6.2 De-registration procedure

23.2043GPPRelease 16Stage 2Support of Short Message Service (SMS) over generic 3GPP Internet Protocol (IP) accessTS

6.2.1 UE initiated

Figure 6.2: UE initiated de-registration procedure

1) At any time after the registration procedure, the UE may initiate a de-registration procedure. The UE sends a De-Register request (Register request with Expires header having value 0) to the S-CSCF.

2) S-CSCF responds to the UE with OK.

3) S-CSCF checks the initial filter criteria retrieved from the HSS during the IMS registration procedure.

4) Based on initial filter criteria the S-CSCF informs the IP-SM-GW (AS) about the de-registration of the user.

5) The IP-SM-GW (AS) returns OK to the S-CSCF.

6) The IP-SM-GW (AS) de-registers the UE at the HSS sending a De-register Req.

7) The HSS de-registers the UE and responds to the IP-SM-GW (AS) with De-register Res.

NOTE: The pre-configured IP‑SM‑GW address in the HSS, if any, is not removed, as it is used for subsequent SM termination.

6.2.2 Network initiated

Figure 6.2a: Network initiated de-registration procedure

1) After receiving a trigger (e.g. De-Register message from the S‑CSCF), the IP‑SM‑GW shall de-register the IP‑SM‑GW of a subscriber from the HSS sending a De-Register Req.

2) The HSS de-registers the UE and responds to the IP‑SM‑GW (AS) with De‑register Res.