OSImodellen

The OSImodellen, or Open Systems Interconnection model, is a conceptual framework developed by the International Organization for Standardization (ISO) that standardizes the functions of a telecommunication or computing system in terms of abstraction layers. It is not a protocol but rather a model for understanding and designing network protocols. The model divides network communication into seven distinct layers, each with its own set of responsibilities.

Starting from the bottom, the Physical Layer is responsible for the physical connection between devices and transmits raw bit streams. The Data Link Layer provides reliable node-to-node data transfer and handles error detection and correction. The Network Layer manages logical addressing and determines the best path for data packets across networks. The Transport Layer ensures reliable data transfer between end systems, often using protocols like TCP or UDP.

The Session Layer establishes, manages, and terminates communication sessions between applications. The Presentation Layer handles data translation, encryption, and compression, ensuring data is in a usable format. Finally, the Application Layer provides network services directly to end-user applications, such as email, file transfer, and web browsing.

While the OSImodellen is a theoretical model, it provides a valuable tool for network engineers and developers to understand the complex interactions within network communication. It helps in troubleshooting, designing new protocols, and ensuring interoperability between different systems. Many real-world networking protocols, like the Internet Protocol Suite (TCP/IP), are often discussed and understood in relation to the OSImodellen, even though they do not strictly adhere to its seven layers.