Question: What triggers the increment of the 'Number of additional QoS flows attempted to setup via untrusted non-3GPP access' measurement in a 5GS network?
Option 1: Receipt by the N3IWF of a PDU SESSION RESOURCE SETUP REQUEST message or a PDU SESSION RESOURCE MODIFY REQUEST message.
Option 2: Successful establishment of a QoS flow over trusted 3GPP access.
Option 3: Expiration of a timer related to QoS flow setup attempts.
Option 4: Change in the network slice identifier (S-NSSAI) without a new setup request.
Explanation: This is correct because the measurement is incremented upon the N3IWF receiving specific messages related to setting up or modifying PDU session resources, directly pertaining to attempting to set up additional QoS flows via untrusted non-3GPP access.