OSI 7 LAYERS

 The OSI (Open Systems Interconnection) model is a conceptual framework used to understand and describe how different networking protocols and technologies interact with each other. It consists of seven layers, each responsible for specific functions in data communication. These layers, from top to bottom, are:

1. **Application Layer (Layer 7):** This layer interacts with software applications that implement a communicating component. It provides services directly to user applications, enabling network services such as email, file transfer, and remote access.

2. **Presentation Layer (Layer 6):** The presentation layer is responsible for data translation, encryption, compression, and formatting. It ensures that data sent from the application layer of one system can be read by the application layer of another system.

3. **Session Layer (Layer 5):** The session layer establishes, manages, and terminates communication sessions between devices. It controls dialogues (connections) between computers, including synchronization and checkpointing.

4. **Transport Layer (Layer 4):** This layer manages end-to-end communication, ensuring that data packets are delivered error-free, in sequence, and without loss or duplication. It also handles flow control and error checking.

5. **Network Layer (Layer 3):** The network layer is responsible for logical addressing and routing, determining the best path for data to travel from the source to the destination across multiple networks. It deals with IP addresses and performs routing of packets.

6. **Data Link Layer (Layer 2):** This layer provides node-to-node data transfer, framing, error detection, and flow control across a physical link. It ensures that data transmitted between adjacent network nodes is error-free and manages access to the physical media.

7. **Physical Layer (Layer 1):** The physical layer deals with the physical connection between devices. It specifies the hardware requirements for transmitting data on a network, including cables, switches, connectors, and network interface cards (NICs).

Each layer has its own specific functions and protocols that help facilitate communication between different devices across a network. The OSI model serves as a reference point for understanding and designing network systems, allowing different network technologies to work together effectively.