Shared-Tree selection method for aggregated multicast

Aggregated multicast methods have been proposed in order to reduce the size of routing tables in routers for multicast communications, where plural multicast sessions share a single multicast tree called Shared-Tree. STA (Scalable-Tree-Aggregation) method has been proposed as a Shared-Tree selection method, where a minimum size Shared-Tree has been selected among Shared-Trees which contain all destination nodes of a multicast session. In the STA method, the selected Shared-Tree sometimes contains invalid destination nodes for the multicast session and causes the unnecessary traffic load. In this paper, we proposed a novel Shared-Tree selection method which makes it possible to select smaller size Shared-Tree compared with the multicast session by a grafting method. By the grafting method, destination nodes not involved in the selected Shared-Tree can be connected to the Shared-Tree. We can expand the search range of Shared-Trees by the grafting method and select a Shared-Tree, destination nodes of which overlap those of the multicast session as many as possible. In our proposed selection method, Shared-Trees are selected by the measurement of overlapping degree, which indicates how many destination nodes in the multicast session overlap with those in Shared-Trees. Moreover, we introduce a replacement method for reducing the entry size of Shared-Trees. We evaluate our selection method by simulation experiments and show the effectiveness of our proposed method.