Question: What happens when a lower layer failure is detected by the network before receiving an IDENTITY RESPONSE message?
Option 1: The network shall retransmit the IDENTITY REQUEST message and reset the timer T3370.
Option 2: The network shall abort any ongoing GMM procedure.
Option 3: The network shall proceed with a GPRS attach procedure.
Option 4: The network shall progress both identification and routing area updating procedures.
Explanation: According to the text, upon detection of a lower layer failure before receiving an IDENTITY RESPONSE message, the network shall abort any ongoing GMM procedure. This is because the lower layer failure indicates a problem with the underlying communication infrastructure, making it impossible for the identification procedure to continue successfully.