ARPANET : Addressing
ARPANET addressing are unimportant, they illustrate an alternative way in which wide area networks form physical addresses. Unlike the flat address schemes used by LAN technologies, wide area networks usually embed information in the address that helps the network route packets to their destination efficiently.
In the ARPANET technology, each packet switch is assigned a unique integer, P, and each host port on the switch is numbered from 0 to N-I. Conceptually, a destination address consists of a pair of small integers, (P, N). In practice, the hardware uses a single, large integer address, with some bits of the address used to represent N and others used to represent P.