Question: In a non-3GPP access Interworking System, what is the primary reason for measuring tunnel establishment performance between a non-3GPP UE (User Equipment) and an ePDG (Evolved Packet Data Gateway)?
Option 1: To optimize QoS (Quality of Service) profile requests for voice services.
Option 2: Exclusively for policy enforcement in AAA (Authentication, Authorization, and Accounting) servers.
Option 3: To proactively identify potential massive rejections that could impact user experience before data transmission begins.
Option 4: Solely to monitor the geographical location of non-3GPP UEs.
Explanation: Measuring tunnel establishment performance is crucial for operators to anticipate and mitigate large-scale issues (massive rejections) that could degrade user experience. This proactive approach helps in ensuring seamless data transmission by addressing potential problems before they occur, making Option 3 the most appropriate answer.