Network bus.
  Broadcast
  
  Packetized

  Virtual - address, data, and control transmitted over same lines.
    Packet includes flags to indicate function of contents.

  Early Ethernet used broadcast to all devices within a local network.
    Devices responsible for accepting/ignoring addressed packets.

    Modern implementation allows  switching hubs to do a large amount of 
      pre-routing and buffering. 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 in series.
    Devices responsible for accepting/ignoring addressed packets.

    All nodes linked point to point but network implemented as a ring.
    A token/transmission packet had to traverse whole ring.

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

    Device requests a reserved time for uninterrupted communication with
      access point on particular channel. 

      If granted, guaranteed that time period.

    Devices responsible for accepting/ignoring addressed packets.
      This is why we encrypt transmissions now.

  Addressing.
    Physical Source/destination address. Physical/MAC layer
      MAC (Media access controller) ID
      Physical address only valid on local network.

      WiFi uses a Basic BSSID (Basic service set identifier) to identify node.
        Functionally equivalent to MAC.

    Virtual - much of network addressing is implemented as virtual IDs.

      WIFI
        SSID - an alias for a local WiFi network . 
          A set of access points can function as a single local network
          This allows your device to keep a connection if you move to a 
            different room/access point on the same network.

      Internet Source/destination address. IP layer
        Universal address used for routing communication anywhere in world.
        Domains receive a Class level ID and are allowed to assign device
          level IDs as desired.
          e.g. NIU is 131.156.x.x to the world.

      Source/destination ports.
        Identifies specific service request/service provider process
        Certain port IDs are reserved
        e.g port 22 is ssh.

  Transmission mediums.
    Copper Ethernet - pair of unidirectional lanes. 
      May use multiple lanes for higher band width.

    Optical fiber - fiber doesn't care.
      Simplex - fiber implemented to transmit in one direction.
      Half Duplex - fiber implemented to transmit in either direction,
        but not a the same time.
      Full Duplex - using pair simplex fibers.
      Full Duplex - using single fiber, different 'colors'.

    Electro-magnetic.
      Infra-red - remote controls.
        very short range.
        dedicated device to device.

      BlueTooth - up to 7 devices.
        very short range - 
          up to 100M in ideal conditions (visual line of sight).
          10 meters more common.           
        uses a master.
        master uses round robin time slice for each device.

      WiFi - unlimited(?) devices.
        client devices request time with access point.
          Negotiates a time slice.
        20 meters range, larger if in open area.
        Lower frequencies better range but lower throughput.  
 
      Microwave 
        distance measured in kilometers.
        used as link between nodes.
        although broadcast, often implemented as a focused or guided beam.
          implemented as point to point.
        
      Radiowave.
        Broadcast radio.
        Satellite
          combination of broadcast and point to point.
          think DirectTV

  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.