The description of the logical structure, formats, protocols, and operational sequences for transmitting information units through, and controlling the configuration and operation of, networks. The layered structure of SNA allows the ultimate origins and destinations of information, that is, the end users, to be independent of and unaffected by the specific SNA network services and facilities used for information exchange.
A collection of rules that brings uniformity to communications systems and the ways they interact. These rules define various functions that allow information to be transferred from one computer to another in a form that is usable by the receiving computer.