This procedure depicted in Figure 16.4.1-1
can be used to deactivate an S2a dedicated bearer or deactivate all S2a bearers belonging to a PDN address, for e.g., due to IP CAN session modification requests from the PCRF. If the default S2a bearer belonging to a PDN connection is deactivated, the PDN-GW deactivates all S2a bearers belonging to the PDN connection.
This procedure applies to the Non-Roaming, Roaming and Local Breakout cases. In the Local Breakout case, the vPCRF forwards messages between the PDN-GW and the hPCRF. In the non-roaming and home routed roaming cases, the vPCRF is not involved at all.
The optional interaction steps between the PDN-GW and the PCRF in the procedures in Figure 16.4.1-1
only occur if dynamic policy provisioning is deployed. Otherwise policy may be statically configured within the PDN-GW.
If dynamic PCC is deployed, the PDN-GW initiated Bearer Deactivation procedure may for example be triggered due to 'IP CAN session Modification procedure', as defined in TS 23.203
. In this case, the resources associated with the PDN connection in the PDN-GW are released. If requested by the Application Function (e.g. P-CSCF), the PCRF may also include a request to provide the User Location Info and/or the Time zone to the PDN-GW.
The PDN-GW sends a Delete Bearer Request message (EPS Bearer Identity, Cause) to the TWAN. This message can include an indication that all bearers belonging to that PDN connection shall be released.
Steps 3-4 only apply in multi-connection mode:
In multi-connection mode, if all bearers belonging to a PDN connection are released, then the UE is informed of the PDN connection release by means of a WLCP PDN Disconnection Request (PDN Connection ID).
The UE acknowledges the disconnection request.
In multi-connection mode, if a dedicated bearer is marked for deletion in step 2 and multiple WLCP bearers are used, the TWAN sends a WLCP Bearer Delete message with a list of bearer identities to be deleted. The UE acknowledges the Bearer Delete Request.
If supported by the TWAN, the TWAN specific resources may be released in the TWAN. The details of this step are out of the scope of 3GPP.
The TWAN deletes the bearer contexts related to the Delete Bearer Request, and acknowledges the bearer deactivation to the PDN-GW by sending a Delete Bearer Response (EPS Bearer Identity) message. Additionally, the Delete Bearer Response includes the TWAN Identifier as described in clause 16.1.7
, the Timestamp of this TWAN-Identifier and the UE Time Zone.
In the case where the resources corresponding to the PDN connection are released in PDN-GW, the PDN-GW informs the 3GPP AAA Server/HSS of the PDN disconnection.
8. The PDN-GW deletes the bearer context related to the deactivated S2a bearer. If the dedicated bearer deactivation procedure was triggered by receiving a PCC decision message from the PCRF, the PDN-GW indicates to the PCRF whether the requested PCC decision was successfully enforced by completing the PCRF-initiated IP CAN Session Modification procedure or the PCEF initiated IP-CAN Session Modification procedure as defined in TS 23.203
, proceeding after the completion of IP CAN bearer signalling. If requested by the PCRF in step 1, the PDN-GW provides the User Location Information, that contains the TWAN Identifier and/or UE Time Zone that will be forwarded to the Application Function as defined in TS 23.203
The procedure is similar to GTP based S2a call flows in clause 16.4.1
when the resources corresponding to the PDN connection is released, with the following differences:
Step 2 is a Binding Revocation Request. The details of the Binding Revocation message are described in step 2 in clause 6.12.1.
Step 6 is a Binding Revocation Acknowledgement. The details of the Binding Revocation Acknowledgement message are described in step 5 in clause 6.12.1. Additionally, the Binding Revocation Acknowledgement includes the current TWAN Identifier as described in clause 16.1.7, the Timestamp of this TWAN-Identifier and the UE Time Zone.