Symptom:
Slow FC or FCOE Performance with Nexus N6004, N5696Q, or N56128P.Selective Retransmission Request (SRR) may be logged on host or storage.

Drops on the egress on a Nexus 5600/6000, for a no-drop class of traffic. Possible in both 10G & 40 G fabric modes, higher probability with 40G fabric mode. This can be verified by seeing counter increments in show hardware internal bigsur asic <global-asic-num> reg match .*wo_cr and via RX_FRM_DROP counter increments in show platform software qd info counters bm-fabric asic <global-asic-num>

The slowness observed in the application is due to the FCoE packet drops, which triggers retransmission from the application

Conditions:
On a Nexus 5600/600, when multiple ingress ports send data to one egress port for a no drop class of traffic and the egress buffer occupancy reaches the xoff threshold, this is indicated by observing the output of show hardware internal buffer info pkt-stats asic-num <global-asic-num> and verifying it to cross the xoff value for pool1 in Egress buffer allocation with the show platform software qd info command