OSI stands for Open Systems Interconnection. OSI model was developed by the International Organization for Standardization(ISO). It is a reference model for how applications communicate over a network. The OSI model characterizes computing functions into a universal set of rules and requirements in order to support interoperability between different products and software.

The OSI model can be considered as a universal language for computer networking. It is based on the concept of divide and conquers, it splits up the communication system into 7 abstract layers, and the layer is stacked upon the previous layer.

Layers of OSI Model

OSI model has seven layers which are as follows:

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

To learn more about layers, visit Layers of OSI Model

Characteristics

• It is the conceptual model which enables the diverse communication systems to communicate using network.
• It was developed by the ISO (International Organization for Standardization) in 1984.
• It act as an architecture for inter-computer communications.
• It is divided into 7 layers and each layer performs a particular task.
• Each layer is independent of each other and can perform its operations independently.

Advantages

• It is a layered model and each layer is independent in nature. Thus, changes in one layer doesn’t affect the other layers.
• It divides the complex function into smaller parts.
• It is a generic model as it has flexibility to adapt to many protocols.
• It supports both connection-oriented as well as connectionless services.
• It is more secure and adaptable than having all services bundled in the single layer.

Disadvantages

• It is purely a theoretical model and ignores the availability of the resources and technologies. Hence, its practical implementation is somewhat restricted.
• It is very complex. The initial implementation was cumbersome, slow and costly.
• The layers are interdependent on each other, they can’t operate parallely as they have to wait for the data/ packets from the predecessor layer.

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