A model devised by the International Standards Organization for network communication involving computer hardware and software applications. The model is defined in seven layers: application layer, presentation layer, session layer, transport layer, network layer, data link layer, and physical layer (see diagram). Each layer passes data to the layers directly above and below it. The application layer is furthest from the communication link and the physical layer is nearest the link. Data passes over the communication link to the corresponding lowest layer in the remote system. Dashed lines in the diagram represent virtual circuits.

OSI model