In this paper we propose a new routing protocol called the Directional Flow Routing (DFR) which takes advantages of directional antenna technology envisioned in near future for ad hoc networks. DFR is a source routing protocol where the route is completely specified by a Directional Flow Vector (DFV) between the source and the destination. DFV is a time varying straight function joining the source and the destination and is computed using the relative velocity and position vectors between the two. A packet is delivered at the destination by aligning the directional antennas of nodes along the flow vector such that packets flow along the instantaneous line joining the source and the sink. DFR is a stateless source routing protocol which has the potential to efficiently handle large scale and dense ad hoc networks with very high mobility rates. The paper presents the conceptual framework for the DFR routing paradigm. Although we also propose a simple protocol for practical implementation of the concept, we do not intend to analyze the performance of the protocol in this paper. Rather, the focus of this paper lies in discussing the design choices that would be necessary for the protocol implementation. It is also intended to highlight the issues and practical challenges involved in designing algorithms using directional antennas in general and should serve as guidelines for future research.