Data Link Layer
The data link layer is essentially responsible for the transfer of data across the physical layer. The transfer may or may not be reliable depending on the protocol used.
Conceptually the data link layer is commonly split into two sub layers.
Logical Link Sub Layer
Responsible for flow control and error detection.
Media Access Control Sub Layer
This sub layer essentially acts as the interface between the logical link layer and the physical medium. It provides an addressing mechanism known as the physical address or MAC address, which uniquely identifies the NIC (network interface card) in a piece of hardware.
Data Link Layer Protocols
The links below can be used to find out more about some of the common protocols used at the Data Link Layer.
Next: Physical Layer