56.6.23.4 IEEE 802.1Qci: Receive (Ingress) Traffic Policing

The TSN standards enable provisioning the resources in a network in such a way that high priority traffic is guaranteed to get through as long as it does not exceed its frame length and flow rate allocation.

802.1Qci is a policing mechanism that discards frames on ingress (i.e. received frames) if they exceed their allocated frame length or flow rate. The receive queue flush and screener type 2 maximum rate registers are provided for this purpose.

The receive queue flush registers starting at offset 0x0b00 allow frames to be discarded on a per-queue basis when the following events occur:

• All traffic received to a particular queue
• When a receive queue’s buffer descriptor is read with the used bit set
• When a queue’s dedicated memory utilization reaches a programmable depth (specified in 128-byte chunks)
• When a frame is received above a programmable length (specified in bytes)

The screener type 2 maximum rate registers starting at 0x0b40 allow frames to be discarded that exceed a certain flow rate.