Ethernet ring protection (ERP), defined in ITU-T recommendation G.8032, is a promising technology to realize the SONET/SDH-grade resilience in carrier Ethernet infrastructures. With its own loop prevention technique to block a link called ring-protection-link (RPL) in an ERP ring, the ERP introduces a new optimization problem named RPL positioning whose objective is to find the optimal RPL location to minimize the required ring capacity for given traffic demands. In this paper, we derive the optimal RPL positioning as an integer linear programming (ILP) problem and additionally propose an optimal RPL positioning algorithm for more effective ring loading. By evaluations, we demonstrate that our proposed algorithm is indeed capable of finding the optimal RPL equal to the results by an exhaustive search emerged in prior works or the formulated ILP model. But, it is more efficient in computing time than the exhaustive search and the ILP model.