Ø  Physical addressing. If frames are to be distributed to different system on the network, the data link layers add a header to the frame to define the sender and /or receiver of the frame. If the frame is intended for a system outside the sender’s network, the receiver address is the address of the connecting device that connects the network to the next one.

Ø  Flow control. If the rate at which the data is absorbed by the receiver is less than the rate produced at the sender, the data link layer imposes a flow control mechanism to prevent overwhelming the receiver.

Ø  Error control. The data link layer adds reliability to the physical layer by adding mechanism to detect and retransmit damaged or lost frames. It also uses a mechanism to recognize a duplicate frame. Error control is normally achieved through a trailer added to the end of the frame.