Basic point-to-point data link

A traditional point-to-point data link is a communications medium with exactly two endpoints and no data or packet formatting. The host computers at either end had to take full responsibility for formatting the data transmitted between them. The connection between the computer and the communications medium was generally implemented through an RS-232 interface, or something similar. Computers in close proximity may be connected by wires directly between their interface cards .

When connected at a distance, each endpoint would be fitted with a modem to convert analog telecommunications signals into a digital data stream. When the connection used a telecommunications provider, the connections were called a dedicated, leased, or private line. The ARPANET used leased lines to provide point-to-point data links between its packet-switching nodes, which were calledInterface Message Processors.