Must be properly terminated. Fiber optic cable. RF, IR, and Laser. There are several strategies for setting up your cable. These physical topologies can impact on what network protocols you can use.
Some topologies are more common than others.
Ring Topology - Token Ring over Thin coax or UTP and FDDI over Fiber. Bus Topology - Ethernet over Thin coax or Thick Coax. Star Topology - Ethernet over UTP and ATM over UTP or Fiber. The Ring Topology. Depending on Data-Link strategy used, a failed node may or may not bring down the network.