NTPsec

sam.ljay.org.uk

Report generated: Sun Jan 12 15:30:02 2025 UTC
Start Time: Sat Jan 11 06:30:02 2025 UTC
End Time: Sun Jan 12 15:30:02 2025 UTC
Report Period: 1.4 days

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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 -50.315 -26.500 -16.338 -0.586 21.077 33.804 51.979 37.415 60.304 10.405 0.143 µs -3.247 10.28
Local Clock Frequency Offset 11.898 11.914 11.926 12.300 12.497 12.513 12.532 0.571 0.599 0.172 12.258 ppm 3.49e+05 2.458e+07

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 0.614 1.293 2.835 11.466 20.245 24.396 32.310 17.410 23.103 5.337 11.414 µs 5.085 12.96

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 0.172 0.299 0.585 2.327 4.049 4.932 10.496 3.464 4.633 1.105 2.312 ppb 5.018 14.65

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 -50.315 -26.500 -16.338 -0.586 21.077 33.804 51.979 37.415 60.304 10.405 0.143 µs -3.247 10.28

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 11.898 11.914 11.926 12.300 12.497 12.513 12.532 0.571 0.599 0.172 12.258 ppm 3.49e+05 2.458e+07
Temp LM0 34.000 34.000 34.000 36.000 37.000 37.000 37.000 3.000 3.000 0.852 35.632 °C
Temp LM1 14.000 15.000 16.000 18.000 20.000 21.000 25.000 4.000 6.000 1.386 17.859 °C
Temp LM2 29.000 29.000 29.000 31.000 32.000 32.000 34.000 3.000 3.000 0.824 30.594 °C
Temp LM3 29.000 29.000 30.000 31.000 32.000 32.000 34.000 2.000 3.000 0.843 30.829 °C
Temp LM4 28.000 28.000 28.000 30.000 30.000 31.000 32.000 2.000 3.000 0.750 29.509 °C
Temp LM5 27.800 27.800 27.800 27.800 27.800 27.800 27.800 0.000 0.000 0.000 27.800 °C
Temp LM6 29.800 29.800 29.800 29.800 29.800 29.800 29.800 0.000 0.000 0.000 29.800 °C
Temp LM7 25.000 26.000 27.000 29.000 31.000 32.000 34.000 4.000 6.000 1.314 28.970 °C
Temp LM8 25.000 26.000 27.000 29.000 31.000 31.000 35.000 4.000 5.000 1.321 28.962 °C
Temp LM9 23.000 23.000 24.000 26.000 28.000 29.000 30.000 4.000 6.000 1.324 25.791 °C
Temp ZONE0 29.800 29.800 29.800 29.800 29.800 29.800 29.800 0.000 0.000 0.000 29.800 °C
Temp ZONE1 26.000 26.000 27.000 29.000 31.000 32.000 34.000 4.000 6.000 1.251 28.919 °C
Temp ZONE2 27.800 27.800 27.800 27.800 27.800 27.800 27.800 0.000 0.000 0.000 27.800 °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 6.000 6.000 8.000 10.000 10.000 11.000 4.000 4.000 0.994 8.146 nSat 393.7 2989
TDOP 0.520 0.580 0.620 0.920 1.570 2.790 3.170 0.950 2.210 0.378 0.999 11.98 53.19

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.



Refclock Offset 127.127.28.0 SHM(0)

peer offset 127.127.28.0 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Refclock Offset 127.127.28.0 SHM(0) -80.021 -43.418 -25.907 12.424 54.417 72.947 100.868 80.324 116.366 24.463 13.121 ms -1.377 4.365

The offset of a local refclock in seconds. This is useful to see how the measured offset is behaving.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local serial GPS 200 ms; local PPS 20µs.

Clock Offset is field 5 in the peerstats log file.



Refclock Offset 127.127.28.1 SHM(1)

peer offset 127.127.28.1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Refclock Offset 127.127.28.1 SHM(1) -50.316 -26.501 -16.339 -0.587 21.078 33.805 51.980 37.417 60.306 10.406 0.143 µs -3.247 10.28

The offset of a local refclock in seconds. This is useful to see how the measured offset is behaving.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local serial GPS 200 ms; local PPS 20µs.

Clock Offset is field 5 in the peerstats log file.



Server Offset 193.67.79.202

peer offset 193.67.79.202 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 193.67.79.202 -4.345 -4.293 -0.562 -0.412 -0.312 -0.289 -0.241 0.250 4.004 0.694 -0.543 ms -16.15 93.46

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 2001:8b0:0:23::205 (ntp2.aa.net.uk)

peer offset 2001:8b0:0:23::205 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2001:8b0:0:23::205 (ntp2.aa.net.uk) -0.254 -0.078 0.087 0.655 0.977 1.072 1.110 0.890 1.149 0.287 0.581 ms 3.732 7.861

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 81.187.26.174

peer offset 81.187.26.174 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 81.187.26.174 -182.758 -163.490 -139.943 -54.700 65.976 114.489 149.019 205.919 277.979 62.569 -48.511 µs -10.51 28.67

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.



Refclock RMS Jitter 127.127.28.0 SHM(0)

peer jitter 127.127.28.0 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Refclock RMS Jitter 127.127.28.0 SHM(0) 1.218 2.628 4.266 11.952 25.851 35.053 57.199 21.585 32.425 6.745 13.193 ms 4.909 16

The RMS Jitter of a local refclock. 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.



Refclock RMS Jitter 127.127.28.1 SHM(1)

peer jitter 127.127.28.1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Refclock RMS Jitter 127.127.28.1 SHM(1) 0.179 0.322 0.651 10.666 28.915 38.141 64.260 28.264 37.819 9.303 11.213 µs 1.551 4.79

The RMS Jitter of a local refclock. 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 193.67.79.202

peer jitter 193.67.79.202 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 193.67.79.202 0.034 0.039 0.052 0.143 3.489 4.633 22.392 3.436 4.594 1.423 0.540 ms 7.462 113.5

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 2001:8b0:0:23::205 (ntp2.aa.net.uk)

peer jitter 2001:8b0:0:23::205 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2001:8b0:0:23::205 (ntp2.aa.net.uk) 0.072 0.081 0.138 0.586 1.503 4.254 34.767 1.365 4.173 2.511 0.862 ms 10.51 141.1

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 81.187.26.174

peer jitter 81.187.26.174 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 81.187.26.174 0.031 0.042 0.056 0.139 0.905 23.967 32.515 0.850 23.925 3.415 0.720 ms 5.254 48.59

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 11.898 11.914 11.926 12.300 12.497 12.513 12.532 0.571 0.599 0.172 12.258 ppm 3.49e+05 2.458e+07
Local Clock Time Offset -50.315 -26.500 -16.338 -0.586 21.077 33.804 51.979 37.415 60.304 10.405 0.143 µs -3.247 10.28
Local RMS Frequency Jitter 0.172 0.299 0.585 2.327 4.049 4.932 10.496 3.464 4.633 1.105 2.312 ppb 5.018 14.65
Local RMS Time Jitter 0.614 1.293 2.835 11.466 20.245 24.396 32.310 17.410 23.103 5.337 11.414 µs 5.085 12.96
Refclock Offset 127.127.28.0 SHM(0) -80.021 -43.418 -25.907 12.424 54.417 72.947 100.868 80.324 116.366 24.463 13.121 ms -1.377 4.365
Refclock Offset 127.127.28.1 SHM(1) -50.316 -26.501 -16.339 -0.587 21.078 33.805 51.980 37.417 60.306 10.406 0.143 µs -3.247 10.28
Refclock RMS Jitter 127.127.28.0 SHM(0) 1.218 2.628 4.266 11.952 25.851 35.053 57.199 21.585 32.425 6.745 13.193 ms 4.909 16
Refclock RMS Jitter 127.127.28.1 SHM(1) 0.179 0.322 0.651 10.666 28.915 38.141 64.260 28.264 37.819 9.303 11.213 µs 1.551 4.79
Server Jitter 193.67.79.202 0.034 0.039 0.052 0.143 3.489 4.633 22.392 3.436 4.594 1.423 0.540 ms 7.462 113.5
Server Jitter 2001:8b0:0:23::205 (ntp2.aa.net.uk) 0.072 0.081 0.138 0.586 1.503 4.254 34.767 1.365 4.173 2.511 0.862 ms 10.51 141.1
Server Jitter 81.187.26.174 0.031 0.042 0.056 0.139 0.905 23.967 32.515 0.850 23.925 3.415 0.720 ms 5.254 48.59
Server Offset 193.67.79.202 -4.345 -4.293 -0.562 -0.412 -0.312 -0.289 -0.241 0.250 4.004 0.694 -0.543 ms -16.15 93.46
Server Offset 2001:8b0:0:23::205 (ntp2.aa.net.uk) -0.254 -0.078 0.087 0.655 0.977 1.072 1.110 0.890 1.149 0.287 0.581 ms 3.732 7.861
Server Offset 81.187.26.174 -182.758 -163.490 -139.943 -54.700 65.976 114.489 149.019 205.919 277.979 62.569 -48.511 µs -10.51 28.67
TDOP 0.520 0.580 0.620 0.920 1.570 2.790 3.170 0.950 2.210 0.378 0.999 11.98 53.19
Temp LM0 34.000 34.000 34.000 36.000 37.000 37.000 37.000 3.000 3.000 0.852 35.632 °C
Temp LM1 14.000 15.000 16.000 18.000 20.000 21.000 25.000 4.000 6.000 1.386 17.859 °C
Temp LM2 29.000 29.000 29.000 31.000 32.000 32.000 34.000 3.000 3.000 0.824 30.594 °C
Temp LM3 29.000 29.000 30.000 31.000 32.000 32.000 34.000 2.000 3.000 0.843 30.829 °C
Temp LM4 28.000 28.000 28.000 30.000 30.000 31.000 32.000 2.000 3.000 0.750 29.509 °C
Temp LM5 27.800 27.800 27.800 27.800 27.800 27.800 27.800 0.000 0.000 0.000 27.800 °C
Temp LM6 29.800 29.800 29.800 29.800 29.800 29.800 29.800 0.000 0.000 0.000 29.800 °C
Temp LM7 25.000 26.000 27.000 29.000 31.000 32.000 34.000 4.000 6.000 1.314 28.970 °C
Temp LM8 25.000 26.000 27.000 29.000 31.000 31.000 35.000 4.000 5.000 1.321 28.962 °C
Temp LM9 23.000 23.000 24.000 26.000 28.000 29.000 30.000 4.000 6.000 1.324 25.791 °C
Temp ZONE0 29.800 29.800 29.800 29.800 29.800 29.800 29.800 0.000 0.000 0.000 29.800 °C
Temp ZONE1 26.000 26.000 27.000 29.000 31.000 32.000 34.000 4.000 6.000 1.251 28.919 °C
Temp ZONE2 27.800 27.800 27.800 27.800 27.800 27.800 27.800 0.000 0.000 0.000 27.800 °C
nSats 5.000 6.000 6.000 8.000 10.000 10.000 11.000 4.000 4.000 0.994 8.146 nSat 393.7 2989
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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