Question: What is the primary identifier used for paging a Mobile Station (MS) in non-GPRS services when it is IMSI attached?
Option 1: International Mobile Subscriber Identity (IMSI)
Option 2: Temporary Logical Link Identifier (TLLI)
Option 3: Packet Temporary Mobile Subscriber Identity (P-TMSI)
Option 4: Allocated Temporary Mobile Subscriber Identity (TMSI) if acknowledged by the MS, otherwise IMSI
Explanation: In non-GPRS services, when a Mobile Station is IMSI attached, the primary identifier used for paging is the allocated TMSI if it has been acknowledged by the MS. If not, then the IMSI is used. This ensures that the network can efficiently page the MS while minimizing the use of IMSI for security reasons.