This attribute counts cells received from the interface that were
dropped because they contained invalid VPI or VCI values, or
dropped because they had no associated connection for the VPI or
VCI. On ATM IP FPs this count is included in the rxCell count for
the interface. Note that this attribute does not keep an exact count.
Idle cells and unassigned cells are ignored without being counted as
dropped cells. The counter is reset to zero when the component is
created, or when any critical attribute of the component is changed.
The counter wraps to zero when it exceeds its maximum value of
(2**64)-1.
The VPI and VCI of the last dropped cell are indicated in the
attribute lastDroppedRxCellConnection.