Question: In which scenario should the Integrity protection maximum data rate IE be included in the message for a PDN connection established when in S1 mode?
Option 1: When the UE is operating in dual-registration mode and has previously successfully performed the UE-requested PDU session modification.
Option 2: After an inter-system change from S1 mode to N1 mode, if the UE is a UE operating in single-registration mode in a network supporting N26 interface, and the UE has not previously successfully performed the UE-requested PDU session modification.
Option 3: When the UE is operating in single-registration mode but the network does not support the N26 interface.
Option 4: When the UE has already successfully performed the UE-requested PDU session modification to provide this capability.
Explanation: The Integrity protection maximum data rate IE should be included in the message for a PDN connection established when in S1 mode, after an inter-system change from S1 mode to N1 mode, if the UE is operating in single-registration mode and has not previously successfully performed the UE-requested PDU session modification. This ensures that the UE's capability to provide integrity protection maximum data rate is properly signaled to the network.