pmacct is a set of network tools to gather IP traffic
informations (bytes counter and number of packets); aggregation
of statistics is done using simple primitives (MAC addresses,
source host, destination host, ports and ip protocols) that can
be used alone or combined together to form complex aggregation
methods; counters are either global or historical (broken at
fixed timeslots). Data is either stored in a memory table,
pulled to stdout or in a SQL database (MySQL or PostgreSQL).
Gathering packets off the wire is done either using pcap
library (and promiscuous mode of the listening interface) or
reading Netflow packets coming from the network.

WWW: http://www.ba.cnr.it/~paolo/pmacct/