PCC Architecture Flashcards
Policy Control and Charging (PCC) functionality comprises
Policy and Charging Rules Function (PCRF)
Policy and Charging Enforcement Function (PCEF)
Bearer Binding and Event Reporting Function (BBERF)
Online Charging System (OCS)
Offline Charging System (OFCS)
Subscription Profile Repository (SPR) and Application Function (AF)
PCC Rules Purposes
to detect a packet belonging to an SDF to map that packet to proper IP-CAN bearer in downlink and uplink direction
to identify the service
to provide appropriate applicable charging
to provide policy control
There are 2 different types of PCC rules
Dynamic PCC rules - These PCC rules are dynamically provisioned by PCRF to PCEF over Gx interface.
Pre-defined PCC rules - These PCC rules are pre-configured in the PCEF. The PCRF can advise the PCEF to activate a set of PCC rules over Gx interface.
A PCC rules consists of
- a rule name - the rule name is used to reference a PCC rule during communication between PCRF and PCEF
- service identifier - the service identifier is used to identify a service or service component the SDF relates to
- SDF filter(s) - the SDF filters are used to select the traffic for which the rule applies
- precedence - order of the SDF filter; dynamic rule takes precedence over pre-defined rule in case of same precedence
- gate status - whether the SDF detected should be allowed to pass or blocked
- QoS parameters - includes the QCI, the ARP and bitrates for uplink and downlink
- charging key and charging parameters - online or offline charging
- monitoring key - identifies a monitoring control instance that shall be used for usage monitoring control of the SDFs
The Application Function (AF) (eg. P-CSCF for IMS solution, or Video Streaming Server for non-IMS solution)
interacts with applications or services that require dynamic PCC. The AF extracts session information from the application signalling and provides it to the PCRF. The Rx reference point resides between AF and PCRF.
The AF provides the following application session related information to the PCRF-
Subscriber Identifier IP address of the UE Media Type and Format Bandwidth Flow description eg. Source and Destination IP addresses and the protocol AF Application Identifier AF Communication Service Identifier AF Application Event Identifier AF Record Information Flow Status Priority Indicator Emergency Indicator
The Subscription Profile Repository (SPR)
contains subscriber/subscription information.
The Subscription Profile Repository (SPR) contains information that is per-PDN basis and includes
Subscriber’s allowed services
Information on subscriber’s allowed QoS (MBR and GBR)
Subscriber’s charging related information
Subscriber category
The Sp reference point resides between SPR and PCRF.
It allows the PCRF to request subscription information related to a subscriber’s service/session.
The Online Charging System (OCS) is a credit management system for pre-paid charging.
Within OCS lies a functional entity called Service Data Flow Based Credit Control Function which performs online credit control function. The PCEF interacts with OCS to check out credit and report credit status over Gy interface.
The Offline Charging System (OFCS) is used for offline charging. .
The OFCS receives charging events from PCEF over Gz interface and generates Charging Data Records (CDRs) which are sent to the billing system
For EPS, the Policy Charging and Enforcement Function (PCEF)
is always located in the PDN-GW.
The Bearer Binding and Event Reporting Function (BBERF) location depends on the access technology.
For 3GPP, the BBERF is located in the Serving-GW, whereas for eHRPD, the BBERF is located in the HSGW.
The Policy Charging and Rules Function (PCRF) provides network control regarding service data flow detection, gating (blocking or allowing packets), QoS control and flow-based charging towards the PCEF.
It can also apply security procedures before accepting information from the AF. The PCRF ensures that the PCEF user plane traffic mapping and treatment is in accordance with the user’s subscription profile which it receives from SPR over Sp interface. The PCRF may reject the request received from the AF when the service information is not consistent with subscription information (either locally configured or received from SPR) and the PCRF responds to the AF with appropriate reason.
The PCRF accepts input for PCC decision making from
the PCEF over Gx interface, the BBERF (if available), the SPR and the AF (if available) as well as its own pre-defined information.
