Abstract: The IP ConferEncing with Broadband multimedia over Geostationary Satellites (ICEBERGS) project investigated the provision of IP-based multi-party videoconference services through a communication infrastructure where Next Generation Satellite Systems (NGSS) are fully integrated with the Internet. GEO satellite platform features regenerative payloads with On-Board Processing (OBP) and Bandwidth on-Demand (BoD) capabilities, as well as multi spot-beams coverage. Many issues pertinent to multicast communications (e.g., QoS and users dispersion) can be easily overcome by possible solutions. The ICEBERGS scenario assumes a seamless interoperation of a Connection Oriented (CO) GEO satellite network with Internet multicast domains. This entails that, whenever a satellite transport service is required, connections must be dynamically set-up among different spot-beams bandwidth, depending on both the mutual position of sources and receivers of multicast groups in the satellite footprint area. In addition, fair bandwidth and the QoS requirements of multicast traffic must be met. This paper describes the main features of the interworking function defined between signalling protocols of the Internet multicast domains and the signalling protocol of the satellite network.