Achieving Low Latency for Multipath Transmission in RDMA Based Data Center Network

Remote Direct Memory Access (RDMA) achieves ultra-low latency, high throughput and low CPU overhead in data center by implementing the transport logic in hardware network interface card (NIC). However, RDMA faces new challenges in the heterogeneous multipath environment as it is very sensitive to packet reordering. When some packets are blocked in slow paths, the other packets delivered through fast paths have to be buffered at the receiver's NIC, consuming the limited on-chip memory resources. In this paper, we propose a new RDMA-based multipath transmission scheme with advanced fast retransmission called as AFR-MPRDMA. Specifically, once detecting congestion at the slow path, the sender will retransmit the blocked packets on other fast paths to speed up the transmission of blocked packets. Moreover, the receiver dynamically adjusts the buffer size for the out-of-order packets to avoid either unnecessary retransmission or long latency. The results of large-scale tests show that AFR-MPRDMA effectively mitigates packets blocking issue and reduces average flow completion time (AFCT) by up to 61% compared with the state-of-the-art RDMA-based schemes.