OSI Layers Model

Data Link Layer

The next layer is the data link layer. This is the layer that actually constructs the frames, and it also performs error checking using CRC
It ensures that the frames are sent up to the next layer in the same order that they were received, providing an error free virtual path to the network layer. The data link layer consists of two sub layers; the logical link control (LLC) and the media access control (MAC), which provide reliable communications by ensuring the data link is not broken and also by examining packet address information. A bridge is an example of a device that works at this layer. A bridge learns, forwards and filters traffic by examining the layer 2 MAC address.
This helps segment network traffic. More recently, bridges have been replaced by switches, which performs the same functions as a bridge, but can do so on each port. To find out more about switches, visit the Products link on the left.