(Internet Protocol Version 6) The next generation IP protocol. Started in 1991, the specification was completed in 1997 by the Internet Engineering Task Force (IETF). IPv6 is backward compatible with and is designed to fix the shortcomings of IPv4, such as data security and maximum number of user addresses.

Virtually Unlimited Addresses
IPv6 increases the address space from 32 to 128 bits, providing for a virtually unlimited (for all intents and purposes) number of networks and systems. It also supports quality of service (QoS) parameters for real-time audio and video. Originally called "IP Next Generation" (IPng), IPv6 is expected to slowly replace IPv4, with the two existing side by side for many years.

IPv6 was officially deployed in July 2004 when ICANN added IPv6 records to its DNS root server for the .jp (Japan) and .kr (Korea) country codes.

What Happened to IPv5?
IPv5 was an experimental streaming audio/video protocol, which had nothing to do with the fundamental structure of IP addressing.