Partial offloading of OpenFlow rules on a traditional hardware switch ASIC

OpenFlow represents a new powerful paradigm that combines the flexibility of the software with the efficiency of a programmable hardware switch. However, such an approach is currently reserved for new hardware devices, specifically engineered for this paradigm. This paper presents our experience and findings about selectively offloading OpenFlow rules into a non-OpenFlow compatible hardware switch silicon, which enables existing (legacy) hardware ASIC's to become compatible with the SDN paradigm. We describe our solution that transparently offloads the portion of OpenFlow rules supported by the hardware while keeping in software the remaining ones, and that is able to support the presence of multiple hardware tables although with limited capabilities in terms of matches and actions. Moreover, we illustrate the design choices used to implement all the basic functionalities required by the OpenFlow protocol (e.g., packet-in, packet-out messages) and then wwe demonstrate the considerable advantage in terms of performance that can be obtained by performing switching in hardware, while maintaining an SDN-type ability to program and to instantiate desired network operations from a central controller.