skitter: modeling rtt along a single path champagne.caida.org (UIUC) monitor fewest destinations, most probes/dst per day, 1/5min/dst (270) 63 days 08 July - 08 Sept 2000 exactly 9 weeks, sun-sat only use stable subsets of paths 75% responsive, 33% of paths same per day min 5000 paths same --> gives us 168 pairs to work with