Question: When a UE attaches to the EPC using the S2a reference point with MIPv4, what role does the PDN GW assume in communication with the 3GPP AAA server?
Option 1: LMA (Local Mobility Anchor) using IETF RFC 5779
Option 2: HA (Home Agent) using IETF RFC 5778
Option 3: LMA (Local Mobility Anchor) using IETF RFC 5777 for QoS
Option 4: NAS (Network Access Server) using IETF RFC 4005
Explanation: According to protocol specifications, when a UE attaches to the EPC using the S2a reference point with MIPv4, the PDN GW acts as a Home Agent (HA), with communication between the PDN GW and HA utilizing IETF RFC 5778 for MIPv4 interactions.