It uses two protocols as HDLC and LLC for providing its services. HDLC is known as high Level Data link Control. It is used on point to point data links. It can also be used on multi point data links. We can use it in a number of different ways because it is a general purpose data link control protocol. LLC is known as Logical Link Control. Its function is to provide reliable transfer of data across the data link between two communication bodies.
By using unacknowledged connectionless service user can initiate the transfer of data service with minimum protocol overheads. By using connection oriented services user can establish a logical connection, before sending the transfer of any data service.