Section: 4.11.0a.8 5GC NAS capability (re-)enabled and disabled
Content: When 5G NAS (i.e. N1 mode) capability is (re-)enabled, the UE triggers Tracking Area Update procedure as specified in clause 5.3.3.0 of TS 23.401[ General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access ]  [13]. If the MME determines that interworking with 5GS is changed to Supported and if the MME has selected a standalone PGW, the MME may initiate PDN disconnection with reactivation required as specified in clause 5.10.3 of TS 23.401[ General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access ]  [13] at the end of the tracking area update procedure. NOTE 1: MME requesting PDN disconnection with reactivation required is to allow MME to select a SMF+PGW-C so that session continuity can be achieved when UE moves to 5GS. If a UE disables its support of N1 mode and moves from 5GS to EPS, the UE and the SMF+PGW-C maintain the mapped 5GS parameters for PDU session(s) that are transferred to EPS. NOTE 2: The mapped 5GS parameters are used when the UE re-enables N1 mode and moves back to 5GS.