NTPsec

itchy

Report generated: Wed Mar 22 12:15:01 2023 UTC
Start Time: Tue Mar 21 12:15:01 2023 UTC
End Time: Wed Mar 22 12:15:01 2023 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 -220.267 -220.267 -195.373 12.381 194.080 365.799 365.799 389.453 586.066 124.431 7.005 µs -3.481 8.268
Local Clock Frequency Offset 67.148 67.148 67.153 67.201 67.226 67.226 67.226 0.073 0.078 0.025 67.190 ppm 1.857e+10 4.919e+13

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 65.111 65.111 72.955 101.224 137.185 143.893 143.893 64.230 78.782 19.987 103.730 µs 86.27 418

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 5.549 5.549 6.339 12.105 22.494 25.564 25.564 16.155 20.015 4.835 13.028 ppb 10.47 31.49

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 -220.267 -220.267 -195.373 12.381 194.080 365.799 365.799 389.453 586.066 124.431 7.005 µs -3.481 8.268

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 -241.896 -241.896 -184.217 14.144 264.877 483.907 483.907 449.094 725.803 143.781 40.087 µs -2.058 5.141

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 -16.055 -16.055 -15.952 -15.693 -15.433 -15.360 -15.360 0.519 0.695 0.142 -15.679 ms -1.397e+06 1.561e+08

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) -2.116 -2.116 -2.014 -1.535 -0.775 -0.606 -0.606 1.239 1.510 0.387 -1.441 ms -119.1 627.4

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) 19.797 19.797 78.700 285.788 497.572 539.428 539.428 418.872 519.631 114.238 275.742 µs 7.07 18.76

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 52.803 52.803 62.665 133.856 288.145 472.316 472.316 225.480 419.513 75.090 154.098 µs 5.996 22.08

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 59.731 59.731 77.158 150.495 298.403 313.414 313.414 221.245 253.683 60.049 159.572 µs 10.33 32.64

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) 44.835 44.835 67.271 176.740 901.485 959.673 959.673 834.214 914.838 232.569 265.328 µs 2.033 5.731

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) 64.586 64.586 74.519 129.680 253.837 283.733 283.733 179.318 219.147 49.964 136.154 µs 11.15 35.88

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 67.148 67.148 67.153 67.201 67.226 67.226 67.226 0.073 0.078 0.025 67.190 ppm 1.857e+10 4.919e+13
Local Clock Time Offset -220.267 -220.267 -195.373 12.381 194.080 365.799 365.799 389.453 586.066 124.431 7.005 µs -3.481 8.268
Local RMS Frequency Jitter 5.549 5.549 6.339 12.105 22.494 25.564 25.564 16.155 20.015 4.835 13.028 ppb 10.47 31.49
Local RMS Time Jitter 65.111 65.111 72.955 101.224 137.185 143.893 143.893 64.230 78.782 19.987 103.730 µs 86.27 418
Server Jitter 192.12.19.20 52.803 52.803 62.665 133.856 288.145 472.316 472.316 225.480 419.513 75.090 154.098 µs 5.996 22.08
Server Jitter 204.34.198.40 59.731 59.731 77.158 150.495 298.403 313.414 313.414 221.245 253.683 60.049 159.572 µs 10.33 32.64
Server Jitter 2600:3c03::f03c:91ff:fe0c:601c (scratchy.podsix.net) 44.835 44.835 67.271 176.740 901.485 959.673 959.673 834.214 914.838 232.569 265.328 µs 2.033 5.731
Server Jitter 2610:20:6f96:96::4 (time-d-b.nist.gov) 64.586 64.586 74.519 129.680 253.837 283.733 283.733 179.318 219.147 49.964 136.154 µs 11.15 35.88
Server Offset 192.12.19.20 -241.896 -241.896 -184.217 14.144 264.877 483.907 483.907 449.094 725.803 143.781 40.087 µs -2.058 5.141
Server Offset 204.34.198.40 -16.055 -16.055 -15.952 -15.693 -15.433 -15.360 -15.360 0.519 0.695 0.142 -15.679 ms -1.397e+06 1.561e+08
Server Offset 2600:3c03::f03c:91ff:fe0c:601c (scratchy.podsix.net) -2.116 -2.116 -2.014 -1.535 -0.775 -0.606 -0.606 1.239 1.510 0.387 -1.441 ms -119.1 627.4
Server Offset 2610:20:6f96:96::4 (time-d-b.nist.gov) 19.797 19.797 78.700 285.788 497.572 539.428 539.428 418.872 519.631 114.238 275.742 µs 7.07 18.76
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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