We propose the use of the optimal least weight routing (OLWR) algorithm for routing QoS flows in high-speed networks. The main principle of our algorithm is that the choice of the most appropriate route, is based on a set of parameters that estimate the impact that, the acceptance and routing decision of a call request belonging to a specific class, would have on the network and other classes of service. The performance evaluation results demonstrated that OLWR outperforms both the multi-hop least-loaded routing algorithms and the multihop most-loaded routing algorithms in terms of both revenue and carried load.