Offset SHM(0) -66.616 -58.064 -55.354 -49.634 -45.518 -44.293 -42.670 9.836 13.772 2.962 -49.959 ms -5759 1.039e+05
Server Offset SHM(1) -1.506 -1.049 -0.777 -0.071 0.654 1.034 1.476 1.431 2.083 0.443 -0.063 µs -4.821 12.14
TDOP 0.500 0.520 0.600 0.800 1.220 1.400 1.730 0.620 0.880 0.200 0.859 46.11 195.5
Temp ZONE0 55.844 55.844 56.382 57.996 59.072 59.072 59.610 2.690 3.228 0.976 57.899 °C
nSats 7.000 8.000 8.000 9.000 11.000 12.000 12.000 3.000 4.000 0.999 9.360 nSat 611.7 5346
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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