Revolutionizing AI Backend Networks: Beyond Traditional ECMP Load Balancing

Traditional Flow-based ECMP load balancing struggles with the massive elephant flows generated by GPU-to-GPU communication in RoCEv2-based AI backend networks. This article introduces two alternatives: Flowlet-based Load Balancing with Adaptive Routing, which dynamically redirects traffic to less congested paths, and Packet-based Load Balancing with Packet Spraying, which distributes individual packets across multiple paths but requires RDMA Write Only for reliable operation. Cisco Nexus switches now support Dynamic Load Balancing (DLB) configuration, enabling both flowlet and per-packet load balancing.