NTPsec

itchy

Report generated: Mon May 19 21:15:02 2025 UTC
Start Time: Sun May 18 21:15:02 2025 UTC
End Time: Mon May 19 21:15:02 2025 UTC
Report Period: 1.0 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 -567.632 -567.632 -419.976 -10.344 654.242 877.413 877.413 1,074.218 1,445.045 319.183 57.810 µs -2.409 5.567
Local Clock Frequency Offset 11.445 11.445 11.447 11.535 11.582 11.583 11.583 0.135 0.138 0.040 11.535 ppm 2.414e+07 6.979e+09

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 154.733 154.733 164.037 248.646 379.627 427.307 427.307 215.590 272.574 60.751 255.834 µs 43.41 179.9

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 4.323 4.323 4.934 11.000 20.913 23.892 23.892 15.979 19.569 5.126 12.351 ppb 7.367 19.83

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 -567.632 -567.632 -419.976 -10.344 654.242 877.413 877.413 1,074.218 1,445.045 319.183 57.810 µs -2.409 5.567

The clock offsets of the local clock as a histogram.

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



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 192.12.19.20

peer offset 192.12.19.20 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 192.12.19.20 0.064 0.064 0.134 0.483 1.579 1.689 1.689 1.445 1.624 0.377 0.518 ms 2.66 8.086

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

peer offset 204.34.198.40 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 204.34.198.40 -14.376 -14.376 -14.303 -13.943 -13.128 -13.045 -13.045 1.175 1.331 0.330 -13.850 ms -7.921e+04 3.405e+06

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 2600:3c03::f03c:91ff:fe0c:601c (scratchy.podsix.net)

peer offset 2600:3c03::f03c:91ff:fe0c:601c plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2600:3c03::f03c:91ff:fe0c:601c (scratchy.podsix.net) -6.790 -6.790 -4.797 -3.915 -1.763 1.594 1.594 3.034 8.384 1.175 -3.632 ms -78.96 360.7

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

peer offset 2610:20:6f96:96::4 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2610:20:6f96:96::4 (time-d-b.nist.gov) -0.164 -0.164 -0.107 0.076 0.908 1.027 1.027 1.015 1.191 0.301 0.199 ms 0.0599 2.489

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 192.12.19.20

peer jitter 192.12.19.20 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 192.12.19.20 0.120 0.120 0.157 0.578 28.942 29.010 29.010 28.786 28.890 9.219 3.927 ms 0.4243 3.185

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

peer jitter 204.34.198.40 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 204.34.198.40 93.109 93.109 120.063 222.567 514.384 674.074 674.074 394.321 580.965 118.542 252.958 µs 6.357 21.55

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 2600:3c03::f03c:91ff:fe0c:601c (scratchy.podsix.net)

peer jitter 2600:3c03::f03c:91ff:fe0c:601c plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2600:3c03::f03c:91ff:fe0c:601c (scratchy.podsix.net) 0.047 0.047 0.084 0.193 2.841 12.396 12.396 2.757 12.349 2.346 0.871 ms 2.247 12.71

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.



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

peer jitter 2610:20:6f96:96::4 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2610:20:6f96:96::4 (time-d-b.nist.gov) 20.083 20.083 53.231 162.078 476.673 517.856 517.856 423.442 497.773 112.243 186.212 µs 3.533 10.41

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 11.445 11.445 11.447 11.535 11.582 11.583 11.583 0.135 0.138 0.040 11.535 ppm 2.414e+07 6.979e+09
Local Clock Time Offset -567.632 -567.632 -419.976 -10.344 654.242 877.413 877.413 1,074.218 1,445.045 319.183 57.810 µs -2.409 5.567
Local RMS Frequency Jitter 4.323 4.323 4.934 11.000 20.913 23.892 23.892 15.979 19.569 5.126 12.351 ppb 7.367 19.83
Local RMS Time Jitter 154.733 154.733 164.037 248.646 379.627 427.307 427.307 215.590 272.574 60.751 255.834 µs 43.41 179.9
Server Jitter 192.12.19.20 0.120 0.120 0.157 0.578 28.942 29.010 29.010 28.786 28.890 9.219 3.927 ms 0.4243 3.185
Server Jitter 204.34.198.40 93.109 93.109 120.063 222.567 514.384 674.074 674.074 394.321 580.965 118.542 252.958 µs 6.357 21.55
Server Jitter 2600:3c03::f03c:91ff:fe0c:601c (scratchy.podsix.net) 0.047 0.047 0.084 0.193 2.841 12.396 12.396 2.757 12.349 2.346 0.871 ms 2.247 12.71
Server Jitter 2610:20:6f96:96::4 (time-d-b.nist.gov) 20.083 20.083 53.231 162.078 476.673 517.856 517.856 423.442 497.773 112.243 186.212 µs 3.533 10.41
Server Offset 192.12.19.20 0.064 0.064 0.134 0.483 1.579 1.689 1.689 1.445 1.624 0.377 0.518 ms 2.66 8.086
Server Offset 204.34.198.40 -14.376 -14.376 -14.303 -13.943 -13.128 -13.045 -13.045 1.175 1.331 0.330 -13.850 ms -7.921e+04 3.405e+06
Server Offset 2600:3c03::f03c:91ff:fe0c:601c (scratchy.podsix.net) -6.790 -6.790 -4.797 -3.915 -1.763 1.594 1.594 3.034 8.384 1.175 -3.632 ms -78.96 360.7
Server Offset 2610:20:6f96:96::4 (time-d-b.nist.gov) -0.164 -0.164 -0.107 0.076 0.908 1.027 1.027 1.015 1.191 0.301 0.199 ms 0.0599 2.489
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!