The Open Systems Interconnection (OSI) model is a conceptual model that provides a common basis for the coordination of standards development for the purpose of systems interconnection. It is widely used in the field of information technology to describe networked communication systems. The OSI model divides the flow of data in a communication system into seven abstraction layers. Each layer serves a specific class of functionality to the layer above it and is served by the layer below it. Here are the seven layers of the OSI model:
1. Physical layer: This layer deals with the physical implementation of transmitting bits across a communications medium.
2. Data Link layer: This layer provides reliable transmission of data frames between two nodes connected by a physical layer.
3. Network layer: This layer enables the transfer of data packets from a source to a destination across multiple networks.
4. Transport layer: This layer ensures reliable and error-free data transfer between end systems.
5. Session layer: This layer establishes, manages, and terminates connections between applications.
6. Presentation layer: This layer is responsible for data representation, encryption, and compression.
7. Application layer: This layer provides services directly to the end user and supports network applications.
The OSI model is a widely accepted framework for discussing and teaching networking in the field of information technology. It is important to note that the OSI model is a conceptual model and does not directly correspond to any specific protocol suite, such as the TCP/IP model.