Multicast fat-tree data center networks with bounded link oversubscription

Many data center networks (DCNs) adopt a multi-rooted tree structure called fat-tree, which has the potential to deliver large bisection bandwidth through rich path multiplicity. However, unbalanced traffic load distribution may prevent efficient utilization of such high degree of parallelism. Meanwhile, high bandwidth multicast communication is critical to many data center services and applications. Hence, in this paper we consider multicast traffic load balance problem in fat-tree DCNs from a novel angle, aiming to find the most cost-effective way to build a multicast fat-tree DCN with bounded link oversubscription ratio. First, we present a multi-rate network model to accurately describe the communication environment in a fat-tree DCN. Then, we derive the minimum number of core switches required to achieve bounded link oversubscription ratio under arbitrary multicast traffic. Finally, we provide a comprehensive comparison on the cost of different approaches to building such a multicast fat-tree DCN.