Which interface is used between PCRF and P-CSCF for AAR Request?

Interview
1

Q. Which interface is used between PCRF and P-CSCF for AAR Request?

a) Ro
b) Rf
c) Gx
d) Rx

Check 🔎

:arrow_right: Correct answer: Letter d.

Rx interface is the Diameter-based interface used between the P-CSCF and PCRF in IMS architecture. It is responsible for Application-Level QoS Authorization via messages like AAR (Authorization-Authentication Request) and AAA (Authorization-Authentication Answer).

Q. Which interface is used between PCRF and P-CSCF for AAR Request?

a) :x: Ro
→ Incorrect. Ro is the interface used for online charging between IMS elements and the OCS (Online Charging System), not for policy control.

b) :x: Rf
→ Incorrect. Rf is the offline charging interface, used for event reporting from IMS nodes to the Charging Data Function (CDF).

c) :x: Gx
→ Incorrect. Gx is used between PCRF and P-GW/SGW for bearer-level policy and charging control, not for SIP-based service authorization.

d) :white_check_mark: Rx
→ Correct. Rx interface enables the P-CSCF to communicate with the PCRF for dynamic policy decisions. It carries AAR/AAA messages to request and authorize QoS for SIP sessions.