An NAS message 550 can be transmitted between the NAS layers 515, 520 over a selected one of the NAS links. In some embodiments, one of the NAS links is selected by the transmitting node (either the user equipment 505 or the AMF 510) based on selection criteria such as latencies, congestion, usage costs, priorities, and the like. The NAS message 550 includes an NAS header 555, an NAS payload 560, and integrity check information 565 that is formed using an integrity key. In the illustrated embodiment, the NAS payload 560 includes an SMS payload 570, which includes an encrypted SMS message. For example, the SMS payload 570 can be formed by encrypting an SMS message using the encryption key for the NAS link that is used to convey the NAS message 550. The NAS header 555 includes information identifying the NAS link that is used to convey the NAS message 550. The receiving node can then use this information to access the context information for the NAS link used to convey the NAS message 550, e.g., the receiving node can access the correct encryption key and integrity key that are used to perform the integrity check of the NAS message 550 and decryption of the SMS payload 570.