Fast and Optimal Multicast-Server Selection Based on Receivers' Preference

In this paper, we propose static and dynamic server selection techniques for multicast receivers who receive multiple streams from replicated servers. In the proposed static server selection technique, if (a) the location of servers and receivers and shortest paths between them on a network and (b) each receiver's preference value for each content are given, the optimal server for each content that each receiver receives is decided so that the total sum of the preference values of the receivers is maximized. We use the integer linear programming (ILP) technique to make a decision. When we apply the static server selection technique for each new join/leave request to a multicast group issued by a receiver, it may cause server switchings at existing receivers and may take much time. In such a case, it is desirable to reduce both the number of server switchings and calculation time. Therefore, in the proposed dynamic server selection technique, the optimal server for each content that each receiver receives is also decided so that the total sum of the preference values is maximized, reducing the number of server switchings, by limiting both the number of receivers who may switch servers and the number of their alternative servers. Such restrictions also contribute fast calculation in ILP problems. Through simulations, we have confirmed that our dynamic server selection technique achieves less than 10 % in calculation time, more than 90 % in the total sum of preference values, and less than 5 % in the number of switchings on large-scale hierarchical networks (100 nodes), compared with the static server selection.