An on-chip communication network is most power efficient when it operates just below the saturation point. For any given traffic load the network can be operated in this region by adjusting frequency and voltage. For a deflective routing network we propose the design of a central controller for dynamic frequency and voltage scaling. Given history information including the load and frequency in the network, the controller adjusts the frequency and voltage such that the network operates just below the saturation point. We provide control mechanisms for continuous and discrete frequency ranges. With a discrete frequency range and taking into account voltage switching delays, we evaluate the control mechanism under stochastic, smoothly varying and very bursty traffic. Experiments demonstrate that adaptive control is very effective in minimizing power consumption at reasonable performance. Compared with a fixed high frequency network, the adaptively controlled network is significantly more power efficient. We compare it to fixed frequency networks, which are either too slow exhibiting unbounded delays, or are dimensioned for the worst case with very high frequency and are very power hungry.