1. Configuration Guide
  2. External Policy Servers
  3. Network Provided Location Information
  4. NPLI Implementation
  5. Optimizing Location Information Handling

Optimizing Location Information Handling

The Oracle Communications Session Border Controller (SBC) can perform procedures to identify and manage location over the Rx interface using AAR/AAA transactions with the ext-policy-server. The standard behavior is to issue the AAR after the 200 OK for every register and other SIP messages. The standard SBC behavior also includes sending the Required-Access-Info AVP and a Specific-Action-AVP with a value of ACCESS_NETWORK_INFO_REPORT for every AAR. You can configure the SBC to limit (optimize) the number of times it sends these AVPs and set timers to control when it sends responses to the initial INVITE are sent. This configuration limits the number of times the SBC sends a PANI to the core to once per session and changes the hold timer to start on receipt of the AAA instead of the INVITE.

The SBC issues AARs for a variety of reasons, and includes the AVPs mentioned above when you set the applicable ext-policy-server, specificActionSubscription parameter to access-network-info-report. To implement this optimization, you enable the location-optimization-on-aar option on the applicable ext-policy-server. 

ORACLE(ext-policy-server)# +options location-optimization-on-aar

You can configure this option in conjunction with the start-hold-timer-event in the sip-config to refine when the system starts waiting for the expiry of the hold-emergency-calls-for-loc-info, hold-invite-calls-for-loc-info or msg-hold-for-loc-info timer, depending on the traffic type. During this hold, the system waits for NPLI information to arrive in the RAR. By default, the system begins this timer after it sends out an AAR. You can configure the system to start this timer after it receives the AAA.

Note:

If you turn on the option without changing the start-hold-timer-event parameter, the system provides a configuration verification notice telling you to set the start-hold-timer-event parameter to aaa. This option conflicts with the AAR setting.

This behavior affects SIP calls only, not impacting REGISTER or SMS sessions. It also requires the reserve-incomplete on the applicable ext-policy-server be set to orig-realm-only.

Operational detail includes:

  • When the SBC generates its first AAR for session initiation/establishment and inserts NPLI AVP's, depending on whether you have set the specific-action-subscription to access-network-info-report. This subscribes the to Network Provided Location Information (NPLI) changes.
  • Whenever the AAA includes the RAT-type as WLAN, the SBC uses the value configured in default-location-string-VoWifi from the applicable npli-profile. If default-location-string-VoWifi is empty, the default-location-string in the realm-config.
  • When this feature is enabled, the SBC feature check for NetLocAccess AVP of incoming AAA. If the value of this AVP is zero, the SBC does not start the hold timer even if it is configured and the NPLI feature is enabled.
  • Although the SBC stores the NPLI location when it comes in the AAA, if another location comes in a RAR, the SBC overwrites the saved location with the latest location received in the RAR.
  • If the UE is from a trusted realm, the SBC sends a PANI header to UE once.
  • The SBC implements a timer to determine when to issue these messages, depending on specific configuration and circumstances:
    • For terminating calls and when reserve-incomplete is set to orig-realm-only, and NPLI is enabled, the SBC holds the first a-sdp it finds, which could be provided by a 18x SIP reply with SDP or a 200 OK to the Invite, until the NPLI information is provided through a RAR or the timer expires.
    • For terminating calls and when reserve-incomplete is set to disabled (AAR on SDP answer), the SBC holds the first 18x response with SDP until NPLI is provided through a RAR or the timer expires.

Related Configuration

There are three timers related to NPLI optimization that you can configure on each applicable sip-interface or realm-config. The sip-interface configuration takes precedence:

  • hold-emergency-calls-for-loc-info
  • hold-invite-calls-for-loc-info
  • msg-hold-for-loc-info

If you have enabled asynchronous-mode on the applicable ext-policy-server, the SBC does not hold the INVITE even if hold timers are set, effectively disabling the feature.

The value configured for the sip-interface, npli-upon-register parameter takes precedence over the value configured in sip-config.

Rules for Issuing PANI

This table displays the matrix of different configuration and traffic combinations that result in the SBC issuing UE and Network PANI.

add-ue-location-in-pani allow-pani-for-trusted-only Is endpoint Trusted Req/Res has UE added PANI UE PANI has network-provided string RxDip Done Got Network Provided PANI from PCRF Manipulated PANI (np - network-provided)
Enabled Enabled No Yes Yes Yes Yes No PANI sent to UE
Enabled Enabled Yes Yes Yes Yes Yes UE-PANI (w/o np string),Network-PANI;network-provided
Enabled Disabled No Yes Yes Yes Yes UE-PANI (w/o np string),Network-PANI;network-provided
Disabled Enabled Yes Yes Yes Yes Yes Network-PANI;network-provided
Disabled Enabled No Yes Yes Yes Yes No PANI sent to UE
Disabled Disabled No Yes Yes Yes Yes Network-PANI;network-provided
Enabled Enabled Yes Yes Yes Yes No UE-PANI(w/o np string),default-PANI string(w/o np string)
Enabled Enabled No Yes Yes Yes No No PANI sent to UE
Enabled Enabled Yes No No Yes No Default-PANI string (w/o np string)
Enabled Enabled Yes Yes Yes No No UE-PANI(w/o np string) to core
Enabled Enabled Yes No No No No No PANI sent

Example Call Flows

When the SBC receives an INVITE for a mobile originating call, which originates from inside the core, it sends an AAR with the NPLI AVPs (and other AVPs) to the PCRF. When it receives the AAA, the SBC fetches and stores the IP-CAN and RAT type. The SBC then waits for the RAR, which usually includes the location information to be used for constructing the PANI header in the INVITE to the UAS. When the SBC receives the 200OK with the answer SDP, it sends another AAR to the PCRF. This time, however, the AAR does not contain the NPLI AVPs. Similarly, when it receives a Re-Invite later, the SBC sends the AAR to the PCRF without the NPLI AVPs.

Note that the SBC sends the NPLIs AVP to the PRCF only once in this SIP session.

When the SBC receives an INVITE for a mobile terminating call, which originates from outside the core, it sends an AAR with the NPLI AVPs (and other AVPs) to PCRF. When it receives the AAA, the again SBC fetches and stores the IP-CAN and RAT type. When the RAR comes, the location is stored. When the SBC receives the 200OK with the answer SDP, it sends an AAR to the PCRF. This time, however, the AAR does not contain the NPLI AVPs. The SBC uses the stored location information for the PANI towards the core. Similarly when the SBC later receives a Re-Invite, it sends the AAR to the PCRF without the NPLI AVPs.

Again, the SBC sends the NPLIs AVP to the PRCF only once in this SIP session.