Länksprotokoll

Länksprotokoll, also known simply as link protocols, are communication protocols that operate at the data link layer—layer two—of the OSI model. Their primary role is to manage and control the transmission of data frames between devices that share a common physical medium. By encapsulating higher‑layer packets into frames, a länksprotokoll adds transmission control information such as framing, error detection, addressing, and flow control data.

Typical functions of a länksprotokoll include framing, error detection, error correction, flow control, and the assignment of link‑level addresses. It may also support media access control (MAC) mechanisms for shared media, negotiate link parameters, and manage topology changes. Because the data link layer sits between the physical layer and the network layer, it must interface with both hardware drivers and higher‑layer protocols such as IP.

Common examples of länksprotokoll are Ethernet, which utilizes the 802.3 MAC and framing specification; Wi‑Fi (802.11), which expands Ethernet concepts for wireless media; point‑to‑point protocols such as PPP and its link control protocol (LCP); and high‑speed serial links which employ protocols like HDLC. In many modern networks, VLAN tagging and link aggregation protocols (LACP) also operate at this layer to increase capacity and flexibility.

Link protocols do not directly route traffic between networks; that task is performed by network‑layer protocols such as IP. However, an efficient and reliable länksprotokoll is essential for ensuring that packets are delivered accurately and in order, thereby providing the foundation upon which higher‑layer services depend.