Flow-tools is a set of utilities for collecting and storing NetFlow data, and doing some limited analysis of it. NetFlow is a Cisco-developed protocol for transferring network traffic flow information (usually from a router or switch) to another system that collects and stores this information. More information on NetFlow is available at http://www.cisco.com/cpropart/salestools/cc/pd/iosw/ioft/neflct/index.htm