22-02-2013, 10:32 AM
OSI Reference Model
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Why a layered model?
Easier to teach communication process.
Speeds development, changes in one layer does not affect how the other levels works.
Standardization across manufactures.
Allows different hardware and software to work together.
Reduces complexity
Introduction OSI
The Open System Interconnection Reference Model (OSI Reference Model or OSI Model) is an abstract description for layered communications and computer network protocol design.
It divides network architecture into seven layers which, from top to bottom, are the Application, Presentation, Session, Transport, Network, Data Link, and Physical Layers. It is therefore often referred to as the OSI Seven Layer Model.
OSI History
In 1978, the International Standards Organization (ISO) began to develop its OSI framework architecture.
OSI has two major components: an abstract model of networking, called the Basic Reference Model or seven-layer model, and a set of specific protocols.
The concept of a 7 layer model was provided by the work of Charles Bachman, then of Honeywell.
Various aspects of OSI design evolved from experiences with the Advanced Research Projects Agency Network (ARPANET) and the fledgling Internet.