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480 SIGNALING CONNECTION CONTROL PARTFigure 15.3-4. Address information in the first SCCP Unitdata message of a transaction.SCCP-A enters GT in the CDA field of the Unitdata message, PC ¼ a, SSN ¼ qin the CGA field, and sets the routing indicator (Fig. 15.2-1) to RTI ¼ 0, indicatingthat a GT translation is needed. Since SCCP-A has received a GT called address andknows that the SCCP-E can perform GT translations, it includes the MTP address ofsignaling point E (DPC ¼ e) when passing the message. MTP-A then forms theMSU and transfers it to STP-E.SCCP-E translates the GT and obtains the addresses PC ¼ c, SSN ¼ r andPC ¼ d, SSN ¼ r of the R800 units at databases C and D. Assuming that SCCP-Eselects database D, it enters SSN ¼ r in the CDA of its outgoing message andpasses it to its MTP-E, in a MTP-transfer request that includes destination pointcode DPC ¼ d. It also sets the routing indicator to RTI ¼ 1. The MTP-E routesthe MSU to MTP-H, which routes it to database D.