Question: What triggers the increment of the "Number of GTP tunnels on the Gn interface" performance measurement in a UMTS network?
Option 1: Transmission by the GGSN of a CREATE PDP CONTEXT RESPONSE message with cause "Request Accepted"
Option 2: Receipt by the GGSN of a DELETE PDP CONTEXT REQUEST message from the SGSN
Option 3: Establishment of a new GSM circuit-switched call
Option 4: Handover of a UE from UMTS to GSM
Explanation: The correct answer is Option 1 because, according to the performance measurement definition, the measurement is incremented when the GGSN transmits a CREATE PDP CONTEXT RESPONSE message with cause "Request Accepted", indicating successful establishment of a new GTP tunnel, increasing the total count of simultaneous GTP tunnels on the Gn interface, relating to packet-switched traffic in UMTS networks using GTP for managing IP packets.