It is responsible for transmitting a group of bits among the adjacent nodes. The group of bits is termed as frame. The network layer passes a data unit to the data link layer and data link layer adds the header information to this data unit. The data link layer carry out the following functions:

• Addressing: Headers & trailers are added containing the physical addresses of the adjacent nodes and eliminated on a successful delivery.
• Framing: Grouping of/bits attained from the network layer into manageable units called frame
• Flow control: it is for regulate the amount of data that can be sent to the receiver.
• Media access control (MAC): this layer is decide who can send data, when and how much.
• Synchronization: this layer also has bits to synchronize the timing to know the bit interval to identify the bit correctly.
• Error control: it incorporates the CRC to make sure the correctness of the frame.
• Node to node delivery: it's also for error-free delivery of the whole frame/packet to the next adjacent node.