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Power optimization has become a key challenge in the design of large-scale enterprise data centers. Existing research efforts focus mainly on computer servers to lower their energy consumption, while only few studies have tried to address the energy consumption of data center networks (DCNs), which can account for 20% of the total energy consumption of a data center. In this paper, we propose CARPO, a correlation-aware power optimization algorithm that dynamically consolidates traffic flows onto a small set of links and switches in a DCN and then shuts down unused network devices for energy savings. In sharp contrast to existing work, CARPO is designed based on a key observation from the analysis of real DCN traces that the bandwidth demands of different flows do not peak at exactly the same time. As a result, if the correlations among flows are considered in consolidation, more energy savings can be achieved. In addition, CARPO integrates traffic consolidation with link rate adaptation for maximized energy savings. We implement CARPO on a hardware testbed composed of 10 virtual switches configured with a production 48-port OpenFlow switch and 8 servers. Our empirical results with Wikipedia traces demonstrate that CARPO can save up to 46% of network energy for a DCN, while having only negligible delay increases. CARPO also outperforms two state-of-the-art baselines by 19.6% and 95% on energy savings, respectively. Our simulation results with 61 flows also show the superior energy efficiency of CARPO over the baselines.

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Abstract-Key-value (k-v) storage has been used as a crucial component for many network applications, such as social networks, online retailing, and cloud computing. Such storage usually provides support for operations on key-value pairs, and can be stored in memory to speed up responses to queries. So far, existing methods have been deterministic: they will faithfully return previously inserted key-value pairs. Providing such accuracy, however, comes at the cost of memory and CPU time. In contrast, in this paper, we present an approximate k-v storage that is more compact than existing methods. The tradeoff is that it may, theoretically, return a null value for a valid key with a low probability, or return a valid value for a key that was never inserted. Its design is based on the probabilistic data structure called the "Bloom Filter", which was originally developed to test element membership in sets. In this paper, we extend the bloom filter concept to support key-value operations, and demonstrate that it still retains the compact nature of the original bloom filter. We call the resulting design as the kBF (key-value bloom filter), and systematically analyze its performance advantages and design tradeoffs. Finally, we apply the kBF to a practical problem of implementing a state machine in network intrusion detection to demonstrate how the kBF can be used as a building block for more complicated software infrastructures.