Question: What triggers the measurement of 'Attempted GPRS attach procedures with IMSI already attached' in a Core Network (CN) Packet Switched (PS) domain?
Option 1: Receipt of 'DETACH REQUEST' Message from the User Equipment (UE)
Option 2: Successful Authentication of the International Mobile Subscriber Identity (IMSI)
Option 3: Receipt of 'ATTACH REQUEST' Message with 'Attach type' indicating 'GPRS attach while IMSI attached' from the Mobile Station (MS)
Option 4: Location Update Request from a UE already attached to the network
Explanation: The correct answer is Option 3 because the measurement is triggered by the receipt of an 'ATTACH REQUEST' Message with a specific 'Attach type' indicating 'GPRS attach while IMSI attached' from the Mobile Station (MS). This scenario matches the condition for measuring attempted GPRS attach procedures when the IMSI is already attached, highlighting a key aspect of performance management in telecom networks related to attachment procedures and subscriber management.