FreeBSD (http://www.freebsd.org/)
pfSense (https://www.pfsense.org/)
IPFIX (Netflow) (http://en.wikipedia.org/wiki/IP_Flow_Information_Export, http://en.wikipedia.org/wiki/NetFlow)
- including MAC addresses
VLAN capable
yaf (https://tools.netsa.cert.org/yaf/)
Nfdump (http://nfdump.sourceforge.net/)
MySQL (http://www.mysql.com/)
Simple, yet effective tailored and customizable reports
Intentionaly built without any Deep Packet Inspection (DPI) (http://en.wikipedia.org/wiki/Deep_packet_inspection)
- ensure Net neutrality
- keep costs low for hardware (less computing power) and software (lower complexity)
- no 'cats and dogs' game to run after ever-evolving application and service types
- no insights into the content, no 'spyware', only uses short-lived metadata for reporting
- cheap in hardware & software; no ongoing maintenance/updating of rules required
