tanford University [8]. The target is to develop a system that is amenable to high-performance and low-cost implementations and capable of supporting a broad range of research, can isolate experimental traffic from production, and is consistent with vendors' need for closed platforms. The key technical idea of SDN is to provide an open control interface to the operating system of the network device without compromising the details of the implementation, an important business aspect for equipment manufacturers. This is enabled by support of Open- Flow [8] in the operating system and is based on the Ternary Content Addressable Memory (TCAM)-based flow tables, most routers and switches make use of. In a classical router or switch, the fast packet forwarding data path and the high-level routing decisions in the control path occur on the same device. An OpenFlow-enabled switch separates these two functions. The data path portion still resides in the switch, while high-level routing decisions are moved to a flow controller, typically a standard server. The OpenFlow Switch and Controller communicate via the OpenFlow protocol, which defines operation and management (OAM) messages. Besides this technical view, this split design will enable a cost reduction and new market opportunities by the basic principle of modularization. This is of high importance for supporting flexible network innovations because the development cycles of hardware and software components are extremely different, and the modularization supports a decoupling of the innovations from a market perspective. The right layering approach will enable high market volumes for specific modules (software or hardware). The introduction of the SDN concept into real networks would have a profound impact on the way in which networks are built and operated. In order to understand and evaluate the practical implica- tions of the general concept, it would be beneficial to first test it in research networks. Feedback from the experimental implementation will be crucial 