A path-load based adaptive routing algorithm for networks-on-chip

Applications executing in current MPSoCs present traffic behavior with different characteristics in terms of QoS requirements and traffic modeling. Another important MPSoC traffic feature is its unpredictability and dynamic nature. Networks-on-chip (NoCs) are communication structures being used due to higher degree of parallelism, fault tolerance, and scalability, when compared to busses. Even with increased bandwidth due to parallelism, some flows may compete for the same network resources, affecting the applications performance, and possibly violating QoS requirements. Adaptive routing algorithms may reduce such congestion, enabling dynamic path modification according to some congestion evaluation metric. State of the art approaches have a limited view of the congestion areas, since each router take routing decisions based on its neighbors congestion status. Such local decision may lead packets to another NoC congested region, therefore being inefficient. This paper proposes a new method, using the information of all routers in the source-target path. This method relies on a protocol for QoS session establishment, followed by distributed monitoring, and reroute to non-congested routers. The set of executed experiments presents results concerning latency and buffer utilization when the method proposed is applied.