Method and apparatus for high-capacity circuit switching with an atm

Abstract

A high-capacity multistage switching system includes a second stage ATM switch that interconnects multiple lower-capacity switch modules. The switching system dynamically establishes a connection between the switch ports of two switch modules, using as part of the connection a permanent virtual connection, i.e., a pre-established connection path, through the ATM switch. Each switch module includes one or more switch ports, an ATM interface card and a time-division-multiplexed 'TDM' bus that transfers user data between the switch ports and the ATM interface card. A system controller dynamically establishes connections between two given switch ports establishing one or more virtual trunks to transfer the user data between the TDM buses of the switch modules and cell payloads of ATM cells that are directed over the appropriate pre-established connection path through the ATM switch. The system controller then assigns to the connections transmit and receive timeslots on the TDM bus and octets in virtual trunk structures that are associated with the virtual trunks. The ATM card retrieves user data from the transmit timeslots and places the data in the octets of the virtural trunk structures, and then assembles the structures in ATM cells that are directed along the selected connection path. An ATM card that receives an ATM cell disassembles the cell into the constituent virtual trunk structures and retrieves user data from the octets of the structures and places the data on the TDM bus in the receive timeslots.