IPv3 is not a version of the Internet Protocol that was ever assigned or used. The Internet Protocol (IP) was originally designed to split the original network stack with Transmission Control Protocol (TCP) at layer four and IP at layer three. At the time, the design for TCP was struggling to solve two problems at the same time: how to package data, and how to send that data someplace. That’s how we got to IPv4. IPv4 was built to support efficient delivery of streams of packets to either single or multiple destinations, requiring guaranteed data rates and controlled delay. With IPv5, computer scientists were trying to find a way to transmit voice over packet-switching networks. Originally, IP was not designed in a time before routers were required to maintain state. However, IPv5 was not really assigned, but it was understood to be associated with a separate experimental protocol for streaming that saw limited use.