5 Service Centre and PLMN interconnection

23.0403GPPRelease 17Technical realization of the Short Message Service (SMS)TS

The present document deals with the SC only with regard to the interchange of messages between SC and MS. Only the requirements put upon the SC by the SMS functionality are specified in the present document.

5.1 Service centre connection

One SC may be connected to several PLMNs, and may be connected to several MSCs (SMS‑GMSCs or SMS‑IWMSCs) within one and the same PLMN.

The SC is addressed from the mobile by an E.164 [17] number in the numbering plan of the PLMN to which the SC is connected. This E.164 [17] number shall uniquely identify the SC to that PLMN.

There may be an intermediate network between the PLMN and the SC; in this case the PLMN must autonomously make a connection to the SC using the SC address in this intermediate network.

No mandatory protocol between the SC and the MSC below the transfer layer is specified by GSM/UMTS; this is a matter for agreement between SC and PLMN operators. However, annex A provides an example protocol stack which could be used.

5.2 Routing requirements

5.2.1 Mobile terminated short message

The SC sends the short message to the SMS‑GMSC. The SMS‑GMSC interrogates the HLR to retrieve routing information necessary to forward the short message, and then sends the message to the relevant MSC or SGSN, transiting other networks if necessary and transiting an SMS Router in the HPLMN of the receiving MS if this is deployed. The MSC or SGSN then sends the short message to the MS.

5.2.2 Mobile originated short message

The MS sends the short message to the MSC or the SGSN. The MS shall always address the required SC by an E.164 [17] address. The visited PLMN shall route the message to the appropriate SMS‑IWMSC in the SC’s PLMN, transiting other networks if necessary.

As an operator option, the SMS-IWMSC may interrogate the HLR to retrieve the recipient’s IMSI in order to check that an SMS Interworking agreement exists between the two networks.