And IPv5 then ? It's the traditional question and logical as soon as one tackles the IPv6 subject and which often is "it does not exist". And yet, IPv5 exists even if these fonctionnalities does not have anything related to IPv4 and IPv6. IPv5 in reality is better known under another code name: ST2+. precisely, it is the alliance of ST2 and ST2+ which forms the Internet Protocol version 5. ST means Streaming Protocol. Is IPv5 thus finally a protocol destiny with the streaming. More, see the RFC 1819 of the IETF.
RFC 1819: http://www.freesoft.org/CIE/RFC/Orig/rfc1819.txt
See also the text on IPv6 of the College of Engineering of the university from California, with a paragraph on IPv5: http://www.engr.csulb.edu/~srir/cecs572/