2. IPv6 protocol

2.1 IPv4 addressing capability

An IPv4 address is encoded on 32 bits. With 32-bit addressing, there is a stock of around 4.3 billion IP addresses (2 ³² or 4,294,967,296 addresses).

However, from the 4.3 billion theoretical addresses, we need to subtract the whole of class D, reserved for multicast, as well as a number of addresses lost to end-users (allocated for operating purposes, etc.). We can therefore estimate the total usable theoretical stock at around 3.9 billion addresses.

At the end of 2003, it was estimated that less than a third of the total number of addresses remained unallocated, i.e. around 1.3 billion. This may seem a large number, but in recent years, the global growth rate...