Decoding the Layers of the OSI Model in Computer Networking
Shanthan Cheruku
Application Engineer @ Discover Financial Services | Master's in Computer Science
The OSI (Open Systems Interconnection) model is a conceptual framework used to understand and standardize the functions of a telecommunication or computing system without regard to its underlying internal structure and technology. Developed by the International Organization for Standardization (ISO) in the 1980s, it serves as a guide for product developers and a teaching tool for computer science and networking students.
Layer 1: Physical Layer
The Physical Layer is the foundation layer of OSI model. It deals with physical connections between devices and the transmission and reception of raw bit streams over a physical medium. It includes everything from cables and switches to the electrical and mechanical aspects of the connections.
Layer 2: Data Link Layer
The Datalink layer provides node-to-node transfer- a link between two directly connected nodes. It handles error connection from the physical layer. Two sublayers exist here - the Media Access Control(MAC) layer and Logical Link Control(LLC) layer. The MAC sublayer controls how a computer on the network gains access to the data and permission to transmit it, while the LLC layer controls frame synchronization, flow control and error checking.
Layer 3: Network Layer
The Network layer is responsible for packet routing including, routing through different routers. It determines the best physical path for data to reach its destination. Protocols like Internet Protocol(IP) operate at this layer.
Layer 4: Transport Layer
The Transport layer ensures end-to-end communication services for applications. It provides complete data transfer—handling data integrity, flow control, and error correction. Protocols like Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) work at this layer.
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Layer 5: Session Layer
The session layer manages sessions between end user-applications. It establishes, manages and terminates connections between local and remote applications.
Layer 6: Presentation Layer
This layer translates data from application layer into an intermediary format. It handles data encryption, decryption, compression and translates between application and network formats.
Layer 7: Application Layer
The application layer is the top layer of OSI model. It provides protocols that allow softwares to send and receive information and present meaningful data to users. Protocols like Hypertext Transfer Protocol (HTTP) and Simple Mail Transfer Protocol (SMTP) operate at this layer.
Conclusion
The OSI model remains a fundamental concept for understanding and designing network systems, despite the evolution and changes in networking technologies. Its layered approach helps in troubleshooting network issues and in the development of network-based applications and hardware. Understanding the OSI model is crucial for anyone involved in network technologies or computer science.