Digging into a RB1100AHx4 I see tx-pause packets on switch-cpu interface using “interface ethernet switch port print stats”. So the internal switches do flow-control to the cpu. I see this with 200MBit traffic and <4% load. I guess the buffers of the internal switches are small so it might start pushing back packets on small bursts and start dropping very soon.
This router does not show problems. So it might be negligable but may give some slowdowns customer notices?
May be MT could share some insights on the packet flow and possible optimizations.