ECTCP: An Explicit Centralized Congestion Avoidance for TCP in SDN-based Data Center

Abstract

Data centers provide high aggregate bandwidth for large-scale network services. Traditional TCP protocol does not work well to meet the demand in data center. Before congestion occurs, TCP increases sending window to preempt bandwidth, resulting in buildup queues and increase latency, moreover TCP can only adjust sending window individually for each flow, which lacks global information. This mechanism is ill-suited for the diverse mix of short and long flows, and cannot provide high burst tolerance. Fortunately, Software Defined Networking (SDN) has a global view on data center network, which provides an opportunity to centralized control flows. Leveraging the feature of SDN, we propose an explicit centralized congestion avoidance mechanism (ECTCP). By gaining network topology and the information of flows, SDN controller calculates each flow's fair bandwidth, and adjusts the receive window size of each TCP connection. ECTCP does not need to modify TCP stack, which is easy to implement in the SDN-based data center. In our evaluation, ECTCP achieves fair throughput and improves fairness among different congestion control algorithms. ECTCP also reduces Flow Completion Time (FCT) for burst short flows, and keeps Round-Trip Time (RTT) in small-scale.