Connection styles
  Broadcast vs. Point to point.

  Broadcast - multiple devices connected via a single connection bus.
    Local bus Addressing 
      - ID of both source and target device part of transmission.

    Handshaking - initiating a communication session, error handling, 
      terminating a session, etc.

    Mediation - handling of competition between "users" on connection media.
      (arbitration)

    Sequencing may have to be encoded in data.
      Networking used packet driven data transfers. Stream of data parsed
        into packets that are broadcast sequentially.

      Packets from different 'sessions' can be interleaved on medium.

      Need to recognized 'position' of lost or re-transmitted packet.

    For machines that are close by, broadcast cheaper and better use of 
      lines (or medium, WiFi). 

    Local area networks, old fashion party line telephone systems. 

    Physical topology
      Bus, tree, star, combination.

      Ring.