A system and method establish an Internet protocol (IP) connection between an originating end-system and a destination end-system, incapable of resource reservation protocol (RSVP) signaling, through a switched transport network. A first interworking function (IWF) device inserts its switched transport network address into a first data field of an RSVP path message, received from an RSVP capable proxy signaling device that interfaces with the destination end-system. The first IWF device forwards the path message, through routers in an IP network, which is passed without modification to the first data field. A second IWF device receives the path message and forwards a setup message to the first IWF device through switching devices in the switched transport network, based on the first IWF device's address retrieved from the first data field of the path message. The IP connection is established through the proxy signaling device in response to the setup message.