Section: 4.11.1.3.2A 5GS to EPS Idle mode mobility using N26 interface with data forwarding
Content: Figure 4.11.1.3.2A-1 describes the idle mode mobility registration procedure from 5GS to EPS when N26 is supported with data forwarding. Figure 4.11.1.3.2A-1: 5GS to EPS Idle mode mobility using N26 interface with data forwarding 1. Steps 1-7 from clause 4.11.1.3.2 with the following enhancements: - The (V-)SMF includes the Buffered DL Data Waiting indication in the Nsmf_PDUSession_Response in step 5c of figure 4.11.1.3.2-1, if the Extended buffering timer is running in (V-)SMF. - The AMF forwards the Buffered DL Data Waiting indication to MME in step 6 of figure 4.11.1.3.2-1, if it's received from SMF above. 2. Steps 7-9 from clause 5.3.3.1A of TS 23.401[ General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access ]  [13]. 3. Steps 14, 15, 15a and 16 from clause 4.11.1.3.2. 4. Steps 10-14 from clause 5.3.3.1A of TS 23.401[ General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access ]  [13]. 5. Steps 10a, b, c from clause 4.11.1.2.1 with the following enhancements: - If data forwarding tunnel information (i.e. Forwarding F-TEID) is received from MME in step 14 of figure 5.3.3.1A-1 of TS 23.401[ General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access ]  [13] in step 4 above, the AMF provides the data forwarding tunnel info to (V-)SMF in Nsmf_PDUSession_UpdateSMContext Request. The (V-)SMF provides the data forwarding tunnel info to (V-)UPF if data is buffered in (V-)UPF. - The (V-)SMF and (V-)UPF forwards data using the provided SGW forwarding tunnel above. The (V-)SMF also initiates a timer to release the SM context or data forwarding tunnel of the PDU session. The data received by the Serving GW on the forwarding tunnel is forwarded on the (newly) established tunnel to eNB. 6. Step 15b from clause 4.11.1.3.2 with following enhancements: The (V-)SMF initiates the release of data forwarding tunnel after the timer in step 5 above is expired.