Question: What is the primary purpose of the SWd reference point in the Evolved Packet System (EPS) between the 3GPP AAA Proxy and the 3GPP AAA Server?
Option 1: To manage Quality of Service (QoS) mechanisms exclusively for roaming users.
Option 2: To establish and manage voice over LTE (VoLTE) sessions.
Option 3: To transport authentication, authorization, and related information in AAA messages, including keying data for radio interface integrity protection and encryption.
Option 4: To handle billing and charging for data services only.
Explanation: The SWd reference point's primary functionality encompasses tasks including carrying authentication, authorization, keying data for radio interface integrity protection and encryption, among others, ensuring the integrity and confidentiality of user and network data in EPS between the 3GPP AAA Proxy and Server.