Network bus.
  Early Ethernet used broadcast to all devices within a local network.
    Devices responsible for accepting/ignoring addressed packets.
    Modern implementation allow switches to do a large amount of 
      pre-routing. A lot like how the post office works.
      More closely resembles point to point connections.
 
  Token ring daisy-chained packets to all devices on ring.
    Devices responsible for accepting/ignoring addressed packets.

  Wireless broadcast to all devices.
    But only provides connections to a few devices on separate frequencies
      during a particular time period.

    Devices responsible for accepting/ignoring addressed packets.


  Addressing.
    Physical Source/destination address. Physical/MAC layer
      Phial address only valid on local network.

    Virtual Source/destination address. IP layer
      Universal address used for routing communication anywhere in world.

    Virtual Source/destination ports.
      Identifies specific service request/service provider process

  Uses limited pairs of transmission lines.
    Copper Ethernet - pair of unidirectional lanes. 
      May use multiple lanes for higher band width.

    Optical fiber - both directions on single lane.

  Address, data, and control implemented at the software/packet level.
  
  Can span much greater distances that system level buses.

  Often missing power bus.
    But power transmission possible. 
    Power over Ethernet  
    Used to power IP cameras or Wireless access points in remote locations.
    Usually NOT done over long distances. Max of 15 ft.