3.1.5 Timer Events
InactivityTimer: When the timer expires, the following processing steps are performed:
If ADM_MessageReceivedSinceLastTimerTick is TRUE,
Set ADM_KeepaliveGraceCount to ADM_KeepaliveGraceCountInitialValue.
Set ADM_MessageReceivedSinceLastTimerTick to FALSE.
If ADM_MessageReceivedSinceLastTimerTick is FALSE,
Decrement ADM_KeepaliveGraceCount by 1.
If ADM_KeepaliveGraceCount becomes lesser than 0, notify the lower layer to abort the session.