Open Systems Interconnection (OSI) is a conceptual framework that standardises the functions of communication systems into a structured set of protocols and layers. The OSI model was developed by the International Organisation for Standardisation (ISO) to facilitate interoperability between different computer systems and networking technologies by defining a framework for understanding and implementing network communication.
The seven layers of the OSI model, from the lowest to the highest, are:
- Physical Layer: Concerned with the physical transmission of raw bits over a communication channel. It defines characteristics such as voltage levels, physical connections, and data rates.
- Data Link Layer: Responsible for error detection, framing, and physical addressing. It ensures reliable data transfer across the physical link.
- Network Layer: Manages routing, addressing, and packet forwarding to transmit data between devices across different networks. It provides logical addressing and determines the best path for data transmission.
- Transport Layer: Ensures end-to-end communication between devices by providing reliable and transparent data transfer. It manages flow control, error correction, and data segmentation.
- Session Layer: Manages the establishment, maintenance, and termination of communication sessions between devices. It establishes, maintains, and synchronises the interactions between applications on different systems.
- Presentation Layer: Responsible for data translation, encryption, and compression. It ensures that data exchanged between systems can be understood by the receiving system.
- Application Layer: The topmost layer that interacts directly with end-users. It provides interfaces and services to applications for network communication.