And the main hardware components required to establish a connection between sender and a receiver are message witch is the most useful assets of a data communication system, sender is to transfer messages from source to destination but someone must be there so they can do the role of a source next the receiver is a destination where the message finally arrived from the source next transmission medium in the entire process of data communication there has to be something which can be line a bridge between sender and receiver,next set of rules is like a protocol and it to govern data communication and it is various sets of rules had been already designed by the designers of the communication systems