Reference

TCP/IP Illustrated, Volume 1: The Protocols - http://www.kohala.com/start/tcpipiv1.html	
http://www.rfc-editor.org/rfcsearch.html
RFC 791 Internet Protocol
RFC 793 Transmission Control Protocol
RFC 768 User Datagram Protocol
RFC 792 Internet Control Message Protocol
http://www.iana.org/assignments/protocol-numbers
http://www.iana.org/assignments/port-numbers
http://www.sans.org/resources/tcpip.pdf