Data Communication

Hybrid Topology Disadvantages of Hybrid Topology: 1. Complex in design. 2. Costly. Data Communication Data communication is the exchange of data between two or more computers (a sender/source and a receiver) with the help of a communication medium. The device that transmits the data is known as sender/source and the device that receives the transmitted data is known as receiver. Data communication must fulfill/obey following three conditions : Delivery : Network should deliver the data at the proper place. Accuracy : Data communication should be free from fault. Time limit: Data should reach destination without any delay. Medium : It carries the information from sender to receiver. Receivers : Receiver receives the information. Protocol : There are rules under which data transmission takes place between sender and receiver. Methods of data transmission Methods of data transmissions means direction of flow of data between sender and receiver. Three methods of data transmission are given below: 1. Simplex : In it communication is one direction. So information can flow only in one direction; its reverse is not possible. The message source works as the transmitter. It sends the message over the data channel to the receiver. The receiver is the destination of the message. Example : television communication. 2. Half duplex : In it information can flow in both directions but not at the same time. In other words if information is sent by one system then the second can only receive it or vice versa as shown in figure 3.19. Example : walky-talky system used by police and force. 3. Full duplex : In it information can move in both directions at same time. It provides fast communication as shown in diagram 3.20. Example : telephone system. Communication Channel Communicating data from one location to another requires some form of pathway or medium. These pathways, called communication channels, use two types of media: cable (twisted-pair wire, cable, and fiber-optic cable) and broadcast (microwave, satellite, radio, and infrared). Types of Networks There are several different types of computer networks. Computer networks can be characterized by their size as well as their purpose. The size of a network can be expressed by the geographic area they occupy and the number of computers that are part of the network. Networks can cover anything from a handful of devices within a single room to millions of devices spread across the entire globe. Network may be small or large based on its size, complexity and Distribution area. On the basis of its area of distribution, network is divided into three parts : 1. PAN(Personal Area Network) 2. LAN (Local Area Network) 3. MAN (Metropolitan Area Network) 4. WAN (Wide Area network) Personal Area Network A personal area network, or PAN, is a computer network organized around an individual person within a single building. This could be inside a small office or residence. Personal area networks can be constructed with cables or be wireless. It refers to the interconnection of information technology devices or gadgets (including laptop computers, PDAs, cellphones, printers) within the environment of an individual user (typically within 10 meters). Local Area Network (LAN) A LAN is a network that is used for communicating among computer devices,usually within an office building or home. LAN's enable the sharing of resources.