A method, comprising: sending a session initiation protocol invite message via an internet protocol multimedia subsystem network to establish an internet protocol multimedia subsystem-specific service between a plurality of terminals coupled to the internet protocol multimedia subsystem network; establishing a session initiation protocol dialog between the plurality of terminals based on the session initiation protocol invite message; providing at least one service to at least one of the terminals via the dialog; communicating circuit switched bearer information between the plurality of terminals via the session initiation protocol dialog by way of a session description protocol message (404, 504, 600) having a session description extension (404A, 404B, 504A, 504B, 602) indicating the circuit switched bearer information and including a media description (406, 414, 506, 512, 602) including a media type and a new sub-field type indicating that the media type will be communicated via a circuit switched bearer; parsing the session description protocol message (404, 504, 600) in the plurality of terminals receiving the session description protocol message (404, 504, 600) to identify the circuit switched bearer information; and effecting a circuit switched communication flow between the plurality of terminals upon receiving a session initiation protocol provisional response, via the circuit switched network as directed by the circuit switched bearer information, wherein the circuit switched communication flow is tied together in the plurality of terminals with the internet protocol multimedia subsystem-specific service. sending a session initiation protocol invite message via an internet protocol multimedia subsystem network to establish an internet protocol multimedia subsystem-specific service between a plurality of terminals coupled to the internet protocol multimedia subsystem network; establishing a session initiation protocol dialog between the plurality of terminals based on the session initiation protocol invite message; providing at least one service to at least one of the terminals via the dialog; communicating circuit switched bearer information between the plurality of terminals via the session initiation protocol dialog by way of a session description protocol message (404, 504, 600) having a session description extension (404A, 404B, 504A, 504B, 602) indicating the circuit switched bearer information and including a media description (406, 414, 506, 512, 602) including a media type and a new sub-field type indicating that the media type will be communicated via a circuit switched bearer; parsing the session description protocol message (404, 504, 600) in the plurality of terminals receiving the session description protocol message (404, 504, 600) to identify the circuit switched bearer information; and effecting a circuit switched communication flow between the plurality of terminals upon receiving a session initiation protocol provisional response, via the circuit switched network as directed by the circuit switched bearer information, wherein the circuit switched communication flow is tied together in the plurality of terminals with the internet protocol multimedia subsystem-specific service.