Question: In IMS (IP Multimedia Subsystem), which of the following scenarios can utilize existing IP-CAN bearers without setting up dedicated ones for session establishment?
Option 1: Services with real-time QoS requirements before the session becomes active.
Option 2: Services without real-time QoS requirements before the session becomes active, where the terminating endpoint does not need SIP-level notification of the originating endpoint's IP-CAN bearer availability.
Option 3: All services regardless of their QoS requirements or SIP-level notification needs.
Option 4: Only services that necessitate a THIG (Topology Hiding Interworking Gateway) for session establishment.
Explanation: This is because services without real-time Quality of Service (QoS) requirements before the session activation can utilize existing IP Connectivity Access Network (IP-CAN) bearers. Additionally, this option aligns with scenarios where the terminating endpoint does not require a SIP-level notification when the originating endpoint's IP-CAN bearer becomes available, fitting the described procedure for establishing sessions without preconditions.