S-PFC: Enabling Semi-Lossless RDMA Network with Selective Response to PFC

RoCEv2 (RDMA over Converged Ethernet version 2) is typically used in a PFC-enabled lossless network for high performance, but PFC can cause side effects, such as head-of-line (HoL) blocking and congestion spreading. Optimizing packet loss recovery mechanisms in lossy networks can enhance RDMA network performance, but packet loss can increase FCT of short flows and waste network resources. This paper proposes a novel concept of semi-lossless networks to exploit the advantages of lossless and lossy networks, and reduce their negative effects. Our proposed solution, Selective PFC (S-PFC), implements semi-lossless networks in two dimensions. First, S-PFC ensures no packet loss for short flows while timely dropping long flows. Second, S-PFC guarantees no packet loss at the network edge to prevent premature packet loss and unnecessary resource waste. Typical data center network scenarios and large-scale simulations show that S-PFC can accommodate different traffic demands effectively.