This Recommendation defines the signalling protocol between ITU-T H.323 entities for the control of supplementary services. Detailed procedures applicable to individual supplementary services are specified by other Recommendations of the ITU-T H.450.x-series and by individual manufacturers for proprietary services using the capabilities defined in this Recommendation. The procedures of this Recommendation are derived from the generic functional protocol specified in [ISO/IEC 11582] for private integrated services networks (PISN).