7-2: Communications Networks

Alternative Networking Technologies

A. Signals: Digital vs. Analog

  1. Analog Signal
    • Continuous waveform that passes through a communications medium
    • Used for voice communications
    • telephone handset, speaker, earphone
  1. Digital Signal
    • Discrete, binary waveform, non-continuous
    • Communicate info as strings of two discrete states, one bit and zero bits (represented as on/off pulses)
    • Computers use modems to translate digital signals to analog

B. Types of Networks

  1. Local Area Networks (LANs)
    • Designed to connect personal computers and other devices within 500 meter (half-mile) radius
    • Interconnected LANs can create Campus Area Networks (CANs)
    • Can link to Wide Area Networks (WANs)
    • May use peer-to-peer architecture (p2p)
    • Sometimes described in terms of topology, with star, bus, or ring being the 3 major topologies.
      1. Star - All network components connect to a single hub
      2. Bus - All machines on network receive the same signals; most common topology
      3. Ring - Closed loop; messages pass in one direction around loop
  1. Metropolitan and Wide Area Networks
    • WANs: Span broad geographical distances—entire regions, states, continents, or entire globe
    • MANs: Large network that spans a metro area or campus

C. Physical Transmission Media

  1. Twisted Wire
    • Strands of copper wire twisted in pairs
    • Older medium
    • Telephone systems (analog or digital)
  2. Coaxial Cable
    • Single copper wire
    • Larger volume of data
  3. Fiber Obtics
    • Strands of clear glass fiber bound into cables
    • Faster, lighter, more durable than wire
    • More difficult to work with, expensive, difficult to install
  4. Wireless Transmission Media
    • Microwave - high-volume, long-distance, point-to-point communication
    • Cell-Phones - radio waves

D. Broadband Technologies

  1. Asynchronous Transfer Mode (ATM)
    • Can handle many types of network traffic
    • 1.5 Mbps to +9 Gbps
    • High bandwith digital circuts
    • Data, video, audio over same network (telecom & enterprise backbones)
  2. Integrated Services Digital Network (ISDN)
    • Older, international telephone standard
    • Used for network access that integrates voice, data, image and video
    • Effective for long distance teleconferencing
  3. Digital Subscriber Line (DSL)
    • Operate over existing phone lines to carry voice, data, video
  4. Cable
    • Use cable coaxial lines to deliver high-speed internet access
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