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  • Level: GCSE
  • Subject: ICT
  • Word count: 1380

ICT Unit 4 Networks Notes - LAN and WAN networks

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Introduction

Unit 4 Computer Networks 1. What is a network A network is a system that sends and receives data and messages enabling two or more computers to communicate with each other Networks typically allow computers to share files, share printers and send messages to each other The typical hardware devices that from part of a network are: * Personal computers used as terminals * One or more central processing units acting as dedicated file servers or print servers * Disk drives * Scanners * Printers 2. Types of network There are two types of network: LAN - Local Area Network A network contained within one building or site called a Local Area Network (LAN). WAN - Wide Area Network A network that spans several sites across a city, country or even the world is called Wide Area Network (WAN). a) Local Area Network (LAN) A LAN is a Local Area Network covering a small area such as one building e.g. in a scholl or college. Within a LAN, computers and other hardware devices are connected to the file server. This allows the computers to share resources. b) Wide Area Network (WAN) A WAN is a Wide Area Network covering a large geographical area. A wide area network is not confined to one building. The hardware that forms part of the network can spread around the world. ...read more.

Middle

having to be re-sent * Adding additional devices has very little impact on data transfer speed * Relatively cheap to install and expand Disadvantages: * The least reliable topology as there is total dependence upon the one cable. If it fails, all the workstations will be affected * The hardest topology to troubleshoot if there is a cable failure * Because all stations are wired together, to add a station you must shut down all the network temporarily * In order for all computers to communicate with each other, all the computers must be turned on c) Star topology In a star network all the computers are connected separately to the hub or server Advantages: * The most reliable because cable failure does not affect other users * Good performance because there is a direct path from the central controller to each terminal * Easy to set up and expand Disadvantages: * Uses a lot of cable which is expensive to install * Extra hardware required such as hubs and/or switches * As the central machine controls the whole system, the whole system will be affected if it breaks down 5. Formation of a network A network is not just a number of computers connected by cables. The components found in a typical network are: a) ...read more.

Conclusion

It passes messages from one segment to the other. For example, if there was a LAN segment in two different buildings, the bridge transfers the messages from one building to the other. f) Wi-Fi Wi-Fi is used in a wireless LAN. It allows the wireless exchange of data over a distance of 10 to 20 metres and at a data transfer rate of 50 to 450 Mbps (megabits per second). It is useful for laptops, game consoles, televisions, printers and digital cameras. g) Bluetooth Bluetooth is used for wireless connections over a short distance, e.g. only a few metres. It does not use much power, and the rate of data transfer is low (between one and tree Mbps). It is typically used to connect battery-powered devices, e.g. ear-pieces, mobile phones or MP3 players, with computers. h) Proxy servers Proxy servers are most frequently used on the Internet to improve the performance of Web services to multiple clients. For example, in a school or large office, all client browsers can be connected to a proxy server. The proxy server requests pages from the desired Web sites and returns them to the client. However, it remembers or caches these pages so that if a different client requests the same page, it will be returns immediately from its cache rather than requesting it again from the original Web site. ?? ?? ?? ?? Monday, 19 January 2009 ...read more.

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