Yhteyskerros

Yhteyskerros, often translated as "connection layer" or "link layer," is a fundamental concept in computer networking, representing the second layer of the OSI (Open Systems Interconnection) model. Its primary responsibility is to manage the physical transmission of data over a network medium and to provide reliable data transfer between directly connected nodes. This layer deals with the practical aspects of moving bits across a link, ensuring that data sent from one device reaches its immediate neighbor correctly.

Key functions of the yhteyskerros include framing, which is the process of dividing data from the network layer into manageable packets called frames. It also handles physical addressing, typically using MAC (Media Access Control) addresses, to identify devices on a local network segment. Error detection and correction mechanisms are crucial at this layer, ensuring the integrity of data transmitted over potentially unreliable physical links. Flow control is another important function, regulating the rate of data transmission to prevent a fast sender from overwhelming a slow receiver.

Common protocols operating at the yhteyskerros include Ethernet, Wi-Fi (IEEE 802.11), and PPP (Point-to-Point Protocol). These protocols define the rules and standards for how devices communicate on local area networks (LANs) and point-to-point connections. The yhteyskerros bridges the gap between the higher-level network layer, which handles routing and logical addressing, and the lower-level physical layer, which deals with the transmission of raw bits over the physical medium.