Mild: A Zero-Wait Multi-Round Proactive Transport

With the rapid growth of datacenter network link speed, multi-round matching based proactive solutions (e.g., dcPIM) has become increasingly attractive. Such solutions enable receivers to obtain as much global information as possible through multi-round matching, thereby facilitating them to make near-optimal decisions on bandwidth allocation. However, the matching phase before transmitting data introduces significant latency overhead. In this paper, we present Mild, a zero-wait solution that runs a second sender-driven control loop in parallel, leveraging in-network telemetry (INT) to detect and fill the spare bandwidth during the matching phase. Furthermore, we introduce a selective dropping mechanism to ensure that the packets from the second loop do not impact the data transmission of the primary loop. Additionally, we use the well-protected primary loop to perform loss recovery for the dropped packets efficiently. We integrate Mild into a representative proposal dcPIM and evaluate its performance through 100Gbps large-scale simulations. Compared to the state-of-the-art solution, Mild reduces the tail flow completion time (FCT) of short flows by up to 55% while achieving up to 57%/45% lower average FCT of medium/large flows.