NTPsec

tick

Report generated: Thu Oct 16 06:15:09 2025 UTC
Start Time: Thu Oct 9 06:15:08 2025 UTC
End Time: Thu Oct 16 06:15:08 2025 UTC
Report Period: 7.0 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 -6.795 -1.931 -1.201 0.032 1.254 1.841 4.568 2.455 3.772 0.768 0.025 µs -4.089 12.47
Local Clock Frequency Offset -36.859 -36.827 -36.817 -36.748 -36.666 -36.657 -36.639 0.151 0.171 0.048 -36.746 ppm -4.413e+08 3.36e+11

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 175.000 289.000 330.000 464.000 669.000 830.000 3,038.000 339.000 541.000 131.913 480.683 ns 30.95 192.8

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 53.000 72.000 85.000 144.000 340.000 798.000 2,551.000 255.000 726.000 133.752 177.783 10e-12 6.792 64.46

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 -6.795 -1.931 -1.201 0.032 1.254 1.841 4.568 2.455 3.772 0.768 0.025 µs -4.089 12.47

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 -36.859 -36.827 -36.817 -36.748 -36.666 -36.657 -36.639 0.151 0.171 0.048 -36.746 ppm -4.413e+08 3.36e+11
Temp ZONE0 52.996 52.996 52.996 54.072 55.148 55.148 55.686 2.152 2.152 0.506 54.051 °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 0.000 7.000 8.000 10.000 11.000 12.000 12.000 3.000 5.000 1.073 9.662 nSat 536.3 4486
TDOP 0.470 0.540 0.590 0.820 1.170 1.330 3.090 0.580 0.790 0.178 0.848 65.9 308.9

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

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 PPS(0)

peer offset PPS(0) plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset PPS(0) -6.796 -1.932 -1.202 0.033 1.255 1.842 4.569 2.457 3.774 0.769 0.025 µs -4.088 12.45

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) 91.618 135.316 139.504 153.215 165.123 168.882 177.714 25.619 33.566 7.683 152.916 ms 6811 1.298e+05

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 PPS(0)

peer jitter PPS(0) plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter PPS(0) 0.064 0.171 0.233 0.486 1.014 1.372 6.011 0.781 1.201 0.263 0.537 µs 6.913 45.37

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) 0.677 2.951 4.024 7.468 13.866 17.210 56.907 9.842 14.259 3.044 8.012 ms 10.22 33.85

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 -36.859 -36.827 -36.817 -36.748 -36.666 -36.657 -36.639 0.151 0.171 0.048 -36.746 ppm -4.413e+08 3.36e+11
Local Clock Time Offset -6.795 -1.931 -1.201 0.032 1.254 1.841 4.568 2.455 3.772 0.768 0.025 µs -4.089 12.47
Local RMS Frequency Jitter 53.000 72.000 85.000 144.000 340.000 798.000 2,551.000 255.000 726.000 133.752 177.783 10e-12 6.792 64.46
Local RMS Time Jitter 175.000 289.000 330.000 464.000 669.000 830.000 3,038.000 339.000 541.000 131.913 480.683 ns 30.95 192.8
Server Jitter PPS(0) 0.064 0.171 0.233 0.486 1.014 1.372 6.011 0.781 1.201 0.263 0.537 µs 6.913 45.37
Server Jitter SHM(0) 0.677 2.951 4.024 7.468 13.866 17.210 56.907 9.842 14.259 3.044 8.012 ms 10.22 33.85
Server Offset PPS(0) -6.796 -1.932 -1.202 0.033 1.255 1.842 4.569 2.457 3.774 0.769 0.025 µs -4.088 12.45
Server Offset SHM(0) 91.618 135.316 139.504 153.215 165.123 168.882 177.714 25.619 33.566 7.683 152.916 ms 6811 1.298e+05
TDOP 0.470 0.540 0.590 0.820 1.170 1.330 3.090 0.580 0.790 0.178 0.848 65.9 308.9
Temp ZONE0 52.996 52.996 52.996 54.072 55.148 55.148 55.686 2.152 2.152 0.506 54.051 °C
nSats 0.000 7.000 8.000 10.000 11.000 12.000 12.000 3.000 5.000 1.073 9.662 nSat 536.3 4486
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.



This page autogenerated by ntpviz, part of the NTPsec project
html 5    Valid CSS!