Question: What is the primary purpose of the optional NAS Node Selection Function (NNSF) in the UTRAN Iu interface, as it relates to a User Equipment (UE) setup process?
Option 1: To manage UE mobility between different Radio Access Networks (RANs)
Option 2: To optimize traffic routing within the Core Network (CN)
Option 3: To perform security authentication for UE access
Option 4: To initially assign Core Network resources and setup a signaling connection for a UE
Explanation: The NNSF's primary role is assigning CN resources to serve a UE and setting up a signaling connection, crucial for establishing an initial communication link between the UE and the Core Network. Options 1-3 are incorrect as they describe different network operations (mobility management, traffic optimization, and security authentication) unrelated to NNSF's primary purpose.