PFC Vs ECN

PFC (Priority Flow Control) and ECN (Explicit Congestion Notification) works together to ensure a lossless for GPU and AI workload

ECN (Explicit Congestion Notification) is the first line of defense. When a switch detects early sign of congestion, it marks the packet without dropping them. This allow the receiver to receive ECN marked packet, and then it will ask the sender to slow down by sending CNP (Congest Notification Packet) or using ECE, CWR flag in TCP (Transmission Control Protocol) header

PFC (Priority Flow Control) happens at the switch level to detect if the switch is congested.