Fine-Grained Flow Control Backpressure Mechanism for Wide Area Networks

This document specifies a fine-grained flow control backpressure mechanism for Wide Area Networks (WANs). Leveraging data-plane congestion detection and notification, it enables millisecond-level congestion response. The mechanism enhances Layer 2 PFC by extending network protocols (e.g., ICMPv6) for congestion backpressure messaging in WANs, and leverages network slicing isolation to provide fine-grained flow control at tenant or task granularity. It addresses the limitations of traditional flow control mechanisms in WAN environments through fast and precise backpressure, and supports multi-hop propagation of congestion notifications along the forwarding path.