On the Construction of Low Cost Multicast Trees with Bandwidth Reservation

This report presents routing algorithms for many-to-many multicast connections with band-width requirements. The objective is to compute a connectivity structure among multicast members of low cost, taking into account their bandwidth requirements. We rst study the complexity of routing multicast connections with bandwidth reservation. Based on derived impossibility results , we propose a cluster strategy to connect multicast members, called Bandwidth Constrained Steiner Tree (BCST) strategy. We show that BCST strategy is the best polynomial time algorithm for such routing problems, in the sense of worst case performance. We propose two BCST algorithms, and claim hard bounds on cost and bandwidth overload. We study the proposed algorithms' performance on randomly generated multicast routing problems, and compare them against two well known routing strategies for multicast connection: Shortest Path Tree (SPT), where a SPT is built per multicast source, taking into account bandwidth requirements; and Minimum Spanning Tree (MST), where a single Steiner Tree is built to provide connectivity among multicast members, regardless of their bandwidth requirements. Our simulation experiments show that BCST algorithms strike a balance between blocking probability and tree cost, when compared against both SPT and MST algorithms.