Internet Stream Protocol

family of experimental protocols first defined in Internet Experiment Note IEN-119, using the IP version number 5

The Internet Stream Protocol was a protocol which was developed for streaming content over the internet. It was first developed in 1979, and later revised. Despite this it was never widely used. It used the number 5 for the version field of the internet protocol. For this reason, the extended version of the internet protocol is known as version 6, as the version 5 was already taken.