A switch or other processing element of a communication system is configured to detect automatically the particular version of an asynchronous transfer mode (ATM) user-network interface (UNI) protocol or other signaling protocol utilized by a customer premises equipment (CPE) device or other device coupled to the switch. The switch analyzes at least one message received in a signaling channel from the coupled device in order to determine the particular version of the protocol, and stores an indicator of the particular version of the protocol for use in subsequent interaction with the coupled device. Call processing functions of the switch may be reconfigured based at least in part on the determination of the particular protocol version.