Section: 5.3.3.1A Tracking Area Update procedure with Serving GW change and data forwarding
Content: Figure 5.3.3.1A-1: Tracking Area Update procedure with Serving GW change and data forwarding NOTE 1: The procedure steps (A) and (B) are defined in clause 5.3.3.1. Step 5 in the figure above has compared to clause 5.3.3.1 one additional parameter which is described below. 4. The timer setting by the old S4 SGSN or MME in step 4 (as in clause 5.3.3.1) shall ensure that the buffered data in the old Serving GW can be forwarded before the old Serving GW resource is released. 5. DL data is being buffered in the old Serving GW and the DL Data Expiration Time has not expired, therefore the old MME/old S4-SGSN indicates Buffered DL Data Waiting in the Context Response. This triggers the new MME to setup the user plane and invoke data forwarding. For Control Plane CIoT EPS Optimisation, if the DL data is buffered in the old Serving GW, and when the Buffered DL Data Waiting is indicated, the new MME shall setup the S11 user plane with the new Serving GW and invoke data forwarding. If the DL data is buffered in the old MME and the DL Data Expiration Time has not expired, the old MME shall discard the buffered DL data. 11-12. The user plane is setup. These procedure steps are defined in clause 5.3.4.1, steps 4-7 and steps 8-12 respectively in the UE Triggered Service Request procedure. NOTE 2: It is assumed that Pause of PGW Charging is not invoked by SGW that is performing extended data buffering. For Control Plane CIoT EPS Optimisation, steps 11 and 12 are skipped. 13. Since it was indicated in step 5 that buffered DL data is waiting, the new MME sets up forwarding parameters by sending Create Indirect Data Forwarding Tunnel Request (target eNodeB addresses and TEIDs for forwarding) to the Serving GW. The Serving GW sends a Create Indirect Data Forwarding Tunnel Response (target Serving GW addresses and TEIDs for forwarding) to the target MME. For Control Plane CIoT EPS Optimisation, the new MME sets up forwarding parameters by sending Create Indirect Data Forwarding Tunnel Request (target MME address and TEID for forwarding) to the Serving GW. Upon receipt of the Create Indirect Data Forwarding Tunnel Response message the new MME starts a timer for release of resources if resources for indirect forwarding were allocated in the new S-GW. Indirect forwarding may be performed via a Serving GW which is different from the Serving GW used as the anchor point for the UE. 14. This procedure step is defined in clause 5.3.3.1, step 7. In addition the new MME includes the F-TEID where buffered DL data should be forwarded and a Forwarding indication in the Context Acknowledge message. The F-TEID is the F-TEID for the indirect forwarding received from step 13 or it may be the F-TEID of the eNodeB (when eNodeB supports forwarding). 15. A Modify Bearer Request( F-TEID ) is sent to the old Serving GW. The F-TEID is the Forwarding F-TEID where the buffered DL data shall be forwarded. 16. The old Serving GW forwards its buffered data towards the received F-TEID in step 15. The buffered DL data is sent to the UE over the radio bearers established in step 11. For Control Plane CIoT EPS Optimisation, the buffered DL data is sent to the new MME from the new Serving GW and is sent to the UE as described in steps 12-14 of clause 5.3.4B.3. 17-18. As steps 15-16, 18-19 in clause 5.3.3.1. 19. If indirect forwarding was used, then the expiry of the timer at the new MME started at step 13 triggers the new MME to send a Delete Indirect Data Forwarding Tunnel Request message to the new S-GW to release temporary resources used for indirect forwarding that were allocated at step 13.