Routing policy, also known as selection function, is an important constituent of adaptive routing algorithm for interconnection networks. However, relatively very small research effort has been put on it until now. A generic design framework for it is absent, and the behind mechanism of how it affects the network performance needs further exploration. In this paper we study the routing policy for interconnection networks as a separate topic. The action of routing policy on network traffic is analyzed. We then clarify that routing policy actually works as a traffic scheduler. It together with some other mechanisms constitutes a traffic shaping paradigm for interconnection networks. Five generic routing policies are proposed in conformance to the analysis. They explicitly schedule the real-time network traffic based on traffic measurement. Counters are used as cost-effective measurement facilities. To standardize the design, constituents of a counter-based routing policy (CRP) are formally defined. Simulations covering extensive traffic patterns exhibit potentials of CRP in maximizing the network performance.