Synchronous

       Synchronous can be done if the two devices have to same clock rate in order for them to communicate with each other. Therefore the two devices must have the same frequency.

       In a Synchronous type of communication, data will be sending by packets. The data packets can be in the HDLC format. These packets will contain header and data field and also data checking. The header will contain the address of where data should be send and the error checking will make sure the data is received correctly.

       Advantage: Synchronous system is more advance to send data on a limited bandwidth which it can send more data than the Asynchronous system in the same bandwidth.

                            Synchronous communication is also easy to control as it use frame structure.

       Disadvantage: Expensive to establish Synchronous communication than the Asynchronous communications.