Question: In a 3GPP IMS (IP Multimedia Subsystem) network, when a P-CSCF (Proxy-Call Session Control Function) is triggered to include network-provided location information at mid-call due to an access change, what specific value must the P-CSCF include within the Specific-Action AVP in the AA-request?
Option 1: LOCATION_UPDATE_REQUEST value
Option 2: ACCESS_NETWORK_INFO_REPORT value
Option 3: SERVICE_AREA_UPDATE value
Option 4: NETWORK_CHANGE_NOTIFICATION value
Explanation: According to specified procedures for handling network-provided location information at mid-call in an IMS network, when a P-CSCF is required to include such information due to a trigger like an access change, it must specifically include the ACCESS_NETWORK_INFO_REPORT value within the Specific-Action AVP of the AA-request. This action ensures that necessary network information is requested and subsequently provided for location purposes, highlighting the importance of precise signaling in managing call sessions and location updates across different access networks.