ICT Unit 4

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  • Created by: Leila
  • Created on: 07-04-15 11:16
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  • ICT Unit 4
    • There are two different sorts of computer network:
      • Local Area Network (LAN)- the computers are all in the same building or on one site, connected together by hubs and switches using cables.
        • A Wireless Local Area Network (WLAN) is a LAN whose devices are connected by wireless rather than cable.
      • Wide Area Network (WAN)- the computers are spread over a large geographical area connected to each other by using fibre-optic cable, telephone lines, radio transmitters or satellite links.
      • A Wireless Local Area Network (WLAN) is a LAN whose devices are connected by wireless rather than cable.
    • Router
      • Hardware allowing computer to access the Internet using a phone line
    • Modem (Modulator/Demodualtor)
      • Hardware used to change the analogue signals from the phone line into digital signals needed by the computer, also used to change the signals from digital to analogue.
    • Browser
      • Software used to find and look at information on the web. Each web page has its own unique address known as a Universal Resource Locator (URL)
    • Video conference
      • Webcam and microphone used to allow people to communicate with each other.
    • Hubs and Switches
      • Similar hardware in a network which distribute signals between the server and the individual PCs. A hub sends the signal to all the devices on the network and only one individual PC will accept the signal. A switch sends the signal to only the one individual PC by specifying the individual address.
    • Bridge
      • A bridge allows two different types of network to communicate with each other.
    • LANs
      • Computers can be linked together to form networks. The shape of the network is determined by the way in which links are made.
      • Star Network
        • Every networked device has its own physical link with the hub or switch.
          • This means that if one network crashes, or there is a fault in the network cable, all the other stations are still able to function correctly.
        • This means that if one network crashes, or there is a fault in the network cable, all the other stations are still able to function correctly.
        • This type of network is fast, reliable and inexpensive and is the most common.
      • Bus Network
        • All networked devices are connected to a cable known as a bus.
        • Any break in the bus causes serious problems
        • Needs terminators at each end of the bus
        • Superseded by star networks.
      • Advantages: Share hardware devices like printers, servers, CD-ROM drives, WAN communication links
        • Share data and communicate with other users.
        • Share software- each application package only has to be loaded onto the file server and not onto every workstation.
      • Disadvanatges: Security measures are needed.
        • Additional hardware means that there is more that could go wrong
    • WANs
      • Computers in a WAN are often connected to each other using communication media provided by a third party. An example would be a telephone company providing links via telephone cables or via broadband facilities.
      • A WAN many interconnect several LANs. If a LAN needs to be connected to a WAN a special gateway needs to be set up.
    • Network security
      • Access to networks and data can be kept secure by authenticating users with their user ID and password.
      • Unauthorised access can be reduced by allowing different users different levels of access.
        • Data encryption gives another level of data security.
    • The Internet and intranets
      • The Internet is a communications system linking computers across the world- a network of networks. Data is passed from computer to computer, from server to server, until the required destination is reached.
        • Internet
          • Dangers from the internet: Hackers-prevented by using a firewall.
            • Viruses (spread via email, unsafe links or webpages)- prevented by anti-virus programmes
            • Undesirable adult material ;)
          • Advantages: Easy communication and data exchange with other people.
            • Enables people to work from home (teleworking).
            • A vast amount of information can be accessed
            • Up-to-date information available immediately.
          • Disadvantages: Much of the information isn't checked and may be wrong.
            • A large amount of undesirable material is readily available.
              • Data can be intercepted and put to illegal use.
                • Risk of hackers or viruses being able to damage your computer.
                  • Privacy and security of data is difficult to maintain.
      • Individuals need to use and ISP (internet service provider) to access the network.
      • An intranet is similar to the Internet but is limited to a particular organisation. It will be tightly controlled by the organisation.
        • Intranets
          • Advantages: Tight control by the owning organisation so that: views posted are relevant, information will be useful,accurate and relevant.
            • The amount of information is limited so it is easier to search, safety from inappropriate material and less susceptibility to hackers and viruses.
          • Disadvantages: Low volume and variety of information, tend to have a single view point.

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