While researching IPv6, the Alert Logic team thought it would be a good exercise to tell the short, but interesting story about IPv5. Contrary to popular belief, the Internet Protocol (IP) was not initially developed to manage network addresses. Instead, it was created as part of a solution to split the original network stack, with Transmission Control Protocol (TCP) handling layer four and IP managing layer three. At the time, TCP was grappling with two key challenges: how to package data efficiently and how to reliably send that data to its destination. That’s how we got to IPv4.
The History of TCP
TCP version 1 was designed in 1973 as documented through RFC 675. TCP version 2 was documented in March 1977. In August 1977, Jon Postel realized they were going the wrong direction with the protocol. “We are screwing up in our design of internet protocols by violating the principle of layering. Specifically, we are trying to use TCP to do two things: Serve as a host level end-to-end protocol, and to serve as an internet packaging and routing protocol. These two things should be provided in a layered and modular way. I suggest that a new distinct internetwork protocol is needed, and that TCP be used strictly as a host level end to end protocol.”
At this point, TCP and IP were split, with both being versioned number 3 in spring 1978. Stability was added in the fourth revision and that is how we got to IPv4. Whatever happened to IPv5? It was an experimental protocol that ultimately failed to solve the limitations of IPv4 and was never widely adopted.
IPv4 was built to support efficient delivery of streams of packets to either single or multiple destinations, requiring guaranteed data rates and controlled delay. In other words, it was attempting to solve quality–of-service issues from the original Internet Protocol. IPv5 was an experimental protocol developed by computer scientists to transmit voice over packet-switching networks. Initially, IP was designed without considering the need for routers to maintain state information. As the concept of streaming video and other forms of media became feasible, RFC 1190 proposed a formal implementation of IPv5. Companies like Apple, Sun, and IBM made attempts to adopt it. However, advances in bandwidth, applications, and compression ultimately allowed networks to evolve around IPv4’s limitations, making the widespread adoption of IPv5 unnecessary.
