LEFT: LightwEight and FasT packet Reordering for RDMA
P. Huang, Xin Zhang, Zhigang Chen, Can Liu, Guo Chen
Abstract
RDMA, as a cutting-edge networking technology, has gained extensive adoption in large-scale data centers due to its exceptional characteristics, such as low and stable latency, high throughput and low CPU utilization. However, due to the limited on-chip memory of the RDMA Network Interface Cards (RNIC), commercial RDMA usually only supports single-path transmission and cannot fully utilize the rich parallel paths within the DCN, resulting in insufficient bandwidth utilization. Multipath transmission can improve bandwidth utilization, but the out-of-order (OoO) packets it brings negatively impacts the performance of RNICs. Recent works have attempted to address this issue by using bitmaps to record OoO packets to better support multipath transmission. However, these approaches either consume excessive memory for maintaining bitmaps, leading to poor connection scalability, or introduce high latency in bitmap sharing. Consequently, implementing efficient packet reordering in RDMA remains a challenge.