13.2 SWITCHING TECHNIQUES

The efficiency of a communications system depends not only on the physical transmission medium but also on how communication resources are shared among many users. Rather than providing every pair of users with a permanent dedicated connection, switching enables information to be directed through a network so that available transmission capacity is used efficiently.

Over the history of telecommunications, several switching techniques have been developed to meet different communication requirements. The four classical approaches are circuit switching, message switching, packet switching, and cell switching. Although packet switching now dominates most modern communication networks, each technique has played an important role in the evolution of communications and remains useful in particular applications.