IPv6 stands for Internet Protocol version 6. It is the second version of the Internet Protocol to be used generally across the virtual world. The first version was IPv4. IPv5 was a protocol of a different sort, intended to support video and audio rather than all-purpose addressing. IPv6 is also known as IPng, which stands for IP Next Generation.

One of the main upgrades in IPv6 is in the number of addresses available for networked devices. For example, each mobile phone or other kind of electronic device can have its own IPv6 address. IPv6 allows 3.4x10^38 addresses. This is mainly due to the number of bits in each protocol. IPv4 addresses have 32 bits in them and so allow a maximum of four billion addresses. IPv6 addresses have 128 bits.

However, IPv4 is still the protocol of choice for most of the Internet. The transition will be a steady one, and IPv6 is the future of Internet addressing, mainly because industry experts believe that they are close to running out of available addresses altogether.

Another example of an IPv6 upgrade is multicasting, which is standard in IPv6 but only optional in IPv4. Multicasting is delivering a data stream to multiple destinations at the same time, with no duplication unless called for. Those functionalities are not supported by IPv4. The other two types of addressing that are standard practice for IPv6 are unicast and anycast. The former is a transmission from just one host to just one other host; the latter is from one host to the nearest of many hosts.

IPv6 also has two other significant advantages over IPv4. IPv6 offers a higher level of built-in security, and it has been specifically designed with mobile devices in mind. The security comes in the form of IPsec, which allows authentication, encryption, and compression. The mobility comes in the form of Mobile IP, which allows roaming between different networks without losing an established IP address. Both of these functionalities are requirements of IPv6 and so are designed to be built into every IPv6 stack, address, and network.