Question: In IMS centralized services, when using a specific CSRN to indicate an anchored call for preventing circular looping, which entity is responsible for resolving the MSISDN from the CSRN in the 'MGCF resolution' option?
Option 1: Home Subscriber Server (HSS)
Option 2: Serving Call Session Control Function (S-CSCF)
Option 3: Media Gateway Control Function (MGCF) with integrated GMSC functionality
Option 4: Gateway Mobile Switching Center (GMSC)
Explanation: In preventing circular looping in IMS centralized services, the MGCF with integrated GMSC functionality uses a specific CSRN to recognize an anchored call. The MGCF resolves the MSISDN from the CSRN and proceeds with the CS call terminating procedure, including sending a MAP SRI with the 'Suppress T-CSI' parameter to the HSS, highlighting the MGCF's role in resolving the MSISDN.