NTPsec

A-ntpsec-1-hour-stats

Report generated: Mon Dec 6 21:02:07 2021 UTC
Start Time: Mon Dec 6 20:01:39 2021 UTC
End Time: Mon Dec 6 21:02:07 2021 UTC
Report published: Mon Dec 06 13:02:11 2021 PST
Report Period: 0.0 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 -1,122.000 -922.000 -695.000 -117.000 340.000 690.000 866.000 1,035.000 1,612.000 341.813 -129.867 ns -6.934 19.03
Local Clock Frequency Offset -112.595 -112.396 -111.710 -107.697 -105.652 -105.469 -105.347 6.058 6.927 1.973 -108.252 ppb -1.745e+05 9.761e+06

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 294.000 303.000 316.000 424.000 605.000 651.000 658.000 289.000 348.000 94.669 441.128 ns 60.45 268.5

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 60.000 61.000 66.000 86.000 115.000 126.000 143.000 49.000 65.000 15.614 88.407 10e-12 115.8 614.1

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 -1,122.000 -922.000 -695.000 -117.000 340.000 690.000 866.000 1,035.000 1,612.000 341.813 -129.867 ns -6.934 19.03

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 -112.595 -112.396 -111.710 -107.697 -105.652 -105.469 -105.347 6.058 6.927 1.973 -108.252 ppb -1.745e+05 9.761e+06
Temp ZONE0 57.458 57.458 57.458 57.996 58.534 58.534 58.534 1.076 1.076 0.193 57.996 °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 6.000 6.000 7.000 9.000 9.000 9.000 3.000 3.000 1.092 7.770 nSat 246.8 1621
TDOP 0.680 0.680 0.690 1.360 1.720 1.790 1.790 1.030 1.110 0.381 1.132 13.62 40.33

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 1.073 1.073 1.073 1.213 1.344 1.344 1.344 0.270 0.270 0.077 1.228 ms 3319 4.995e+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 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 -161.077 -161.077 -92.948 29.634 67.201 71.966 71.966 160.149 233.043 49.773 14.555 µs -3.807 11.72

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 2.480 2.480 2.480 2.668 2.860 2.860 2.860 0.380 0.380 0.091 2.663 ms 2.267e+04 6.431e+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 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 2.461 2.461 2.461 2.626 2.701 2.701 2.701 0.240 0.240 0.077 2.591 ms 3.54e+04 1.164e+06

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) -53.284 -52.491 -51.686 -48.546 -46.367 -45.940 -45.778 5.319 6.551 1.688 -48.675 ms -2.667e+04 7.987e+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) -1,123.000 -923.000 -696.000 -118.000 341.000 691.000 867.000 1,037.000 1,614.000 342.546 -130.155 ns -6.931 19.01

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 0.249 0.249 0.249 5.294 13.739 13.739 13.739 13.490 13.490 3.333 4.712 ms 2.316 7.556

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 19.554 19.554 20.233 88.933 239.060 264.747 264.747 218.827 245.193 61.228 96.568 µs 2.991 8.022

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 0.292 0.292 0.292 1.048 21.731 21.731 21.731 21.440 21.440 8.575 5.339 ms 0.194 1.716

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 0.278 0.278 0.278 4.696 18.640 18.640 18.640 18.362 18.362 7.223 6.554 ms 0.6486 1.869

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) 0.190 0.263 0.424 1.013 2.702 3.712 4.023 2.279 3.450 0.712 1.251 ms 4.018 12.6

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) 0.200 0.205 0.234 0.433 0.768 1.055 1.123 0.534 0.850 0.168 0.453 µs 11.11 38.33

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 -112.595 -112.396 -111.710 -107.697 -105.652 -105.469 -105.347 6.058 6.927 1.973 -108.252 ppb -1.745e+05 9.761e+06
Local Clock Time Offset -1,122.000 -922.000 -695.000 -117.000 340.000 690.000 866.000 1,035.000 1,612.000 341.813 -129.867 ns -6.934 19.03
Local RMS Frequency Jitter 60.000 61.000 66.000 86.000 115.000 126.000 143.000 49.000 65.000 15.614 88.407 10e-12 115.8 614.1
Local RMS Time Jitter 294.000 303.000 316.000 424.000 605.000 651.000 658.000 289.000 348.000 94.669 441.128 ns 60.45 268.5
Server Jitter 137.190.2.4 0.249 0.249 0.249 5.294 13.739 13.739 13.739 13.490 13.490 3.333 4.712 ms 2.316 7.556
Server Jitter 192.168.1.12 19.554 19.554 20.233 88.933 239.060 264.747 264.747 218.827 245.193 61.228 96.568 µs 2.991 8.022
Server Jitter 216.218.192.202 0.292 0.292 0.292 1.048 21.731 21.731 21.731 21.440 21.440 8.575 5.339 ms 0.194 1.716
Server Jitter 216.218.254.202 0.278 0.278 0.278 4.696 18.640 18.640 18.640 18.362 18.362 7.223 6.554 ms 0.6486 1.869
Server Jitter SHM(0) 0.190 0.263 0.424 1.013 2.702 3.712 4.023 2.279 3.450 0.712 1.251 ms 4.018 12.6
Server Jitter SHM(1) 0.200 0.205 0.234 0.433 0.768 1.055 1.123 0.534 0.850 0.168 0.453 µs 11.11 38.33
Server Offset 137.190.2.4 1.073 1.073 1.073 1.213 1.344 1.344 1.344 0.270 0.270 0.077 1.228 ms 3319 4.995e+04
Server Offset 192.168.1.12 -161.077 -161.077 -92.948 29.634 67.201 71.966 71.966 160.149 233.043 49.773 14.555 µs -3.807 11.72
Server Offset 216.218.192.202 2.480 2.480 2.480 2.668 2.860 2.860 2.860 0.380 0.380 0.091 2.663 ms 2.267e+04 6.431e+05
Server Offset 216.218.254.202 2.461 2.461 2.461 2.626 2.701 2.701 2.701 0.240 0.240 0.077 2.591 ms 3.54e+04 1.164e+06
Server Offset SHM(0) -53.284 -52.491 -51.686 -48.546 -46.367 -45.940 -45.778 5.319 6.551 1.688 -48.675 ms -2.667e+04 7.987e+05
Server Offset SHM(1) -1,123.000 -923.000 -696.000 -118.000 341.000 691.000 867.000 1,037.000 1,614.000 342.546 -130.155 ns -6.931 19.01
TDOP 0.680 0.680 0.690 1.360 1.720 1.790 1.790 1.030 1.110 0.381 1.132 13.62 40.33
Temp ZONE0 57.458 57.458 57.458 57.996 58.534 58.534 58.534 1.076 1.076 0.193 57.996 °C
nSats 6.000 6.000 6.000 7.000 9.000 9.000 9.000 3.000 3.000 1.092 7.770 nSat 246.8 1621
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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