Internet Stream Protocol

The Internet Stream Protocol (ST) is a family of experimental protocols first defined in Internet Experiment Note IEN-119 in 1979, and later substantially revised in RFC 1190 (ST-II) and RFC 1819 (ST2+). The protocol uses the version number 5 in the version field of the Internet Protocol header, but was never known as IPv5. The successor to IPv4 was thus named IPv6 to eliminate any possible confusion about the actual protocol in use.