RoCE Rocks without PFC: Detailed Evaluation
KBNets@SIGCOMM(2017)
摘要
In recent years, the usage of RDMA in data center networks has increased significantly, with RDMA over Converged Ethernet (RoCE) emerging as the canonical approach for deploying RDMA in Ethernet-based data centers. Initial implementations of RoCE required a lossless fabric for optimal performance. This is typically achieved by enabling Priority Flow Control (PFC) on Ethernet NICs and switches. The RoCEv2 specification introduced RoCE congestion control, which allows throttling the transmission rate in response to congestion. Consequently, packet loss is minimized and performance is maintained, even if the underlying Ethernet network is lossy. In this paper, we discuss the latest developments in RoCE congestion control. Hardware congestion control reduces the latency of the congestion control loop; it reacts promptly in the face of congestion by throttling the transmission rate quickly and accurately. The short control loop also prevents network buffers from overfilling under various congestion scenarios. In addition, fast hardware retransmission complements congestion control in severe congestion scenarios, by significantly reducing the performance penalty of packet drops. We survey architectural features that allow deployment of RoCE over lossy networks and present real lab test results.
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关键词
RoCE,Congestion Control,Performance
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