Abstract—Multicast tree aggregation is a technique thatreduces the control overhead and the number of statesinduced by multicast. The main idea of this protocol is toroute several groups to the same distribution tree in order toreduce the total number of multicast forwarding states. Inthis article, we show that this technique cannot be applied tolarge domains. Indeed, when the number of border routersis large, actual tree aggregation protocols are unable to findsimilar groups to aggregate to the same tree. However, bydividing the domain into several smaller sub-domains, weprove that it is possible to achieve important savings. Ahierarchical protocol is designed to interconnect the trees ofthe sub-domains together. While previous protocols cannotcope with more than 25 border routers, our protocol stillshows significant benefits for domains with 200 borderrouters.

Cite: Joanna Moulierac, Alexandre Guitton, and Mikl´os Moln´ar, "Hierarchical Aggregation of Multicast Trees in Large Domains," Journal of Communications, vol. 1, no. 6, pp. 33-44, 2006.