A dial string is received from a session application that interfaces with a packet-based or circuit-switched system such as VoIP, PSTN, PBX, etc. Regular expression match patterns are compared with the input dial string. The dial plan mapper identifies one of the match patterns providing a longest match with the dial string and outputs call configuration information associated with the identified match pattern. The configuration information contains call parameters necessary for establishing the telephone call with the call destination. The configuration information format allows the dial plan mapper to specify any one of the wide variety of different session protocols that may be associated with a particular call destination.