Rf Interface Support
▀ Introduction
▄ Cisco ASR 5x00 Packet Data Network Gateway Administration Guide
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Introduction
The Rf interface is the offline charging interface between the Charging Trigger Function (CTF) (for example, P-GW, S-
GW, P-CSCF) and the Charging Collection Function (CCF). The Rf interface specification for LTE/GPRS/eHRPD
offline charging is based on 3GPP TS 32.299 V8.6.0, 3GPP TS 32.251 V8.5.0 and other 3GPP specifications. The Rf
interface specification for IP Multimedia Subsystem (IMS) offline charging is based on 3GPP TS 32.260 V8.12.0 and
3GPP TS 32.299 V8.13.0.
Offline charging is used for network services that are paid for periodically. For example, a user may have a subscription
for voice calls that is paid monthly. The Rf protocol allows the CTF (Diameter client) to issue offline charging events to
a Charging Data Function (CDF) (Diameter server). The charging events can either be one-time events or may be
session-based.
The system provides a Diameter Offline Charging Application that can be used by deployed applications to generate
charging events based on the Rf protocol. The offline charging application uses the base Diameter protocol
implementation, and allows any application deployed on chassis to act as CTF to a configured CDF.
In general, accounting information from core network elements is required to be gathered so that the billing system can
generate a consolidated record for each rendered service.
The CCF with the CDF and Charging Gateway Function (CGF) will be implemented as part of the core network
application. The CDF function collects and aggregates Rf messages from the various CTFs and creates CDRs. The CGF
collects CDRs from the CDFs and generates charging data record files for the data mediation/billing system for billing.
Offline Charging Architecture
The following diagram provides the high level charging architecture as specified in 3GPP 32.240. The interface between
CSCF, S-GW, HSGW, P-GW and GGSN with CCF is Rf interface. Rf interface for EPC domain is as per 3GPP
standards applicable to the PS Domain (e.g. 32.240, 32.251, 32.299, etc.).