This counts complete control-plane messages, as opposed to data cells, this card has received over the internal chassis cell bus. Because this tracks control-plane rather than data-plane traffic, a stall in this counter while data traffic, like cardInCells, keeps flowing normally would point an admin toward a control-channel-specific problem, such as a management or signaling issue between this card and the control processor, rather than a data-forwarding fault. For example, cardControlMessagesFromBus flatlining while the card keeps forwarding data traffic normally suggests a control-plane communication problem with the chassis control processor rather than a data-path fault.