Secure ATM-based distributed virtual tandem switching system and method

A system for enforcing switched virtual circuit (SVC) access restrictions across an Asynchronous Transfer Mode (ATM) distributed virtual tandem switching system based on closed user groups of network elements in a communications network, the system comprising:

• a plurality of trunk interworking function (T-IWF) devices in the communications network, configured to convert between voice streams from TDM communications channels to cell streams from ATM communications channels, a first one of the plurality of T-IWF devices receiving a call via at least one TDM communications channel from an end office;
• a centralized control and signaling interworking function (CS-IWF) device that receives narrowband signaling data relating to routing the call, the CS-IWF device converting the narrowband signaling data to broadband signaling data to control the call through an ATM switching network and determining that the call is directed to a second one of the plurality of T-IWF devices, the plurality of T-IWF devices and the CS-IWF device being in a previously established closed user group;
• an ATM switch in the ATM switching network that receives a request from one of the CS-IWF device and the T-IWF devices to establish an SVC connection of the call over the ATM switching network;
• an ATM element management system that stores a list of network elements in the closed user group, including the CS-IWF device and the plurality of T-IWF devices, the determination of whether the CS-IWF device, the first T-IWF device and the second T-IWF device are in the closed user group being based on the list of network elements;
• wherein the ATM switch establishes the SVC connection over the ATM switching network, enabling broadband communication between the first T-IWF device and the second T-IWF device, when the CS-IWF device, the first T-IWF device and the second T-IWF device are determined to be in the closed user group;
• wherein the ATM switch does not establish the SVC connection over the ATM switching network when at least one of the CS-IWF device, the first T-IWF device and the second T-IWF device is determined not to be in the closed user group;
• and
• wherein the ATM switch verifies that an ATM End System Address (AESA) contained in calling party information in the request from the CS-IWF device is consistent with a user-to-network interface between the first T-IWF device and the ATM switch, the ATM switch rejecting the request to establish the SVC connection over the ATM switching network when the AESA is not consistent with the UNI.