This counter is updated only after a frame is fully and properly received from the Ethernet link and all its data bytes are stored in memory. Because it only increments on complete, successful reception, this is the cleanest 'Ethernet Rx path is healthy' indicator -- comparing its growth rate to the CRC-error or FIFO-overrun counters shows what fraction of inbound Ethernet traffic is actually being usably received. A management workstation polling this router over Ethernet would expect this counter to increment by roughly one frame per SNMP poll cycle at minimum, so a stall here while the workstation reports timeouts points to a receive-path problem on the router rather than the workstation.