CAPS：微调 CCA 定时
CAPS: Fine-Tuning CCA Timing
AI总结：
研究数据中心拥塞控制，提出 CAPS 轻量级分布式调度层，通过将发送方传输与 ACK 时钟瓶颈时隙锁相及每流校正补偿异构 RTT，刻画多种拓扑稳态并验证，能降低队列占用率且不损失吞吐量。
AI中文摘要：
数据中心拥塞控制旨在实现高吞吐量、公平带宽分配和低延迟。现代传输将速率计算和数据包调度耦合到单个反馈回路中，虽能收敛到接近最优的速率，但会留下随流数量增长的队列。我们认为将两者分离会带来更简单的设计点。在给定稳定可行速率的情况下，剩余队列问题可简化为定时问题。时钟 ACK 节奏同步（CAPS）是一个轻量级分布式调度层，通过将每个发送方的传输与 ACK 时钟瓶颈时隙锁相，并进行每流校正以补偿异构 RTT 来实现这一点。我们刻画了在相等 RTT、异构 RTT 和双向流量下哑铃拓扑的锁相稳态，并在胖树网络的内播、置换和全对全流量场景下验证了该机制。CAPS 在所有测试场景中，将最坏情况下的队列占用率降低了 5 到 10 倍，且无吞吐量损失。
英文摘要：
Data-center congestion control targets high throughput, fair bandwidth allocation, and low latency. Modern transports couple rate computation and packet scheduling into a single feedback loop, converging to near-optimal rates but leaving standing queues that can scale with the number of flows. We argue that separating the two reveals a simpler design point. Given stable feasible rates, the residual queue problem reduces to a timing problem: if every flow's packets arrive at the bottleneck in the correct slot, the link stays busy and the queue stays empty. Clocked ACK-Paced Synchronization CAPS is a lightweight distributed scheduling layer that achieves this by phase-locking each sender's transmissions to ACK-clocked bottleneck slots, with a per-flow correction that compensates for heterogeneous RTTs. We characterize the phase-locked steady state for dumbbell topologies under equal RTT, heterogeneous RTT, and bidirectional traffic, and validate the mechanism on a fat-tree under incast, permutation, and all-to-all traffic. CAPS reduces worst-case queue occupancy by 5-10x across all tested scenarios without throughput loss.
