LAPS: Joint Load Balancing and Congestion Control on Unequal-cost Multi-path Data Center Networks

The assumption of equal-cost paths no longer holds for newer data center network topologies catering for HPC/AI workloads, challenging both load balancing and congestion control. The existing load-balancing schemes, including random packet spraying, fail to adapt to such networks. In this paper, we propose LAPS, a simple latency-aware packet spraying scheme, to achieve joint load balancing and congestion control regardless of network topology and traffic pattern. As a coherent load-balancing and congestion-control solution, LAPS manages the packet sending rate and distribution simultaneously based on real-time path latency. It adapts to both TCP and RoCE-based transport protocols and can be deployed on Smart-NICs at a low implementation cost. Evaluations show that LAPS consistently outperforms the other load-balancing and congestion-control schemes in unequal-cost multi-path topologies for HPC/AI workloads.