 conveyed between the mobile and the MSC server entity, and is supported by the following messages: - non-access stratum (NAS) message between the mobile and the MME entity; - SGsAP message between the MME and MSC server entities. Short Message Service SGs interface is the reference point between the MME and MSC server entities for signaling. This interface supports SGsAP signaling. For an incoming SMS message, the MSC server entity generates a paging to the MME entity. If the mobile is in standby state on the 4G network, the MME entity triggers the paging procedure for establishing the signaling bearer on LTE-Uu and S1-MME interfaces, allowing the transport of NAS messages. 10.2.2. Procedures 10.2.2.1. Originating side The transfer procedure for outgoing SMS messages is given in Figure 10.4. Server IWMSC SMS / SMS-SUBMIT / RP-DATA / CP-DATA NAS UPLINK NAS TRANSPORT SMS / SMS-SUBMIT/RP-DATA / CP-DATA SGsAP UPLINK UNITDATA CP-ACK SGsAP DOWNLINK UNITDATA CP-ACK NAS DOWNLINK NAS TRANSPORT SMS / SMS-SUBMIT / RP-DATA MAP FORWARD SHORT MESSAGE SMS / SMS-SUBMIT SMS-SUBMIT-REPORT SMS-SUBMIT-REPORT / RP-ACK MAP FORWARD SHORT MESSAGE ACK SMS-SUBMIT-REPORT / RP-ACK / CP-DATA SGsAP DOWNLINK UNITDATA SMS-SUBMIT-REPORT / RP-ACK / CP-DATA NAS DOWNLINK NAS TRANSPORT CP-ACK NAS UPLINK NAS TRANSPORT CP-ACK SGsAP UPLINK UNITDATA SGsAP RELEASE REQUEST Figure 10.4. Procedure at originating side for SMS over SGsAP 278 VoLTE and ViLTE 1) The message SMS/SMS-SUBMIT/RP-DATA/CP-DATA is carried by the message NAS UPLINK NAS TRANSPORT between the mobile and the MME entity. 2) The message SMS/SMS-SUBMIT/RP-DATA/CP-DATA is conveyed by the message SGsAP UPLINK UNITDAT between the MME and MSC Server entities. The CP-ACK message is transmitted by the MSC server entity to acknowledge the receipt of the message SMS/SMS-SUBMIT/RP- DATA/CP-DATA. 3) The CP-ACK message is conveyed by the message SGsAP DOWNLINK UNITDATA between the MSC Server and MME entities. 4) The CP-ACK message is conveyed by the message NAS DOWNLINK NAS TRANSPORT between the MME e