The data link layer or layer 2 is the second layer of the seven-layer OSI model of computer networking. This layer is a protocol layer that moves data between adjacent network nodes in an area network or between nodes on the corresponding LAN segment.
The functional data link layer supplies the substantive and procedural means to transfer data between network entities and might furnish the means to detect and correct errors that may occur in the physical layer.
At the data link layer, either a span or a layer two switch can be installed to a segment. Hubs and repeaters at the physical layer only serve to extend a network.
There are different devices that are needed to ensure that the Data Link Layer will work properly. First of all, NICs. These are in charge of providing the physical layer needed by the device. Switches can be used in order to fix the data of the network layer.
The switches can make the whole data layer become more functional than before. Bridges are also needed as they can provide the physical addressing. These things are needed to ensure that the Data Link Layer will do things properly and things will go exactly as planned. When there are some issues with this then the data link layer will not work.
The data link layer is concerned with physical addressing, the mac addresses which are stored in the nics. Layer-2 switches are fast because they do not look at the network layer header information, looking instead at the frames hardware addresses before deciding to either forward the frame or drop it.
A bridge is used to break larger network segments into smaller network segments. It works much like a repeater, but because a bridge works solely with layer 2 protocols and layer 2 mac sublayer addresses, it operates at the data link layer.