Open Systems Interconnection
ISO seven layer model
Open Systems Interconnect
OSI Model
OSI Reference Model
OSI-RM
OSI seven layer model
seven layer model
(OSI-RM, OSI Reference Model, seven layer model)
A model of network architecture and a suite of protocols (a
protocol stack) to implement it, developed by ISO in 1978
as a framework for international standards in heterogeneous
computer network architecture.
The OSI architecture is split between seven layers, from
lowest to highest: 1 physical layer, 2 data link 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. In some implementations a layer
may itself be composed of sub-layers.
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.
Apart from its actual application to real protocols, it also
serves as a useful teaching model.
(2004-02-13)
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