L2

• Computer networks


  Devices/nodes pass data to each other along data connections
• Types of network media

  • Wire/cables
  • Wireless/air
• Connections or network links between devices/nodes

  • Established using either cable media or wireless media
• Network media


  Physical or wireless channel used for transmission in the network
• Cables Standards

  • CAT 5
  • CAT6
  • 6a (Augmented Cat 6)
• Unshielded Twisted Pair (UTP)


  • Most popular and cheapest form of cables in the network, has four pairs of wires inside plastic sheathing to protect from interference
• Types of Twisted Pair Cables

  • Shielded Twisted Pair
  • Unshielded Twisted Pair (UTP)
• Fiber Optic Cable


  Technology using glass or plastic threads to transmit data, consists of a bundle of glass threads capable of transmitting messages modulated onto light waves
• Wireless Transmission Media

  • Broadcast radio
  • Cellular radio
  • Microwaves
  • Satellites
  • Infrared signals
• Advantages of Fiber Optics


  • Greater bandwidth than metal cables, less susceptible to interference, thinner and lighter than metal wires, can transmit data digitally
• The South Africa Far East cable is an optical fiber submarine communications cable linking South Africa and Malaysia
• Twisted pair cabling

  Two conductors of a single circuit twisted together to cancel out electromagnetic interference
• Microwaves


  Radio waves providing high-speed signal transmission, limited to line-of-sight transmission
• Disadvantages of Fiber Optics

  • Expensive, difficult to install, fragile, difficult to splice
• Radio Waves


  Wireless transmission medium distributing radio signals through the air, widely used in radio communication
• Shielded Twisted Pair


  • Uses metallic shield wrapping to protect the wire from interference
• Coaxial Cable


  A type of cable used for cable TV and data communications, made up of a single center solid wire surrounded by a braided or foil conductor with insulating dielectrics
• Types of Wired/Cable Media

  • Twisted pair
  • Coaxial cable
  • Fiber optic
• Microwaves transmission

  • Fast transmission but limited to line-of-sight, often located on tops of buildings, towers, or mountains
• SAT-3/WASC or South Atlantic 3/West Africa Submarine Cable links Portugal and Spain to South Africa, forming part of the SAT-3/WASC/SAFE cable system
• Bridges


  • Connect two networks, break segments of one network into smaller groups
  • Filter incoming traffic and decide whether to forward or discard it
• Routers


  • Determine where information packets should go and send them to their destination by the shortest, most efficient route
• Network Devices

  • Repeaters
  • Switches
  • Bridges
  • Routers
  • Network Interface Cards
  • Patch Panel
• Infrared


  • Wireless transmission media sending signals using infrared light waves
  • Requires line-of-sight transmission like microwaves
  • Used for devices like mouse, printer, digital camera with IrDA port for data transfer
• Network Interface Cards


  • Installed in a computer to connect it to a network
  • Provide a dedicated, full-time connection to the network
• Bluetooth


  • Short-range broadcast radio communications transmitting data at 1 Mbps among Bluetooth-enabled devices
  • Examples include desktop computers, notebook computers, handheld computers, Internet appliances, cellular telephones, printers
• Patch Panel


  • Mounted hardware unit containing port locations in a communications system
  • Serves as a static switchboard, interconnecting computers within a local area network
• Microwaves


  • Provide high-speed signal transmission
  • Transmission involves sending signals from one microwave station to another
  • Limited to line-of-sight transmission, must transmit in a straight line with no obstructions between antennas
  • Stations located on tops of buildings, towers, or mountains to avoid obstructions
  • Used where installing physical transmission media is difficult or impossible, but line-of-sight transmission is available
• Radio waves


  Have long-distance communication capabilities compared to microwaves
• Repeaters


  • Amplify signals that have traveled a long distance
• Cellular Radio


  • Form of broadcast radio used widely for mobile communications
  • Used over land areas called cells, each served by at least one fixed location transceiver
  • Cells provide radio coverage over a wide geographic area enabling communication between portable transceivers and fixed transceivers and telephones
• Satellite Communication


  • Communications satellite receives microwaves signals from an earth-based station, amplifies and broadcasts them back over a wide area
  • Satellites usually placed about 22,300 miles above Earth's equator and move at the same rate as the Earth
  • Applications include television and radio broadcasts, videoconferencing, paging, and GPS
• Switches


  • Join multiple computers within one local area network
  • Selectively forward data packets to a specific destination