Furnish Charging Information

Description

Furnish Charging Information (FCI) is a critical Diameter Application Command within the 3GPP Online Charging System (OCS) architecture, defined for the Ro reference point (between the OCS and the network's Charging Trigger Function). It is not a channel or a standalone protocol, but a specific request-and-answer transaction (Diameter Command Code 272). The primary function of the FCI command is for the OCS to deliver authorized charging information to a network element, such as a Gateway GPRS Support Node (GGSN), Packet Data Network Gateway (PGW), or Telephony Application Server (TAS), which acts as a Charging Trigger Function (CTF). This transaction occurs after the CTF has sent a Credit Control Request (CCR) to the OCS to request quota for a subscriber's service usage.

The FCI command, sent as a Credit Control Answer (CCA), carries the OCS's decision in the form of specific Attribute-Value Pairs (AVPs). These AVPs constitute the 'furnished' information and include the granted service units (e.g., data volume in bytes, call duration in seconds, or monetary credit), the associated rating group identifiers, the validity time of the quota, and the final unit indication (signaling the last granted quota). Crucially, the FCI may also include cost information AVPs, which provide the CTF with the monetary cost of the service units granted. This allows the CTF to potentially inform the subscriber in real-time about charging, a feature known as Advice of Charge (AoC). The OCS determines this information by performing real-time rating and balance management based on the subscriber's account and the service requested.

Architecturally, FCI is a core component of the Event-Based Charging (EBC) and Session-Based Charging (SBC) functions within the OCS. It enables the 'credit authorization' process. When a CTF receives an FCI command, it applies the granted quota to the user's session, allowing the service to proceed. It then monitors resource usage in real-time. When the quota is exhausted or the session ends, the CTF sends a new CCR to report the used units and, if the session continues, triggers another FCI/CCA exchange to obtain a new quota. This cycle of CCR (request) and CCA with FCI (answer) forms the heartbeat of real-time, prepaid, and convergent charging in 3GPP networks, ensuring services are only delivered if the subscriber has sufficient credit.

Purpose & Motivation

FCI was created to support the evolution from traditional offline (postpaid) billing to real-time online charging, which is essential for prepaid services and spending control. Prior to online charging, networks provided services first and calculated charges later (offline), which carried the risk of bad debt and did not allow for real-time credit control. The purpose of the FCI command is to enable a secure, standardized, and real-time dialogue where the network's charging system (OCS) can authorize and meter service delivery instantaneously.

It solves the problem of how to integrate a centralized, intelligent charging system with diverse network elements that actually deliver services (voice calls, data sessions, SMS, IMS services). The FCI command within the Diameter protocol provides the specific mechanism for the OCS to 'furnish' or supply the CTF with the precise terms of service authorization: how much service (quota) is allowed and at what cost. This addresses the limitation of non-interactive charging by enabling immediate credit checks, prepaid balance deductions, and quota enforcement.

Its creation was motivated by the commercial need for flexible, real-time charging models to drive new revenue streams, particularly for prepaid mobile services which dominate many markets. The FCI protocol operation allows operators to implement not just simple prepaid, but also hybrid accounts, promotional offers, and real-time spending limits. By standardizing this command in the Ro interface, 3GPP ensured interoperability between OCS platforms from different vendors and the multitude of network elements that generate charging events, forming the backbone of modern telecom monetization.

Key Features

• Defined as Diameter Command Code 272 for the Credit-Control-Answer (CCA) message on the Ro reference point.
• Carries granted service units (volume, time, money) from the OCS to the Charging Trigger Function (CTF).
• Includes rating group and cost information AVPs, enabling real-time rating and Advice of Charge (AoC).
• Supports both session-based and event-based online charging scenarios.
• Triggers the CTF to apply a quota and allow service delivery to the subscriber.
• Central to the credit authorization loop between network elements and the Online Charging System.

Evolution Across Releases

Defining Specifications