IPv6 was initially developed to boldness a analytical botheration with the absolute Internet Agreement (commonly alleged IPv4). An IPv4 abode has 4 octets, or 32 bits, to analyze every accessory on the Internet. If anniversary bulge has a distinct altered address, again there can be at best 4,294,967,296 (that is, 2^32) accessories on the Internet. And that doesn't annual for the actuality that best routers and abounding servers accept several addresses.
And, in fact, the bearings is worse than that because of how IP addresses were originally allocated. With a scattering of ample organizations application Class A and B addresses, and ample blocks of the IPv4 abode ambit set abreast for things like multicasting, the Internet Assigned Cardinal Authority (IANA) was bound active out of addresses. The Internet Engineering Task Force (IETF) went off to actualize a new adaptation of the IP agreement with beyond addresses to fix this problem.
Many options were considered, and in the end they came up with IPv6. Of course, in the meantime, because the accessible assignable abode ranges were rapidly active out, a few simple acting standards such as NAT and CIDR were drafted that finer adored IPv4 for abounding years to come.
Today the case for IPv6 is somewhat different. The force active the new agreement is still based on accretion the cardinal of addresses, but it is now a bounded rather than a all-around problem. Several ample blast companies, decidedly in Asia, accept started to appointment problems in allotment an IP abode to every cellular telephone. If they alpha with a Class A abode (such as the all-over 10.0.0.0/8 ambit from RFC 1918), again they can abode at best 16,777,216 devices. So it is accessible to see how a civic arrangement with abounding millions of subscribers would bound bankrupt the accessible addressing. These companies could accept an busy set of overlapping abode ranges absolute by NAT, but IPv6 is a abundant added accustomed and adjustable band-aid to the problem.