<networking> (OSI, seven layer model) The OSI Reference Model of network architecture and a suite of protocols (protocol stack) to implement it were developed by ISO in 1978 as a framework for international standards in heterogeneous computer network architecture.
The architecture is split between seven layers, from lowest to highest: 1 physical layer, 2 datalink layer, 3 network layer, 4 transport layer, 5 session layer, 6 presentation layer, 7 application layer.
Each layer uses the layer immediately below it and provides a service to the layer above.
OSI is the umbrella name for a series of non-proprietary protocols and specifications, comprising, among others, the OSI reference model, ASN.1 (Abstract Syntax Notation 1), BER (Basic Encoding Rules), CMIP and CMIS (Common Management Information Protocol and Services), X.400 (Message Handling System, or MHS), X.500 (Directory Service), Z39.50 (search and retrieval protocol used by WAIS), and many others.
(12 Jan 1995)