BGP-Based Congestion Signaling for Leaf-Spine Data Center Fabrics

This article proposes BGP-CN, a congestion notification mechanism that uses BGP extended communities to distribute congestion information across leaf-spine data center fabrics. Rather than relying solely on local mechanisms such as ECN, PFC, and DCQCN, BGP-CN provides fabric-wide visibility, allowing switches to proactively adjust ECMP weights before congestion spreads. Prototype testing on a SONiC/FRR environment showed a 47% reduction in P99 tail latency and a 63% improvement in path utilization balance.