PCRF uses which command on Gx to install rules?

Interview
1

Q. PCRF uses which command on Gx to install rules?

a) UDR
b) STR
c) RAR
d) Charging Rule Install (CCR U)

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:arrow_right: Correct answer: Letter d.

On the Gx interface, the PCRF communicates with the PCEF (e.g., PGW) using Diameter messages. To install or modify policy and charging rules, it uses the Credit-Control Request Update (CCR-U) command.

This message enables the PCRF to send dynamic policy rules, such as QoS parameters, gating controls, or charging rules, to be enforced by the PCEF.

CCR-U is part of the Diameter Credit-Control Application (DCCA) and is essential for real-time policy control and charging in IMS and LTE networks.

Q. PCRF uses which command on Gx to install rules?

a) :x: UDR
→ Incorrect. UDR (User Data Request) is used on the Sd or Ud interface (from PCRF to UDRF or HSS), not on Gx.

b) :x: STR
→ Incorrect. Session Termination Request (STR) is used on the Cx or Rx interface for IMS sessions, not for rule installation.

c) :x: RAR
→ Incorrect. Re-Auth Request (RAR) is used on Rx (between PCRF and AF) or Gy, not for rule installs on Gx.

d) :white_check_mark: Charging Rule Install (CCR U)
→ Correct. CCR-U is the update request from PCRF to install, modify, or remove PCC rules via the Gx interface. CCR Update delivers PCC rules with TFT and QoS.