16.9 UE/TWAN Initiated PDN disconnection for Multi-connection Mode

23.4023GPPArchitecture enhancements for non-3GPP accessesRelease 18TS

16.9.1 Supporting GTP S2a

Figure 16.9.1-1: UE/TWAN requested PDN disconnection procedure in WLAN on GTP S2a for Multi-Connection Mode

This procedure applies to the Non-Roaming, Roaming with home routed and romaing with local breakout. In the Local Breakout case, the vPCRF forwards messages between the PDN GW and the hPCRF. In the LBO cases, the 3GPP AAA Proxy serves as an intermediary between the Trusted WLAN Access and the 3GPP AAA Server in the HPLMN. In the non-roaming and Home Routed Roaming case, the vPCRF is not involved at all.

If dynamic policy provisioning is not deployed, the optional steps of interaction between the PDN GW and PCRF do not occur.

1. If the PDN disconnection is initiated by the UE, the UE sends a WLCP PDN Disconnection Request containing a PDN Connection ID to the TWAG.

2-5. Steps 2-5 are the same as steps 2-5 in clause 16.3.1.1.

6. If the PDN disconnection was initiated by the UE in step 1, then the UE is informed of the disconnection by means of a WLCP PDN Disconnection Response.

7. If the PDN disconnection was initiated by the TWAG, then the UE is informed of the disconnection by means of a WLCP PDN Disconnection Request containing the PDN Connection ID.

NOTE 1: Steps 2-5 and Steps 7-8 may occur in parallel.

8. The UE acknowledges the disconnection request received in step 7.

9. The TWAN specific reousces belonging to the PDN connection are released with a method which is out of 3GPP scope.

NOTE 2: Either step 1 and 6, or step 7 and 8, are performed

16.9.2 Supporting PMIP S2a

Figure 16.9.2-1: UE/TWAN requested PDN disconnection in WLAN on PMIP S2a for Multi-connection Mode

The procedure is similar to GTP based S2a call flows in clause 16.9.1 with the following differences:

– Step 2 is a Proxy Binding Update (lifetime=0) for the PDN connection to be deleted sent by TWAN to the PDN GW. The details of the Proxy Binding Update message are described in step3 in clause 6.4.1.1. Additionally, the Proxy Binding Update includes the current TWAN Identifier as described in clause 16.1.7, the Timestamp of this TWAN-Identifier and the UE Time Zone.

– Step 5 is a Proxy Binding Acknowledgement sent by the PDN GW to TWAN. The details of the Proxy Binding Acknowledgement message are described in step6 in clause 6.4.1.1.