Question: When an IMS-ALG (P-CSCF) supporting Alternate Connection (ALTC) functionality decides to insert ALTC information in the SDP offer, what action is taken towards the IMS-AGW regarding transport addresses/resources for each media line associated with ALTC information?
Option 1: The IMS-ALG requests the IMS-AGW to reserve a single set of transport addresses/resources.
Option 2: The IMS-ALG instructs the IMS-AGW to release all previously reserved transport resources.
Option 3: The IMS-ALG does not interact with the IMS-AGW for resource reservation in this context.
Option 4: The IMS-ALG requests the IMS-AGW to reserve two sets of transport addresses/resources, one for each media line associated with ALTC information.
Explanation: Supporting dual-stack UEs with ALTC functionality requires handling both possible connection types (e.g., IPv4 and IPv6). By reserving two sets of transport addresses/resources, the IMS-AGW ensures seamless media traversal regardless of which address type is used, facilitating a smoother user experience for dual-stack capable User Equipment (UEs), with subsequent release of unused resources optimizing network utilization.