n order to better support data-intensive applications in data centers, these “richly-connected” network architectures are designed with the major purpose of ensuring high communication performance and robustness. These architectures have two characteristics in common: over-provisioned network resources and inefficient power usage. An excessive number of network devices and redundant links are provided aggressively for the busy-hour load. However, most of the time, the traffic in a data center is far below the peak value and varies greatly between daytime and night, which leaves a large number of network devices to stay idle.