the SMS-GMSC indicates in the ForwardShortMsg that it is capable to retransmit the Short Message until a maximum retransmission time.
Operation 4c:
If the MS is using extended idle mode DRX, and if the ForwardShortMsg includes a maximum retransmission time, the MSC in Deployment Option 2 (see clause 8.2.4a.1 of TS 23.272), SGSN or MME may return a Delivery Report with a cause indicating that the user is temporarily unreachable and with an indication requesting the SMS-GMSC to retransmit the Short Message at a later requested retransmission time prior to the maximum retransmission time. In that case, the MSC in Deployment Option 2 (see clause 8.2.4a.1 of TS 23.272), SGSN or MME shall not set the MNRF, MNRG or MNRF flag respectively. The SMS-GMSC shall not send an SM-Delivery Report Status to the HLR or HSS.
Operation 5a:
the SMS-GMSC retransmits the Short Message at the requested retransmission time.