...
As we review the logs we will determine whether probing from some landmarks is reliable enough to warrant their use.
Landmark Failures
The typical failure mechanisms for the target www.cern.ch with a timeout of 2 and 10 seconds made in the evening (PDT) of September 8th 2007 is seen in the table below. The multiple numbers in each cell are for different requests. It is seen that increasing the timeout from 2 to 10 seconds does not provide much, if any help. So we utilize a timeout of 2 seconds.
Timeout | 2 secs | 10 secs |
|---|---|---|
100% loss | 7, 10, 9 | 10, 11, 8 |
Success | 22, 16, 17 | 20, 14, 21 |
Fail to connect | 10, 8, 9 | 8, 6, 5 |
Timeout | 45, 50, 49 | 46, 51, 46 |
Performance
Some spot measures of performance indicate that for 10 pings per target and 86 PlanetLab landmarks for region=northamerica as we vary the number of landmarks accessed simultaneously, the number of parallel requests per landmark, and the timeout for each request the duration is as follows (n.b. there is a timeout of 100 seconds on the complete process, and the default values are ins boldface in the table below:
...