This example visualizes pairwise round-trip times between PlanetLab hosts, plotting measured latency against geographic distance. It shows scatterplots and cumulative distribution functions for two measurement sets taken at different times of day, revealing the relationship between network delay and physical separation. The code uses gnuplot to render the graphs, while Perl scripts compute great-circle distances from latitude/longitude coordinates. Ping commands with ten packets per host pair generate the underlying latency data.