Dell EMC Configuration Guide for the S4048T–ON System 9.14.2.4

Classification rules on ingress (Ingress FP CAM region) matches incoming packet-dot1p and assigns an internal priority (to select queue as per Table 1 and Table 2).

The internal Priority assigned for the packet by Ingress FP is used by the memory management unit (MMU) to assign the packet to right queue by indexing the internal-priority to queue map table (TABLE 1) in hardware.

PRIO2COS setting for honoring the PFC protocol packets from the Peer switches is as per above Packet-Dot1p->queue table (Table 2).

The packets come in with packet-dot1p 2 alone are assign to PG6 on ingress.

The packets come in with packet-dot1p 2 alone use Q1 (as per dot1p to Queue classification – Table 2) on the egress port.

• When Peer sends a PFC message for Priority 2, based on above PRIO2COS table (TABLE 2), Queue 1 is halted.

• Queue 1 starts buffering the packets with Dot1p 2. This causes PG6 buffer counter to increase on the ingress, since P-dot1p 2 is mapped to PG6.

• As the PG6 watermark threshold is reached, PFC generates for dot1p 2.