NTPsec

Pi4/Uputronics

Report generated: Sun Dec 10 16:13:05 2017 UTC
Start Time: Sun Dec 3 16:13:01 2017 UTC
End Time: Sun Dec 10 16:13:01 2017 UTC
Report Period: 7.0 days

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

Local Clock Time/Frequency Offsets

local offset plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%95%StdDev  MeanUnits nessosis
Local Clock Time Offset-1,023.095-624.535-427.681-7.598409.550 640.0701,162.688837.2311,264.605234.586-7.621µs-4.065 11.82
Local Clock Frequency Offset-4.264-3.862-3.559-2.424-1.776 -1.1640.1711.7842.6970.618-2.559ppm -151 858.7

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%95%StdDev  MeanUnits nessosis
Local RMS Time Jitter13.47324.07037.786260.116483.793 586.440773.635446.007562.370145.971252.710µs 2.756 6.25

This shows 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%95%StdDev  MeanUnits nessosis
Local RMS Frequency Jitter5.33411.07415.89995.429205.975 261.602336.066190.076250.52859.94398.602ppb 2.767 7.134

This shows 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%95%StdDev  MeanUnits nessosis
Local Clock Offset-1,023.095-624.535-427.681-7.598409.550 640.0701,162.688837.2311,264.605234.586-7.621µs-4.065 11.82

This shows 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 on what temperature sensors you have and 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 the single most important component of frequency drift.

The Local Termperatures 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%95%StdDev  MeanUnits nessosis
Local Clock Frequency Offset-4.264-3.862-3.559-2.424-1.776 -1.1640.1711.7842.6970.618-2.559ppm -151 858.7
Temp ZONE045.08445.08445.62249.38851.540 53.69277.3645.9188.6082.64849.038°C

The frequency offsets and temperatures. Showing frequency offset (red, in parts per million, scale on right) and the temeratures.

These are field 4 (frequency) from the loopstats log file, and field 3 from the temp log .



Peer Offsets

peer offsets plot

This shows the offset of all refclocks, peers 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.



Peer Offset 2001:470:e815::8 (spidey.rellim.com)

peer offset 2001:470:e815::8 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%95%StdDev  MeanUnits nessosis
Peer Offset 2001:470:e815::8 (spidey.rellim.com)-1,110.887-484.949-242.176-0.968466.681 722.4151,121.176708.8571,207.364218.69443.834µs-2.248 7.568

This shows the offset of a peer or 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 remote. 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 peer 80µs; 90% ranges for WAN servers 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 file.



Peer Offset 204.17.205.1

peer offset 204.17.205.1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%95%StdDev  MeanUnits nessosis
Peer Offset 204.17.205.1-0.197-0.0310.0820.3440.833 1.0261.3490.7511.0570.2240.389ms 3.443 9.861

This shows the offset of a peer or 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 remote. 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 peer 80µs; 90% ranges for WAN servers 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 file.



Peer Offset 204.17.205.17

peer offset 204.17.205.17 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%95%StdDev  MeanUnits nessosis
Peer Offset 204.17.205.17-602.036-254.822-119.52146.698614.756 817.2041,261.457734.2771,072.026236.898143.362µs-0.2236 3.091

This shows the offset of a peer or 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 remote. 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 peer 80µs; 90% ranges for WAN servers 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 file.



Peer Offset 204.17.205.23

peer offset 204.17.205.23 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%95%StdDev  MeanUnits nessosis
Peer Offset 204.17.205.23-566.613-260.803-124.57838.847620.912 824.4311,311.329745.4901,085.234241.170140.646µs-0.2969 3.104

This shows the offset of a peer or 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 remote. 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 peer 80µs; 90% ranges for WAN servers 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 file.



Peer Offset 204.17.205.27

peer offset 204.17.205.27 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%95%StdDev  MeanUnits nessosis
Peer Offset 204.17.205.27-30.338-5.231-1.842-0.3020.257 0.4731.6662.0995.7041.575-0.531ms -17.6 244.1

This shows the offset of a peer or 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 remote. 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 peer 80µs; 90% ranges for WAN servers 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 file.



Peer Offset 204.17.205.30

peer offset 204.17.205.30 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%95%StdDev  MeanUnits nessosis
Peer Offset 204.17.205.30-4.418-1.356-0.837-0.1110.171 0.4061.3761.0081.7620.376-0.210ms-10.78 53.15

This shows the offset of a peer or 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 remote. 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 peer 80µs; 90% ranges for WAN servers 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 file.



Peer Jitters

peer jitters plot

This shows the RMS Jitter of all refclocks, peers and servers. Jitter is the current estimated dispersion; 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.



Peer Jitter 2001:470:e815::8 (spidey.rellim.com)

peer jitter 2001:470:e815::8 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%95%StdDev  MeanUnits nessosis
Peer Jitter 2001:470:e815::8 (spidey.rellim.com)3.8409.62317.76892.802373.432 590.998955.335355.664581.375122.281131.839µs 2.177 8.588

This shows the RMS Jitter of a remote peer or server. Jitter is the current estimated dispersion; 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.



Peer Jitter 204.17.205.1

peer jitter 204.17.205.1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%95%StdDev  MeanUnits nessosis
Peer Jitter 204.17.205.117.17327.08036.76199.044321.929 438.982924.185285.168411.90292.452127.760µs 2.946 10.71

This shows the RMS Jitter of a remote peer or server. Jitter is the current estimated dispersion; 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.



Peer Jitter 204.17.205.17

peer jitter 204.17.205.17 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%95%StdDev  MeanUnits nessosis
Peer Jitter 204.17.205.172.6155.3818.51055.396272.831 403.388682.728264.321398.00789.05287.023µs 1.835 7.33

This shows the RMS Jitter of a remote peer or server. Jitter is the current estimated dispersion; 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.



Peer Jitter 204.17.205.23

peer jitter 204.17.205.23 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%95%StdDev  MeanUnits nessosis
Peer Jitter 204.17.205.232.2795.5528.70953.970262.717 395.229650.888254.008389.67787.18684.849µs 1.751 6.832

This shows the RMS Jitter of a remote peer or server. Jitter is the current estimated dispersion; 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.



Peer Jitter 204.17.205.27

peer jitter 204.17.205.27 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%95%StdDev  MeanUnits nessosis
Peer Jitter 204.17.205.270.0040.0110.0240.3731.559 3.04716.2951.5353.0360.6370.482ms 7.188 142.8

This shows the RMS Jitter of a remote peer or server. Jitter is the current estimated dispersion; 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.



Peer Jitter 204.17.205.30

peer jitter 204.17.205.30 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%95%StdDev  MeanUnits nessosis
Peer Jitter 204.17.205.302.3266.24012.88379.981507.408 986.0273,399.087494.525979.787209.766149.481µs 4.104 42.2

This shows the RMS Jitter of a remote peer or server. Jitter is the current estimated dispersion; 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%95%StdDev  MeanUnits nessosis
Local Clock Frequency Offset-4.264-3.862-3.559-2.424-1.776 -1.1640.1711.7842.6970.618-2.559ppm -151 858.7
Local Clock Time Offset-1,023.095-624.535-427.681-7.598409.550 640.0701,162.688837.2311,264.605234.586-7.621µs-4.065 11.82
Local RMS Frequency Jitter5.33411.07415.89995.429205.975 261.602336.066190.076250.52859.94398.602ppb 2.767 7.134
Local RMS Time Jitter13.47324.07037.786260.116483.793 586.440773.635446.007562.370145.971252.710µs 2.756 6.25
Peer Jitter 2001:470:e815::8 (spidey.rellim.com)3.8409.62317.76892.802373.432 590.998955.335355.664581.375122.281131.839µs 2.177 8.588
Peer Jitter 204.17.205.117.17327.08036.76199.044321.929 438.982924.185285.168411.90292.452127.760µs 2.946 10.71
Peer Jitter 204.17.205.172.6155.3818.51055.396272.831 403.388682.728264.321398.00789.05287.023µs 1.835 7.33
Peer Jitter 204.17.205.232.2795.5528.70953.970262.717 395.229650.888254.008389.67787.18684.849µs 1.751 6.832
Peer Jitter 204.17.205.270.0040.0110.0240.3731.559 3.04716.2951.5353.0360.6370.482ms 7.188 142.8
Peer Jitter 204.17.205.302.3266.24012.88379.981507.408 986.0273,399.087494.525979.787209.766149.481µs 4.104 42.2
Peer Offset 2001:470:e815::8 (spidey.rellim.com)-1,110.887-484.949-242.176-0.968466.681 722.4151,121.176708.8571,207.364218.69443.834µs-2.248 7.568
Peer Offset 204.17.205.1-0.197-0.0310.0820.3440.833 1.0261.3490.7511.0570.2240.389ms 3.443 9.861
Peer Offset 204.17.205.17-602.036-254.822-119.52146.698614.756 817.2041,261.457734.2771,072.026236.898143.362µs-0.2236 3.091
Peer Offset 204.17.205.23-566.613-260.803-124.57838.847620.912 824.4311,311.329745.4901,085.234241.170140.646µs-0.2969 3.104
Peer Offset 204.17.205.27-30.338-5.231-1.842-0.3020.257 0.4731.6662.0995.7041.575-0.531ms -17.6 244.1
Peer Offset 204.17.205.30-4.418-1.356-0.837-0.1110.171 0.4061.3761.0081.7620.376-0.210ms-10.78 53.15
Temp ZONE045.08445.08445.62249.38851.540 53.69277.3645.9188.6082.64849.038°C
Summary as CSV file


This server:

Motherboard: Raspberry Pi 2
OS: Gentoo stable
GPS; Uputronics HAT
GPS/PPS server: gpsd
NTP server: NTPsec
../ntp.conf

Notes:

22:00 29 Nov 2017 SD card crash, start over

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 Peer 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 remote clock 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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