Question: In a Public Land Mobile Network (PLMN), which of the following accurately describes the Short Message Service (SMS) for Mobile-Originated (MO)/Mobile-Terminated (MT) messages?
Option 1: It is a connection-oriented service, utilizing ISDN transfer attributes for message transmission.
Option 2: It provides transmission of short messages from User Equipment (UE) to an SMS Service Centre (SMS-SC), with the SMS-SC being functionally separated from the PLMN and acknowledging receipt.
Option 3: Connections from the fixed network directly to the UE are supported for SMS, as specified within the 3GPP scope.
Option 4: SMS MO/MT teleservice is exclusively provided via the Packet Switched (PS) domain, without support in the Circuit Switched (CS) domain.
Explanation: This option correctly describes the SMS MO/MT service. It highlights the functional separation of the SMS-SC from the PLMN and the acknowledgement process, key aspects of how SMS operates within a telecom network. The other options are incorrect because SMS is not connection-oriented (contrary to Option 1), direct fixed network connections to the UE for SMS are out of 3GPP's scope (contrary to Option 3), and SMS can be provided via both CS and PS domains (contrary to Option 4).