Tuesday, November 6, 2012

Notes - Uses of Computer Networks

The following are notes from Computer Networks written by Tanenbaum 5th edition.

Business Applications
  • Computers in business require resource sharing
    • make programs equipment and data available to everyone in network
    • i.e. group printer
  • Share information
    • i.e. customer records, product information, inventories
    • between multiple geographic locations
    • VPNs
      • join individual networks at different sites
  • Client-Server Model
    • Servers
      • i.e. Centrally located, powerful computers
      • Web applications, server maintains web pages
      • process request, sends reply to clients
    • Clients
      • i.e. employees of a company
        • remote access to servers
      • requests access to server
  • Communication Medium
    • employees in a company require daily communication
      • e-mail
      • telephone calls
        • if this is handled over the computer network
          • VoIP(Voice over IP)
          • IP Telephony
          • saves on telephone bills
      • Desktop Sharing
        • when one worker changes an online document, the other can see instantly
        • "shared blackboard"
  • E-commerce
    • shopping and services from home
Home Applications


  • Initial use for word processing and games
  • Now internet access
    • connectivity to remote computers
    • Bob Metcalfe - Inventor of Ethernet
      • the value of a network is proportional to the square of the number of users because this is roughly the number of different connections that may be made
  • Peer to Peer Communication
    • Individual communicate in loose group, no fixed division into server client
      • BitTorrent file sharing
    • Share music and videos
    • Napster
    • Instant Messaging
      • derived from UNIX talk program 1970
    • Twitter
      • tweets to circle of friends
    • Youtube
  • Social Network Applications
    • Facebook
  • Group Content
    • Wikipedia
    • B2C - Business to Consumer
    • B2B - Business to Business
    • G2C - Government to Consumer
    • C2C - Consumer to Consumer
    • P2P - Peer to Peer
  • IPTV (IP TeleVision)
  • Ubiquitous Computing
    • Sensors, smart home meters
    • power-line networks
  • RFID (Radio Frequency Identification)
    • passive tags to locate items
Mobile Users
    • Connectivity non wired connection
    • Wireless hotspots
    • Text messaging
      • Short Message Service
      • Smart Phones
    • GPS(Global Positioning System)
    • M-Commerce
      • text messages to authorize payments
    • NFC (Near Field Communication)
    • Sensor Networks
      • nodes that relay information about the state of the world
  • Wearable computers
    • hackable
Social Issues
  • Sharing of views
    • sensitive topics
      • politics
      • religion
      • sex
  • Network Neutrality
    • communications not differentiated by network or source
  • DMCA(Digital Millenium Copyright Act)
    • Employee rights vs Employer rights
      • private e-mails
  • Profiling users
    • Cookies
      • track activity
      • store personal information
    • Google Ads
  • Anonymous messages
  • Misleading information
    • improper sites
  • Botnet
    • pool of compromised machines
  • Phishing
    • messages that are supposed to be trustworthy but there to just gain information
    • usually malacious
  • CAPTCHAs
    • Solve short recognition test
    • used to prevent brute force methods
  • Interact with old laws
    • gambling

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