Question: In UTRAN's Iu-PS interface using IP Transport Option, what protocol(s) are mandated for transporting data streams, and over which lower-layer protocol do they operate?
Option 1: TCP over IP
Option 2: GTP-U over UDP over IP
Option 3: SCTP over IPv6
Option 4: RTP over TCP
Explanation: According to the telecom standard for UTRAN's Iu-PS interface, when utilizing the IP Transport Option, the protocol stack for data stream transport is explicitly defined as GTP-U (General Packet Radio Service Tunnelling Protocol - User Plane) encapsulated over UDP (User Datagram Protocol), which in turn operates over IP (Internet Protocol). This setup ensures efficient and reliable transport of user plane data. GTP-U provides tunneling for the user data, UDP offers connectionless, best-effort delivery, and IP enables routing across the network.