23.2043GPPRelease 17Stage 2Support of Short Message Service (SMS) over generic 3GPP Internet Protocol (IP) accessTS
Figure 6.4a: Short Message termination procedure without MSISDN
1) The UE-B registers to the S-CSCF according to the IMS registration procedure.
2) The originating IMS network which received the SM from the UE-A forwards the Short Message (SMS-DELIVER) to the terminating IMS network. It reaches the IP-SM-GW responsible for UE-B. For brevity, the intermediate IMS nodes interactions prior to reaching IP-SM-GW are not shown.
3) If local policy allows MSISDN-less SMS operation, IP-SM-GW tries to deliver the SM to UE-B.
4a-4b) SM is successfully delivered to UE-B. A success Delivery report is sent to the originating IMS network.
5a) If IP-SM-GW tried to deliver the SM but encountered some error (e.g. UE is memory full, UE not reachable, etc) then:
5b) IP-SM-GW returns a MSISDN-less Correlation ID to originating IMS network along with an indication of temporary failure.
6a-6b) if the IP-SM-GW refuses the MSISDN-less SMS operation due to local policy or other permanent errors (e.g. protocol error), IP-SM-GW returns a permanent error indication to the originating IMS network.