Modeling the branching characteristics and efficiency gains in global multicast trees

We investigate two issues. First, what level of efficiency gain does multicast offer over unicast? Second, how does the shape of multicast trees impact multicast efficiency? We address the first issue by developing a metric to measure multicast efficiency for a number of real and synthetic datasets. We find that group sizes as small as 20 to 40 receivers offer a 60-70% reduction in the number of links traversed compared to separately delivered unicast streams. Addressing the second issue, we have found that almost all multicast trees have similar characteristics in terms of key parameters such as depth, degree frequency and average degree. A final contribution of our work is that we have taken multicast group membership data and multicast path data and compiled datasets which can be used to generate large, realistic multicast trees.