nnection is determined based on the operator policy and is sent to the UE in the PCO together with a PLMN ID that the S-NSSAI relates to. X2 and S1-based handover for EPS. When the UE is attached to E-UTRAN, all handover procedures will result in SMF+PGW-C seeing only a Modify Bearer Request message from SGW for either location change and/or SGW change during handover. The following diagram denotes the detailed flow: Packet Core Procedures 4G Access Registration to 5GC SMF(+S5-C) UPF(+S5-U Create Session Request IMSI. ULI, Serving Network, RAT-Type=EUTRAN F-TEID=SGW Tunnel, APN, Pdn-Type, AMBR PCO With PDU Session ID, BearerContext with SGW-u Tunnel MSISDN UDM Selection (Local config/NRF) PUT/nudm-uecm/v1/imsi-$IMSI/registrations/smf-registrations/$PDN-SESSION-ID dnn.pduSessionId, pdwFqdn from configuration (gtp bind address if pgwFqdn not configured), plmnid,smfinstance 201 Created GET /nudm-sdm/v1/imsi-$IMSI/sm-data?dnn=$DNN&plmn-id =PLMN&supi=imsi-$IMS 200 OK (sessionManagementSubscriptionl POST nudm-sdm/v1/imsi-123456789012345/sdm -subscriptions callbackReference, dnn 201 Created PCF Selection (Local config/NRF) POST nudm-sdm/v1/imsi-123456789012345/sdm-subscriptions accessType, dnn notificationURI, pduSessionid, pduSessionType, ratType, SliceInfo, SUPI, subsDefQos from CSR, subsSessAmbr from CSR CHF discovery; Spending Limit Context Creation in CHF 201 Created PCC rules, session rules, QOS description Update PCF with allocated IP Address POST /nupcf-smpolicy/control/v1/sm-policies/imsi-$IMSI-SPDU-SESSION-ID/update ipAddress CHF Selection (Local config/NRF) POST Charging Data 201 Created Charging Data UPF Selection PFCP Session Establishment PFCP Session Establishment Response Map 5G Qos to 4G Qos Create Session Response PCO {SessAmbr, SNSSAI, QosRules}, PAA, F-TEID=GTPC Tunnel BearerContext {EBI, QOS, FTEID= GTPU-Tunnel, Charging-ID) Router Solicitation Router Advertisement SMF(+S5-C) UPF(+S5-U) Figure 7.11 - 4G initial attach with IWF (5G core) - part 2 IMS 5G PDU session establishment In this section, we h