Content for TS 23.204 Word version: 19.0.0
6.5 Transport-level interworking: Delivery Report procedure
6.5a Unsuccessful SM termination procedure
6.5b Alert Service Centre procedure when UE is available
...
...
6.5 Transport-level interworking: Delivery Report procedure p. 24
Step 1.
The UE has received the Short Message as described in clause 6.4 or clause 6.4a.
Step 2.
The UE sends a Delivery report (SMS-DELIVER-REPORT) to the S-CSCF, including either a positive or a negative acknowledgement to the Short Message received in step 1.
Step 3.
The S-CSCF forwards the Delivery report to the IP-SM-GW (AS). It shall be ensured that the Delivery report reaches the same IP-SM-GW that forwarded the Short Message in step 1.
Step 4.
IP-SM-GW (AS) acknowledges, at the SIP level, the Delivery report to S-CSCF.
Step 5.
S-CSCF forwards the SIP acknowledgement to the Delivery report to the UE.
Step 6.
The IP-SM-GW (AS) sends a Delivery report to the SMS-GMSC or to originating IMS network for MSISDN-less SMS operation.
Step 7.
The IP-SM-GW may send a Report SM Delivery Status to the HSS. This may trigger the Alert service centre procedure or an update of the message waiting data in the HSS as described in TS 23.040, if necessary.
Step 8.
The SMS-GMSC may send a Report SM Delivery Status to the HSS. The HSS shall ignore the information provided in this report.
6.5a Unsuccessful SM termination procedure p. 24
When a Short Message fails to reach the UE via the selected domain, a failure delivery report is returned to the IP-SM-GW. The IP-SM-GW takes responsibility to re-attempt the delivery of the message in another domain which is listed in the sequence of the priority in the IP-SM-GW while the domain selection is performed during the SM termination procedure. If the message successfully reaches the UE after re-delivery, the IP-SM-GW forwards the received successful Delivery report to the SMS-GMSC. Otherwise, if the message still fails after the IP-SM-GW has tried all selectable domains, the IP-SM-GW forwards the received unsuccessful Delivery report to the SMS-GMSC and sends Report SM Delivery Status message to the HLR/HSS. The HLR/HSS then records the corresponding Messages Waiting Data (MWD), and an Alert service centre procedure may be initiated as described in clause 6.5b or 6.6. The IP-SM-GW sets UE-Not-Reachable-for-IP (UNRI) locally as defined in TS 23.040.
The order in which domains are selected for message delivery by the IP-SM-GW is subject to operator policy and/or user preferences and any known or assumed timer values in the SMS-GMSC for the Forward Short Message message (see NOTE 1).
The following flow shows only an example order of selected domains, i.e. the IMS is the preferred domain, followed by the PS domain, and finally the CS domain.
Step 1.
As described in clause 6.4, the Short Message is routed to the UE via S-CSCF after the domain selection is performed in the IP-SM-GW and all the available domains have been listed in the sequence of the priority in the IP-SM-GW. The message fails to reach the UE, e.g. due to the UE not being reachable in IMS, or exceeded memory capacity of the UE.
Step 2.
The S-CSCF sends an appropriate failure message according to normal IMS procedure as defined in TS 23.228, and sends it to the IP-SM-GW (AS) including an appropriate error value. This Delivery report is an acknowledgement to the Short Message received by the S-CSCF in step 1.
Step 3.
IP-SM-GW (AS) acknowledges the failure message to S-CSCF.
Step 4.
The IP-SM-GW verifies the error cause of the failure delivery report. If the error is due to exceeded memory capacity of the UE, the IP-SM-GW forwards the Delivery report (SMS-DELIVER-REPORT) back to the SMS-GMSC and the procedure continues as described in step 16. Otherwise, the IP-SM-GW forwards the Short Message to the domain which is listed in the second place in its priority list. It is supposed that the SGSN is selected.
Step 5.
The SGSN delivers the message to the UE but the message fails to reach the UE, e.g. the UE is not reachable in PS domain.
Step 6.
The SGSN generates a Delivery report (SMS-DELIVER-REPORT) and sends it to the IP-SM-GW, including an appropriate error value. This Delivery report is an acknowledgement to the Short Message received by the SGSN in step 5.
Step 7.
The IP-SM-GW forwards the Short Message to the domain which is listed in the third place in its priority list. It is supposed that the MSC is selected.
Step 8.
The MSC delivers the message to the UE but the message fails to reach the UE, e.g. the UE is not reachable in CS domain.
Step 9.
The MSC generates a Delivery report (SMS-DELIVER-REPORT) and sends it to the IP-SM-GW, including an appropriate error value. This Delivery report is an acknowledgement to the Short Message received by the MSC in step 8.
Step 10.
The IP-SM-GW forwards the Short Message to the domain which is listed in the forth place in its priority list. It is supposed that the MME is selected.
Step 11.
The MME delivers the message to the UE but the message fails to reach the UE, e.g., the UE is not reachable in PS domain.
Step 12.
The MME generates a Delivery report (SMS-DELIVER-REPORT) and sends it to the IP-SM-GW, including an appropriate error value. This Delivery report is an acknowledgement to the Short Message received by the MME in step 11.
Step 13.
The IP-SM-GW forwards the Short Message to the domain which is listed in the fifth place in its priority list. It is supposed that the SMSF is selected.
Step 14.
The SMSF delivers the message to the UE but the message fails to reach the UE, e.g. the UE is not reachable in PS domain.
Step 15.
The SMSF generates a Delivery report (SMS-DELIVER-REPORT) and sends it to the IP-SM-GW, including an appropriate error value. This Delivery report is an acknowledgement to the Short Message received by the SMSF in step 14.
Step 16.
The IP-SM-GW sends a Delivery report to the SMS-GMSC.
Step 17.
The IP-SM-GW sends a Report SM Delivery Status to the HSS with accurate results from different domains. The HSS records the corresponding MWD, i.e. the SMS-SC address which stores the un-delivered message and the failure reason which indicates that the message failed to be sent by IP-SM-GW due to the UE not being available or the memory capacity of the UE being exceeded. The IP-SM-GW sets UNRI locally.
Step 18.
The IP-SM-GW subscribes to the HSS for a one-time notification of the UE being reachable again. The HSS records the subscription and instructs the transport layer to report when the UE is reachable.
Step 19.
The SMS-GMSC sends a Report SM Delivery Status to the HSS. The HSS shall ignore the information provided in this report.
6.5b Alert Service Centre procedure when UE is available p. 27
When a Short Message is received in the IP-SM-GW for delivery to an IMS subscriber, the IP-SM-GW shall verify the registration status of the UE. If the UE is not registered in IMS, or is registered in IMS but does not advertise the Converged IP Messaging, SIMPLE IM or SMSIP capability, the Short Message shall not be interworked; neither at service level nor at transport level. Based on operator policy and user preferences, either the message is sent over CS/PS or an error indication is sent back to the SMS-SC. In the latter case, when the UE registers in IMS advertising the Converged IP Messaging, SIMPLE IM and/or the SMSIP capability at a later time, this information is sent to the SMS-SC and the delivery is attempted at that time, as an Instant Message or an encapsulated Short Message as appropriate.
If the IP-SM-GW detects the UE is reachable for SMS over IP and the UE is registered with support of Converged IP Messaging, SIMPLE IM or SMSIP capability, the IP-SM-GW clears local UNRI and informs HLR/HSS that the UE is available again.
If the HLR/HSS has recorded the MWD with a failure reason that the message failed to be sent by IP-SM-GW due to the UE not being available, once the HLR/HSS receives a message from any of the domains indicating that the UE is available again, e.g. IMSI attached, or IMS registered, the HLR/HSS initiates an Alert service centre procedure to request the SMS-SC to re-send the stored message.
The following Figure shows an example of how a deferred message is re-transmitted to an IMS UE upon the UE availability.
Step 1.
The message is transmitted from SMS-SC to IP-SM-GW for delivery to the subscriber, possibly after transport-level and/or service-level interworking. Prior to this interworking, the IP-SM-GW shall check for UE availability. If the UE is not registered in IMS, and delivery over CS/PS is unsuccessful (see clause 6.5a), the IP-SM-GW returns an appropriate error response to SMS-SC. The SMS-SC then informs the HSS/HLR about the unavailability of the UE. After an unsuccessful SM termination procedure due to the UE being unavailable, the HSS records the MWD i.e. the SMS-SC address which stores the un-delivered message and the failure reason which indicates that the message failed to be sent by IP-SM-GW due to the UE not being available, for a subsequent Alert service centre procedure.
At any time after the unsuccessful SM termination procedure, the UE may attach in the PS and or CS domain again, in which case a Ready for SM message from the SGSN, MSC, MME or SMSF is sent to the HLR/HSS as described in TS 23.040. The HLR/HSS initiates an Alert service centre procedure to the SM-IWMSC when the user's MWD is not NULL, and the procedure continues as described in step 3.
Step 2.
At any time after the unsuccessful SM termination procedure, the status of the UE may indicate that the UE is available due to, e.g. registration in IMS (step 2a). At that point UE-Not-Reachable-for-IP (UNRI) is updated in HLR/HSS, as described in TS 23.040. After the IMS registration is finished, the procedure continues as described in step 3.
At any time after the unsuccessful SM termination procedure, the HSS can receive a notification from the transport layer e.g. MME that the UE is reachable again (step 2b). As the IP-SM-GW has subscribed to the event as described in clause 6.5a, the HSS shall notify the IP-SM-GW of the UE being reachable again (step 2c). If the UE is already registered in IMS, the IP-SM-GW shall then send a Ready for SM message to the HLR/HSS (step 2d) and the procedure continues as described in step 3. Otherwise, the IP-SM-GW discards the notification message. The procedure will resume when one of the conditions described in steps 1 and 2 is fulfilled.
Step 3.
The HLR/HSS checks the user's MWD. If MWD is not Null, the HLR/HSS initiates an Alert service centre message to the SMS-IWMSC.
Step 4.
The SMS-IWMSC forwards the Alert service centre procedure to the responding SMS-SC.
Step 5.
Upon receipt of the Alert service centre message, the SMS-SC re-attempts to send the stored Short Message. The message is transmitted to IP-SM-GW and thereafter to the UE after appropriate interworking (transport-level and/or service-level interworking) is performed. The UE acknowledges the reception of the message.
