Traffic Load Balancing Schemes for Devolved Controllers in Mega Data Centers

In most existing cloud services, a centralized controller is used for resource management and coordination. However, such infrastructure is gradually not sufficient to meet the rapid growth of mega data centers. In recent literature, a new approach named devolved controller was proposed for scalability concern. This approach splits the whole network into several regions, each with one controller to monitor and reroute a portion of the flows. This technique alleviates the problem of an overloaded single controller, but brings other problems such as unbalanced work load among controllers and reconfiguration complexities. In this paper, we make an exploration on the usage of devolved controllers for mega data centers, and design some new schemes to overcome these shortcomings and improve the performance of the system. We first formulate <italic>Load Balancing problem for Devolved Controllers</italic>  (LBDC) in data centers, and prove that it is NP-complete. We then design an <inline-formula> <tex-math notation="LaTeX">$f$</tex-math><alternatives><inline-graphic xlink:href="gao-ieq1-2579622.gif"/> </alternatives></inline-formula>-approximation for LBDC, where <inline-formula><tex-math notation="LaTeX">$f$</tex-math> <alternatives><inline-graphic xlink:href="gao-ieq2-2579622.gif"/></alternatives></inline-formula> is the largest number of potential controllers for a switch in the network. Furthermore, we propose both centralized and distributed greedy approaches to solve the LBDC problem effectively. The numerical results validate the efficiency of our schemes, which can become a solution to monitoring, managing, and coordinating mega data centers with multiple controllers working together.