This section describes how Diameter Request and Answer messages are routed to the PCA application.
Requests
Diameter Routing for Requests checks three conditions to determine whether to route a Request to a DSR Application:
- Does the request include a DSR-Application-Invoked AVP, indicating that the request has already been processed and should not be processed again by a DSR application?
If this AVP is present, the request will not be routed to any DSR application. Otherwise the next condition is checked.
- Does the request match a rule in the Application Routing Table (ART)?
If no rule is matched, the request is not routed to any DSR application. Otherwise the next condition is checked.
- If the request matches an ART rule, is the application operational status for this DA-MP server set to Available?
If the DSR Application is not Available, then the “Unavailability action” is performed by Diameter. For PCA, the Unavailability action for Request is "Reject", which means PCA reject the Diameter Request messages by generating and sending an Answer message with a failure response with Result-Code AVP set to value configured for the error condition "PCA Unavailable or Degraded".
If the DSR Application is Available, then Diameter routes the Request to the DSR Application specified in the matching Application Routing Rule.
Ingress Requests are examined by Diameter to determine whether they should be routed to a DSR Application. The rules for deciding how to route ingress requests are defined in an Application Routing Table, or ART.
Table 1 describes the expected configuration of Application Routing Rules for PCA. These rules will cause every Request that includes one of these values in the Application-Id in the Diameter Header to be routed to the PCA application. Some of these rules can be omitted, depending on which interfaces are used for PCA.
- The Rule Name can be any name that is chosen to identify the rule.
- The Priority is a value from 1 to 99 where 1 is the highest priority. Rules with higher priority will be evaluated for matching before rules with lower priority. Rules that overlap (i.e. one rule is more specific than another) should use the priority field remove ambiguity about which should be chosen. ART processing does not support "best match" semantics. Priority in an ART rule is an important factor to support DSR Applications interworking.
- Conditions can include Destination-Realm, Destination-Host, Application-Id, Command Code, Origin-Realm, and Origin-Host. If more than one condition is specified, the conditions are logically ANDed together to determine if a rule is matched.
- The Application Name will always be PCA for the Policy and Charging application. PCA will show up in the Application Name drop-down only if the PCA application has been activated
P-DRA Application Routing Table Configuration | Rule Name |
Priority |
Conditions |
Application Name |
| PcaGxRule |
5 |
AppId Equal 16777238 - 3GPP Gx |
PCA |
| PcaGxxRule |
5 |
AppId Equal 16777266 - 3GPP Gxx |
PCA |
| PcaRxRule |
5 |
AppId Equal 16777236 - 3GPP Rx |
PCA |
| PcaGxPRule |
5 |
AppId Equal 16777238 - 3GPP Gx-Prime |
PCA |
| PcaS9Rule |
5 |
AppId Equal 16777267 - 3GPP S9 |
PCA |
| PcaRoGyRule |
5 |
AppId Equal 4 - 3GPP |
PCA |
Answers
Diameter Answers, to which the related Diameter requests have been processed successfully by PCA, will be forwarded to PCA application for processing.
If PCA has requested to receive an answer, but the PCA has an operational status of "If PCA becomes Unavailable when an Answer" is received, the answer message will be relayed directly to the remote peer.
Note: Relaying an answer while the PCA application is unavailable may result in exposing a PCRF name that was supposed to be topology hidden for the P-DRA function
Note: All the Online Charging answer messages are always processed by the Online Charging DRA.