6.16 Service-level Interworking: CPM capable UE tearing down a Chat session between a CPM user and an SMS user

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

6.16.1 IP-SM-GW in the originating network

Figure 6.16.1: Chat session teardown request to SMS (IP-SM-GW in originating network)

1) The CPM UE sends a SIP BYE for an ongoing session to the S-CSCF.

2) 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.

3) The IP-SM-GW forwards the Short Message towards the SMS-SC (SC Address) via the SMS-IWMSC (as described in TS 23.040 [2]). 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.

NOTE 1: The MSISDN used as the sender of the Short Message is either the MSISDN of the CPM user or one that was assigned by the IP-SM-GW at session establishment, depending on operator configuration.

4) The SMS-IWMSC forwards the Short Message (SMS- SUBMIT) to the SMS-SC (see TS 23.040 [2]).

NOTE 2: Steps 3 to 4 are only executed if the operator policy requires that the SMS user be told the session is being torn down. Otherwise, the process continues with step 5.

5) The IP-SM-GW acknowledges the session teardown request and tears down the associated resources.

6) The session teardown acknowledgement is forwarded by the S-CSCF to the CPM UE.

6.16.2 IP-SM-GW in the terminating network

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.

Figure 6.16.2: Chat session teardown request to SMS (IP-SM-GW in terminating network)

1) The CPM user’s originating network sends a session teardown request for an ongoing chat session to the terminating S-CSCF.

2) 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.

3) The IP-SM-GW obtains the routeing information for the destination UE from the HLR/HSS.

4) 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.

NOTE: Steps 3 to 5 are only executed if the operator policy requires that the SMS user be told the session is being torn down. Otherwise, the process continues with step 6.

5) The MSC/SGSN/MME/SMSF sends the Short Message to the SMS user.

6) The IP-SM-GW acknowledges the session teardown request and tears down the associated resources.

7) The session teardown acknowledgement is forwarded by S-CSCF towards the CPM user’s originating network.