7 Layers of OSI Model

If network communications need to happen with out any trouble, many problems must be solved. Coordinating all these problems are so complex and not easy to manage. To make these tasks smooth, in 1977 the International Standards Organization (ISO) proposed the Open Systems Interconnection (OSI) network model. The Open Systems Interconnection (OSI) model breaks down the problems involved in moving data from one computer to another computer. Open Systems Interconnection (OSI) model categorizes these hundreds of problems to Seven Layers. A layer in Open Systems Interconnection (OSI) model is a portion that is used to categorize specific problems.


Open Systems Interconnection (OSI) Seven Layered reference model is only just a reference model. All the problems which are related to the communications are answered by specific protocols operating at different layers. The following image shows the seven layers described in Open Systems Interconnection (OSI) model.

7	Application	Consists of standard communication services and applications that everyone can use.
6	Presentation	Ensures that information is delivered to the receiving system in a form that the system can understand.
5	Session	Manages the connections and terminations between cooperating systems.
4	Transport	Manages the transfer of data. Also assures that the received data are identical to the transmitted data.
3	Network	Manages data addressing and delivery between networks.
2	Data link	Handles the transfer of data across the network media.
1	Physical	Defines the characteristics of the network hardware.

Layer 1. Physical Layer
Layer 2. Datalink Layer
Layer 3. Network Layer
Layer 4. Transport Layer
Layer 5. Session Layer
Layer 6. Presentation Layer
Layer 7. Application Layer

TPC/IP Model Layer

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