The data link layer (DLL) is layer 2 in the open systems interconnection (OSI) reference model. The DLL identifies the network protocol type, provides error control, and assembles frames of data for transport. The medium access control (MAC) and logical link control (LLC) sublayers of the DLL are responsible for providing an error free link between two nodes sharing the same channel. In the OSI reference model, the DLL sits between the network layer (layer 3) and physical layer (layer 1) and assembles data packets for transmission by the PHY layer.
Examples presented in this section demonstrate DLL layer operations for system-level links.