The recent literature on data center networks often propose the use of centralized control server to manage resources or for coordination. These controllers are always a single omniscient device. While we see no problems in practice yet as it works for small scale networks, there is a scalability concern. This paper proposes the idea of devolved controllers, namely, a number of controllers that each with only limited information about the network, but they together can replace a omniscient

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... oller. Thus it permits the controllers' workload to scale up. We use dynamic flow reroute as an example, to study how we can build a network with devolved controllers, how to configure them, how they operate, and especially how they provide resilience. We show that these devolved controllers can remove the scalability concern and provide redundancy to each other; externally, they are as easy to use as a single omniscient controller. We describe how these controllers are prepared and used to prove that devolved controllers is feasible idea, and provide a precursor to a new direction on the control aspect of networking. 1 The reroute path is from in a reduced solution space as full topology is not available. It may not hurt the effectiveness of reroute, especially when we mandate only shortest paths to be used. The shortest paths can be included in the topology stored in the controller at configuration time. See [10] for detail. 978-1-4244-9268-8/11/$26.00 ©2011 IEEE This full text paper was peer reviewed at the direction of IEEE Communications Society subject matter experts for publication in the IEEE Globecom 2011 proceedings.