LoCoSDN: A local controller for operation of of switches in non-SDN networks

Hybrid OpenFlow (OF) switches can be operated as legacy switches with a local control plane or as OF switches that are controlled by an SDN controller. As a first thought, hybrid switches are the first choice for network administrators as they facilitate the transition from a traditionally operated towards a software-defined network. However, we encountered several limitations as most of these switches are based on a legacy hardware platform that is augmented with a limited set of OF features. As a consequence, some packet processing pipelines of hybrid switches filter out packets before they pass the OF part. To avoid these issues, we developed LoCoSDN, an SDN architecture that imitates the hybrid switch behavior on OF-only devices, i.e., they can be operated in traditional networks and without any special knowledge about SDN. LoCoSDN contains a Cisco-like CLI and configuration format so that configurations from existing devices can be imported. It differentiates between a startup and running configuration, and provides reconfigurability during operation and support for an additional SDN controller. We implemented LoCoSDN as a lightweight SDN controller for the Ryu SDN controller framework that can be run on a single-board computer.