Narrowband applications using atm switching and transport

ATM is used as a transport and switching mechanism in a hybrid STM/ATM network while the signaling remains normal narrowband signaling. The narrowband signaling is transported on permanent paths over ATM connections, and the narrowband speech channels are transported on ATM and switched on a "Per call basis" (on-demand) through an ATM switch. A translator formats a call-setup-related signaling message into ATM cells so that the signaling message can be routed through an ATM switch to a circuit switched (STM) node. The circuit switched node (PSTN/ISDN) sets up a physical connection for the call and generates a further signaling message therefor that relates to the physical connection. The ATM switch routes an ATM cell-formatted version of the further signaling message to another ATM switch over an ATM physical interface. Thus, the ATM switch switches both narrowband traffic and signaling for the call over the ATM physical interface.