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Diameter Responses

When a Diameter response is received, the N2IWF will parse the message to determine the action(s) to take with the session being processed.

Response configuration may be applied as LogicApp global variables:

Extract values from arbitrary returned AVPs to enrich processing within the READ_AVPS global.
Act on the Diameter Result-Code AVP value returned using selector rules within the RESULT_CODES global.

A sample Diameter response configuration for CAMEL/INAP calls might be:

<global name="READ_AVPS" type="array">
    <avp name="Cost-Information" type="array">
        <avp name="Unit-Value" type="array">
            <avp name="Value-Digits" to_var="cost_value" />
            <avp name="Exponent" to_var="cost_exp" />
        </avp>
    </avp>
</global>

<global name="RESULT_CODES" type="array">
    <rule code="4011" action="free" />
    <rule code="4012" service.at_terminate="false" action="release" announcement="ann1" />
    <rule code="4012" is_bf="true" action="release" cause="16" />
    <rule from="4000" to="5999" action="release" announcement="ann2" />
</global>

This configuration would parse Diameter answers with the following behaviour when handling CAMEL/INAP calls:

If the Diameter Result-Code value 4011 (DIAMETER_CREDIT_CONTROL_NOT_APPLICABLE) is returned, allow the call to continue without monitoring or rating.
If the Diameter Result-Code value 4012 (DIAMETER_CREDIT_LIMIT_REACHED) is returned prior to final interrogation, the announcement ann1, then release the call with the default release cause.
If the Diameter Result-Code value 4012 is returned at final interrogation, release the call with release cause 16 and mark the EDR as a billing failure.
If the Diameter Result-Code value returned is for a transient (4xxx) or permanent error (5xxx), play announcement 2, then release the call with the default release cause.
For all other Diameter Result-Code values, apply default Result-Code rule handling.
Read the value of the Cost-Information → Unit-Value → Value-Digits and Exponent AVPs and write them to the rule engine variables cost_value and cost_exp respectively.

Result-Code Rules

Result-Code rules are described elsewhere as a special case of N2IWF action rules.

Read AVPs

The LogicApp global variable READ_AVPS holds additional AVP definitions that are read from the Diameter response.

This global is an array of AVPs, with each avp definition containing either a source value or other avp definitions.

If a defined AVP (or a parent of a defined AVP) is not sent by the OCS, AVP parsing will not occur.

Note that all AVPs listed for parsing must exist in the N2SVCD Diameter codec or be specified in the Diameter application as custom AVPs.

In addition to the standard IWF selector rule extensions, each avp definition supports additional parameters:

Parameter	Type	Description
`name`	String	[Required] The AVP name for this definition. This name must be present in the default N2SVCD Diameter codec or configured as a custom AVP in the Diameter application.
`edr`	String	If provided, the AVP’s populated value will be written to EDRs produced in the field named. EDR population is influenced by the `repeat` and `persist` parameters if `to_var` is also present.
`to_var`	String	If provided, the AVP’s populated value will be written to the rule engine variable named. Variable population is influenced by the `repeat` parameter.
`to_bal_units`	String	If provided, the AVP’s populated value will be treated as the unit value for the balance named. This value will be modified by the balance exponent. Only one of `to_bal_units`, `to_bal_exponent`, and `to_bal_currency` may be specified for a single AVP. (Default = `0`)
`to_bal_exponent`	String	If provided, the AVP’s populated value will be treated as the exponent of the unit value for the balance named. Only one of `to_bal_units`, `to_bal_exponent`, and `to_bal_currency` may be specified for a single AVP. (Default = `0`, no modification of unit value)
`to_bal_currency`	String	If provided, the AVP’s populated value will be treated as the currency lookup value for the balance named. Only one of `to_bal_units`, `to_bal_exponent`, and `to_bal_currency` may be specified for a single AVP. (Default = no currency translation)
`repeat`	String	Control the recording of each incidence via `to_var` and `edr` of the AVP being encountered in a single response. Possible values are: `overwrite`: replace any existing value with the latest version `append`: write the first instance of the AVP as normal and write any subsequent instances separated by a comma. `index`: write each instance of the AVP separately with the name of the storage location followed by the instance number. For example, with `to_var` set to `foo`, the AVPs encountered would be written to `foo1`, `foo2`, etc. Note that this same numbering scheme applies even when the AVP is not repeated. (Default = `repeat`)
`persist`	Boolean	Controls the behaviour of the `to_var` parameter if this AVP is not present or does not have a value in a response. When set to `true`, the rule engine variable will always be set to the last received value of this AVP. If set to `false`, the named variable will be removed if the AVP value is not present. Does not modify EDR storage - each DIAMETER or DIAMETER-A EDR will only write the AVP values received for a single response. (Default: `true`)
`value`	Array	Holds the child AVPs to parse for Grouped AVPs. Note that this must specifically be marked as `type="array"` in order to be correctly processed as a complex global.

Note that specifying the repeat or persist parameters on a Grouped AVP will cause that behaviour to be applied to all children of that AVP unless specified again against a leaf AVP (in which case the re-specified value will be used for that AVP only) or against a grouped AVP (in which case the re-specified value will be used for all children unless re-re-specified, and so forth).

At least one of to_var, edr, to_bal_units, to_bal_currency, or to_bal_exponent must be present for AVPs that are not Grouped.

Balance Variables

When reading AVP values, the to_bal_* directives may be used to create an internal representation of balance information provided. These balances may be populated dynamically into notifications.

Balance information returned from the OCS may populate any or all of:

The balance units, representing the integer amount of the balance. If not present, will default to zero.
The balance unit exponent, representing the shifting of the decimal point for presentation of the balance units. If not present, will default to zero.
The balance currency, specifying the type of balance represented.

Balance information is cleared prior to every request to the OCS.

If balance target name information is repeated within a single response, the balance units will be summed. Note that only the first balance currency will apply to the entire balance.

Balance units and exponents are paired via a depth-first traversal of the AVP structure. If balance target name information is repeated, ensure the returned AVP structure aligns the order of units and exponents accordingly.

Balance Currencies

For currency translation, the CURRENCIES LogicApp service global variable array may be configured to provide a list of translations from the OCS-provided value to the external representation, e.g.:

<global name="CURRENCIES" type="array">
  <currency from="554" to="$"/> <!-- ISO 4217 USD -->
  <currency from="9997" to="minutes"/> <!-- custom code for non-cash type -->
</global>

Each currency can support the following parameters:

Attribute	Type	Description
`from`	String	[Required] The unique value provided by the OCS for balances using this currency.
`to`	String	[Required] The display value to use for this currency within notifications.