
OSI Seven-Layer Model |
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Written by Administrator |
Thursday, 06 May 2010 16:56 |
In the 1980s, the European-dominated International Standards Organization (ISO), began to develop its Open Systems Interconnection (OSI) networking suite. OSI has two major components: an abstract model of networking (the Basic Reference Model, or seven-layer model), and a set of concrete protocols. The standard documents that describe OSI are for sale and not currently available online. Parts of OSI have influenced Internet protocol development, but none more than the abstract model itself, documented in OSI 7498 and its various addenda. In this model, a networking system is divided into layers. Within each layer, one or more entities implement its functionality. Each entity interacts directly only with the layer immediately beneath it, and provides facilities for use by the layer above it. Protocols enable an entity in one host to interact with a corresponding entity at the same layer in a remote host.
![]() The seven layers of the OSI Basic Reference Model are (from bottom to top):
The original Internet protocol specifications defined a four-level model, and protocols designed around it (like TCP) have difficulty fitting neatly into the seven-layer model. Most newer designs use the seven-layer model. |