S-CSCF forwards the session teardown request to the IP-SM-GW. The IP-SM-GW performs service-level interworking by converting the session teardown request to a Short Message (SMS-SUBMIT) carrying the SC Address and including operator provided teardown text. The IP-SM-GW uses the SC Address in the subscriber data retrieved from the HSS at registration or provisioned by configuration.
The IP-SM-GW forwards the Short Message towards the SMS-SC (SC Address) via the SMS-IWMSC (as described in TS 23.040). The text in the Short Message is defined by the operator and should convey information to the SMS user that the chat session is ending.
The SMS user (SMS user B) in this flow is a CPM user (CPM user B) who has set his preferences in his home network to receive his incoming chat sessions as Short Messages.
The terminating S-CSCF forwards the session teardown request to the IP-SM-GW serving the SMS user. The IP-SM-GW performs service-level interworking by converting the session teardown request to a Short Message including operator provided teardown text.
The IP-SM-GW sends the Forward Short Message to the target MSC/SGSN/MME/SMSF. The IP-SM-GW inserts the MSISDN it had previously assigned to represent this chat session as the sender of the message.