Network processors offer a new flexibility for network applications and reduce the time to market for data processing systems. In this paper, we describe the changed development process of the data plane using the Motorola C-5 Network Processor. We implemented a Resilient Packet Ring line card for a SDH cross connect. We show a solution for the support of different Quality of Service classes with a Network Processor and to achieve the necessary system stability. Additionally we carried out some simulations to verify the performance of a fairness algorithm over the ring and the system behavior. Keywords—Network processors, High-speed LAN, Quality of Service, Simulation