Software Defined Networking (SDN) is rapidly emerging as a technology with potential to improve network flexibility via software-based management and control. A consortium of researchers from nine universities and the CSIRO, led by UNSW and including Swinburne, has been awarded a LIEF grant by the Australian Research Council to deploy SDN equipment within each of their labs. These sites are being interconnected by AARNet to create a national wide-area SDN testbed environment, with the potential to peer internationally with testbeds in the USA, Europe and elsewhere. This testbed is helping us better understand the SDN ecosystem - Openflow-enabled hardware (Noviflow, Pica8, Corsa), controller software (Floodlight, Ryu, ONOS), application development APIs, and SDN applications themselves. Building this wide-area testbed is helping us learn the complexity, maturity, performance, and scalability aspects of carrier SDN deployment, as well as identify current gaps. The intended result is a growing store of knowledge and experience, to be shared with network operators who are potentially interested in exploring SDN solutions. In this presentation, the architecture of the SDN testbed will be presented, along with examples of the planned research experiments and potential use-cases.