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20 Networks A LANS (Local Area Networks) B Networking allows two or more computer systems to exchange information and share resources and peripherals. LANs are usually placed in the same building. They can be built with two main types of architecture: peer-to-peer, where the two computers have the same capabilities, or client-server, where one computer acts as the server containing the main hard disk and controlling the other workstations or nodes, all the devices linked in the network (e.g. printers, computers, etc.). Computers in a LAN need to use the same protocol, or standard of communication. Ethernet is one of the most common protocols for LANs. A router, a device that forwards data packets, is needed to link a LAN to another network, e.g. to the Net. Most networks are linked with cables or wires but new Wi-Fi, wireless fidelity, technologies allow the creation of WLANs, where cables or wires are replaced by radio waves. To build a WLAN you need access points, radio-based receiver-transmitters that are connected to the wired LAN, and wireless adapters installed in your computer to link it to the network. Hotspots are WLANs available for public use in places like airports and hotels, but sometimes the service is also available outdoors (e.g. university campuses, squares, etc.). Network topology Topology refers to the shape of a network. There are three basic physical topologies. Networks Star: there is a central device to which all the workstations are directly connected. This central position can be occupied by a server, or a hub, a connection point of the elements of a network that redistributes the data. Bus: every workstation is connected to a main cable called a bus. Ring: the workstations are connected to one another in a closed loop configuration. There are also mixed topologies like the tree, a group of stars connected to a central bus. C WANS (Wide Area Networks) star bus ring The three basic network topologies WANs have no geographical limit and may connect computers or LANS on opposite sides of the world. They are usually linked through telephone lines, fibre-optic cables or satellites. The main transmission paths within a WAN are high-speed lines called backbones. Wireless WANs use mobile telephone networks. The largest WAN in existence is the Internet. 50 50 Professional English in Use ICT 0.1 Read the information opposite and correct the following statements. 1 LANs link computers and other devices that are placed far apart. 2 In a client-server architecture, all the workstations have the same capabilities. The word protocol refers to the shape of the network. 4 Routers are used to link two computers. 5 Access points don't need to be connected to a wired LAN. 6 Wireless adapters are optional when you are using a WLAN. 7 Hotspots can only be found inside a building. 8 The Internet is an example of a LAN. 9 Wireless WANs use fibre and cable as linking devices. 0.2 Use the words in the box to complete the sentences. LAN WLAN nodes peer-to-peer 1 All the PCs on a 2 The style of. hub server are connected to one backbones 9 which is a powerful PC with a large hard disk that can be shared by everyone. printers. ............ networking permits each user to share resources such as 3 The star is a topology for a computer network in which one computer occupies the central part and the remaining. are linked solely to it. 4 At present Wi-Fi systems transmit data at much more than 100 times the rate of a dial- up modem, making it an ideal technology for linking computers to one another and to the Net in a 5 All of the fibre-optic cross Panama. 6 A. _ of the United States, Canada and Latin America joins multiple computers (or other network devices) together to form a single network segment, where all computers can communicate directly with each other. 0.3 Read these descriptions of different physical topologies of communication networks and match them with the terms in B opposite. 1 All the devices are connected to a central station. 2 In this type of network there is a cable to which all the computers and peripherals are connected. 3 Two or more star networks connected together; the central computers are connected to a main bus. 4 All devices (computers, printers, etc.) are connected to one another forming a continuous loop. 0.4 A network administrator has set up a new network in a school. Which topology has she chosen? We have decided to install computers in all the departments but we haven't spent a lot of money on them. Actually, only the one in the staff room is really powerful (and expensive!). They all have common access to the Net and share a laser printer. The teachers in this school have built up a general file of resources kept in the main computer to which all the others in the network have access. You and computers Write a list of the advantages and disadvantages of using networks. A BACALL "When I was a student, wireless data transmission meant passing notes in class." Professional English in Use ICT 51