Or, "”Why are we skipping from IPv4 to IPv6?
IPv5 never existed. The version number “5” in the IP header was assigned to identify packets carrying an experimental non-IP real-time stream protocol called ST. ST was never widely used, but since the version number 5 had already been allocated the new version of IP was given its own unique identifying number, 6. ST is described in RFC 1819. • What is the 6bone? The 6bone is the experimental IPv6 backbone being developed using IPv6-in-IPv4 tunnels. This is intended for early experimentation with IPv6 and is not a production service. • What is the MBONE? The Multicast backBONE (MBONE) is a multicast-capable portion of the Internet backbone. Multicast support over IP is provided by a protocol called IGMP (Internet Group Management Protocol) which is defined in RFC 1112. The MBONE is still a research prototype, but it extends through most of the core of the Internet (including North America, Europe, and Australia). It is typically used to relay multimedia (audio and low bandwidth video)
