Instantiation of Gx overrides

For a list of Gx related AVPs supported on the node, see the 7750 SR and VSR Gx AVPs Reference Guide.

Gx overrides are installed via Charging-Rule-Install AVP (for ESM or AA) or ADC-Rule-Install AVP (for AA only – 3GPP Release 11) sent from the PCRF toward the node.

AVP Format:

Charging-Rule-Install ::=       < AVP Header: 1001 >
                                       *[ Charging-Rule-Definition ]
                                       *[ Charging-Rule-Name ]
                                       *[ AVP ]

ADC-Rule-Install ::=       < AVP Header: 1092 >
                                       *[ ADC-Rule-Definition ]
                                       *[ ADC-Rule-Name ]
                                       *[ AVP ]

Every Gx override must have a Charging-Rule-Name (ESM) or ADC-Rule-Name (AA - 3GPP Release 11 and Release 12) associated with it. This is important for returning the override status from the node to the PCRF upon the override instantiation.

The objects (subscriber-hosts) to which the new overrides are applied must exist on the node; otherwise, the override installation fails.

The parameters defining a new override simply replaces the existing parameters that are already applied to the subscriber-host, without the need to remove the previously installed parameters.

There are four types of overrides that are currently supported via Gx:

ESM string overrides (sla/sub/app-profiles, subscriber-id)
update of subscriber host QoS information (queue rate change)
filter override for the subscriber host (including one-time http redirect)
category-map installation/override
HTTP redirect override within the filter

A Charging-Rule-Name AVP within the Charging-Rule-Install grouped AVP can have several meanings:

It can directly reference a preconfigured filter in the system.
It can directly reference a preconfigured subscriber profile (sla and sub).
It can directly reference a preconfigured category map.
It can directly reference an ESM string (such as an inter-destination-string used to associate the subscriber host with a Vport configuration).
Or, if there is an HTTP redirect override, it serves as a special container within which the HTTP redirect URL is defined. Note that HTTP redirect override is not to be confused with PCC rule-based HTTP redirect.

In all of the above cases, the existing objects applied to the subscriber-host is replaced with the referenced object.

It is important to distinguish two locations for invoking the Charging-Rule-Name AVP for overrides:

directly under the Charging-Rule-Install AVP

Then, the Charging-Rule-Name references the predefined structures (profiles, filter-ids, cat-maps, and so on) on the node. The type of the structure is contained within the Charging-Rule-Name AVP in the form of a reserved keyword that has to be prepended to the identifier of structure:

Filter installation/overrides:
- Charging-Rule-Name = Ingr-v4:<id>
- Charging-Rule-Name = Ingr-v6:<id>
- Charging-Rule-Name = Egr-v4:<id>
- Charging-Rule-Name = Egr-v6:<id>
- Charging-Rule-Name = In-Othr-v4:<id> (othr - one-time-http-redirect)
- Charging-Rule-Name = In-Othr-v6:<id> (othr - one-time-http-redirect)
Subscriber-Id override:
- Charging-Rule-Name = Sub-Id:sub-id-string
Profile installation/overrides:
- Charging-Rule-Name = Sla-Profile:sla-profile-name
- Charging-Rule-Name = Sub-Profile:sub-profile-name
Inter-destination string override:
- Charging-Rule-Name = Inter-Dest:inter-dest-string
Usage-Monitoring:
- Charging-Rule-Name = Cat-Map:category-map-name
AA:
- Charging-Rule-Name = AA-UM:<string-name>
- Charging-Rule-Name=AA-Functions:<string-name>
In summary, the reserved prefixes ingr-v4:,ingr-v6:, egr-v4:, egr-v6:, in-othr-v4:, in-othr-v6:, sub-id:, sla-profile:, sub-profile:, inter-dest:, cat-map:, aa-um: and aa-functions: have special meaning within the Charging-Rule-Name AVP on the node.

One exception to this is HTTP redirect override, which is described separately.
under the Charging-Rule-Install

Charging-Rule-Definition AVP. In this case, the override itself is not pre-provisioned on the node but instead, directly defined in the Charging-Rule-Definition. Part of the override definition is the name assignment via Charging-Rule-Name AVP. The Charging-Rule-Name AVP is used to report on the override status.

For example, the Charging-Rule-Name AVP for QoS overrides is an arbitrary name. This AVP is part of Charging-Rule-Definition AVP in which QoS-Information is provided. Such Charging-Rule-Name is used to report errors related to instantiation of the override.

Another example of the override defined within the Charging-Rule-Definition AVP is HTTP redirect override:
```
Charging-Rule-Name = v4-http-url:<name>
Redirect-Information ::= < AVP Header: 1085 >

[ Redirect-Address-Type ]
[ Redirect-Server-Address ]
```
and
```
Charging-Rule-Name = v6-http-url:<name>
Redirect-Information ::= < AVP Header: 1085 >
[ Redirect-Address-Type ]
 [ Redirect-Server-Address ]
```
The ADC-Rule-Name AVP within the ADC-Rule-Install grouped AVP handles application policy related processing (AA). This AVP is applicable under the ADC-Rule-Install—ADC-Rule-Definition AVP. In this case the ADC rule itself is not pre-provisioned on the node but instead directly defined in the ADC-Rule-Definition. In AA, such rule definition can define AA overrides that are applied to the subscriber. In other words, the existing objects for the subscriber are replaced with the ones referenced in the rule. Part of the ADC rule definition is the ADC rule name assignment via ADC-Rule-Name AVP. The ADC-Rule-Name defined in such manner is used to report on the rule status.

The AA-Functions: prefix in the ADC rule name is reserved for ADC rule definitions applicable to AA-functions (namely, app-profile and ASOs):

ADC-Rule-Name = AA-Functions:aa-rule-name

Then the aa-rule-name is an arbitrary name that is used in rule status reporting.

If that ADC-Rule-Name is used in AA Usage-Monitoring, the ‟AA-Functions:” prefix must not be present (Usage-Monitoring in AA is covered in detail in the 7450 ESS, 7750 SR, and VSR Multiservice ISA and ESA Guide).

Note: AA-Function AVP and AA-Usage-Monitoring cannot coexist in the same ADC rule.

The Charging-Rule-Definition AVP (AVP code 1003, 3GPP 29.212 §5.3.4) is of type Grouped, and it defines the override sent by the PCRF to the node.

The Charging-Rule-Name in this AVP can be arbitrarily set and it is used to uniquely identify the override in error reporting.

Charging-Rule-Definition ::= < AVP Header: 1003 >
                                 { Charging-Rule-Name }
                                 [ QoS-Information ]
                                 [ Nas-Filter-Rule]
                                 [ Alc-NAS-Filter-Rule-Shared]
                                 *[ AVP ]

The ADC-Rule-Definition AVP (AVP code 1094, 3GPP 29.212 §5.3.87) is of type Grouped, and it defines the ADC override sent by the PCRF to the node. The ADC-Rule-Name AVP within the ADC-Rule-Definition AVP uniquely identifies the ADC policy rule and it is used to reference to a policy rule in communication between the node and the PCRF within one IP CAN session.

ADC-Rule-Definition ::= < AVP Header: 1094 >
              { ADC-Rule-Name }
              [AA-Functions]
              *[ AVP ]