IPv6 addresses: why such a high number of bits?
During the design of IPv4, people thought that 32 bits were enough for the world. Looking back into the past, 32 bits were enough until now and will perhaps be enough for another few years. However, 32 bits are not enough to provide each network device with a global address in the future. Think about mobile phones, cars (including electronic devices on its CAN-bus), toasters, refrigerators, light switches, and so on… So designers have chosen 128 bits, 4 times more in length than in IPv4 today. The usable size is smaller than it may appear however. This is because in the currently defined address schema, 64 bits are used for interface identifiers. The other 64 bits are used for routing. Assuming the current strict levels of aggregation (/48, /32, …), it is still possible to “run out” of space, but hopefully not in the near future. See also for more information RFC 1715 / The H Ratio for Address Assignment Efficiency and RFC 3194 / The Host-Density Ratio for Address Assignment Effici
