Communications protocol

A communications protocol is a standard that defines the way in which data is passed between two or more pieces of computer equipment over a telephone line or other communications link. Two pieces of equipment must be using the same protocol to communicate.

There are several different families of communications protocols, each governing a different aspect of the communications process. For example, modem protocols govern the way in which modems convert digital signals into analog signals for transmission over telephone lines, while other protocols govern the way in which computers attached to those modems convert data into a series of bits for transmission.