5.1.4 Successful Mobile Terminated short message transfer via IP-SM-GW

23.5403GPP5G System: Technical realization of Service Based Short Message ServiceRelease 17Stage 2TS

Figure 5.1.4-1: MT SMS over NAS via IP-SM-GW

1. MT SMS interaction between SC and SMS-GMSC follow the current procedure as defined in 3GPP TS 23.040 [2].

2a-2b. The SMS-GMSC should query the NRF to find the UDM instance(s), supporting SMS SBI interfaces, and managing that manages the user subscriptions of the GPSI. The SMS-GMSC may need to retrieve the PLMN ID of the recipients GPSI before the discovery of the UDM instance based on the GPSI-to-Subscription-Network resolution procedure defined in clause 5.1.7.

3. The SMS-GMSC invokes Nudm_UECM_SendRoutingInfoForSM (GPSI) to the UDM to get the serving node information for all access types for the UE.

4. The UDM shall check the registration/reachability flags to determine the potential target nodes, e.g. SMSF. For MT SM transfer via IP-SM-GW, the UDM shall invoke the Nipsmgw_SMService_RoutingInfo to provide the SMSF Instance Id to the IP-SM-GW. The address of the IP-SM-GW to be contacted by the UDM may be configured locally.

5. The IP-SM-GW shall send Nipsmgw_SMService_RoutingInfo response to the UDM.

6. The UDM responds to the SMS-GMSC by sending Nudm_UECM_SendRoutingInfoForSM response, including IP-SM-GW address, the indication for SMSF SMS_SBI support and the indication for IP-SM-GW SMS_SBI support.

7-8. The SMS-GMSC forwards the SMS message to the IP-SM-GW, and then IP-SM-GW performs service authorization and domain selection to determine the domain for delivery of the Short Message as defined in 3GPP TS 23.204 [15]. If the SMSF is selected, the IP-SM-GW forwards the SMS message to the SMSF. If the IP-SM-GW has more than one SMSF address to use for SMS transport towards the UE, then the IP-SM-GW chooses which SMSF address to use first based on operator local policy.

The SMS-GMSC selects protocol based on the indication for SMSF SMS_SBI support and IP-SM-GW SBI support:

If both SMSF and IP-SM-GW indicate support for SMS_SBI, SMS-GMSC forwards the SMS message to the IP-SM-GW by invoking Nipsmgw_SMService_MtForwardSm service operation. And then the IP-SM-GW forwards the SMS message to the SMSF by invoking Nsmsf_SMService_MtForwardSm service operation.

If SMSF or IP-SM-GW indicates that it does not support SMS_SBI, SMS-GMSC should forward SMS message to IP-SM-GW by legacy MAP/Diameter protocol. Then IP-SM-GW forwards the SMS message to the SMSF by legacy MAP/Diameter protocol. The following steps follow the procedures for legacy MT SMS message transfer, as illustrated in Figure 15aa of TS23.040 [2].

9. The MT SMS over NAS procedure between SMSF, AMF and UE is the same as in step 4a to 6b of Figure 4.13.3.6-1 of 3GPP TS 23.502 [4].

10. The SMSF delivers the delivery report to the IP-SM-GW by sending the Nsmsf_SMService_MtForwardSm response to the IP-SM-GW.

11. The IP-SM-GW delivers the delivery report to the SMS-GMSC by sending the Nipsmgw_SMService_MtForwardSm response to the SMS-GMSC.

12. The IP-SM-GW may report the SM-Delivery Status to the UDM by invoking Nudm_ReportSMDeliveryStatus_Request.

13. The UDM responses with Nudm_ReportSMDeliveryStatus_Request response to the IP-SM-GW.

14-15. The SMS-GMSC may report the SM-Delivery Status to the UDM by invoking Nudm_ReportSMDeliveryStatus_Request and the UDM shall ignore the information provided in this report.

16. The SMS-GMSC delivers the delivery report to the SC as defined in 3GPP TS 23.040 [2].

17. The MT SMS over NAS procedure between SMSF, AMF and UE is the same as in step 6c to 6d of Figure 4.13.3.6-1 of 3GPP TS 23.502 [4].