Communication networks employ a variety of transmission media ranging from copper wires to
   satellite channels to transport user's information. The transmission media is the physical path
   for the communication signal. Transmission media can be classified into two major categories :
   guided media, which may constrain and guide the communication signal, and unguided media,
   which permits signal to be transmitted but not guide them. Examples of guided transmission
   media are metallic cable and optical fibres. Examples of unguided transmission media are
   the radio signals and satellite signals. An important characteristic of these different media
   is the bandwidth or simply the range of frequencies each can transmit. In general, the
   greater the bandwidth of a given media, the more it can carry.