verkkotasot

Verkkotasot, or network layers, refer to abstract conceptualizations of communication protocols that organize the complex task of computer networking into manageable parts. These layers are designed to be independent of each other, meaning a change in one layer does not affect the others. This layered approach simplifies design, troubleshooting, and the development of new network technologies.

The most widely recognized model is the OSI (Open Systems Interconnection) model, which divides network communication into seven layers. These are, from top to bottom: the Application Layer (user-facing services), the Presentation Layer (data formatting and encryption), the Session Layer (managing communication sessions), the Transport Layer (end-to-end data transfer and reliability), the Network Layer (routing and logical addressing), the Data Link Layer (physical addressing and error detection on a local network), and the Physical Layer (transmission of raw data bits over a physical medium).

Another influential model is the TCP/IP (Transmission Control Protocol/Internet Protocol) model, which is more practical and forms the basis of the internet. It typically includes four or five layers, often mapping to the OSI layers but with some differences in scope and naming. The common layers are the Application Layer, the Transport Layer, the Internet Layer (equivalent to the OSI Network Layer), and the Network Access Layer (combining the OSI Data Link and Physical Layers).

Each layer has a specific function and interacts with the layers directly above and below it. Data is encapsulated as it moves down through the layers, with each layer adding its own header information. As data is received, it is de-encapsulated as it moves up through the layers, with each layer processing and removing its corresponding header. This structured approach ensures interoperability between different hardware and software systems.