When a packet is sent from one host to the other@ one normally expects that exactly one copy of the packet that was sent arrives at the destination. It is@ however@ possible that a packet is either lost or that multiple copies arrive. In earlier work@ a metric for packet loss was defined. This metric quantifies the case where a packet that is sent does not arrive at its destination within a reasonable time. In this memo@ a metric for another case is defined: a packet is sent@ but multiple copies arrive. The document also discusses streams and methods to summarize the results of streams.