IPv6 is the newest version of the IP protocol.
It was developad to overcome many deficiencias of IPv4, most notably the problem of IPv4 address exhausteon..
Unlike IPv4, which has only about 4.3 billion (232) available addresses, IPv6 allows for 3.4 × 1038, which is over 10,000,000,000,000,000,000,000,000,000 times as many addresses as IPv4.
IPv6 defines the same general functions as IPv4, but with different methods of implementing them. The IPv6 header and address structure has been completely changed, and many of the features that were basically just afterthoughts and addendums in IPv4 are included as full-blown standards in IPv6. Of course, to support IPv6 routing, routers must understanding IPv6 addresses and routing.
Here is a list of the most important IPv6 features
Large address space: IPv6 uses 128-bit addresses, which means that for each person on the Earth there are 48,000,000,000,000,000,000,000,000,000 addresses!
Enhanced security: IPSec (Internet Protocol Security) is built into IPv6 as part of the protocol . This means that two devices can dynamically create a secure tunnel without user intervention.
Header improvements: the packed header used in IPv6 is simpler than the one used in IPv4.
The IPv6 header is not protected by a checksum so routers do not need to calculate a checksum for every packet.
No need for NAT: since every device has a globally unique IPv6 address, there is no need for NAT.
Stateless address autoconfiguration: IPv6 hosts can automatically configure themselves with an IPv6 address.