itchy

Report generated: Thu May 21 16:15:01 2026 UTC
Start Time: Wed May 20 16:15:01 2026 UTC
End Time: Thu May 21 16:15:01 2026 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	-3.197	-3.197	-1.539	0.027	1.643	1.939	1.939	3.182	5.137	0.844	0.012	ms	-4.979	18.2
Local Clock Frequency Offset	17.464	17.464	17.589	18.004	18.296	18.315	18.315	0.706	0.851	0.167	17.984	ppm	1.214e+06	1.295e+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

	Percentiles......							Ranges......					Skew-	Kurt-
Name	Min	1%	5%	50%	95%	99%	Max	90%	98%	StdDev	Mean	Units	ness	osis
Local RMS Time Jitter	0.204	0.204	0.227	0.430	1.042	1.071	1.071	0.815	0.867	0.285	0.539	ms	3.894	8.986

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	24.280	24.280	27.724	68.656	161.986	167.856	167.856	134.262	143.576	46.407	78.034	ppb	2.981	6.691

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	-3.197	-3.197	-1.539	0.027	1.643	1.939	1.939	3.182	5.137	0.844	0.012	ms	-4.979	18.2

The clock offsets of the local clock as a histogram.

The Local Clock Offset is field 3 from the loopstats log file.

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 192.12.19.20

	Percentiles......							Ranges......					Skew-	Kurt-
Name	Min	1%	5%	50%	95%	99%	Max	90%	98%	StdDev	Mean	Units	ness	osis
Server Offset 192.12.19.20	-1.644	-1.644	-1.575	1.817	3.664	4.011	4.011	5.239	5.655	1.242	1.716	ms	-0.03222	3.997

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 204.34.198.40

	Percentiles......							Ranges......					Skew-	Kurt-
Name	Min	1%	5%	50%	95%	99%	Max	90%	98%	StdDev	Mean	Units	ness	osis
Server Offset 204.34.198.40	-15.286	-15.286	-12.614	-12.100	1.224	2.089	2.089	13.838	17.375	3.627	-11.075	ms	-75.73	330.2

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 Offset 2610:20:6f96:96::4 (time-d-b.nist.gov)

	Percentiles......							Ranges......					Skew-	Kurt-
Name	Min	1%	5%	50%	95%	99%	Max	90%	98%	StdDev	Mean	Units	ness	osis
Server Offset 2610:20:6f96:96::4 (time-d-b.nist.gov)	-1.483	-1.483	-1.042	2.188	3.763	4.123	4.123	4.805	5.606	1.082	2.009	ms	1.697	5.808

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 192.12.19.20

	Percentiles......							Ranges......					Skew-	Kurt-
Name	Min	1%	5%	50%	95%	99%	Max	90%	98%	StdDev	Mean	Units	ness	osis
Server Jitter 192.12.19.20	0.118	0.118	0.158	0.613	2.753	3.188	3.188	2.594	3.070	0.765	0.905	ms	2.049	5.802

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 204.34.198.40

	Percentiles......							Ranges......					Skew-	Kurt-
Name	Min	1%	5%	50%	95%	99%	Max	90%	98%	StdDev	Mean	Units	ness	osis
Server Jitter 204.34.198.40	0.069	0.069	0.168	0.371	10.386	14.064	14.064	10.218	13.994	3.257	1.693	ms	1.12	5.279

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 2610:20:6f96:96::4 (time-d-b.nist.gov)

	Percentiles......							Ranges......					Skew-	Kurt-
Name	Min	1%	5%	50%	95%	99%	Max	90%	98%	StdDev	Mean	Units	ness	osis
Server Jitter 2610:20:6f96:96::4 (time-d-b.nist.gov)	0.092	0.092	0.102	0.368	2.317	3.286	3.286	2.216	3.193	0.756	0.684	ms	1.537	5.122

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	17.464	17.464	17.589	18.004	18.296	18.315	18.315	0.706	0.851	0.167	17.984	ppm	1.214e+06	1.295e+08
Local Clock Time Offset	-3.197	-3.197	-1.539	0.027	1.643	1.939	1.939	3.182	5.137	0.844	0.012	ms	-4.979	18.2
Local RMS Frequency Jitter	24.280	24.280	27.724	68.656	161.986	167.856	167.856	134.262	143.576	46.407	78.034	ppb	2.981	6.691
Local RMS Time Jitter	0.204	0.204	0.227	0.430	1.042	1.071	1.071	0.815	0.867	0.285	0.539	ms	3.894	8.986
Server Jitter 192.12.19.20	0.118	0.118	0.158	0.613	2.753	3.188	3.188	2.594	3.070	0.765	0.905	ms	2.049	5.802
Server Jitter 204.34.198.40	0.069	0.069	0.168	0.371	10.386	14.064	14.064	10.218	13.994	3.257	1.693	ms	1.12	5.279
Server Jitter 2610:20:6f96:96::4 (time-d-b.nist.gov)	0.092	0.092	0.102	0.368	2.317	3.286	3.286	2.216	3.193	0.756	0.684	ms	1.537	5.122
Server Offset 192.12.19.20	-1.644	-1.644	-1.575	1.817	3.664	4.011	4.011	5.239	5.655	1.242	1.716	ms	-0.03222	3.997
Server Offset 204.34.198.40	-15.286	-15.286	-12.614	-12.100	1.224	2.089	2.089	13.838	17.375	3.627	-11.075	ms	-75.73	330.2
Server Offset 2610:20:6f96:96::4 (time-d-b.nist.gov)	-1.483	-1.483	-1.042	2.188	3.763	4.123	4.123	4.805	5.606	1.082	2.009	ms	1.697	5.808

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.

This page autogenerated by ntpviz, part of the NTPsec project