COMPUTER NETWORKS

COMPUTER NETWORKS

1. Background

   • Computer networks allow computers to communicate and share data and information
   • They require certain hardware to work

2. Hardware Devices

   • Network interface Card
     • Enables the computer to cable or radio waves to connect to the network
   • Hubs and Switches
     • All cables in a network are plugged into hubs ort switches. Hub joins together computers in a network. Switches look at and send data packets to target computer
   • Bridges
     • Allows different networks to communicate. e.g. insurance department needs to look at account details
   • Routers
     • Like a bridge, links networks together. It formats data packets and decides bets route to take
   • Wireless Networks
     • Allows devices to be connected to network without physical wires

3. Network Structures

   • Star Network
     • Each device has a direct connection to a switch or hub that is connected to a server
   • Ring Network
     • Each device is connected to two others, forms a ring for signal to travel only one direction
   • Bus Network
     • All devices are connected to one main cable. Each end of the cable has a terminator: preventing signals being reflected

4. Types of Cable

   • Fibre Optic Cable
     • Carry data as light signals. Transmit very quickly. Not affected by interferance
   • Twisted Pair Cable
     • Usually 4 pairs of copper wire, twisted to reduce interference

5. Types of Networks

   • Local Area Network
     • LAN Consists of computers and peripheral devices, spread over a small area. Usually connected to a server via cables
   • Wireless Local Area Network
     • WLAN are different to LANs because they link computers wirelessly. Include wireless access points, network interface cards, boosters, wireless repeaters, routers
   • Wide Area Network
     • Connects local area networks over a large geographical area. LANs connect to the WAN via router or modem.
       • Likely to be used by large organisations based in multiple countries

6. Internet/Intranet

   • Internet
     • International Network
     • Made up of billions of web pages
       • Each has a Uniform Resource Locator (URL)
         • Protocol - Host Name - Second level domain - Sub domain - Top level domain - File path - Filename
           • http:// - www - .HarperCollins - .co - .uk/ - about-HarperCollins/Pages/ - About-us.aspx
     • Users need an ISP (internet service provider) to connect
     • Main methods of connecting
       • Dial-up
       • Cable
       • Broadband (DSL - Digital subscriber line)
   • Intranet
     • Used by organisations
     • Allows workers to access storage data
       • Barriers can be set
       • Data is relevant
       • Data has been validated
       • Smaller size makes searching for info faster

7. Use in business (Processing)

   • Online Processing
     • Provides access to network for customer. E.g. Online booking
     • Provide almost instant response. Prevents doub le booking
   • Batch Processing
     • When a number of tasks are processed together in a batch
     • It processes large amounts of non-critical data
     • E.g. gas service provider
   • Real-time Processing
     • Used when an immediate response is required
     • Importance of reliability and longevity makes this expensive

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