networks and communications

Basics, look in textbook for more info or more indepth.

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  • Created by: Charlotte
  • Created on: 14-04-13 16:47
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  • Networks
    • Extranet
      • Secure access to an intranet from outside the LAN or company WAN
      • username and password required
    • Connecting a LAN & WAN
      • Router
      • ISP
    • Intranet
      • Same services as the internet
      • only exists on a LAN or company WAN
    • Characteristics of Wide Area Networks
      • Computers are not close together
      • External telecommunications
      • Physical device needed to connect to WAN
    • Client server network
      • Servers  needed to manage file storage, back-up, application sharing, print management.
      • clients can access services provided by servers
      • clients log onto server
    • Internet
      • Communication links e.g. leased lines
      • open network
      • email
      • World Wide  Web
      • Internet relay chat
      • File transfer
    • Virtual Network
      • Can be accross a LAN or WAN
      • Behaves like a single network
      • Will have physical connections to  computers outside the virtual network
      • Cannot see computers outside the virtual network
    • Characteristics of Local Area Networks
      • Local geographic area
      • Network cards/wirelessconnectiveity
      • Dedicated cables owned by company
      • shared peripherals and software.
    • Peer-to-peer network
      • no central server
      • Each computer (peer) may offer shared services
    • Importance of Bandwidth
      • Measured in bits per second, often megabits
      • Amount of data that can travel at one time along a communication link
      • Bottlenecks reduce bandwidth available
      • Higher bandwidth needed for live applications e.g. video conferencing or videos
    • Cable
      • Coaxiel
        • Two wires, outer cable acts as a shield to electro =magnetic interference which reduces signal loss. Used in TVs. Speed: 10Gbps. Only 1 cable core.
      • UTP (Unshielded  twisted Pair)
        • 2 bits of copper twisted together with no shield or earth wire, a.k.a. ethernet.
      • STP (Shielded Twisted Pair)
        • each pair of wires has a metal shield which reduces electromagnetic interference. Used in high-speed networks where higher bandwidths are required.
    • Fibre-optics
      • Reflects light along tiny tubes of flexible glass
      • Very high bandwidth
      • speed: 100-200mb/s
    • Wireless
      • Smaller bandwidths than cable and fibre-optics
      • Obstacles reduce bandwidth available
    • Network Components
      • Network Interface Cards
      • Wireless Access Point
      • Routers
      • Hub
      • Repeaters
      • Switch
      • Bridges
      • Servers
        • File
        • Applications
        • Mail
        • Proxy
        • Print
        • Back-up
    • Optical Communications
      • Infrared
        • requires line of sight and bandwidth restricted to 115.2kbps.
      • Fibreoptic
        • used in  LANs where distances of more than 100m need to be covered in WANs.
      • Laser
        • Each device sends a laser beam to the other device and is able to erceive laser bean from another device
    • Wireless Communications
      • Radio
        • more commonly known as WiFi... Supports 3 standards: 802.11a, 802.11b and 802.11g
      • Bluetooth
        • range of 10m and does not require a line of sight. Used for transferring files.
    • Communication Applications
      • Fax
        • 2D document fed through a fax machine and sent electronically via a telephone line to another fax machine which will print the document
      • Bulletin Boards
        • enable people to discuss topics with other people who are interested in the same topic.
          • 'Threads' are the topic of discussion
      • Tele/video conferencing
        • Enable communications between groups of people to take place. Tele =  talk & video = see eachother aswell
      • Internet Relay Chat (IRC)
        • for sharing ideas with colleagues
        • two or more people can communicate using text
      • Email
        • includes messages and attatched files sent between two or more people who have an email address.
    • ADSL (Asymmetric Digital Subscriber Line)
      • when a range of frequencies are used on an existing copper telephone line to provide a broadband connection to the internet.
        • doesnot prevent a telephone being used at the same time.
  • Characteristics of Local Area Networks
    • Local geographic area
    • Network cards/wirelessconnectiveity
    • Dedicated cables owned by company
    • shared peripherals and software.

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