What is the OSI (Open Systems Interconnection) model?

The OSI (Open Systems Interconnection) model is a conceptual framework that standardizes the functions of a communication system into seven different layers. It was developed by the International Organization for Standardization (ISO) to ensure interoperability and compatibility between different computer systems and network devices.

The seven layers of the OSI model are:

1. Physical Layer: This layer deals with the physical transmission of data over the network, including the electrical, mechanical, and physical aspects of the network interface.

2. Data Link Layer: The data link layer is responsible for the reliable transmission of data frames between adjacent nodes on a network. It also handles error detection and correction.

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 reliable and error-free end-to-end data delivery. It breaks down large data into smaller segments, manages flow control, and provides error recovery mechanisms.

5. Session Layer: The session layer establishes, manages, and terminates communication sessions between applications. It also handles synchronization and checkpointing of data.

6. Presentation Layer: The presentation layer is responsible for data representation and conversion. It ensures that data from different systems can be understood by the receiving system by handling data encryption, compression, and formatting.

7. Application Layer: The application layer provides services directly to the end-user applications. It includes protocols for various network services such as email, file transfer, and remote login.

The OSI model serves as a reference model for network communication, allowing different vendors and technologies to communicate with each other. It provides a clear and structured approach to network design, troubleshooting, and understanding the different layers involved in data transmission.