Open System Interconnection

(O-S-I)

A network model that divides the communications task into layers. In theory, each layer would feed the layer above. The layers allow standards to be applied to each layer but also allow implementation of the layer to be machine-specific. From top (layer #7) to bottom, the layers are:

• 7 Application layer
• 6 Presentation layer
• 5 Session layer
• 4 Transport layer
• 3 Network layer
• 2 Data link layer
• 1 Physical layer

More Information

• OSI Standards
• ISO Home Page
• Understanding OSI