This read-only counter, in cells, tracks the number of valid RM cells in the ingress direction of this channel discarded at the class-of-service queue due to overflow. An admin cares because losing RM cells to congestion undermines the ABR closed-loop feedback mechanism itself, potentially causing the rate-control algorithm to react incorrectly or too slowly to actual congestion. For example, if an ABR connection behaves erratically during congestion, the admin checking this discard counter might find RM cells themselves are being dropped, which would explain unreliable rate adaptation.