On the impact of packet spraying in data center networks
On the impact of packet spraying in data center networks
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DOI：
10.1109/infcom.2013.6567015
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发表时间：
2013-04
期刊：
影响因子：
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通讯作者：
A. Dixit;P. Prakash;Y. C. Hu;R. Kompella
中科院分区：
文献类型：
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作者：
A. Dixit;P. Prakash;Y. C. Hu;R. Kompella
现代数据中心网络通常以多根树形拓扑结构组织。它们通常依靠等成本多路径将流量拆分到多个路径上，这可能会导致严重的负载不平衡。拆分各个流可以提供更好的负载平衡，但不是首选，因为传统观点认为可能会与 TCP 拥塞控制产生负面相互作用，因此潜在的数据包重新排序。在本文中，我们在具有规则拓扑（例如多根树）的数据中心网络的背景下重新审视这个“神话”。我们认为，由于对称性，两个主机之间的多个等价路径由表现出相似排队属性的链路组成。因此，TCP 能够容忍引起的数据包重新排序并维持 RTT 的单一估计。我们使用包含真实硬件交换机的数据中心测试台验证随机数据包喷射 (RPS) 的功效。我们还揭示了当对称性受到干扰时（例如，在链路故障期间）对 RPS 性能的不利影响，并提出了减轻这种影响的解决方案。
Modern data center networks are commonly organized in multi-rooted tree topologies. They typically rely on equal-cost multipath to split flows across multiple paths, which can lead to significant load imbalance. Splitting individual flows can provide better load balance, but is not preferred because of potential packet reordering that conventional wisdom suggests may negatively interact with TCP congestion control. In this paper, we revisit this “myth” in the context of data center networks which have regular topologies such as multi-rooted trees. We argue that due to symmetry, the multiple equal-cost paths between two hosts are composed of links that exhibit similar queuing properties. As a result, TCP is able to tolerate the induced packet reordering and maintain a single estimate of RTT. We validate the efficacy of random packet spraying (RPS) using a data center testbed comprising real hardware switches. We also reveal the adverse impact on the performance of RPS when the symmetry is disturbed (e.g., during link failures) and suggest solutions to mitigate this effect.