NPLI Implementation

The Oracle Communications Session Border Controller provides for an explicit subscription to NPLI changes resulting in the dynamic update of NPLI.

This NPLI implementation triggered by an originating mobile device typically involves a message exchange similar to the following.

1. Upon receiving the initial INVITE from the mobile handset, the P-CSCF sends an AAR command to the PCRF via the Rx Interface. This AAR contains a Required-Access-Info AVP that requests user location reports as they become available to the PCRF.
2. The P-CSCF buffers the INVITE pending the receipt of an AAA command from the PCRF. The AAA contains a 3GPP-User-Location-Info AVP along with a RAT-Type AVP. Depending upon network design, the AAA may also contain a proprietary MSISDN AVP, although this is not usually the case.
3. Upon receiving the AAA, the P-CSCF, using values contained in the 3GPP-User-Location-Info attribute, and the RAT-Type attribute, adds an extended PANI header to the buffered INVITE. If an MSISDN is included within the AAA, the P-CSCF also adds a P-Subscription-MSISDN header to the buffered INVITE.
4. The P-CSCF caches received attribute values, and forwards the altered INVITE to the IMS core.
5. At any point during the call (from initial session establishment to session termination) the PCRF can send a Re-Auth Request (RAR) that contains updated NPLI conveyed by the 3GPP-User-Location-Info, RAT-Type, IP-CAN-Type, or MSISDN AVPs.
6. After receiving the RAR, the P-CSCF updates the cached attribute values.
7. All subsequent re-INVITES and UPDATES contain the PANI and P-Subscription-MSISDN headers populated with the most recent cache values.

The following call flow depicts a successful, mobile-originated call containing a Re-INVITE. NPLI updates are requested in the initial AAR (P-CSCF-to-PCRF). NPLI is first provided with the initial AAA (PCRF-to-P-CSCF). Updated NPLI is provided with the initial RAR (PCRF-to-P-CSCF). All requests/responses toward the IMS core contain the latest available NPLI.