To improve the application-level communication performance, scheduling of coflows, a collection of parallel flows sharing the same objective, is prevalent in modern data center networks (DCNs). Meanwhile, a hybrid-switched DCN design combining optical circuit switches (OPS) and electrical packet switches (EPS) for transmitting high-volume traffic and low-volume traffic separately has received considerable research attention recently. Efficient scheduling of coflows on hybrid network links is crucial for reducing the overall communication time. However, because of the reconfiguration delay in the circuit switch due to the ultra-high transmission rate and the limitation of bandwidth in the packet switch, coflow scheduling becomes increasingly challenging. The existing coflow scheduling algorithms in hybrid-switched DCNs are all heuristic and provide no performance guarantees. In this work, we propose an approximation algorithm with the worst-case performance guarantee of 2+ \lambda?, where \lambda? is a factor related to system parameters and demand characteristics, for single coflow scheduling in hybridswitched DCN to minimize the coflow completion time (CCT). Extensive simulations based on Facebook data traces show that our algorithm outperforms the state-of-the-art schemes Solstice by 1.14? and Reco-Sin by 1.42? in terms of minimizing CCT.

翻译：为提升应用层通信性能，对具有相同目标的并行流集合——协同流进行调度在现代数据中心网络中十分普遍。同时，结合光电路交换和电分组交换分别传输高容量流量与低容量流量的混合交换数据中心网络设计近期受到广泛关注。在混合网络链路上高效调度协同流对于减少整体通信时间至关重要。然而，由于电路交换中超高传输速率导致的重新配置延迟以及分组交换带宽限制，协同流调度变得愈发具有挑战性。现有混合交换数据中心网络中的协同流调度算法均为启发式方法，不提供任何性能保证。本文针对混合交换数据中心网络中的单协同流调度问题，提出一种最坏情况性能保证为2+λ?的近似算法（其中λ?是与系统参数和需求特征相关的因子），以最小化协同流完成时间。基于Facebook数据轨迹的广泛仿真表明，在最小化协同流完成时间方面，本算法相较于现有最优方案Solstice和Reco-Sin分别提升1.14倍和1.42倍。