Question: In an IP Multimedia Subsystem (IMS), when utilizing a dedicated signaling IP-CAN bearer for IMS related signaling, what is a key restriction on message destinations from the User Equipment (UE) that must be enforced by the IP-CAN?
Option 1: Any server within the visited network operator's domain.
Option 2: Only servers located outside the IMS operator's domain.
Option 3: All possible P-CSCFs in any network and external HTTP servers.
Option 4: The P-CSCF assigned for this UE, or possible P-CSCFs that may be assigned to this UE, and towards DHCP and DNS servers within the IMS operator's domain where the P-CSCF is located.
Explanation: This option correctly reflects the specified restrictions for dedicated signaling IP-CAN bearers in IMS. The IP-CAN must enforce that messages from the UE are restricted to: (1) the assigned P-CSCF or any possible P-CSCFs for the UE, and (2) DHCP and DNS servers within the same domain as the P-CSCF. This ensures controlled and secure signaling traffic management by the operator, particularly under roaming conditions, without relying on UE compliance.