a method of announcing a description of a media session , for example a multimedia conference , that is to take place over multicast capable links is provided in networks configured for internet protocol operation . a modular method of announcing media sessions includes : generating a first base module having a first data structure having user oriented data relevant to the media session ; generating at least one media module having a second data structure with media oriented data necessary for a user to receive a respective media stream of the media session ; providing a link between the first base module and the at least one media module ; and , announcing the media session by making at least the first base module available to potential recipients of the media session .