Section: 4.23.9.5 Simultaneous change of Branching Points or UL CLs controlled by different I-SMFs
Content: This clause describes simultaneous change of UL-CL/BP function and additional PSA, e.g. addition of a new UL CL/BP and PDU Session Anchor (i.e. PSA2) and release of the existing UL CL/BP and PDU Session Anchor (i.e. PSA0), with target UPF(s) and source UPF(s) are all controlled by different I-SMF(s). This procedure may be triggered after N2 handover or Xn based handover procedure. Figure 4.23.9.5-1: Simultaneous change of Branching Point or UL CL and additional PSA controlled by different I-SMFs 1. UE has established PDU Session with Source Branching Point or UL CL and Source UPF (PSA0) controlled by source I-SMF and Remote PSA. The UE has mobility with I-SMF change, e.g. handed over from a source RAN to a target RAN. After mobility, the path between Target I-UPF and Remote PSA (PSA1) has been established. 2. This step is the same as steps 2 in clause 4.23.9.3. 3. Same as in step 3 of Figure 4.23.9.4-1. 4. Same as in step 4 of Figure 4.23.9.4-1. 5. Same as in step 5 of Figure 4.23.9.4-1.. 6-8. These steps are the same as steps 4-6 in clause 4.23.9.3 with the following enhancement: In step 7, to support EAS session continuity upon UL CL relocation the SMF provides the target I-SMF with an indication that a N9 forwarding tunnel to support the EAS session continuity is required, UL traffic filter for N9 forwarding by the target UL CL and the value of the timer to detect the end of activity on the N9 forwarding tunnel to support the EAS session continuity. Based on the received information, the target I-SMF installs corresponding N4 rules in the target UL CL for forwarding of uplink traffics via the N9 forwarding tunnel. The time interval for User Plane inactivity report is also provisioned to UL CL per the timer value received from SMF. 9. Same as in step 9 of Figure 4.23.9.4-1. 10. This step is the same as step 9 in clause 4.23.9.3. The SMF triggers the procedure from step 11 onwards to support EAS session continuity upon UL CL relocation. 11. If N9 forwarding tunnel to support the EAS session continuity is required based on indication received from SMF in step 7, the target I-SMF request target UL CL to allocate N9 forwarding tunnel info via N4 session modification procedure. 12. The target I-SMF invokes Nsmf_PDUSession_UpdateSMContext Request (N9 forwarding tunnel required, target UL CL N9 forwarding tunnel info, value of the timer to detect the end of activity on the N9 forwarding tunnel to support the EAS session continuity) toward the source I-SMF. 13. The source I-SMF triggers N4 modification procedure to request the source UL CL to establish the N9 forwarding tunnel to support the EAS session continuity. The source I-SMF provides the target UL CL N9 forwarding tunnel info to the source UL CL and receives the source UL CL N9 forwarding tunnel info from the source UL CL. The source I-SMF configures the source UL CL to forward traffic received from source L-PSA related to that PDU session toward the target UL CL via the N9 forwarding tunnel. The source I-SMF configures a time interval for the source ULCL for the detection of no active traffic over the N9 forwarding tunnel, which is based on the value of the timer to detect the end of activity on the N9 forwarding tunnel to support the EAS session continuity as received from target I-SMF. After this step, the downlink data can be forwarded via N9 forwarding tunnel from the source L-PSA (PSA0). 14. The source I-SMF sends Nsmf_PDUSession_UpdateSMContext Response (source UL CL N9 forwarding to support the EAS session continuity tunnel info). 15. Based on the traffic filter information received from SMF at step 7 and source UL CL N9 forwarding tunnel to support the EAS session continuity info, the target I-SMF request the target UL CL to forward related UL traffic via N9 forwarding tunnel to support the EAS session continuity. The target I-SMF configures a time interval for the target ULCL for the detection of no active traffic over the N9 forwarding tunnel, which is based on the value of the timer to detect the end of activity on the N9 forwarding tunnel to support the EAS session continuity received from SMF. After this step, the uplink data can be forwarded via N9 forwarding tunnel toward the source L-PSA (PSA0). 16-17. Upon detection of no active traffic over the N9 forwarding tunnel to support the EAS session continuity, the source I-SMF releases via N4 the source UL-CL/BP The Source I-SMF also releases via N4 the PSA0 if PSA0 is not collocated with source UL CL/BP. 17a. The source I-SMF invokes Nsmf_PDUSession_Update Request to inform the SMF of the release of the resource in the UL CL/BP and the PSA0 for this PDU Session. 18. Upon detection of no active traffic over the N9 forwarding tunnel to support the EAS session continuity, the Target I-SMF releases the N9 forwarding tunnel in Target UL CL and remove the related filter.