A dedicated path between the source node and the destination node is set up for the duration of communication session to transfer data. That path is a connected sequence of links between network nodes. On each physical link, a logical channel is dedicated to the connection. Communication via circuit switching involves three phases,

  1. Circuit Establishment: Before any signals can be transmitted, an end-to-end (station-to-station) circuit must be established.
  2. Data Transfer: The data may be analog or digital, depending on the nature of the network
  3. Circuit Disconnect: After some period of data transfer, the connection is terminated, usually by the action of one of the two stations


Circuit-switching telecommunication networks were originally designed to handle voice traffic, and the majority of the traffic on these networks continues to be a voice. A key characteristic of circuit switching is that resources within the network are dedicated to a particular call. For voice communication, the resulting circuit will enjoy a high percentage of utilization because most of the time one party or the other is talking. However, as the circuit-switching network began to be used increasingly for data connections, two shortcomings became apparent:

  1. In a typical user host data connection (e.g., personal computer user logged on to a database server), much of the time the line is idle. Thus, with data connections, a circuit-switching approach is inefficient.
  2. In a circuit-switching network, the connection provides for transmission at a constant data rate. Thus, each of the two devices that are connected must transmit and receive at the same data rate as the other; this limits the utility of the network in interconnecting a variety of host computers and terminals.