Abstract: A wireless communication network handles Session Management Function (SMF) outage in a Tracking Area (TA). An external SMF that is outside the TA registers with an internal Network Repository Function (NRF) that is inside in the TA. The internal NRF detects the SMF outage for an internal SMF inside the TA. The internal NRF receives an SMF request from an internal Access and Mobility Management Function (AMF) inside the TA. In response to the SMF outage, the internal NRF transfers an SMF response to the internal AMF that indicates the external SMF. The external SMF receives network signaling from the internal AMF and responsively directs an external User Plane Function (UPF) that is outside the TA to exchange user data with internal wireless access nodes that are inside the TA.