23.2.1 Procedure in the Intermediate MSC
29.1203GPPMobile Application Part (MAP) specification for Gateway Location Register (GLR)Release 17TS
When initiating the dialogue with the IM-MSC, the SMS Gateway MSC must provide the IMSI of the subscriber to whom the short message is directed.
The IMSI can be included either in the Destination Reference of the MAP_OPEN indication received from the SMS Gateway MSC or in the sm-RP-DA information field of the MAP_MT_FORWARD_SHORT_MESSAGE indication.
When receiving a MAP_OPEN indication primitive that is not associated with any MAP service indication primitive and if the dialogue is accepted, the MAP service-user in the IM-MSC issues a MAP_DELIMITER request primitive in order to trigger the local MAP service-provider to confirm the dialogue.
When receiving the first MAP_MT_FORWARD_SHORT_MESSAGE indication from the gateway MSC, the IM- MSC retrieves the E.164 Number of the servicing MSC from the GLR if the MAP service primitive is accepted.
The MAP_MT_FORWARD_SHORT_MESSAGE indication primitive is checked by the macro "Check_Indication". If the received MAP service primitive contains errors, the service is aborted and an unexpected data value error or data missing error is returned to the GMSC.
The subscriber identity information that may be included in the MAP_OPEN indication primitive and in the MAP service indication primitive is checked by the macro "Check_Subscr_Identity_For_MT_SMS" as follows.
If a Destination Reference has been received in the MAP_OPEN indication, an LMSI must be present in the sm-RP-DA information field of the MAP_MT_FORWARD_SHORT_MESSAGE indication. The LMSI shall be key information for retrieving the MSC Number in the GLR.
Otherwise, if the IMSI is included in the sm-RP-DA information field of the MAP_MT_FORWARD_SHORT_MESSAGE indication, it is used to retrieve the MSC Number in the GLR.
If:
a Destination Reference has been received in the IM-MSC and the sm-RP-DA information field of the MAP_MT_FORWARD_SHORT_MESSAGE indication does not include an LMSI, or
no Destination Reference has been received and the sm-RP-DA information field does not cover an IMSI;
the service is aborted in the IM-MSC and the error "Unexpected Data Value" is returned to the SMS GMSC.
The interaction between the IM-MSC and the GLR for the MSC Number retrieval is described in 3GPP TS 23.119 GLR‑stage2.
If the IM-MSC is successfully retrieves the MSC Number it initiates the forward short message procedure to the servicing MSC. The presence of the Destination Reference in the MAP_OPEN request and the LMSI or IMSI in the first MAP_MT_FORWARD_SHORT_MESSAGE request follows the message received from the GMSC. The More Messages To Send flag is set to TRUE or FALSE depending on the information received from the GMSC.
If the grouping of MAP_OPEN request and MAP_MT_FORWARD_SHORT_MESSAGE request together would need segmenting, these primitives must not be grouped together. The MAP_OPEN request primitive is sent first without any associated MAP service request primitive and the dialogue confirmation must be received before the MAP_MT_FORWARD_SHORT_MESSAGE request is sent.
As a response to the procedure, the IM-MSC will receive the MAP_MT_FORWARD_SHORT_MESSAGE confirmation indicating:
– a successful forwarding of the short message. This indication is passed to the GMSC;
– unsuccessful forwarding of the short message. This indication is passed to the GMSC.
The IM-MSC informs the delivery failure to the GLR, if an absent subscriber_SM, an unidentified subscriber or SM delivery failure with error cause MS memory capacity exceeded indication is received from the servicing MSC. That enables the GLR set the MNRF. The interaction between the IM-MSC and the GLR regarding the procedure is described in 3GPP TS 23.119 GLR-stage2.
Unexpected data value, system failure errors and other errors are simply passed to the GMSC.
If the More Messages To Send flag was TRUE in the MAP_MT_FORWARD_SHORT_MESSAGE request and the previous short message transfer succeeded, then the IM-MSC awaits the next short message.
When receiving the next short message from the GMSC, the IM-MSC sets the More Messages To Send flag according to the information received and starts the service MAP_MT_FORWARD_SHORT_MESSAGE again.
If the More Messages To Send flag was FALSE or the service MAP_MT_FORWARD_SHORT_MESSAGE ends unsuccessfully, the transaction to the gateway MSC is terminated.
The mobile terminated short message transfer procedure in the IM-MSC is shown in figure 23.2/1 and 23.2/2.
Figure 23.2/1 (sheet1 of 3): Procedure_MT_SM_Transfer_IM-MSC
Figure 23.2/1 (sheet 2 of 3): Procedure MT_SM_Transfer_IM-MSC
Figure 23.2/1 (sheet 3 of 3): Procedure MT_SM_Transfer_IM-MSC
Figure 23.2/2 (sheet1 of 2): Macro MT_SM_IM-MSC
Figure 23.2/2 (sheet2 of 2): Macro MT_SM_IM-MSC