Note: Many topics at this site are reduced versions of the text in "The Encyclopedia of Networking and Telecommunications." Search results will not be as extensive as a search of the book's CD-ROM.

Data communications is about transmitting information from one device to another. Protocols define the rules for communication so that sender and receiver can coordinate their activities. At the physical level, information is converted into signals that can be transmitted across a guided (copper or fiber-optic cable) or unguided (radio or infrared transmission) medium. Higher-level protocols define the packaging of information for transmission, flow controls, and techniques for recovering information that was lost or corrupted during transmission.