Skip to content

Cable

  • RJ45 is the name for the connectors on the ends of the Ethernet cables

  • gigabit ethernet is full duplex

  • signal strength drops over distance

  • VGA

auto-mdix - why standards - if frame goes from point A to B, may go over cables w diff capabilities - may be doing a lot of standards translating - but also everyone uses Ethernet frame so kinda okay

types of cables

  • twisted pair
    • modern Ethernet + telephone
      • 2 types
        • unshielded twisted pair (UTP)
          • most common kind
          • managed by IEEE as 802.3
        • shielded twisted pair (STP)
          • slight damage = a lot more electromag interf/crosstalk
          • more easily damaged than UTP
          • cost more → rarer
  • coaxial - copper cable within insulator within copper shield
    • for higher frequency than twisted pair
    • technically faster than twisted pair
    • difficult to install/maintain bc of the layers
  • fiber-optic

  • what kind of endings do you use? (straight-through, crossover, rollover)

    • DTE - data terminal equipment 
    • DCE - data circuit-terminating equipment
    • DTE to DCE or whatever determines this

  • referring to the pins at the end - these below are all copper

    • straight-through - pin order is the same to the other side
    • crossover - data input pins are now reversed to be data output pins
    • rollover/console cable - reverse pin order
      • reverse the pin order of each wire in a cable
        • if it rolled over, looks same
      • somewhat legacy bc used for RS-232 connectors for PC, printer, monitor serial ports

  • [[wireless networking]]

    • most wireless devices are half-duplex bc a device's transmitted signals are generally much stronger than signals it receives
    • if need to transmit and receive at same time -> use dif frequencies

how use

  • typical net connection is PC-> switch -> router = all straight-through
  • anything else is cross-over, as in any like devices as well (includes PC -> router)

mgmt

  • out-of-band mgmt
    • network isn't available
    • serial connection/[[USB]] port can be used -> connect a modem to manage device
      • sometimes have dedicated comm router/server that does this