VSP-4000 port clocking up HCInFlowCtrlPkts

[WindyMiller]

Hi,

When graphing an up link port we are seeing HCInFlowCtrlPkts increasing can offer any advice why we are seeing this?

The port is not very busy. It’s copper port running at 1Gb.

Many thanks

[Ludovico_Steven]

It means the device connected to that port is generating Ethernet Flow Control Pause frames.

Which is probably because that device cannot cope with too much traffic, so it tells the switch it is connected to to slow down transmission. Hence the egress buffers on the VSP will allow traffic bursts to that port to be smoothed out. Of course if the egress buffers for that port congest, then the VSP will throw away packets destined for that port, but it will do so in a QoS aware manner. Which is much better than if the device was not generating Flow Control frames, and would be blinded by the bursts of traffic it cannot process anyway. So not necessarily a problem.