Cascaded multicast: scalability through mediation

IP multicast routing between domains can be based on roles which border routers possess with regards to datagram forwarding to a particular group. We show that distributed role based routing is sufficient for the Internet backbone where topology is relatively poor. As a solution for necessary mediation between the backbone and domains the multicast mediator is proposed with multi-dimensional caching of IP multicast addresses enriched by group membership information. This brings an opportunity to co- ordinate multicast address allocation management between domain and to achieve more than best effort address availability.