MCL: A Cost-Efficient Nonblocking Multicast Interconnection Network

Interconnection networks lie in the heart of all types of parallel architectures, because how processors or memory modules are connected to each other has a significant impact on the scalability, reliability, cost and performance. For example, a nonblocking interconnection network delivers guaranteed path availability to any connection requests, without interference to existing connections. Also, an interconnection network with multicast capability can distribute data from a single source to all the destinations in a one-shot manner, eliminating unnecessary duplications and minimizing communication delays. However, implementing nonblocking multicast networks imposes great challenges to designers because both of them demand high hardware cost. To deal with this problem, in this paper we propose a novel interconnection network, named Multicast Capable Low-cost Network (MCL), which is both nonblocking for multicast traffic and cost-efficient. We first design the topologies and routing algorithms for MCL, and then prove its nonblocking multicast properties. Most importantly, we show that MCL achieves the lowest hardware cost in terms of asymptotic number of crosspoints. Specifically, the theoretical upper bound on the crosspoints of an N x N MCL is O(N log(3.39)N). The explicitly constructed instance of an N x N MCL has a cost of O(N-5/4) and constant delay from the input ports to the output ports. These theoretical and practical costs are both the lowest compared to previous designs which deliver the same performance.