Recently, several wireless/optical datacenter architectures are designed to#R##N#   overcome the drawbacks of wired datacenter topologies, such as expensive#R##N#   high-end switches, high cabling complexity, congestion caused by a few hot#R##N#   nodes. Compared with wired switches, current commodity wireless switches#R##N#   usually suffer lower throughput as well as higher packet loss ratio and#R##N#   latency. However, todays datacenter applications, such as web search,#R##N#   require quite low latency to improve user experience. In this paper, a#R##N#   mechanism, named pECN, is proposed to achieve low latency for#R##N#   delay-sensitive flows. pECN makes use of Explicit Congestion Notification#R##N#   (ECN) to maintain a small queue length and a priority-based scheduling#R##N#   mechanism to provide delay differentiated services. The priority-based#R##N#   scheduling mechanism works at the packet level. When transmitting, the#R##N#   packet with the highest priority will be sent. Since the queue length is#R##N#   controlled within a small value by the ECN mechanism, the scheduling#R##N#   mechanism does not incur large overhead. Also, since it works at the packet#R##N#   level, it can support unlimited number of services. Besides, pECN does not#R##N#   need to maintain any flow state at switches. We implemented the proposed#R##N#   mechanism and evaluated the performance on the ns-2 platform. The simulation#R##N#   results show that pECN works better compared with TCP, DCTCP and D2TCP in#R##N#   terms of the flow completion time and the number of flows that can be#R##N#   supported without compromising deadlines.
['Tao Huang', 'Jiao Zhang', 'Yunjie Liu']
A mechanism achieving low latency for wireless datacenter applications