Hermes: Architecting a top-performing fault-tolerant routing algorithm for Networks-on-Chips

Networks-on-Chips (NoCs) are experiencing escalating susceptibility to wear-out and reduced reliability, with the risk of becoming the key point of failure in an entire multicore chip. Aiming towards seamless NoC operation in the presence of faulty communication links, in this paper we propose Hermes, a highly-robust, distributed and lightweight fault-tolerant routing algorithm, whose performance degrades gracefully with increasing faulty link counts. Hermes is a deadlock-free hybrid routing algorithm, utilizing load-balancing routing on fault-free paths to sustain high-performance, while providing pre-reconfigured escape path selection in the vicinity of faults. Additionally, Hermes identifies non-communicating network partitions in scenarios where faulty links are topologically densely distributed. An extensive experimental evaluation, including utilizing traffic benchmarks gathered from full-system chip multi-processor simulations, shows that Hermes improves network throughput by up to 3× when compared against prior-art.