Towards an efficient combination of adaptive routing and queuing schemes in Fat-Tree topologies

The interconnection network is a key element in High-Performance Computing (HPC) and Datacenter (DC) systems whose performance depends on several design parameters, such as the topology, the switch architecture, and the routing algorithm. Among the most common topologies in HPC systems, the Fat-Tree offers several shortest-path routes between any pair of end-nodes, which allows multi-path routing schemes to balance traffic flows among the available links, thus reducing congestion probability. However, traffic balance cannot solve by itself some congestion situations that may still degrade network performance. Another approach to reduce congestion is queue-based flow separation, but our previous work shows that multi-path routing may spread congested flows across several queues, thus being counterproductive. In this paper, we propose a set of restrictions to improve alternative routes selection for multi-path routing algorithms in Fat-Tree networks, so that they can be positively combined with queuing schemes.