Internet Protocol Version 6 (IPv6) is a version of the Internet Protocol that is designed to succeed Internet Protocol version 4 (IPv4), the first publicly used Internet Protocol in operation since 1981. IPv6 is an Internet Layer protocol for packet-switched internetworking. The main driving force for the redesign of Internet Protocol was the foreseeable IPv4 address exhaustion. IPv6 was developed by the Internet Engineering Task Force (IETF), and is described in Internet standard document RFC 2460, published in December 1998.
IPv6 has a vastly larger address space than IPv4. This results from the use of a 128-bit address, whereas IPv4 uses only 32 bits. The new address space thus supports 2128 addresses. This expansion provides flexibility in allocating addresses and routing traffic and eliminates the primary need for network address translation (NAT), which gained widespread deployment as an effort to alleviate IPv4 address exhaustion.
IPv6 also implements many other new features. It simplifies aspects of address assignment (stateless address autoconfiguration) and network renumbering (prefix and router announcements) when changing Internet connectivity providers.
The IPv6 subnet size has been standardized by fixing the size of the host identifier portion of an address to 64 bits to facilitate an automatic mechanism for forming the host identifier from Link Layer media addressing information (MAC address). Network security is also integrated into the design of the IPv6 architecture, and the IPv6 specification mandates support for IPsec as a fundamental interoperability requirement.
For deployment, IPv6 is largely incompatible with IPv4 at the packet level, and translation services have practical issues that make them controversial. IPv6 and IPv4 are therefore treated as almost entirely separate networks with devices having two separate protocol stacks if they need to access both networks, with tunneling of IPv6 on IPv4 and vice versa. In December 2008, despite marking its 10th anniversary as a Standards Track protocol, IPv6 was only in its infancy in terms of general worldwide deployment.
A 2008 study by Google Inc. indicated that penetration was still less than one percent of Internet-enabled hosts in any country. IPv6 has been implemented on all major operating systems in use in commercial, business, and home consumer environments.
