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The Open Systems InterConnection (OSI) model is a reference model developed by International Organization for Standardization (ISO) in 1984. Which describes how communication should take place between two nodes in a network.

Description

• Framework design to communicate across all types of computer systems.
• Consists of seven separate but related layers.
• Each layer performs specific functions and then passes result to another layer.
• Each layer defines the process of moving information across a network.
• Request of data moves from top application layer to bottom physical layer and reverse happens at the receiving end.
• Remember its not a protocol but its a model.

Diagram

Layers

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

Details of each layer is explained in further points of this chapter.