NTPsec

C-ntpsec-6-hour-stats

Report generated: Wed May 19 02:01:24 2021 UTC
Start Time: Tue May 18 20:01:24 2021 UTC
End Time: Wed May 19 02:01:24 2021 UTC
Report published: Tue May 18 19:01:27 2021 PDT
Report Period: 0.2 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 -0.587 -0.278 -0.122 0.277 0.844 1.082 1.400 0.966 1.360 0.295 0.304 µs 0.5725 3.233
Local Clock Frequency Offset -5.060 -5.059 -5.054 -4.988 -4.947 -4.946 -4.945 0.107 0.113 0.035 -4.993 ppm -3.061e+06 4.446e+08

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 91.000 107.000 122.000 176.000 265.000 329.000 407.000 143.000 222.000 45.619 182.830 ns 37.27 153.3

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 24.000 31.000 41.000 93.000 205.000 304.000 395.000 164.000 273.000 54.617 104.443 10e-12 5.087 18.36

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 -0.587 -0.278 -0.122 0.277 0.844 1.082 1.400 0.966 1.360 0.295 0.304 µs 0.5725 3.233

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 -5.060 -5.059 -5.054 -4.988 -4.947 -4.946 -4.945 0.107 0.113 0.035 -4.993 ppm -3.061e+06 4.446e+08
Temp ZONE0 57.996 57.996 58.534 59.610 60.686 60.686 60.686 2.152 2.690 0.645 59.511 °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 7.000 7.000 8.000 9.000 12.000 12.000 12.000 4.000 5.000 1.305 9.464 nSat 263.1 1768
TDOP 0.540 0.550 0.570 0.810 1.260 1.300 1.460 0.690 0.750 0.199 0.881 50.94 217.4

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 173.11.101.155

peer offset 173.11.101.155 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 173.11.101.155 -0.959 -0.959 -0.584 0.114 0.761 1.922 1.922 1.346 2.881 0.422 0.134 ms -1.76 8.149

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 192.168.1.10

peer offset 192.168.1.10 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 192.168.1.10 -6.800 28.941 85.100 158.179 246.357 254.871 260.203 161.257 225.930 51.192 157.145 µs 14.98 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 204.123.2.5

peer offset 204.123.2.5 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 204.123.2.5 1.763 1.763 1.913 2.162 2.365 2.421 2.421 0.452 0.658 0.139 2.155 ms 3098 4.556e+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 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) -66.334 -63.458 -62.577 -54.236 -46.172 -45.105 -44.096 16.405 18.353 4.836 -54.128 ms -1849 2.299e+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 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) -0.588 -0.279 -0.123 0.278 0.845 1.083 1.400 0.968 1.362 0.296 0.305 µs 0.5706 3.232

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 173.11.101.155

peer jitter 173.11.101.155 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 173.11.101.155 0.259 0.259 0.537 1.787 9.063 9.506 9.506 8.525 9.247 2.754 2.930 ms 1.464 3.526

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 192.168.1.10

peer jitter 192.168.1.10 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 192.168.1.10 0.015 0.019 0.038 0.130 8.658 8.805 8.951 8.621 8.786 2.783 1.291 ms 0.3585 2.946

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 204.123.2.5

peer jitter 204.123.2.5 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 204.123.2.5 0.254 0.254 0.275 0.971 8.415 8.800 8.800 8.140 8.546 2.083 1.745 ms 1.866 6.282

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) 0.087 0.172 0.283 0.868 2.792 5.655 7.275 2.509 5.483 0.958 1.133 ms 3.427 15.97

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) 50.000 69.000 97.000 218.000 531.000 721.000 1,189.000 434.000 652.000 141.566 251.593 ns 4.656 18.45

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 -5.060 -5.059 -5.054 -4.988 -4.947 -4.946 -4.945 0.107 0.113 0.035 -4.993 ppm -3.061e+06 4.446e+08
Local Clock Time Offset -0.587 -0.278 -0.122 0.277 0.844 1.082 1.400 0.966 1.360 0.295 0.304 µs 0.5725 3.233
Local RMS Frequency Jitter 24.000 31.000 41.000 93.000 205.000 304.000 395.000 164.000 273.000 54.617 104.443 10e-12 5.087 18.36
Local RMS Time Jitter 91.000 107.000 122.000 176.000 265.000 329.000 407.000 143.000 222.000 45.619 182.830 ns 37.27 153.3
Server Jitter 173.11.101.155 0.259 0.259 0.537 1.787 9.063 9.506 9.506 8.525 9.247 2.754 2.930 ms 1.464 3.526
Server Jitter 192.168.1.10 0.015 0.019 0.038 0.130 8.658 8.805 8.951 8.621 8.786 2.783 1.291 ms 0.3585 2.946
Server Jitter 204.123.2.5 0.254 0.254 0.275 0.971 8.415 8.800 8.800 8.140 8.546 2.083 1.745 ms 1.866 6.282
Server Jitter SHM(0) 0.087 0.172 0.283 0.868 2.792 5.655 7.275 2.509 5.483 0.958 1.133 ms 3.427 15.97
Server Jitter SHM(1) 50.000 69.000 97.000 218.000 531.000 721.000 1,189.000 434.000 652.000 141.566 251.593 ns 4.656 18.45
Server Offset 173.11.101.155 -0.959 -0.959 -0.584 0.114 0.761 1.922 1.922 1.346 2.881 0.422 0.134 ms -1.76 8.149
Server Offset 192.168.1.10 -6.800 28.941 85.100 158.179 246.357 254.871 260.203 161.257 225.930 51.192 157.145 µs 14.98 46
Server Offset 204.123.2.5 1.763 1.763 1.913 2.162 2.365 2.421 2.421 0.452 0.658 0.139 2.155 ms 3098 4.556e+04
Server Offset SHM(0) -66.334 -63.458 -62.577 -54.236 -46.172 -45.105 -44.096 16.405 18.353 4.836 -54.128 ms -1849 2.299e+04
Server Offset SHM(1) -0.588 -0.279 -0.123 0.278 0.845 1.083 1.400 0.968 1.362 0.296 0.305 µs 0.5706 3.232
TDOP 0.540 0.550 0.570 0.810 1.260 1.300 1.460 0.690 0.750 0.199 0.881 50.94 217.4
Temp ZONE0 57.996 57.996 58.534 59.610 60.686 60.686 60.686 2.152 2.690 0.645 59.511 °C
nSats 7.000 7.000 8.000 9.000 12.000 12.000 12.000 4.000 5.000 1.305 9.464 nSat 263.1 1768
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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