NTPsec

Pi/GR-601W

Report generated: Thu Jun 18 04:03:03 2020 UTC
Start Time: Wed Jun 17 04:03:01 2020 UTC
End Time: Thu Jun 18 04:03:01 2020 UTC
Report Period: 1.0 days
Warning: plots clipped

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 -894.264 -856.792 -707.362 139.198 198.378 207.033 210.977 905.740 1,063.825 281.004 -0.704 µs -5.794 19.21
Local Clock Frequency Offset -3.301 -3.244 -3.125 -2.485 -1.836 -1.560 -1.417 1.289 1.684 0.398 -2.478 ppm -398.5 3036

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 40.246 57.090 73.961 175.975 342.018 364.524 369.884 268.057 307.434 87.326 189.539 µs 5.503 13.87

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 32.727 37.210 42.356 59.732 99.806 102.932 116.025 57.450 65.722 18.959 65.970 ppb 23.22 82.01

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 -894.264 -856.792 -707.362 139.198 198.378 207.033 210.977 905.740 1,063.825 281.004 -0.704 µs -5.794 19.21

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 -3.301 -3.244 -3.125 -2.485 -1.836 -1.560 -1.417 1.289 1.684 0.398 -2.478 ppm -398.5 3036
Temp ZONE0 49.388 49.388 50.464 55.844 69.294 70.908 78.440 18.830 21.520 5.220 55.969 °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 7.000 8.000 10.000 12.000 13.000 14.000 4.000 6.000 1.305 9.796 nSat 295 2052
TDOP 0.590 0.660 0.770 1.180 2.090 3.220 5.830 1.320 2.560 0.461 1.270 12.75 52.99

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) 187.202 244.187 293.063 670.886 864.655 915.553 944.271 571.592 671.366 191.335 633.363 µs 18.78 58.05

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 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 -0.924 -0.681 -0.247 0.543 1.025 1.183 1.298 1.272 1.864 0.389 0.507 ms 0.06062 3.396

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 204.17.205.24 201.516 245.106 293.992 660.731 891.103 947.004 968.741 597.111 701.898 196.944 630.481 µs 16.94 51.53

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 -162.403 -5.782 82.120 506.559 785.433 842.555 943.113 703.313 848.337 217.538 470.626 µs 4.714 10.6

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 -0.858 -0.786 -0.512 0.192 1.379 1.604 1.732 1.891 2.390 0.575 0.299 ms -1.06 3.017

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) -17.050 -13.413 -7.262 0.335 8.883 12.167 14.295 16.145 25.580 5.144 0.288 ms -3.735 9.492

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) -894.265 -856.793 -707.363 139.199 198.379 207.034 210.978 905.742 1,063.827 281.005 -0.704 µs -5.794 19.21

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) 155.233 160.921 176.616 263.941 396.411 462.132 512.741 219.795 301.211 67.360 269.053 µs 36.61 147.1

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 86.752 115.197 149.580 257.031 396.966 460.527 533.561 247.386 345.330 81.610 266.025 µs 18.63 61.99

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 91.263 111.771 147.238 266.513 405.548 479.483 593.598 258.310 367.712 82.788 269.093 µs 18.5 62.05

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 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 42.673 91.573 128.582 265.874 442.665 529.269 681.247 314.083 437.696 99.010 275.671 µs 11.49 35.41

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 76.752 107.925 145.362 268.485 414.432 482.042 632.606 269.070 374.117 86.130 270.321 µs 16.55 54.3

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) 0.222 0.513 0.800 2.189 4.845 6.433 8.190 4.045 5.921 1.264 2.444 ms 4.693 14.42

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 0.003 0.005 0.135 0.797 1.010 1.026 0.793 1.006 0.268 0.248 ms 0.8865 3.278

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 -3.301 -3.244 -3.125 -2.485 -1.836 -1.560 -1.417 1.289 1.684 0.398 -2.478 ppm -398.5 3036
Local Clock Time Offset -894.264 -856.792 -707.362 139.198 198.378 207.033 210.977 905.740 1,063.825 281.004 -0.704 µs -5.794 19.21
Local RMS Frequency Jitter 32.727 37.210 42.356 59.732 99.806 102.932 116.025 57.450 65.722 18.959 65.970 ppb 23.22 82.01
Local RMS Time Jitter 40.246 57.090 73.961 175.975 342.018 364.524 369.884 268.057 307.434 87.326 189.539 µs 5.503 13.87
Server Jitter 2001:470:e815::23 (pi3.rellim.com) 155.233 160.921 176.616 263.941 396.411 462.132 512.741 219.795 301.211 67.360 269.053 µs 36.61 147.1
Server Jitter 204.17.205.1 86.752 115.197 149.580 257.031 396.966 460.527 533.561 247.386 345.330 81.610 266.025 µs 18.63 61.99
Server Jitter 204.17.205.24 91.263 111.771 147.238 266.513 405.548 479.483 593.598 258.310 367.712 82.788 269.093 µs 18.5 62.05
Server Jitter 204.17.205.27 42.673 91.573 128.582 265.874 442.665 529.269 681.247 314.083 437.696 99.010 275.671 µs 11.49 35.41
Server Jitter 204.17.205.30 76.752 107.925 145.362 268.485 414.432 482.042 632.606 269.070 374.117 86.130 270.321 µs 16.55 54.3
Server Jitter SHM(0) 0.222 0.513 0.800 2.189 4.845 6.433 8.190 4.045 5.921 1.264 2.444 ms 4.693 14.42
Server Jitter SHM(1) 0.002 0.003 0.005 0.135 0.797 1.010 1.026 0.793 1.006 0.268 0.248 ms 0.8865 3.278
Server Offset 2001:470:e815::23 (pi3.rellim.com) 187.202 244.187 293.063 670.886 864.655 915.553 944.271 571.592 671.366 191.335 633.363 µs 18.78 58.05
Server Offset 204.17.205.1 -0.924 -0.681 -0.247 0.543 1.025 1.183 1.298 1.272 1.864 0.389 0.507 ms 0.06062 3.396
Server Offset 204.17.205.24 201.516 245.106 293.992 660.731 891.103 947.004 968.741 597.111 701.898 196.944 630.481 µs 16.94 51.53
Server Offset 204.17.205.27 -162.403 -5.782 82.120 506.559 785.433 842.555 943.113 703.313 848.337 217.538 470.626 µs 4.714 10.6
Server Offset 204.17.205.30 -0.858 -0.786 -0.512 0.192 1.379 1.604 1.732 1.891 2.390 0.575 0.299 ms -1.06 3.017
Server Offset SHM(0) -17.050 -13.413 -7.262 0.335 8.883 12.167 14.295 16.145 25.580 5.144 0.288 ms -3.735 9.492
Server Offset SHM(1) -894.265 -856.793 -707.363 139.199 198.379 207.034 210.978 905.742 1,063.827 281.005 -0.704 µs -5.794 19.21
TDOP 0.590 0.660 0.770 1.180 2.090 3.220 5.830 1.320 2.560 0.461 1.270 12.75 52.99
Temp ZONE0 49.388 49.388 50.464 55.844 69.294 70.908 78.440 18.830 21.520 5.220 55.969 °C
nSats 6.000 7.000 8.000 10.000 12.000 13.000 14.000 4.000 6.000 1.305 9.796 nSat 295 2052
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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