Achieving Fast Convergence and High Efficiency using Differential Explicit Feedback in Data Center

Since most flows are short-lived in data center networks, fast convergence becomes very important to help the short flows effectively utilize high bandwidth. Though current explicit feedback-based transport control protocols (TCPs) provide fast convergence via fine-grained congestion information from customized switches, they unavoidably incur large traffic overhead for widely existing small packets in data center applications, resulting in suboptimal network efficiency. To solve this issue, we propose a datacenter TCP based on Differential Explicit Congestion Notification, called DECN, to achieve fast convergence without any traffic overhead. Specifically, DECN feeds rate difference between the target and current rate back to the source by using multiple consecutive packets. Besides, we propose an enhanced version DECN* which obtains the optimal number of consecutive packets according to the packet loss rate. The experimental results of NS2 simulation and testbed implementation show that DECN and its enhanced version DECN* achieve comparable fast convergence as XCP without incurring any extra feedback overhead. Compared with the state-of-the-art explicit feedback-based TCPs, they reduce the flow completion time by up to 34% in typical data center applications.

Automated summary

This study proposes a datacenter TCP based on Differential Explicit Congestion Notification (DECN) to achieve fast convergence without any additional feedback overhead. By feeding the rate difference between the target and current rate back to the source using multiple consecutive packets, DECN and its enhanced version DECN* achieve comparable fast convergence as existing explicit feedback-based TCPs without incurring any extra traffic or feedback overhead. Experimental results show that they reduce the flow completion time by up to 34% in typical data center applications.