As per the current implementation, during an initial attach, P-GW selects Mobile Directory Number (MDN) or Mobile Station International Subscriber Directory Number (MSISDN) from the S6b interface. Later, when the call is handed off from P-GW to other services like eHRPD/trusted WiFi/untrusted WiFi or the handoff is done from these services to the P-GW, then the MDN/MSISDN is picked from the create session (CS) request and the S6b authorized MDN/MSISDN is lost. As a result, different values of MDN/MSISDN are sent in the Rf records. Since, typically, operators use MDN to charge subscribers, this results in revenue loss.
This feature retains the MDN/MSISDN value from the S6b interface or the CS request, during the initial attach and even during handoff between P-GW and eHRPD/ trusted WiFi/untrusted WiFi. The MDN/MSISDN value does not change in the call lifetime. As a result, all Rf records of a session have the same MDN/MSISDN values.
A new keyword retain-mdn has been added to the CLI command authorize-with-hss. This CLI command keyword, when configured, retains the MDN/MSISDN value. If the CLI command keyword is not configured, the MDN/MSISDN value is not received from the S6b interface. In this case, the MDN/MSISDN value received in the CS request is used.
This feature is not applicable to GnGp handoff.
Old Behavior: MSISDN value was overwritten during handoffs between P-GW and services like eHRPD/trusted/untrusted WiFi.
New Behavior: MSISDN value is retained during the lifetime of call, including handoffs between P-GW and services like eHRPD/trusted/untrusted WiFi.