Evolution of IPv4:
In 1969, ARPA (Advanced Research Project Agency) of United States Department of Defense came up with ARPAnet during Cold war and this is the first Packet Switched Network. They connected 4 computers on ARPAnet. ARPAnet eventually turned into NSFnet, a network used by National Science Foundation and primarily used by scientists for research purpose. NSFnet then grows into modern Internet.
ARPAnet initially used NCP (Network Control Program) to establish reliable, flow-controlled, bidirectional communication. In 1983, they decided to replace NCP with TCP as the principal protocol.
For many years, TCP was already used by scientists as end-to-end delivery protocol and they decided to split the load to IP. By the time, developers’ starts working on split work to create IP, TCP was in Version 3. So the new developed IP was marked as Version 4.
So IP version 4 is the first standardized version of Internet Protocol.
What is IPv5?
In early 1970s, Engineers developed Internet Stream protocol (ST) to support efficient delivery of packets to single or multiple destination that requires guaranteed data rate and controller delay characteristics (like Voice traffic).
As IPv4 starts exhausting around 1993, people realized they need network layer protocol and started developing ST2. IBM, NeXT, Sun Microsystems used this version of network layer protocol in their network.
This network layer protocol is designated as IPv5
Features like NAT, dynamic address allocation keeps IPv4 address exhaustion under control and developers had enough time for IPng development. IPng was officially designated as IPv6 and people started moving from IPv4 to IPv6 instead of IPv4 to IPv5 to IPv6. So IPv5 was not used by or supported in our modern computers.