NTPsec

Pi/GR-601W

Report generated: Wed Jun 17 15:13:11 2020 UTC
Start Time: Wed Jun 10 15:13:01 2020 UTC
End Time: Wed Jun 17 15:13:01 2020 UTC
Report Period: 7.0 days

Daily stats   Weekly stats   24 Hour Scatter Plots: ( 1   2   3   )

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 -896.870 -838.681 -695.592 147.360 195.252 207.365 215.784 890.844 1,046.046 284.078 -0.013 µs -5.716 18.65
Local Clock Frequency Offset -3.366 -3.249 -3.090 -2.622 -2.058 -1.829 -1.443 1.032 1.420 0.314 -2.601 ppm -826 7916

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 38.211 69.085 84.604 178.229 343.920 364.804 370.326 259.316 295.719 84.911 194.862 µs 6.448 16.86

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 33.049 41.392 45.809 60.303 98.989 101.608 113.771 53.180 60.216 17.921 67.009 ppb 29.34 109.5

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 -896.870 -838.681 -695.592 147.360 195.252 207.365 215.784 890.844 1,046.046 284.078 -0.013 µs -5.716 18.65

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 -3.366 -3.249 -3.090 -2.622 -2.058 -1.829 -1.443 1.032 1.420 0.314 -2.601 ppm -826 7916
Temp ZONE0 49.388 49.926 50.464 53.692 58.534 68.756 77.364 8.070 18.830 3.203 54.447 °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 7.000 8.000 10.000 12.000 13.000 14.000 4.000 6.000 1.328 9.820 nSat 280.6 1922
TDOP 0.580 0.660 0.760 1.160 2.070 3.120 4.900 1.310 2.460 0.449 1.251 13.12 54.4

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. 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 2001:470:e815::23 (pi3.rellim.com)

peer offset 2001:470:e815::23 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2001:470:e815::23 (pi3.rellim.com) 195.240 253.265 289.757 658.741 846.136 884.591 970.470 556.379 631.326 183.541 622.859 µs 20.44 64.8

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 204.17.205.1

peer offset 204.17.205.1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 204.17.205.1 -1.247 -0.780 -0.349 0.552 1.093 1.383 1.600 1.441 2.163 0.429 0.489 ms -0.2988 3.572

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 204.17.205.24

peer offset 204.17.205.24 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 204.17.205.24 158.039 252.595 305.028 679.433 877.454 907.687 980.189 572.426 655.092 189.989 643.233 µs 20.27 64.09

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 204.17.205.27

peer offset 204.17.205.27 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 204.17.205.27 -80.953 101.247 225.900 578.021 817.781 843.321 923.091 591.881 742.074 200.973 553.093 µs 10.26 27.3

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 204.17.205.30

peer offset 204.17.205.30 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 204.17.205.30 -0.515 -0.034 0.265 0.676 1.073 1.538 2.354 0.808 1.573 0.282 0.656 ms 7.045 24.41

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) -18.460 -13.954 -7.934 -0.019 8.454 12.307 19.705 16.388 26.261 5.323 -0.073 ms -4.118 10.4

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 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) -896.871 -838.682 -695.593 147.361 195.253 207.366 215.785 890.846 1,046.048 284.079 -0.013 µs -5.716 18.65

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 2001:470:e815::23 (pi3.rellim.com)

peer jitter 2001:470:e815::23 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2001:470:e815::23 (pi3.rellim.com) 146.972 161.634 175.287 248.828 374.773 437.509 504.345 199.486 275.875 62.493 258.102 µs 40.83 167.9

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 204.17.205.1

peer jitter 204.17.205.1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 204.17.205.1 89.367 116.906 154.550 261.454 393.408 451.860 2,777.976 238.858 334.954 102.399 268.680 µs 18.57 289.5

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 204.17.205.24

peer jitter 204.17.205.24 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 204.17.205.24 76.710 116.065 151.696 262.333 395.662 438.974 547.647 243.966 322.909 78.717 266.415 µs 20.93 70.91

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 204.17.205.27

peer jitter 204.17.205.27 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 204.17.205.27 71.114 109.836 147.847 263.713 410.534 480.236 2,442.475 262.687 370.400 103.993 271.204 µs 16.16 208

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 204.17.205.30

peer jitter 204.17.205.30 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 204.17.205.30 89.662 113.732 149.371 261.930 390.197 457.770 2,413.844 240.826 344.038 97.290 268.591 µs 18.07 236.4

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) 0.198 0.598 0.887 2.192 4.949 6.678 11.319 4.062 6.080 1.283 2.453 ms 4.824 16.05

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) 0.002 0.004 0.004 0.171 0.797 1.009 1.020 0.792 1.006 0.268 0.258 ms 0.947 3.337

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 -3.366 -3.249 -3.090 -2.622 -2.058 -1.829 -1.443 1.032 1.420 0.314 -2.601 ppm -826 7916
Local Clock Time Offset -896.870 -838.681 -695.592 147.360 195.252 207.365 215.784 890.844 1,046.046 284.078 -0.013 µs -5.716 18.65
Local RMS Frequency Jitter 33.049 41.392 45.809 60.303 98.989 101.608 113.771 53.180 60.216 17.921 67.009 ppb 29.34 109.5
Local RMS Time Jitter 38.211 69.085 84.604 178.229 343.920 364.804 370.326 259.316 295.719 84.911 194.862 µs 6.448 16.86
Server Jitter 2001:470:e815::23 (pi3.rellim.com) 146.972 161.634 175.287 248.828 374.773 437.509 504.345 199.486 275.875 62.493 258.102 µs 40.83 167.9
Server Jitter 204.17.205.1 89.367 116.906 154.550 261.454 393.408 451.860 2,777.976 238.858 334.954 102.399 268.680 µs 18.57 289.5
Server Jitter 204.17.205.24 76.710 116.065 151.696 262.333 395.662 438.974 547.647 243.966 322.909 78.717 266.415 µs 20.93 70.91
Server Jitter 204.17.205.27 71.114 109.836 147.847 263.713 410.534 480.236 2,442.475 262.687 370.400 103.993 271.204 µs 16.16 208
Server Jitter 204.17.205.30 89.662 113.732 149.371 261.930 390.197 457.770 2,413.844 240.826 344.038 97.290 268.591 µs 18.07 236.4
Server Jitter SHM(0) 0.198 0.598 0.887 2.192 4.949 6.678 11.319 4.062 6.080 1.283 2.453 ms 4.824 16.05
Server Jitter SHM(1) 0.002 0.004 0.004 0.171 0.797 1.009 1.020 0.792 1.006 0.268 0.258 ms 0.947 3.337
Server Offset 2001:470:e815::23 (pi3.rellim.com) 195.240 253.265 289.757 658.741 846.136 884.591 970.470 556.379 631.326 183.541 622.859 µs 20.44 64.8
Server Offset 204.17.205.1 -1.247 -0.780 -0.349 0.552 1.093 1.383 1.600 1.441 2.163 0.429 0.489 ms -0.2988 3.572
Server Offset 204.17.205.24 158.039 252.595 305.028 679.433 877.454 907.687 980.189 572.426 655.092 189.989 643.233 µs 20.27 64.09
Server Offset 204.17.205.27 -80.953 101.247 225.900 578.021 817.781 843.321 923.091 591.881 742.074 200.973 553.093 µs 10.26 27.3
Server Offset 204.17.205.30 -0.515 -0.034 0.265 0.676 1.073 1.538 2.354 0.808 1.573 0.282 0.656 ms 7.045 24.41
Server Offset SHM(0) -18.460 -13.954 -7.934 -0.019 8.454 12.307 19.705 16.388 26.261 5.323 -0.073 ms -4.118 10.4
Server Offset SHM(1) -896.871 -838.682 -695.593 147.361 195.253 207.366 215.785 890.846 1,046.048 284.079 -0.013 µs -5.716 18.65
TDOP 0.580 0.660 0.760 1.160 2.070 3.120 4.900 1.310 2.460 0.449 1.251 13.12 54.4
Temp ZONE0 49.388 49.926 50.464 53.692 58.534 68.756 77.364 8.070 18.830 3.203 54.447 °C
nSats 5.000 7.000 8.000 10.000 12.000 13.000 14.000 4.000 6.000 1.328 9.820 nSat 280.6 1922
Summary as CSV file


This server:

Motherboard: Raspberry Pi 2
OS: Gentoo stable
GPS; GR-601W USB
GPS/PPS server: gpsd
NTP server: NTPsec
../ntp.conf

Notes:

22:00 29 Mar 2017 Updated kernel 4.4 to 4.9.17
00:00  3 Feb 2017 Upgraded from Pi B to Pi 2
19:30 15 Oct 2016 UTC precision -10 to -20

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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