Overview This document provides a deep-dive analysis of ECN (Explicit Congestion Notification) and CNP (Congestion Notification Packet) in RoCEv2 networks, based on real packet captures from an 8-node RDMA AI cluster. What You'll Learn: How ECN marks packets during congestion How CNP packets trigger rate reduction How DCQCN algorithm maintains lossless operation Real packet analysis with Wireshark Why This Matters Modern AI/ML training requires lossless networking for GPU-

Understanding Lossless Ethernet: Why PFC and ECN Matter for AI Training.