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In this report the jitter is represented by the Inter Packet Delay (IPD), the absolute values of the IPF (Abs(IPD)) and the Stdev(IPD).
Methodology
The measurement tool was a PingER MA in all cases. PingER (Ping End-to-end Reporting) is the name given to the Internet End-to-end Performance Measurement (IEPM) project to monitor end-to-end performance of Internet links. Originally, in 1995 it was for the High Energy Physics community, however, this century it has been more focused on measuring the Digital Divide from an Internet Performance viewpoint. The project now involves measurements to over 700 sites in over 160 countries. It uses the ubiquitous ping facility so no special software has to be installed on the targets being measured by the MAs..
PingER measurements are made by ~60 MAs in 23 countries. They make measurements to over 700 targets in ~ 160 countries containing more than 99% of the world's connected population. The measurement cycle is scheduled at roughly 30 minute intervals. The actual scheduled timing of a measurement is deliberately randomized so measurements from one MA are not synchronized with another MA. Typical absolute separation of the timestamp of a measurement from say pinger.slac.stanford.edu to sitka.triumf.ca versus pinger-raspberry.slac.stanford.edu to sitka.triumf.ca is several minutes (e.g. ~ 8 mins for measurements during the time frame June 17 to July 14, 2015), see spreadsheet. At each measurement cycle, each MA issues a set of 100 Byte pings and a set of 1000 Byte ping requests to each target in the MA’s list of targets, stopping when the MA receives 10 ping responses or it has issued 30 ping requests. The number of ping responses is referred to as N and is in the range 0 - 10. The data recorded for each set of pings consists of: the MA and target names and IP addresses; a time-stamp; the number of bytes in the ping request; the number of ping requests and responses (N); the minimum Round Trip Time (RTT) (Min_RTT), the average RTT (Avg_RTT) and maximum RTT (Max_RTT) of the N ping responses; followed by the N ping sequence numbers, followed by the N RTTs. From the N RTTs we derive various metrics including: the minimum ping RTT; average RTT; maximum RTT; standard deviation (stdev) of RTTs, 25% probability (first quartile) of RTT; 75% probability (third quartile) of RTT; Inter Quartile Range (IQR); loss; and reachability (host is unreachable if it gets 100 % loss). We also derive the Inter Packet delay (IPD) and the Inter Packet Delay Variability (IPDV) as the IQR of the IPDs.
The data is publicly available and since the online data goes back to January 1998, it currently provides ~19 years of historical data on worldwide Internet performance.
Measurements
We chose to make detailed measurements to and from two MAs at SLAC.
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| Metric \ Monitor Target | pinger to pinger-raspberry | pinger-raspberry to pinger | pinger to sitka | pinger-raspberry to sitka | sitka to pinger | sitka to pinger-raspberry | pinger to CERN | pinger-raspberry to CERN |
|---|---|---|---|---|---|---|---|---|
| Time period | June 17 - July 13, 2015 | June 17 - July 13, 2015 | June 17 - July 14, 2015 | June 17 - July 14 | July 15 - July 16 2015 | July 15 - July 16 2015 | June 17 - July 12, 2015 | June 17 - July 12, 2015 |
| Samples | 10890 | 10850 | 10900 | 10850 | 820 | 820 | 10900 | 10900 |
Min RTT | 0.43 ms | 0.41 ms | 22 +- 1 ms | 22.3 +- 1 ms | 22 ms | 22.4 ms | 150 +- 1 ms | 151 ms |
| Avg RTT | 0.542 +- 0.06 ms | 0.529 +- 0.5ms | 23.9 +- 1ms | 23.827 +- 1 ms | 22.30 ms | 22.709 ms | 150.307 +- 2.4 ms | 151.024 +- 1.3 ms |
Max RTT | 1.15 ms | 20.8 ms | 761 ms | 334 ms | 26.3 ms | 25.9 ms | 288 ms | 183 ms |
| Stdev | 0.055 ms | 0.540 ms | 9.58 ms | 9.60 ms | 0.219 ms | 0.222 ms | 2.37 ms | 1.3 ms |
| Median RTT | 0.542 +- 0.05 ms | 0.51 ms +- 0.052 ms | 22.3 +- 0.2 ms | 22.7 +- 0.11 ms | 22.3 +- 0.11 ms | 22.7 +- 0.21 ms | 150 +- 1 ms | 151 +- 0.01 ms |
| 25% | 0.514 ms | 0.48 ms | 22.2 ms | 22.69 ms | 22.3 ms | 22.8 ms | 149.99 ms | 150.99 ms |
| 75% | 0.564 ms | 0.532 ms | 22.4 ms | 22.8 ms | 22.19 ms | 22.59 ms | 151 ms | 151 ms |
| IQR | 0.05 ms | 0.052 ms | 0.2 ms | 0.11 ms | 0.113 ms | 0.210 ms | 1.01 ms | 0.01 ms |
| Min IPD | -0.59 ms | -20.29 ms | -244 ms | -235.1 ms | -0.4 ms | -0.39 ms | -137 ms | -32 ms |
| Avg IPD | 0 ms | 0 ms | 0 ms | 0 ms | 0 ms | 0 ms | 0 ms | 0 |
| Max IPD | 0.62 ms | 20.26 ms | 268 ms | 146 ms | 3.6 ms | 3.29 ms | 138 ms | 32 ms |
| Median IPD | 0 +- 0.07 ms | 0 +- 0.05 ms | 0 +- 0.2 ms | 0 +- 0.2ms | 0 ms +- 0.2 ms | 0 +- 0.2 ms | 0 +- 0.01 ms | 0 +- 0.01 ms |
| Stdev | 0.248 ms | 0.296 ms | ||||||
| 25% IPD | -0.04 ms | -0.03 ms | -0.1 ms | -0.11 ms | -0.1 ms | -0.1 ms | -0.01 ms | -0.01 ms |
| 75% IPD | 0.03 ms | 0.02 ms | 0.09 ms | 0.1 ms | 0.01 ms | 0.09 ms | 0 ms | 0 ms |
| IQR IPD | 0.07 ms | 0.05 ms | 0.190 +- 0.5 ms | 0.210 +- 0.4 ms | 0.2 ms | 0.190ms | 0.01 ms | 0.01 ms |
| Min(abs(IPD)) | 0 ms | 0 ms | 0 ms | 0 ms | 0 ms | 0 ms | 0 ms | 0 ms |
| Avg(abs(IPD)) | 0.041 ms | 0.066 ms | 0.424 ms | 0.406 ms | 0.120 ms | 0.139 ms | 0.386 ms | 0.046 ms |
| Max(abs(IPD)) | 0.0628ms | 20.294 ms | 268 ms | 235.1 ms | 4 ms | 3.29 ms | 138 ms | 32 ms |
| Stdev | 0.248 ms | 0.262 ms | ||||||
| Median(abs(IPD)) | 0.03ms | 0.024 ms | 0.09 ms | 0.1 ms | 0.1 ms | 0.09 ms | 0 ms | 0 ms |
| 25%(abs(IPD)) | 0.01ms | 0.008 ms | 0.01 ms | 0.01 ms | -0.01 ms | -0.01 ms | 0.01 ms | 0.01 ms |
| 75%(abs(IPD)) | 0.058 ms | 0.05 ms | 0.1 ms | 0.19 ms | 0.1 ms | 0.19 ms | 1 ms | 0 ms |
| IQR(abs(IPD) | 0.048 ms | 0.042 ms | 0.09 ms | 0.11 ms | 0.11 ms | 0.2 ms | 0.009 ms | 0.01 ms |
| Loss | 0% | 0% | 0% | 0.008% | 0% | 0% | 0% | 0% |
Since the timestamps of measurements for one MA to a target are not synchronized with another MA to the same target, they are sampling the network at different times. Thus we decided not to use the residuals in the RTTs between on pair and another. To find the probability of the distributions overlapping use a nomogram of mean differences versus error ratios given in Overlapping Normal Distributions. John M. Linacre for normal distributions.
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