What is the OSI model?
The OSI (Open Systems Interconnection) model is a standard developed by the ISO (International Standards Organization) to describe the flow of data on a computer network. The model takes into account the flow of data from the physical connections up to the end user application.
The OSI model defines a "layered" architecture in the form of a protocol stack. There are specific, discrete functions that take place at each layer of the protocol stack with lower level layers providing services to upper layers. When two systems communicate on the network, information is sent down through the protocol stack of one system, over the cable and then up through the protocol stack to the appropriate layer on the other system.
Data flow under the OSI model is organized into the following seven layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.