Inter-domain group-communications

The present invention is concerned with group communications service, i. e., communications service accompanied by two or more users (or service participant). The present invention provides a method of distributing multicasting data of multicasting service in a different domain, and a method of distributing multicasting data to a service participant in a domain. The present invention is further concerned with a control node and a system which perform each method. It is the present invention in order to improve resource use at the time of providing multicasting service, division, and PoC service for a service participant, A mechanism for avoiding unnecessary increase of multicasting data in a distribution tree of multicasting service to a service participant in a different domain is provided. For this reason, a control node for which which domain should be provided with multicasting data starts multicasting service in the case of a determined demand sends multicasting data for every domain. In another mode of the present invention, it is avoided that multicasting data is superfluously reproduced in each domain.