What is the OSI Model and what are its seven layers?

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

The seven layers of the OSI Model are as follows:

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 transfer of data between directly connected nodes. It provides error detection and correction, as well as flow control mechanisms to ensure data integrity.

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 segments and reassembles data into manageable units, provides error recovery, and ensures proper sequencing of data.

5. Session Layer: The session layer establishes, manages, and terminates communication sessions between applications. It provides mechanisms for synchronization, checkpointing, and recovery of data in case of failures.

6. Presentation Layer: The presentation layer is responsible for the formatting, encryption, and compression of data to be transmitted. It ensures that data from the application layer is properly formatted and understood by the receiving system.

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

Each layer of the OSI Model has its own specific functions and protocols, and they work together to ensure reliable and efficient communication between network devices. The model provides a standardized framework that allows different systems to communicate with each other, regardless of their underlying hardware or software.