Use cases and Requirement for Flow Control Collaboration Across DCNs and WAN

The demand for lossless network transmission and the application of flow control mechanisms have expanded from DCNs (Data Center Networks) to WANs(Wide Area Networks). To mitigate PFC - related issues in WANs, the fine - grained flow control is proposed. This mechanism aims to achieve precise control at flow / tenant levels, limits flow control to specified paths and slices, and provides intelligent congestion backpressure. As current DCN already adopts PFC mechanisms, the fine-grained flow control in WANs needs to work with PFC in DCNs to achieve end-to-end flow control. This document describes the use cases and requirements for the collaboration of flow control mechanisms across DCNs and WANs.