Question: In a 3GPP IMS network supporting Volume-Based Charging (VBC), how does the P-CSCF determine the type of IMS content for a session component with an SDP payload referring to a Customized Alerting Tones (CAT) service?
Option 1: By checking for a media-level "a=content" SDP attribute with a value "g.3gpp.cat" and setting the IMS-Content-Type AVP to "CAT".
Option 2: Through the Called-Party-Address, which directly indicates the type of IMS service.
Option 3: By analyzing the Callee-Information AVP for specific patterns indicating CAT services.
Option 4: Based on the rating group or combination of rating group and service id provided by the PCRF.
Explanation: According to the specified behavior for determining IMS content types, if an SDP payload contains a media-level "a=content" attribute with a value "g.3gpp.cat", the P-CSCF sets the IMS-Content-Type AVP to "CAT", specifically identifying the Customized Alerting Tones (CAT) service. This method ensures accurate identification of the IMS content type for applying appropriate charging controls.