Content for  TS 23.172  Word version:  18.0.0

When the terminating MSC receives a request for a multimedia call, it shall check if the called user is provisioned for the service (see subclause 4.2.2.1). The terminating MSC shall include in the SETUP message towards the UE both BC-IEs in the same order as indicated by the incoming request together with the Repeat Indicator set to "service change and fallback" in order to invoke the SCUDIF functionality in the called terminal (see Figure 4.5). The terminating UE, based on its capabilities and internal settings, may return the two BC-IEs in the same order (to indicate that it accepts the proposed settings - see Figure 4.6), reversed order (see Figure 4.7), or just one BC-IE (either speech or multimedia - see Figure 4.8) to the terminating MSC in the CALL CONFIRMED message. If the terminal supports Network-initiated service upgrade to multimedia, then it shall also indicate this in the CALL CONFIRMED message with the"Enhanced Network-initiated ICM" (ENICM) Capability (see TS 24.008). In the case the UE ignores the SETUP message due to the presence of a reserved value for the Repeat Indicator, it sends a STATUS message back to the terminating MSC (see Figure 4.9), with the Cause Value set to #100, "Conditional IE error" (see clause 8.7.2 of TS 24.008). The terminating MSC shall then react according to clause 5.5.3.2.2 of TS 24.008, and it shall send a new SETUP message with a single BC, either the preferred service BC-IE or the speech BC-IE (fallback to speech), depending on configuration. The call setup then proceeds accordingly.