Gx Interface Support
▀ Rel. 7 Gx Interface
▄ Cisco ASR 5x00 Packet Data Network Gateway Administration Guide
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For the purpose of charging correlation between SDF level and application level (for example, IMS) as well as on-line
charging support at the application level, applicable charging identifiers and IP-CAN type identifiers are passed from
the PCRF to the AF, if such identifiers are available.
For IMS bearer charging, the IP Multimedia Core Network (IM CN) subsystem and the Packet Switched (PS) domain
entities are required to generate correlated charging data.
In order to achieve this, the Gateway provides the GGSN Charging Identifier (GCID) associated with the PDP context
along with its address to the PCRF. The PCRF in turn sends the IMS Charging Identifier (ICID), which is provided by
the P-CSCF, to the Gateway. The Gateway generates the charging records including the GCID as well as the ICID if
received from PCRF, so that the correlation of charging data can be done with the billing system.
PCRF also provides the flow identifier, which uniquely identifies an IP flow in an IMS session.
Policy and Charging Control (PCC) Rules
A PCC rule enables the detection of an SDF and provides parameters for policy control and/or charging control. The
purpose of the PCC rule is to:
Detect a packet belonging to an SDF.
Select downlink IP CAN bearers based on SDF filters in the PCC rule.
Enforce uplink IP flows are transported in the correct IP CAN bearer using the SDF filters within the
PCC rule.
Identify the service that the SDF contributes to.
Provide applicable charging parameters for an SDF.
Provide policy control for an SDF.
The PCEF selects a PCC rule for each packet received by evaluating received packets against SDF filters of PCC rules
in the order of precedence of the PCC rules. When a packet matches a SDF filter, the packet matching process for that
packet is completed, and the PCC rule for that filter is applied.
There are two types of PCC rules:
Dynamic PCC Rules: Rules dynamically provisioned by the PCRF to the PCEF via the Gx interface. These PCC
rules may be either predefined or dynamically generated in the PCRF. Dynamic PCC rules can be installed,
modified, and removed at any time.
Predefined PCC Rule: Rules preconfigured in the PCEF by the operators. Predefined PCC rules can be activated
or deactivated by the PCRF at any time. Predefined PCC rules within the PCEF may be grouped allowing the
PCRF to dynamically activate a set of PCC rules over the Gx reference point.
Important:
A third type of rule, the static PCC rule can be preconfigured in the chassis by the operators. Static
PCC rules are not explicitly known in the PCRF, and are not under control of the PCRF. Static PCC rules are bound to
general purpose bearer with no Gx control.
A PCC rule consists of:
Rule Name: The rule name is used to reference a PCC rule in the communication between the PCEF and PCRF.
Service Identifier: The service identifier is used to identify the service or the service component the SDF relates
to.
Service Data Flow Filter(s): The service flow filter(s) is used to select the traffic for which the rule applies.
