Open Systems Interconnection

Open Systems Interconnection (OSI) is an effort to standardize computer networking that was started in 1977 by the International Organization for Standardization (ISO), along with the ITU-T.

Prior to OSI, networking was largely either government-sponsored (ARPANET in the US, CYCLADES in France) or vendor-developed and proprietary standards (such as the System network architecture (SNA) of IBM and DECnet of Digital Equipment Corporation). An Experimental Packet Switched system in the UK circa 1973, also identified the need to define higher level protocols. The NCC (UK) publication 'Why Distributed Computing' which came from considerable research into future configurations for computer systems, resulted in the UK presenting the case for an international standards committee to cover this area at the ISO meeting in Sydney in March 1977. OSI was hence an industry effort, attempting to get industry participants to agree on common network standards to provide multi-vendor interoperability. It was common for large networks to support multiple network protocol suites, with many devices unable to interoperate with other devices because of a lack of common protocols. However, while OSI developed its networking standards, TCP/IP came into widespread use on multivendor networks for internetworking, while on the local network level both Ethernet and token ring gained prominence.

The OSI reference model was a major advance in the teaching of network concepts. It promoted the idea of a consistent model of protocol layers, defining interoperability between network devices and software. The OSI model was defined in raw form in Washington, DC in February 1978 by Hubert Zimmermann of France and the refined standard was published by the ISO in 1984.

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