The compelling reason behind the formation of IPv6 was lack of address space, especially in the heavily populated countries of Asia such as India and China among others which do not have enough address space for their use.
The most dramatic change from IPv4 to IPv6 is the length of the network addresses used. IPv6 addresses, as defined by RFC 2373[?] and RFC 2374[?], are 128 bits long and are written in hexadecimal with colons. The number of available addresses in IPv6 is 2128 = 3.4 x 1038 (cf. 232 = 4 billion addresses in IPv4).
For example, 243f:6a88:85a3:08d3:1319:8a2e:0370:7344. If a 16-bit group is 0000, it may be omitted, and if more than two consecutive colons result from this omission, they may be reduced to two colons, as long as there is only one group of more than two consecutive colons. Thus 0588:2353::1428:57ab is the same as 0588:2353:0000:0000:0000:0000:1428:57ab, but 3906::25de::cade is invalid. If the address is an IPv4 address in disguise, the last 32 bits may be written in decimal; thus ::ffff:192.168.89.9 is the same as ::ffff:c0a8:5909.
IPv6 addresses are divided into two parts: a 64-bit routing part, and a 64-bit host-addressing part.
IPv6 deployment To do: