Abstract— Network-on-Chip (NoC) are considered the promi- nent interconnection solution for current and future many-core architectures. While power is a key concern to deal with during architectural design, power-performance trade-off exploitation requires suitable analytical models to highlight the relations between actuators and such optimization metrics. This paper presents a model of the dynamic relation between the frequency of a NoC router and its performance, to be used for the design of run-time Dynamic Voltage and Frequency Scaling (DVFS) schemes capable of optimizing the power consumption of a NoC. The model has been obtained starting from both physical considerations on the NoC routers and identification from traffic data collected using a cycle-accurate simulator. Experimental results show that the obtained model can explain the dependence of a router congestion on its operating frequency allowing to use it as a starting point to develop power-performance optimal control policies.