The term layer 2 refers to the data link layer in the conceptual Open Systems Interconnection (OSI) data communication model. The OSI framework includes seven total layers. The data link layer (Layer 2) of the OSI moves data across a linked physical network. A layer 2 device on a computing network will transmit data to a destination according to Media Access Control (MAC) addresses, also known as Ethernet addresses. The data link layer of a multipoint network can establish a connection, segment data into frames, and manages data arrivals. This layer also verifies that incoming data has been received.
Data Link Layer of the OSI Model
Known as Layer 2, the Data Link Layer is comprised of two sublayers according to IEEE-802 LAN standards. The upper sublayer of the data link layer is described as the Logical Link Control (LLC) sublayer. The LLC layer handles error checking and helps to synchronize data packets. This sublayer can also detect and potentially correct data errors within the network. The Media Access Control, or MAC, sublayer of Layer 2 manages how the network receives and disseminates data. The MAC sublayer and LLC sublayer interface with each other and with the physical network.
Layer 2 Switch Operation
A Layer 2 switch is a device that operates according to the Layer 2 data communications protocol. A Layer 2 device decides how to forward data based on the MAC address. Ethernet hubs and network switches work at the data link layer, with a switch delivering greater performance than a hub. Bridge devices inspect Ethernet frames. They identify frame sources and destination MAC addresses before making forwarding decisions.