As we already mentioned, the growing number of Internet hosts causes a severe shortage in IP addresses and eventually will consume the entire address space. The theoretical address space size (2^32 nodes) is largely wasted due to assignment inefficiencies. Dividing the address space into classes (A, B and C) has its own contribution to the inefficiency of addresses assignment. Changing the IP addressing scheme is a matter concerning all Internet users and is an opportunity for providing additional functionality to the IP.

The new version of IP is often referred to as IPng: "Internet Protocol: Next Generation", is also known as IP version 6 (in oppose to the currently used version 4). Most Internet users agreed IPng should have a hierarchical address structure (like CIDR - see ahead). This new address structure should be large enough to meet the needs of the Internet community for a very long time.

There were several proposals for IPng. The most likely to become a standard were: "Common Architecture for the Internet" (CATNIP), "Simple Internet Protocol Plus" (SIPP), and "The TCP/UDP Over CLNP"-Addressed Networks (TUBA) proposals. The main considerations in choosing one proposal over the others were:
* Current address assignment policies should not be changed.
* There is no need to reclaim assigned network numbers.
* There is no need to renumber most of the Internet
Eventually the "Simple Internet Protocol Plus (SIPP) Spec. (128 bit version)" was adopted (with several changes) as the basis for IPng.
As mentioned before, IPng was assigned the name IPv6.

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