Question: In a UMTS/GSM network, when a 'combined RA/LA with IMSI Attach' inter-SGSN Routing Area Update procedure fails, what determines how the relevant measurement is incremented in the SGSN?
Option 1: The type of access technology (GSM or UMTS) used for the update request.
Option 2: The reject cause transmitted back to the MS via a ROUTING AREA UPDATE REJECT message, defining the reason for the failure.
Option 3: The concatenation of MCC, MNC, LAC, and RAC specifying the RA.
Option 4: The sum of all supported per-cause measurements.
Explanation: When an inter-SGSN Routing Area Update procedure with 'combined RA/LA and IMSI Attach' fails, the SGSN increments the relevant measurement based on the specific reason for the failure, known as the reject cause, communicated to the MS via a ROUTING AREA UPDATE REJECT message.