OCR Computing Chapter 6

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  • Ch. 6 - Networking
    • LAN
      • Convenient data sharing, easy to back up, update and monitor computer use. users can easily communicate
      • Expensive to maintain, specialist staff needed, viruses spread quickly, data easily hacked
    • WAN
      • Widely available, convenient data sharing, communication & development is easy
      • Harder to set up, private WANs expensive, can be slower than LANs
    • Hardware
      • Cables - Fibre optic cheaper & faster
      • NICs - make and recieve electrical signals, every device needs one, simple MAC addressing
      • Hubs connect devices. Transmit signals to all deivces
      • Switches - connect hubs/ networks together. Only send messages to intended devices
      • Routers connect computers to the Internet
    • Topologies
      • Ring - very fast, BUT vulnerable, backbone problems bring it down
      • Bus - easy to set up, cheap, BUT back bone issues bring it down
      • Star - robust, faster than bus BUT harder to maintain, expensive to set up
    • Types
      • Client Server - very common, good computers, serve many other computers. Efficient & high speed
      • Peer to Peer - all computers are equal, servers & clients. Easy to set up, hard to maintain, poor security, slow bc multi tasking
    • Protocols
      • TCP - connection of hosts (remote computers)
      • IP - packet (data bundle) construction - check it has length, data, correct address
      • Packet switching - packets take diff. routes, saves time, decongestion
      • HTTP distributes webpages
      • I/P address every computer has one, can change
      • MAC address Unique hex no. in the NIC
    • Internet
      • Biggest WAN - connects millions of computers - no owner
      • www uses internet to share HTML pages
      • Hardware: Modem converts phone to digital signals, router connects networks together or connects computer to ISP
      • HTML used to run webpages, & CSS
    • Security
      • Easy access = data loss, theft of data, malware, system damage
      • Failover - if danger is detected, the system shifts to a different system
      • Authentication user ID & password
      • Backups - store data off site (cloud)
      • Archives data that is no longer in use. Kept for legal reasons
      • Disaster recovery, prevention, backups, plan for loss
      • Acceptable Use Policy - what users can/can't do
    • File Standards
      • JPG, MPEG - lossy
      • GIF, MP3 PDF -lossless
      • Compression
        • Lossy - removes some data, can't be recovered
        • Lossless - allows file to be reconstructed, removes repeated data


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