NTPsec

tock

Report generated: Fri Nov 22 21:15:42 2019 UTC
Start Time: Thu Nov 21 21:15:42 2019 UTC
End Time: Fri Nov 22 21:15:42 2019 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 -548.000 -383.000 -267.000 16.000 300.000 450.000 850.000 567.000 833.000 173.208 17.858 ns -3.251 8.315
Local Clock Frequency Offset -21.910 -21.909 -21.905 -21.889 -21.882 -21.881 -21.881 0.023 0.027 0.0084 -21.893 ppm -1.743e+10 4.519e+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 87.000 120.000 138.000 191.000 263.000 301.000 374.000 125.000 181.000 38.532 194.469 ns 78.94 378.3

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 21.000 26.000 29.000 40.000 56.000 104.000 153.000 27.000 78.000 12.369 41.349 10e-12 23.84 127.6

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 -548.000 -383.000 -267.000 16.000 300.000 450.000 850.000 567.000 833.000 173.208 17.858 ns -3.251 8.315

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 -21.910 -21.909 -21.905 -21.889 -21.882 -21.881 -21.881 0.023 0.027 0.0084 -21.893 ppm -1.743e+10 4.519e+13
Temp ZONE0 53.069 53.556 54.043 55.017 55.504 55.991 56.965 1.461 2.435 0.545 54.836 °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 4.000 5.000 5.000 7.000 8.000 9.000 9.000 3.000 4.000 0.963 6.538 nSat 211.8 1333
TDOP 1.000 1.060 1.180 1.670 4.830 6.400 10.860 3.650 5.340 1.214 2.083 5.361 24.67

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 10.4.2.51

peer offset 10.4.2.51 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 10.4.2.51 -17.380 -12.395 -9.174 2.026 13.207 15.731 17.912 22.381 28.126 6.854 2.504 µs -2.274 5.23

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 10.4.2.53

peer offset 10.4.2.53 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 10.4.2.53 -116.164 -87.372 -80.831 -68.016 -56.988 -52.307 -44.694 23.843 35.065 7.278 -68.405 µs -1156 1.237e+04

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 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) -549.000 -384.000 -268.000 17.000 301.000 450.000 850.000 569.000 834.000 173.959 17.941 ns -3.254 8.303

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) -17.238 -10.954 -7.873 5.182 16.040 19.726 24.599 23.913 30.680 7.261 4.511 ms -1.302 3.471

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 10.4.2.51

peer jitter 10.4.2.51 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 10.4.2.51 1.711 3.454 5.437 13.836 23.419 27.716 47.931 17.982 24.262 5.587 14.070 µs 8.595 26.68

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 10.4.2.53

peer jitter 10.4.2.53 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 10.4.2.53 3.049 5.959 8.405 17.167 30.606 43.336 59.884 22.201 37.377 7.119 18.016 µs 9.325 32.52

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 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) 34.000 71.000 101.000 186.000 355.000 438.000 654.000 254.000 367.000 77.856 201.448 ns 9.771 32.16

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)

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) 0.593 1.204 1.854 3.895 7.424 9.675 14.655 5.570 8.470 1.765 4.199 ms 7.813 25.85

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 -21.910 -21.909 -21.905 -21.889 -21.882 -21.881 -21.881 0.023 0.027 0.0084 -21.893 ppm -1.743e+10 4.519e+13
Local Clock Time Offset -548.000 -383.000 -267.000 16.000 300.000 450.000 850.000 567.000 833.000 173.208 17.858 ns -3.251 8.315
Local RMS Frequency Jitter 21.000 26.000 29.000 40.000 56.000 104.000 153.000 27.000 78.000 12.369 41.349 10e-12 23.84 127.6
Local RMS Time Jitter 87.000 120.000 138.000 191.000 263.000 301.000 374.000 125.000 181.000 38.532 194.469 ns 78.94 378.3
Server Jitter 10.4.2.51 1.711 3.454 5.437 13.836 23.419 27.716 47.931 17.982 24.262 5.587 14.070 µs 8.595 26.68
Server Jitter 10.4.2.53 3.049 5.959 8.405 17.167 30.606 43.336 59.884 22.201 37.377 7.119 18.016 µs 9.325 32.52
Server Jitter PPS(0) 34.000 71.000 101.000 186.000 355.000 438.000 654.000 254.000 367.000 77.856 201.448 ns 9.771 32.16
Server Jitter SHM(0) 0.593 1.204 1.854 3.895 7.424 9.675 14.655 5.570 8.470 1.765 4.199 ms 7.813 25.85
Server Offset 10.4.2.51 -17.380 -12.395 -9.174 2.026 13.207 15.731 17.912 22.381 28.126 6.854 2.504 µs -2.274 5.23
Server Offset 10.4.2.53 -116.164 -87.372 -80.831 -68.016 -56.988 -52.307 -44.694 23.843 35.065 7.278 -68.405 µs -1156 1.237e+04
Server Offset PPS(0) -549.000 -384.000 -268.000 17.000 301.000 450.000 850.000 569.000 834.000 173.959 17.941 ns -3.254 8.303
Server Offset SHM(0) -17.238 -10.954 -7.873 5.182 16.040 19.726 24.599 23.913 30.680 7.261 4.511 ms -1.302 3.471
TDOP 1.000 1.060 1.180 1.670 4.830 6.400 10.860 3.650 5.340 1.214 2.083 5.361 24.67
Temp ZONE0 53.069 53.556 54.043 55.017 55.504 55.991 56.965 1.461 2.435 0.545 54.836 °C
nSats 4.000 5.000 5.000 7.000 8.000 9.000 9.000 3.000 4.000 0.963 6.538 nSat 211.8 1333
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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