Viestintäkerrokset

Viestintäkerrokset refer to the layered structure of communication protocols used in computer networks. This concept, famously illustrated by models like the OSI (Open Systems Interconnection) model and the TCP/IP (Transmission Control Protocol/Internet Protocol) model, divides the complex task of network communication into distinct, manageable layers. Each layer performs a specific set of functions and provides services to the layer above it, while relying on the services of the layer below.

The OSI model, a conceptual framework, defines seven layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application. The Physical layer deals with the raw transmission of bits over a physical medium. The Data Link layer handles error detection and correction for data frames. The Network layer manages logical addressing and routing of packets across networks. The Transport layer ensures reliable end-to-end data transfer and segmentation. The Session layer establishes, manages, and terminates communication sessions. The Presentation layer handles data formatting, encryption, and compression. Finally, the Application layer provides network services directly to end-user applications.

The TCP/IP model, which is more practical and widely implemented, typically describes four or five layers: Network Interface, Internet, Transport, and Application. It merges some of the OSI layers for a more streamlined approach. Understanding these communication layers is fundamental to comprehending how data travels across the internet and other networks, enabling the development and troubleshooting of network applications and infrastructure.