An Effective Congestion-Aware Selection Function for Adaptive Routing in Interconnection Networks

The performance of interconnection networks is heavily influenced by routing algorithms. The selection function, which decides the final output channel when a set of admissible output channels exist, is essential for an adaptive routing algorithm. Congestion is usually a major cause of performance degradation in interconnection networks. In this paper, we present a simple and efficient selection function based on the concept of dynamic-bandwidth-estimation (DBE) to relieve network congestion and improve network performance. With the proposed selection function, each router grasps congestion information locally, estimates the actual bandwidth of each output channel dynamically using grasped information and try to distribute the traffic through the channel that will allow the packet to be routed as free as possible of congested nodes and links. In this way, traffic loads of links in the network also get more balanced. The DBE selection function can be coupled with any type of network topology and adaptive routing algorithm. Performance evaluation was carried out by using a flit-accurate network simulator under various routing algorithms and traffic patterns. Results obtained show that the DBE selection function consistently improves performance in both throughput and average latency.