This attribute counts the number of times the mobile Radio Link
Protocol (RLP) entity is busy (that is, it is in Asynchronous
Balanced Mode (ABM) and is not ready to receive Information
frames). The RLP entity is considered to be not ready to receive
information frames if the mobile sends a flow control indication
RNR (Receive Not Ready). A Receive Ready is sent to the RLP
entity when the mobile is ready to receive data. The counter wraps
when it exceeds the maximum value.