This read-only counter tracks the number of ingress cells received with a non-zero value in the Generic Flow Control field of the ATM cell header, which is normally expected to be zero on UNI interfaces. An administrator watches this counter to detect a misbehaving or misconfigured attached device sending malformed cell headers. A nonzero and growing count on a port that should carry standard UNI traffic points to a header-formatting problem at the customer end.