Manav Goyal

Physical Layer - Computer Networks

  • Basic
    • Last Layer to add functionality for Sender's side and First Layer for Receiver's side
    • Defines the procedures and functions that physical devices and interfaces have to perform for transmission occur
    • Converting Bits > Signal > Bits
    • Deals with Hardware
    • Physical Layer
  • Physical Topology
    • Mesh
      • All Devices are connected with each other
      • No. of Cables = nC2
      • Total No. of Ports = (n-1)*n
      • Highest Reliability
      • High Cost
      • Provides Security
      • Supports Point-to-Point, Dedicated communication => Multiple devices are not connected with a single wire
      • High Maintenance
    • Star/Hub
      • Multi-port Device, Connected with a centralized Port
      • No. of Cables = n
      • Total No. of Ports = 1*n
      • No Reliability => Network stops with Single point of faliure
      • Lower Cost
      • Less Security
      • Supports Point-to-Point
    • Bus
      • Back Bone/Co-axial/Thick Ethernet Cable with high Bandwidth connected with Devices through Tap & Drop lines (Wires)
      • Terminator/Repeater => User at the end of Cable to increase strength of Signal
      • No. of Cables = n + 1
      • Total No. of Ports = 1*n
      • No Reliability => Network stops with Single point of faliure in Back Bone
      • Low Cost
      • No Security
      • Max Collision = n
      • Supports Multi-Point/Multi-drop
      • Token => Used to reduce Collision
    • Ring
      • By connecting both ends of Bus
      • No. of Cables = n + 1
      • Total No. of Ports = 1*n
      • No Reliability => Network stops with Single point of faliure in Back Bone
      • Low Cost
      • No Security
      • Max Collision = n
      • Supports Multi-Point
      • Unidirectional
      • Token => Used to reduce Collision
    • Hybrid
  • Hardwares
    • Cables & Connectors
    • Repeaters => To increase energy
    • Hubs => Used for Multi-point Connection
  • Transmission Modes (Direction of Data Flow)
    • Simplex
      • One direction only
      • Eg = Monitor, Keyboard
    • Half Duplex
      • Both directions, One at a time
      • Eg = Walkie-Talkies
    • Full Duplex
      • Both directions simultaneously
      • Eg = Telephone
  • Multiplexing/De-multiplexing
    • Wired & Wireless medium
    • Diving Channels for multiple devices
  • Encoding
    • Digital-to-Digital
      1. Manchester
      2. Differential Manchester
        • Manchester vs Differential
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