Selective INVITE Holding for NPLI

When configured to use external policy servers, the Oracle Communications Session Border Controller allows the user to manage INVITE forwarding behavior based on preferences for inclusion of NPLI information. This forwarding behavior differs, depending on whether or not the call is an emergency call. The system also refers to external policy server, sip-interface and sip-config configuration to further specify when it forwards applicable INVITEs.

By default, the Oracle Communications Session Border Controller holds non-emergency calls until an AAR/AAA transaction is complete, but does not wait for this exchange before forwarding emergency calls. These AAR/AAA transactions may or may not provide NPLI information. If not, the system may forward the INVITE using location information that comes from sources other than the network. As the call proceeds, the system may also correct and/or update location information with NPLI from subsequent SDP and Re-Authentication Request (RAR) transactions.

The system uses the parameters below to specify location information in addition to or as alternatives to NPLI:

When enabled, the sip-config's include-ue-loc-info instructs the system to use location information provided by the endpoint as an additional PANI location header. In this case, the system always waits for the AAA before forwarding the INVITE.
The sip-interface's default-location-str parameter allows the user to configure a default location string, which the system can use if, for example, it is not provided by any other means.

To further manage this INVITE holding, the user configures sip-config timers to wait for AAR/AAA transactions, including:

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

When set, these timers modify system behavior as follows:

For non-emergency INVITEs, the system sends AAR requests and waits for the AAA response.
- If NPLI is in the AAA, The system forward the INVITE using that NPLI.
- If the AAA does not include NPLI, the system continues to holds the INVITE waiting for a RAR.
- If the hold-invite-calls-for-loc-info timer expires and the system has still not received location information, it forwards the INVITE with PANI headers populated with either or both the default-location-str value and the location provided by the UE.
- If the system later receives a RAR with NPLI, it sends subsequent messages using that information.
For emergency INVITEs, the system sends AAR requests and waits for the AAA response.
- If NPLI is in the AAA, The system forward the INVITE using that NPLI.
- If the AAA does not include NPLI, the system continues to holds the INVITE waiting for a RAR.
- If the hold-emergency-calls-for-loc-info timer expires and the system has still not received location information, it forwards the INVITE with PANI headers populated with either or both the default-location-str value and the location provided by the UE.
- If the system later receives a RAR with NPLI, it sends subsequent messages using that information.

There are two situations that cause the system to ignore these timers:

If the PCRF configuration has reserve-incomplete=disabled, the system skips the AAR request. The system ignores the timer and sends the INVITE out with the default location string, if configured.
If the initial INVITE arrives with no SDP, the system does not send out an AAR. The system ignores the timer and sends the INVITE out with the default location string, if configured.

The user can also configure the sip-config's hold-invite-calls-for-aaa option to further refine the system's behavior. This option's syntax, set to wifi, is shown below:

(sip-config)# options +hold-invite-calls-for-aaa=emergency
(sip-config)# options +hold-invite-calls-for-aaa=wifi

The hold-invite-calls-for-aaa option functions as follows:

If set to wifi, the system sends an AAR when it receives an initial INVITE. This is true for both emergency and non-emergency calls. If the AAA response has its Radio Access Technology (RAT) type set to WLAN, the system forwards the INVITE with the default-location-str value as NPLI. The system would also do this for Re-Invite, UPDATE, PRACK messages. If the RAT type is not set to WLAN, the system uses the NPLI in the AAA.
If set to emergency, the system sends an AAR when it receives an initial INVITE. The system does not forward the INVITE until it receives an AAA response from the PCRF. If the AAA includes a RAT type set to WLAN, the system forwards the INVITE only with the default-location-str value as NPLI.

The wifi and emergency parameters are exclusive; only one value can be set.