1. Configuration Guide
  2. External Policy Servers
  3. Network Provided Location Information
  4. NPLI Implementation
  5. NPLI Support for 5G NR
  6. 5G NPLI Operation

5G NPLI Operation

When the SBC receives a SIP message with a PANI header that has its access-class set to 3GPP-NR, 3GPP-NR-FDD or 3GPP-NR-TDD, it recognizes and treats the header as a 5G supported PANI header. Behavior, timing and header population of the SBC refer to the same configurations it uses to handle PANI prior to 5G. When working from information presented over diameter, the SBC continues to build the PANI based on information received over the Rx interface.Having received 5G location information from the PCRF, the SBC processes and populates the outgoing PANI header with the appropriate information, based on configuration. The provider can then use this location information for purposes including Charging, Emergency Call Routing, and so forth.

As soon as it receives the initial SIP message, the SBC sends a request for location information to the PCF/PCRF by sending an AAR with the Required-Access-Info AVP set to the value LOCATION(0) and the Specific-Action AVP set to the value ACCESS_NETWORK_INFO_REPORT(12). After performing this Rx dip, the SBC builds the 5G NPLI string for the SIP PANI header using 5G values received within the RAR from the PCF/PCRF in the following AVPs:

  • RAT-Type—Builds the access-class using the RAT type received in the RAT-Type AVP
  • IP-CAN-Type—3GPP-5GS
  • 3GPP-User-Location-Info—The SBC builds the "utran-cell-id-3gpp" parameter for SIP PANI header (for 5G) is encoded as per Section 7.2A.4.3, points 22/22A of 3GPP TS 24.229 v16.4.0. It is a concatenation of:
    • MCC (3 decimal digits)
    • MNC (2 or 3 decimal digits depending on MCC value)
    • Tracking Area Code (6 hexadecimal digits) as described in 3GPP TS 23.003
    • The NR Cell Identity (NCI) (9 hexadecimal digits)

Note:

Be sure to configure the applicable default-location-string with a valid 5G value. The SBC does not validate this string.
When creating a SIP PANI header for 5G, the SBC follows the 3GPP-specific extended syntax of the PANI header field per 3GPP TS 24.229 v16.8.0, RFC 7315 and RFC 7913. The SBC restricts its changes to the header to the following fields: 
<access-class>;<access-info>=<location>;<np>
  • access-class = “3GPP-NR”—Set based on RAT type received in Diameter RAT-Type AVP
  • access-info = utran-cell-id-3gpp—If the access-class is “3GPP-NR” and the 3GPP-User-Location-Info contains “137 – 5GS TAI and NCGI”, then the SBC sets the utran-cell-id-3gpp to "MCC+MNC+TAC+NCI"
  • np = “network-provided” (if applicable)