This Recommendation specifies signalling requirements and signalling flows of touch screen terminal-based interactive voice response (TS-IVR) services. The TS-IVR services@ including session initiation protocol (SIP) based TS-IVR services and web based TS-IVR services@ are defined in the next generation network (NGN). The normative part of this Recommendation uses or refers to messages that are defined in and whose behaviours are described in one or more IETF RFCs. A list of all referenced messages and their origins are provided in Annex B.