The simulation of the flight following system i6 primarilyrnchosen in the interest of Ethiopian Airlines need to implementrnthe system to replace the currently used flight followingrnsystem which is based on verbal communication betweenrnaircraft and ground control people.rnThe first section of this paper discusses the components ofrndata communication system, aspects and objective of datarncommunication system.rnThe second section laid the emphasis on the fundamental communicationrnconcepts parallel transmission, serial transmissionrnand the different types of serial transmission. Therntheory behind the simulation is basically based on the differentrntypes of transmission modes. The third section buildrnthe foundation for the characteristics of data transmission,rndirection of information flow: simplex, half-duplex and fullrnduplex and finally rate of transmiesion effect on datarntransmission. In section 4 the different coding technologyrnand structures are presented.rnA unique feature of the paper is section 5 protocol. Therernare sections on identifying and defining a problem in datarncommunication specially for good understanding between arnsender and a receiver.