The origin of IPv6 work lay in the imminent exhaustion of address space and global routing table growth; both could be summarized as Internet growth.
The Internet is a victim of his own success. No one in the 1970s could have predicted this level of penetration into our lives.
In theory, 32 bits of IPv4 address space enables 4 billion hosts. Studies [RFC1715] have shown that the effectiveness of an address space is far less. For example, RFC1715 defines a H ratio as: H = log (number of objects using the network)/number of bits of the address space. Based on some empirical studies of phone numbers and other addressing schemes, the author concluded that this H ratio usually never reaches the value of 0.3, even with the most efficient addressing schemes. An optimistic H ratio is 0.26 and a pessimistic one (for not very efficient addressing schemes) is 0,14. At H = 0 26, with an addressing of 32 bits, the maximum number of objects, in the case of IPv4 the number of reachable hosts, is 200 000 000.1 When IPv4 Internet reaches 200 million reachable nodes, the IPv4 addresses will be exhausted.
Moreover, the IPv4 address space was designed with three classes (A, B and C)2 which makes the address space usage even less efficient than with the optimistic H ratio. In August 1990 at Vancouver IETF, a study [Solensky, 1990] demonstrated the exhaustion of class B address space by March 1994. Figure 1.1 shows the summary slide presented during that IETF. This was ...