Theory and History
By the late 1980s, members of the IETF (Internet Engineering Task Force) started discussing the possible future limitations and conceptual problems of IPv4. With the invention of the World Wide Web protocol by Tim Berners-Lee in the early 1990s came an explosion of interest in the Internet outside the academic and research oriented non-commercial Internet user base. Much of that explosion hastened the discussions of the successor to IPv4. The end result was the creation of the IPv6 protocol family whose RFCs began rolling out in 1995.
Note that there was an IPv5 specification produced in the late 1980s. However, even within the RFCs defining IPv5 it was referred to and considered as an "experimental" protocol. It was never ...