From Vern in GH-846: This is a conscious decision in the TCP analysis to
consider a connection's "duration" to run up through the end of its
productive (= data can be delivered) lifetime, not extending beyond that. So
once it's closed, packets seen subsequently (until the state-holding for the
connection times out) get processed in terms of updating the associated
history, but not the duration. This can include (unnecessarily) retransmitted
data packets, like in one of the examples above. An advantage of this definition
of "duration" is it allows more accurate computation of connection data rates.
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