(Internet Protocol version 6) is a version of the Internet Protocol (IP) intended to succeed IPv4, which is the protocol currently used to direct almost all Internet traffic.
The Internet operates by transferring data between hosts in packets that are routed across networks as specified by routing protocols. These packets require an addressing scheme, such as IPv4 or IPv6, to specify their source and destination addresses. Each host, computer or other device on the Internet requires an IP address in order to communicate. The growth of the Internet has created a need for more addresses than are possible with IPv4. The last top level (/8) block of free IPv4 addresses was assigned in February 2011 by IANA to the 5 RIRs, although many free addresses still remain in most assigned blocks and RIRs will continue with standard policy until it is at its last /8. After that, only 1024 addresses (a /22) are made available from the RIR for each LIR: currently, only APNIC has already reached this stage.
IPv6 was developed by the Internet Engineering Task Force (IETF) to deal with this long-anticipated IPv4 address exhaustion, and is described in Internet standard document RFC 2460, published in December 1998. Like IPv4, IPv6 is an internet-layer protocol for packet-switched internetworking and provides end-to-end datagram transmission across multiple IP networks. While IPv4 allows 32 bits for an IP address, and therefore has 232 (4 294 967 296) possible addresses, IPv6 uses 128-bit addresses, for an address space of 2128 (approximately 3.4×1038) addresses. This expansion allows for many more devices and users on the internet as well as extra flexibility in allocating addresses and efficiency for routing traffic. It also eliminates the primary need for network address translation (NAT), which gained widespread deployment as an effort to alleviate IPv4 address exhaustion.
IPv6 also implements additional features not present in IPv4. It simplifies aspects of address assignment (stateless address autoconfiguration), network renumbering and router announcements when changing network 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, including the option of IPsec.
For the Internet to make use of the advantages of IPv6 over IPv4, most hosts on the Internet, as well as the networks connecting them, need to deploy this protocol. However, IPv6 deployment has been slow. While deployment of IPv6 is accelerating, especially in the Asia-Pacific region and some European countries, areas such as the Americas and Africa are comparatively lagging in deployment of IPv6. IPv6 does not implement interoperability features with IPv4, and creates essentially a parallel, independent network. Exchanging traffic between the two networks requires special translator gateways, but modern computer operating systems implement dual-protocol software for transparent access to both networks either natively or using a tunneling protocol such as 6to4, 6in4, or Teredo. In December 2010, despite marking its 12th 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 at that time