Quiz 10: Local-Area Networks
Local-area networks (LANs) are small data networks that cover small geographical area. Local -area networks are intended for use within a building are group of buildings, such as college campus or office. A well-constructed LAN allows several people to use same software at the same time and even to work on the same document. Local area network (LANs) which is used to connect the computer systems in one area having spread over the range of less than 1 Km. It is restricted to one area or a small group of users within one area. These are small area networks. The data rate of LAN is very small compared to other networks. Wide-area networks (WAN) can extended over very large areas and can even be worldwide. Wide-area networks connects is a large area network spread over an area greater than cities. Hence these wide area networks are used for internet connections. The data rate of WAN is very large compared to other networks. The main difference between the LAN and WAN is local area networks are limited to particular areas and wide area networks are for very large areas even the world can be covered under the wide area networks. For LAN the data rate is very small and the data rate for WAN is very high.
Analog telephone lines are very old way to transferring data to the computers. These are the connections between the telephone and central telephone office. Whenever the user wants to talk on telephone it produces an analog signal that travels to the central office. The signal switches to another local destination or other switching offices that connect it to a remote destination. The telephone exchange is used in the public switched telephone network (PSTN) or large enterprises. An exchange consists of electronic components that inter connect (switch) telephone subscriber lines or virtual circuits of digital systems between subscribers to establish telephone calls. In the old telephone exchange systems connections would made by manually connected wires using a switchboard. But the modern telephone exchange systems connections would make by electronic equipment. A PSTN is a wired system through which landline telephone calls are made and received and. This circuit is based on successful circuit switching. A phone call will be routed through a number of switches to connect one phone to another. The connection established between two phones is referred to as a circuit. The central office converts the analog signals to digital signals. This switches the data. Using the telephone lines we can switch the data in two ways: By using the telephone companies' switched network for low speed modem traffic or by using the high speed switching circuit's data can be switched over the telephones.
Local-area networks (LANs) are small data networks that cover small geographical area. Local -area networks are intended for use within a building are group of buildings, such as college campus or office. A well-constructed LAN allows several people to use same software at the same time and even to work on the same document. The three basic topologies of LAN are, 1. Star 2. Ring 3. Bus Star: In a star network, microcomputers, individual terminals of computers or workstations are directly connected to the central computer. The central computer is referred as a server and each of the connections to the network are referred as nodes. A star network is shown in Figure 1. The maximum data transmission rate for the star network is generally less than with a dedicated network. The star topology is oldest and it is suitable for a centralized system. In this network the central hub controls all the systems connected to the hub or mainframe computer. The drawback of this topology is that the failure of hub causes to the whole network to go down. Ring: In a ring network cables run from each node to the next node. All the nodes are connected in series and they receive all the information that moves around the ring. A ring network is shown in Figure 2. In this network, if any problem occurs, it is easy to point out defective connection. Ring is a good network for longer distances to carry high traffic since every computer can act as a booster. If any node in the network fails, entire network goes down. This is the drawback of the ring network. Bus: In a bus network, all systems are connected to a single cable called bus. The bus is the back bone for the network. The advantage of the network is it is easy to connect a computer or a peripheral device. This system requires relatively small cables, resulting in lower cost. The main disadvantage of the network is that if the bus fails, entire network goes down. It is also difficult to troubleshoot this type of network. So this type of network is not suitable for longer distances. A bus network is shown in Figure 3.