关于Diameter Final Unit Indication AVP能否在Gx接口使用的技术问询

Great question—let’s break this down clearly using 3GPP standards and the core roles of these interfaces.

First, let’s ground the context:

• The Gx interface is strictly focused on policy control between PCRF and PCEF. Its primary job is managing QoS rules, service gating, and policy enforcement triggers—it doesn’t handle direct quota management or exhaustion notifications.
• The Gy interface is dedicated to online charging, where the Online Charging System (OCS) uses the Final Unit Indication AVP to signal to PCEF that a user’s quota has been exhausted.

Now, the straight answer: The Diameter Final Unit Indication AVP cannot be used on the Gx interface. Here’s why:

• This AVP is defined in 3GPP TS 32.299 (the online charging specification) and is explicitly reserved for Gy interface messages—specifically Credit-Control-Answer (CCA) or Re-Auth-Request (RAR) messages sent from OCS to PCEF.
• The Gx interface’s allowed message set (outlined in 3GPP TS 29.212) does not include the Final Unit Indication AVP. PCRF and PCEF never exchange this attribute over Gx, as it falls outside the interface’s policy-focused scope.

If you’re curious how quota exhaustion ties into Gx actions, here’s the typical flow:

1. OCS sends the Final Unit Indication AVP to PCEF via Gy when quota runs out.
2. PCEF triggers a policy update request to PCRF over Gx.
3. PCRF responds with the appropriate enforcement action (e.g., restricting bandwidth, terminating the session) via Gx.

To recap: Final Unit Indication is a Gy-exclusive AVP—you won’t see it used directly between PCRF and PCEF on the Gx interface.

内容的提问来源于stack exchange，提问作者mhmn