PFC Headroom Testing in SONiC with Snappi
Background In data center networks, Priority Flow Control (PFC) is a mechanism defined in IEEE 802.1Qbb that allows a receiver to pause traffic on a per-priority basis, enabling lossless transport for high-priority traffic such as RDMA over Converged Ethernet (RoCE). When a switch’s ingress buffer starts filling up, it sends a PFC PAUSE frame to the upstream sender. However, there is always some in-flight traffic between the time the PAUSE is sent and when the sender actually stops — this in-flight data must be absorbed by the headroom buffer. ...