Internet Protocol version 6 (IPv6) is a network layer protocol for packet-switched internetworks. It is designated as the successor of IPv4, the current version of the Internet Protocol, for general use on the Internet.
The main improvement brought by IPv6 is the increase in the number of addresses available for networked devices, allowing, for example, each mobile phone and mobile electronic device to have its own address. IPv4 supports 232 (about 4.3 billion) addresses, which is inadequate for giving even one address to every living person, let alone supporting embedded and portable devices. IPv6, however, supports 2128 (about 340 billion billion billion billion) addresses, or approximately 5×۱۰۲۸ addresses for each of the roughly 6.5 billion people alive today. With such a large address space available, IPv6 nodes can have as many universally scoped addresses as they need, and network address translation is not required.
By the early 1990s, it was clear that the change to a classless network introduced a decade earlier was not enough to prevent the IPv4 address exhaustion and that further changes to IPv4 were needed. By the winter of 1992, several proposed systems were being circulated and by the fall of 1993, the IETF announced a call for white papers (RFC 1550) and the creation of the “IPng Area” of working groups.
IPng was adopted by the Internet Engineering Task Force on July 25, 1994 with the formation of several “IP Next Generation” (IPng) working groups. By 1996, a series of RFCs were released defining IPv6, starting with RFC 2460. (Incidentally, IPv5 was not a successor to IPv4, but an experimental flow-oriented streaming protocol intended to support video and audio.)