Performance, reliability and security are important concerns in modern data networks and mission critical systems increasingly depend on them. This thesis investigates these concerns on software-defined networks (SDNs) that are built using Ethernet networking technology. We propose and evaluate some solutions to the problems identified in this process, keeping in mind that our solutions should be simple retrofits as far as possible to minimize change or frustration for the data network user. We then present field findings from a practical deployment of our SDN controller, Ironstack, on an enterprise network setting. Finally, based on this operational experience, we develop a drop-in network switch augmentation that combines our aforementioned solutions and controller into an operator-friendly box, providing a turnkey solution for deploying all the systems described in this thesis.