Calibration of ping
Sanity checks:
- host pings itself, host pings host at same site
- high statistics between a few sites:
- look at subtle behaviors, e.g. distribution of tail
- check wire time (sniffer) vs. ping reported times, at monitor & responder
- see http://www.slac.stanford.edu/comp/net/wan-mon/error.html
Correlate with Surveyor one-way measures