Question: What transport protocols and ports must a TURN server, as specified in 3GPP security standards for IP-based services, support for communication with an IMS (IP Multimedia Subsystem) client?
Option 1: UDP on standard port 53 and TCP on standard port 443
Option 2: TLS/UDP on non-standard port 80 and TCP on non-standard port 22
Option 3: TLS/TCP on non-standard port 443 and (optionally) TCP on non-standard port 80
Option 4: DTLS/UDP on standard port 1194 and HTTP on standard port 8080
Explanation: This question requires understanding of the specific security protocols and ports mandated for TURN servers in the context of IP-based services, as outlined in 3GPP security standards. The correct answer, Option 3, accurately reflects the required functionality: supporting TLS (Transport Layer Security) over TCP (Transmission Control Protocol) on a non-standard port 443, with the additional optional support for plain TCP on a non-standard port 80, ensuring secure and flexible communication with IMS clients. This highlights the importance of tailored security measures in telecom networks to protect IP-based services.