What are the layers of the OSI model?

The OSI (Open Systems Interconnection) model is a conceptual framework that standardizes the functions of a communication system into seven different layers. These layers are:

1. Physical Layer: This is the lowest layer of the OSI model and deals with the physical transmission of data over the network. It defines the electrical, mechanical, and procedural aspects of the physical connection between devices.

2. Data Link Layer: The data link layer is responsible for the reliable transmission of data frames between adjacent nodes over a physical link. It provides error detection and correction, as well as flow control mechanisms.

3. Network Layer: The network layer is responsible for the logical addressing and routing of data packets across different networks. It determines the best path for data transmission and handles congestion control.

4. Transport Layer: The transport layer ensures the reliable delivery of data between end systems. It provides end-to-end error recovery, flow control, and segmentation of data into smaller units for efficient transmission.

5. Session Layer: The session layer establishes, manages, and terminates communication sessions between applications. It allows synchronization and checkpointing of data exchange, ensuring that data is delivered in the correct order.

6. Presentation Layer: The presentation layer is responsible for the formatting, encryption, and compression of data to be transmitted. It ensures that data is presented in a format that can be understood by the receiving application.

7. Application Layer: The application layer is the topmost layer of the OSI model and provides services directly to the end-user applications. It includes protocols for various applications such as email, file transfer, and web browsing.

These seven layers of the OSI model work together to ensure reliable and efficient communication between devices in a computer network.