A communication system provides PSTN access to a user device coupled to a packet network over a packet connection. The user device exchanges telephony signaling and telephony communications in an analog format with an analog telephone, exchanges the telephony signaling and the telephony communications in the packet format over the packet connection, and exchanges Internet communications over the packet connection. A service node exchanges the telephony signaling in the packet format with the user device, processes the telephony signaling to select a PSTN connection, transfers a control message indicating the PSTN connection, and exchanges the telephony signaling in a PSTN format with the PSTN. An interworking unit receives the control message, and in response, exchanges the telephony communications in the packet format with the user device and exchanges the telephony communications in the PSTN format with the selected PSTN connection.