forward indicator bit (SS7) (FIB)

Structure of the Message Signalling Unit (MSU)

Forward Indicator Bit (FIB) is a data field in the Message Transfer Part ( MTP) of the Message Signal Unit( MSU). The FIB data field has only one bit and, like the Backward Indicator Bit( BIB), is used to confirm correctly or incorrectly received character units. Unlike the BIB indicator, which acknowledges in the backward direction, the Forward Indicator Bit operates in the forward direction. If there is no fault, both indicator bits have identical states.