Section: 4.11.1.5.3 Tracking Area Update
Content: The following changes are applied to clause 5.3.3.1 (Tracking area update procedure with Serving GW change) in TS 23.401[ General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access ]  [13]: - Step 2: The UE shall in Access Stratum signalling include GUMMEI that is mapped from 5G-GUTI following the mapping rules specified in TS 23.501[ System architecture for the 5G System (5GS) ]  [2] and the UE indicates it as a native GUMMEI and should in addition indicate it as "Mapped from 5G-GUTI". The UE shall, in the TAU request message, include EPS GUTI that is mapped from 5G-GUTI following the mapping rules specified in TS 23.501[ System architecture for the 5G System (5GS) ]  [2]. The UE indicates that it is moving from 5GC. The UE integrity protects the TAU request message using the 5G security context. If the UE supports any of the CIoT 5GS Optimisations included in 5GC Preferred Network Behaviour, then the UE shall include its 5GC Preferred Network Behaviour if it included its EPC Preferred Network Behaviour in the TAU request. MME may steer the UE from EPC by rejecting the TAU request with an appropriate cause value. The MME should take into account availability of 5GC to the UE and the Preferred and Supported Network Behaviour (see clause 5.31.2 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2]) before steering the UE from EPC. - Step 5 and message Context Response may include new information Return preferred. Return preferred is an indication by the AMF of a preferred return of the UE to the last used 5GS PLMN at a later access change to a 5GS shared network. RFSP in Use Validity Time is provided by the AMF to the MME if the AMF selects the RFSP Index in use identical to the authorized RFSP Index as specified in clause 5.4.3.4 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2] and validity time is received from PCF as specified in clause 4.16.2.2 and in clause 6.1.2.1 of TS 23.503[ Policy and charging control framework for the 5G System (5GS); Stage 2 ]  [20]. The MME handles RFSP Index as specified in clause 4.11.1.5.8. The MME may store the last used 5GS PLMN ID in UE's MM Context. The MME may provide E-UTRAN with a Handover Restriction List taking into account the last used 5GS PLMN ID and the Return Preferred indication. The Handover Restriction List contains a list of PLMN IDs as specified by TS 23.251[ Network sharing; Architecture and functional description ]  [35]. - Step 9a IP-CAN Session Modification procedure: It is replaced by SM Policy Association Modification as specified in clause 4.16.5. - Step 13 and HSS use of Cancel Location The HSS/UDM de-registers any old AMF node by sending an Nudm_UECM_DeregistrationNotification service operation to the registered AMF for 3GPP access. The registered AMF for 3GPP access initiates AM Policy Association Termination procedure as defined in clause 4.16.3.2 and UE Policy Association Termination procedure as defined in clause 4.16.13.1. - Step 17: If the DNN and SMF+PGW-C FQDN for S5/S8 interface association exist, the HSS/UDM sends APN mapped form DNN and SMF+PGW-C FQDN for S5/S8 to UE. - Step 20 and MME processing of the partial Tracking Area Update (TAU) procedure. The MME may use an indication Return preferred from Context Response at step 6 when deciding the PLMN list content. The MME may provide the eNodeB with a PLMN list. The Handover Restriction List contains a list of PLMN IDs as specified by TS 23.501[ System architecture for the 5G System (5GS) ]  [2].