The decoupled architecture and the fine- grained flowcontrol feature limit the scalability of a flow-based software-defined network (SDN). In order to address this problem, some studies construct a flat control plane architecture, others build a hierarchical control plane architecture to improve the scalability of an SDN[1]. However, the two kinds of structure still have unresolved issues: A flat control plane structure cannot solve the super linear computational complexity growth of the control plane when the SDN scales to a large size, and the centralized abstracted hierarchical control plane structure brings a path stretch problem[2].
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