The Data Link Layer

The Data Link Layer (layer 2) of the OSI model is responsible for allowing the messages of the upper layers to access the network. It also controls how the data is placed onto the physical network (media), and handles error detection.

Within the Data Link Layer there are two sublayers, the Logical Link Control (LLC) sublayer and the Media Access Control (MAC) sublayer. Switches only operate at this second sublayer, as they are only able to read and understand frames containing MAC addresses.