Source selection problem in multi-source multi-destination multicasting

Multicast is designed to jointly deliver content from a single source to a set of destinations; hence, it can efficiently save the bandwidth consumption and reduce the load on the source. In many important applications, the appearance of multiple sources brings new opportunities and challenges to reduce the bandwidth consumption of a multicast transfer. In this paper, we focus on such type of multi-source multicast and construct an efficient routing forest with the minimum cost (MCF). MCF spans each destination by one and only one source, while minimizing the total cost (i.e. the weight sum of all links in one multicast routing) for delivering the same content from the source side to all destinations. Prior approaches for single source multicast do not exploit the opportunities of a collection of sources; hence, they remain inapplicable to the MCF problem. Actually, the MCF problem for a multi-source multicast is proved to be NP-hard. Therefore, we propose two (2 + ε)-approximation methods, named P-MCF and E-MCF. We conduct experiments on our SDN testbed together with large-scale simulations under the random SDN network, regular SDN network and scale-free SDN network. All manifest that our MCF approach always occupies fewer network links and incurs less network cost for any multi-source multicast than the traditional Steiner minimum tree (SMT) of any related single source multicast, irrespective of the used network topology and the setting of multicast transfers.