promiscuous mode traffic accountant

 pmacct is a tool designed to gather traffic information (bytes and number
 of packets) by listening on a promiscuous interface or for Netflow data,
 which may facilitate billing, bandwidth management, traffic analysis, or
 creating usage graphs.
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 Data can be stored in memory and queried, displayed directly, or written
 to a database; storage methods are quite flexible and may aggregate totals
 or keep them separate.