Circuit Switched Versus Packet Switched
A circuit-switched connection is brought up on an as-needed basis. In fact, a circuit-switched connection is analogous to a phone call, for which you pick up your phone, dial a number, and a connection is established based on the number you dial. As discussed earlier in this chapter, Integrated Services Digital Network (ISDN) can operate as a circuit-switched connection, bringing up a virtual circuit on demand. This approach to on-demand bandwidth can be a cost savings for some customers who need only periodic connectivity to a remote site.
A packet-switched connection is similar to a dedicated leased line because most packet-switched networks are always on. However, unlike a dedicated leased line, packet-switched connections enable multiple customers to share a service provider’s bandwidth.