Question: In E-UTRAN, what triggers both Authentication and Key Setting, which can be initiated by the network at the operator's discretion?
Option 1: Successful Completion of NAS Security Mode Setup
Option 2: The Authentication Procedure
Option 3: Change of UE's Location Area
Option 4: Establishment of RRC Connection
Explanation: According to E-UTRAN security architecture, the authentication procedure triggers both authentication and key setting. This process can be initiated by the network as frequently as desired by the network operator, highlighting flexible security management in telecom networks.