http://www.hyperorg.com/misc/stupidnet.html
http://www.ietf.org/rfc/rfc2993.txt
http://www.potaroo.net/papers/isoc/2003-09/nats.html
http://www.cisco.com/en/US/about/ac123/ac147/archived_issues/ipj_7-3/anatomy.html
http://www.ietf.org/rfc/rfc2663.txt
http://www.ietf.org/rfc/rfc3022.txt