Internet Protocol version 6 (IPv6) is the next-generation Internet Protocol version designated as the successor to IPv4. It was defined in December 1998 by the Internet Engineering Task Force (IETF) with the publication of an Internet standard specification, RFC 2460. IPv6 provides for an expanded address space. It uses 128-bit addressing (versus 32 bits in IPv4), which results in 340 undecillion unique addresses that is, 340 billion billion billion billion.

IPv6 addresses typically have two parts: a 64-bit network prefix and a 64-bit host address. The host address can be assigned sequentially or automatically generated from the interfaces MAC address. The IPv6 addressing structure uses hexadecimal notation, normally written as eight groups of four hexadecimal digits, and colons replace the periods used in IPv4, as in the following example:

2001:0db8:85a3:0000:1319:8a2e:0370:7344

IPv6 has four address types: unicast (one-to-one), anycast (one-to-nearest), multicast (one-to-many), and a reserved class. A single interface may be assigned multiple IPv6 addresses of unicast, anycast, or multicast addresses. Note that IPv6 does not support broadcasting.
IPv6 is designed to be an evolutionary step from IPv4. It can be installed as a normal software upgrade in Internet devices and is interoperable with IPv4. IPv6 runs well in high-performance networks, such as Gigabit Ethernet and ATM networks, and it is also efficient for low-bandwidth networks such as wireless networks. In addition, it provides a platform for new Internet functionality that will be required in the near future. IPv6 simplifies the packet header format (see figure below that shows IP Packet Header). It supports autoconfiguration and multihoming. IPv6 includes the DiffServ Code Point (DSCP) in the traffic class, and it addresses authentication and privacy capabilities.