Question: In the context of IP-based services in IMS (IP Multimedia Subsystem), how is the TURN (Traversal Using Relays around NAT) credential securely transferred to a WebRTC Interworking Controller (WIC) for authentication?
Option 1: Via insecure HTTP request with credentials in plain text
Option 2: Through secure signaling messages (e.g., secure Websocket) between WIC and eP-CSCF (Emergency Call Session Control Function)
Option 3: By pre-configuring the credential on both WIC and TURN server
Option 4: Using a public key infrastructure (PKI) for certificate exchange
Explanation: This is correct because, according to the described security mechanism for IP-based services in IMS, signaling messages between WIC and eP-CSCF are protected by secure protocols like secure Websocket, ensuring the secure transfer of TURN credentials.