PCA and Application Chaining

The PCA and RBAR chaining function provides the needed capability to enable operators to perform regionalized routing in such a way that a policy or charging server (for example, a PCRF or an OCS) will only serve the subscribers whose subscriber identities, for example, IMSIs or MSISDNs, are within the range of the IDs that has been assigned to this PCRF or OCS.

Some Diameter signaling networks may need to be segmented based on the ranges of the subscriber identities such as IMSI and MSISDN and associate the subscriber ID ranges to Diameter severs (such as HSS, OCS, or PCRF). With such a subscriber ID range <-> Diameter server mapping, a subscriber can be served by a pre-determined Diameter server or a group of servers such that all messages with this subscriber's ID (IMSI or MSISDN or both) will be routed to the pre-determined Diameter servers consequently. The routing based on the subscriber ID <-> Diameter server mapping is referred to as regionalized routing.

It may also be necessary to be able to bind a subscriber to a policy server (for example, PCRF) or correlate sessions such that all messages on behalf of the subscriber can be routed to the same PCRF regardless what the Diameter interfaces are used. DSR with Policy DRA functionality provides subscriber <-> PCRF binding capability. The same will occur for Online Charging DRA (OC-DRA) in the segmented network.

P-DRA may receive the incoming Diameter request messages over binding capable interfaces (for example, Gx and Gxx) or over binding dependent interfaces (for example, Rx and Gx-Prime). The RBAR and PCA application chaining function is applicable ONLY on binding capable interfaces for the P-DRA feature, and binding independent interface (Ro/Gy) for the OC-DRA feature, but NOT on binding dependent interfaces. Specifically, the Diameter request messages over binding dependent interfaces (Rx or Gx-Prime) intending for being processed by P-DRA should never be routed to RBAR for address resolution.

With respect to DSR application chaining, an accessing region is a DSR network segment where the DSR has a direct connection to a policy and charging client who initiates and sends a Diameter request directly to the DSR and a serving region is a DSR network segment where the PCA (either P-DRA or OC-DRA functionality) actually receives and processes the Diameter request message as forwarded by DRL. Accessing region and serving region are all relative concepts, which make sense only relevant to a specific policy and charging client and a specific DSR application (for example, PCA). A serving region can be an accessing region as well for a policy and online charging client and PCA application, for example, the DSR that receives a Diameter requests hosts the PCA that processes the Diameter requests.

Request messages over binding capable interfaces (Gx/Gxx) and binding independent interfaces (Gy/Ro) are subject to RBAR and PCA application chaining while request messages over binding dependent interfaces (Rx or Gx-Prime) are not. Consequently, the topology hiding for Rx or Gx-Prime session of a subscriber may be performed by a P-DRA/DSR that is different from the P-DRA/DSR that has created the binding for the subscriber.

For the P-DRA function, the different treatment of binding capable and binding dependent sessions in the regionalized routing situation results in different requirements for topology hiding configuration. The configuration for enabling/disabling topology hiding and for the scope of topology hiding will be done on the NOAM GUI, which allows the management of the topology hiding to be handled on the NOAM level for all the P-DRA/DSRs within the same NOAM network. While the policy clients that are subject to topology hiding handling are still be configured on the SOAM, the configured data on the SOAM and NOAM will be communicated to each other such that a complete list of policy clients from all SOAMs can be consolidated on the NOAM. The consolidated list of policy clients for topology hiding can then be replicated to each of the SOAMs.

Note:

For the OC-DRA function, topology hiding is not supported.