Switched services operate on landline and cellular networks. When a person makes a
call, the network sets up a path between the caller and the dialed party. Importantly, the
path is available exclusively for the duration of the call. The path is not shared. Natural
pauses in conversation and data transmission are not used for other voice or data calls.
Capacity is reserved in the network for the entire duration of the transmission. This
exclusivity causes wasteful utilization of network capacity.
Circuit switching is being gradually phased out in public and wireless networks.
Because of circuit switching’s smaller capacity and inefficiencies, advanced, fourthgeneration
mobile protocols specify non-circuit-switched, IP packet technology. Carriers
increasingly add IP equipment when replacing fully depreciated, older voice
switches or when building new infrastructure.
Last-mile access networks use a mix of IP and circuit switching to carry voice.
Traditional telephone companies, which have investments in older infrastructure, are
in the process of transitioning to IP in their last-mile infrastructure as they move customers
to IP voice. When customers select their telephone provider for Internet access
and TV services, the provider offers to move the subscriber’s voice service to the same
broadband infrastructure as that used for data and TV. Most of them provide VoIP over
the broadband.
