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PingER simply reports whether there were duplicates or not. A useful metric is to report the number of pings received/number pings sent. The number received may depend on the ping command options. One option will send a given number of pings until it receives that many back or times out. Another option will send 10 pings and wait (or time out) until they are received. So the metric value may also depend on the ping command.
CERN
For each ping sent to www.cern.ch it responds with ~3 pings consistently. Using the normal traceroute www.cern.ch does not respond. Using the ICMP traceroute it does respond (twice). Pinging each node along the route using pingroute.pl, it is seen that only www.cern.ch responds with duplicate packets.