High-Quality Fault Resiliency in Fat Trees

Overview & Synopsis

Coupling regular topologies with optimised routing algorithms is key in pushing the performance of interconnection networks of supercomputers. In this paper we present Dmodc, a fast deterministic routing algorithm for Parallel Generalised Fat-Trees (PGFTs) which minimises congestion risk even under massive network degradation caused by equipment failure. Dmodc computes forwarding tables with a closed-form arithmetic formula by relying on a fast preprocessing phase. This allows complete re-routing of networks with tens of thousands of nodes in less than a second. In turn, this greatly helps centralised fabric management react to faults with high-quality routing tables and no impact to running applications in current and future very large-scale HPC clusters.