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Report generated: Tue Apr 22 18:15:06 2025 UTC
Start Time: Mon Apr 21 18:15:06 2025 UTC
End Time: Tue Apr 22 18:15:06 2025 UTC
Report Period: 1.0 days

Local Clock Time/Frequency Offsets

	Percentiles......							Ranges......					Skew-	Kurt-
Name	Min	1%	5%	50%	95%	99%	Max	90%	98%	StdDev	Mean	Units	ness	osis
Local Clock Time Offset	-7.318	-2.306	-1.393	0.078	1.383	1.928	3.244	2.776	4.234	0.882	0.037	µs	-4.292	13.43
Local Clock Frequency Offset	-36.563	-36.562	-36.557	-36.511	-36.488	-36.482	-36.481	0.069	0.080	0.023	-36.517	ppm	-4.214e+09	6.807e+12

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

	Percentiles......							Ranges......					Skew-	Kurt-
Name	Min	1%	5%	50%	95%	99%	Max	90%	98%	StdDev	Mean	Units	ness	osis
Local RMS Time Jitter	272.000	321.000	362.000	488.000	690.000	974.000	3,191.000	328.000	653.000	164.713	510.316	ns	22.91	197.5

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

	Percentiles......							Ranges......					Skew-	Kurt-
Name	Min	1%	5%	50%	95%	99%	Max	90%	98%	StdDev	Mean	Units	ness	osis
Local RMS Frequency Jitter	79.000	97.000	115.000	175.000	364.000	620.000	1,349.000	249.000	523.000	105.713	200.528	10e-12	7.672	52.39

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

	Percentiles......							Ranges......					Skew-	Kurt-
Name	Min	1%	5%	50%	95%	99%	Max	90%	98%	StdDev	Mean	Units	ness	osis
Local Clock Offset	-7.318	-2.306	-1.393	0.078	1.383	1.928	3.244	2.776	4.234	0.882	0.037	µs	-4.292	13.43

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 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

	Percentiles......							Ranges......					Skew-	Kurt-
Name	Min	1%	5%	50%	95%	99%	Max	90%	98%	StdDev	Mean	Units	ness	osis
Local Clock Frequency Offset	-36.563	-36.562	-36.557	-36.511	-36.488	-36.482	-36.481	0.069	0.080	0.023	-36.517	ppm	-4.214e+09	6.807e+12
Temp ZONE0	49.768	49.768	49.768	50.844	50.844	51.382	51.382	1.076	1.614	0.414	50.537	°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

	Percentiles......							Ranges......					Skew-	Kurt-
Name	Min	1%	5%	50%	95%	99%	Max	90%	98%	StdDev	Mean	Units	ness	osis
nSats	7.000	8.000	8.000	10.000	11.000	12.000	12.000	3.000	4.000	0.935	9.514	nSat	800.3	7601
TDOP	0.510	0.530	0.590	0.790	1.210	1.370	1.880	0.620	0.840	0.190	0.845		52.56	234.3

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. TDOP ranges from 1 to greater than 20. 1 denotes the highest possible confidence level. 2 to 5 is good. Greater than 20 means there will be significant inaccuracy and error.

Server Offsets

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 PPS(0)

	Percentiles......							Ranges......					Skew-	Kurt-
Name	Min	1%	5%	50%	95%	99%	Max	90%	98%	StdDev	Mean	Units	ness	osis
Server Offset PPS(0)	-7.319	-2.307	-1.394	0.079	1.384	1.929	3.245	2.778	4.236	0.883	0.037	µs	-4.29	13.42

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)

	Percentiles......							Ranges......					Skew-	Kurt-
Name	Min	1%	5%	50%	95%	99%	Max	90%	98%	StdDev	Mean	Units	ness	osis
Server Offset SHM(0)	128.015	135.023	139.801	152.898	164.057	167.416	173.859	24.256	32.393	7.268	152.511	ms	8040	1.619e+05

The offset of a server 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 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

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 PPS(0)

	Percentiles......							Ranges......					Skew-	Kurt-
Name	Min	1%	5%	50%	95%	99%	Max	90%	98%	StdDev	Mean	Units	ness	osis
Server Jitter PPS(0)	0.129	0.224	0.321	0.679	1.407	1.809	5.638	1.086	1.585	0.364	0.759	µs	6.467	33.16

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)

	Percentiles......							Ranges......					Skew-	Kurt-
Name	Min	1%	5%	50%	95%	99%	Max	90%	98%	StdDev	Mean	Units	ness	osis
Server Jitter SHM(0)	0.902	2.935	4.004	7.410	13.808	16.921	26.636	9.804	13.986	3.008	7.950	ms	10.31	33.71

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	Min	1%	5%	50%	95%	99%	Max	90%	98%	StdDev	Mean	Units	ness	osis
Local Clock Frequency Offset	-36.563	-36.562	-36.557	-36.511	-36.488	-36.482	-36.481	0.069	0.080	0.023	-36.517	ppm	-4.214e+09	6.807e+12
Local Clock Time Offset	-7.318	-2.306	-1.393	0.078	1.383	1.928	3.244	2.776	4.234	0.882	0.037	µs	-4.292	13.43
Local RMS Frequency Jitter	79.000	97.000	115.000	175.000	364.000	620.000	1,349.000	249.000	523.000	105.713	200.528	10e-12	7.672	52.39
Local RMS Time Jitter	272.000	321.000	362.000	488.000	690.000	974.000	3,191.000	328.000	653.000	164.713	510.316	ns	22.91	197.5
Server Jitter PPS(0)	0.129	0.224	0.321	0.679	1.407	1.809	5.638	1.086	1.585	0.364	0.759	µs	6.467	33.16
Server Jitter SHM(0)	0.902	2.935	4.004	7.410	13.808	16.921	26.636	9.804	13.986	3.008	7.950	ms	10.31	33.71
Server Offset PPS(0)	-7.319	-2.307	-1.394	0.079	1.384	1.929	3.245	2.778	4.236	0.883	0.037	µs	-4.29	13.42
Server Offset SHM(0)	128.015	135.023	139.801	152.898	164.057	167.416	173.859	24.256	32.393	7.268	152.511	ms	8040	1.619e+05
TDOP	0.510	0.530	0.590	0.790	1.210	1.370	1.880	0.620	0.840	0.190	0.845		52.56	234.3
Temp ZONE0	49.768	49.768	49.768	50.844	50.844	51.382	51.382	1.076	1.614	0.414	50.537	°C
nSats	7.000	8.000	8.000	10.000	11.000	12.000	12.000	3.000	4.000	0.935	9.514	nSat	800.3	7601

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 = (∑x_i) / N". Where x_i 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 = √[ ∑(x_i-mu)^2 / N ]". Where x_i 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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