Question: In UTRAN Iu interface, who allocates the tunnel identifier for the uplink direction when establishing a GTP-U tunnel upon a radio access bearer service request?
Option 1: The tunnel identifier is dynamically negotiated between the CN and UTRAN.
Option 2: The Core Network (CN) allocates the tunnel identifier for the uplink.
Option 3: The UTRAN allocates the tunnel identifiers for both downlink and uplink directions.
Option 4: The allocation of uplink tunnel identifier is not specified and can vary based on implementation.
Explanation: According to GTP-U tunnels management principles in the context of UTRAN Iu interface, the Core Network (CN) allocates the tunnel identifier for the uplink direction. This ensures each tunnel direction is uniquely identified and managed by the entity best suited for its oversight.