Question: In IMS (IP Multimedia Subsystem), when a Serving-CSCF (S-CSCF) handling session origination determines that the destination address belongs to a subscriber of the same network operator, what is the next step in the signalling path?
Option 1: The S-CSCF directly forwards the request to another S-CSCF responsible for session termination.
Option 2: The S-CSCF passes the request to a local I-CSCF (Interrogating-CSCF), which then queries the HSS (Home Subscriber Server) for current location information.
Option 3: The S-CSCF translates ISUP/BICC messages to SIP signalling without involving any other CSCF.
Option 4: The S-CSCF invokes Service Control to analyze the destination address further.
Explanation: According to IMS procedures, when the destination address is determined to belong to a subscriber of the same network operator, the Serving-CSCF handling session origination passes the request to a local Interrogating-CSCF (I-CSCF). The I-CSCF then queries the Home Subscriber Server (HSS) for current location information before forwarding the request to the appropriate S-CSCF. This process ensures efficient routing and accurate location updating within the same operator's network.