1. Message

• It is the information to be communicated (like text, numbers, pictures, audio, and video)

2. Sender

• The device that sends the message (can be a computer, telephone, handset, a video camera, etc.)

3. Receiver

• The device that receives the message (can be a computer, workstation, telephone handset, television, etc.)

  4. Transmission medium

• It is the physical path by which a message travels from sender to receiver (eg: twisted-pair wire, coaxial cable, fibre-optic cable, radio waves, etc.)
• It acts as a bridge

5. Protocol

• It is a set of rules that govern the data communications
• It represents an agreement between two devices

• Without protocol two devices cannot communicate (eg: person speaking English cannot understand Spanish)