In order to communicate on a TCP/IP network, a node must have an IP address. TCP/IP currently supports two methods of addressing: IPv4 and IPv6. IPv5 was strictly an experimental addressing standard and was never formally adopted. As mentioned in the previous chapter, IPv4 was the first publicly used version of the Internet Protocol, and it called for addressing using four octets of 8 bits each, for a total of 32 bits. This allows for about 4.3 billion addresses. While this addressing scheme was adequate for its time, by the early 1990s it became clear that as more nodes connected to the internet, IPv4 address exhaustion was inevitable, even after classless addressing and private addresses were introduced to conserve IPv4 address space.
As a result, the IPv6 project began in the 1990s. IPv6 addressing uses 128 bits, and the standard size of an IPv6 subnet...