We need to emphasize several points here:
❑ Circuit switching takes place at the physical layer.
❑ Before starting communication, the stations must make a reservation for the resources
to be used during the communication. These resources, such as channels (bandwidth
in FDM and time slots in TDM), switch buffers, switch processing time, and switch
input/output ports, must remain dedicated during the entire duration of data transfer
until the teardown phase.
❑ Data transferred between the two stations are not packetized (physical layer transfer
of the signal). The data are a continuous flow sent by the source station and received
by the destination station, although there may be periods of silence.