The sustainable growth of bandwidth has been an inevitable tendency in current Data Center Networks (DCN). However, the dramatic expansion of link capacity offers a remarkable challenge to the transport layer protocols of DCN, i.e., how to converge fast and enable data flow to utilize the high bandwidth effectively. Meanwhile, the new protocol should be compatible to the traditional TCP because the applications with old TCP versions are still widely deployed. Therefore, it is important to achieve a trade-off between the aggressiveness and TCP-friendliness in protocol design. In this article, we first empirically investigate why the existing typical data center TCP variants naturally fail to guarantee both fast convergence and TCP friendliness. Then, we design a new transport protocol for DCN, namely Fast and Friendly Converging (FFC), which makes independent decisions and self-adjustment through retrieving the two-dimensional congestion notification from both RTT and ECN. We further present a mathematic model to analyze its competing behavior and converging process. The results from simulation experiments and real implementation show that FFC can achieve fast convergence, thus benefiting the flow completion time. Moreover, when coexisting with the traditional TCP, FFC also presents a moderate behavior, while introducing trivial deployment overhead only at the end-hosts.

中文翻译：

---

重新考虑数据中心网络中的快速友好的传输

带宽的可持续增长已成为当前数据中心网络（DCN）的必然趋势。但是，链路容量的急剧扩展给DCN的传输层协议带来了巨大挑战，即如何快速收敛并使数据流有效地利用高带宽。同时，新协议应与传统TCP兼容，因为具有旧TCP版本的应用程序仍被广泛部署。因此，重要的是要在协议设计的积极性和TCP友好性之间进行权衡。在本文中，我们首先根据经验研究为什么现有的典型数据中心TCP变体自然无法同时保证快速收敛和TCP友好性。然后，我们为DCN设计一种新的传输协议，即快速友好融合（FFC），通过从RTT和ECN检索二维拥塞通知，可以做出独立的决策和自我调整。我们进一步提出了一个数学模型来分析其竞争行为和收敛过程。仿真实验和实际实现的结果表明，FFC可以实现快速收敛，从而缩短了流程完成时间。此外，当与传统TCP共存时，FFC还表现出适度的行为，同时仅在终端主机处引入了琐碎的部署开销。仿真实验和实际实现的结果表明，FFC可以实现快速收敛，从而缩短了流程完成时间。此外，当与传统TCP共存时，FFC还表现出适度的行为，同时仅在终端主机处引入了琐碎的部署开销。仿真实验和实际实现的结果表明，FFC可以实现快速收敛，从而缩短了流程完成时间。此外，当与传统TCP共存时，FFC还表现出适度的行为，同时仅在终端主机处引入了琐碎的部署开销。