NPLI Emergency Call Processing

Currently, when the P-CSCF sends AAR requests to the PCRF for an emergency call, the P-CSCF does not wait for the response (AAA) to forward the INVITE to the core. Instead, it forwards the INVITE as soon as it sends the AAR to the PCRF. Even if the subsequent AAA reports a failure response, the P-CSCF ignores the failure and allows emergency call processing.

Recent requirements issued by Bundesnetzagentur (BNetzA), the German telecom regulator, affect the processing of emergency calls originated by mobile handsets. The German requirements mandate that INVITES for establishment of emergency calls, be buffered, for some specified period of time, pending receipt of NPLI from the PCRF. If the PCRF fails to provide NPLI within that time period, the P-CSCF forwards the emergency INVITE to the network core with a PANI header populated with both the default-location-str value (if configured) and with any UE-provided location information (if available, and if configured to do so). If location information is unavailable, the P-CSCF forwards the INVITE without a PANI header.

Use the following procedure to configure a hold-timer that specifies the time (in seconds) that emergency INVITES are buffered while waiting for NPLI from the PCRF. Such a timer ensures compliance with BNetzA regulations. Users who are not subject to BNetzA authority can choose to implement a minimum timer value, which provides the network some period of time to report possibly more accurate location information.