The agent DmaQueueMonitor provides visibility into packets coming up to the CPU via CPU queues. Packets are continuously sampled on monitored queues and kept available for reporting when a CPU congestion event occurs. When a queue that leads to CPU processing is congested a PCAP file may be created from the sampled packets that were captured from before and after the congestion event.  The PCAP file is written to the file system for off-line examination.

 

In some situations, packets received by an ASIC need to be redirected to the control plane: packets that have the destination address of the router or packets that need special handling from the CPU for example. The control plane cannot handle as many packets as the ASIC. A system that protects the control plane against DOS and prioritizes packets to send to the CPU is needed.  This is accomplished by CoPP (control-plane policing). CoPP is already functioning, however, the CPU queues are statically allocated to a specific feature. If a feature is not used, the CPU queue statically allocated to the feature is not used either. This is a loss of resources.

EOS 4.32.1F CPU Queue