Section: 5.5.2 Inter RAT handover 5.5.2.0 General
Content: During Inter RAT handover indirect forwarding may apply for the downlink data forwarding performed as part of the handover. From its configuration data the MME knows whether indirect forwarding applies and it allocates a downlink data forwarding path on a Serving GWs for indirect forwarding. From its configuration data the S4 SGSN knows whether indirect forwarding applies and it allocates downlink data forwarding paths on Serving GWs for indirect forwarding. It is configured on MME and S4 SGSN whether indirect downlink data forwarding does not apply, applies always or applies only for inter PLMN inter RAT handovers. During the handover procedure, the source MME shall reject any PDN GW initiated EPS bearer(s) request received since handover procedure started and shall include an indication that the request has been temporarily rejected due to handover procedure in progress. The rejection is forwarded by the Serving GW to the PDN GW, with the indication that the request has been temporarily rejected. Upon reception of a rejection for an EPS bearer(s) PDN GW initiated procedure with an indication that the request has been temporarily rejected due to handover procedure in progress, the PDN GW behaves as specified in clause 5.5.1.2.1. For inter-PLMN handover to a CSG cell, if the source MME/S4-SGSN has the CSG-ID list of the target PLMN, the source MME/S4-SGSN shall use it to validate the CSG membership of the UE in the target CSG cell. Otherwise, based on operator's configuration the source MME/S4-SGSN may allow the handover by validating the CSG membership of the UE in the target CSG cell using the CSG-ID list of the registered PLMN-ID. If neither the CSG-ID list of the target PLMN nor the operator's configuration permits the handover, the source MME/S4-SGSN shall reject the handover due to no CSG membership information of the target PLMN-ID NOTE 1: Inter-PLMN handover to a CSG cell in a PLMN which is not an equivalent PLMN for the UE is not supported. NOTE 2: Inter-PLMN handover to a CSG cell of an equivalent PLMN is only supported if the CSG-ID of the cell is in the CSG-ID list of both equivalent PLMNs. NOTE 3: Upon bearer loss or UE-detected bearer QoS degradation during inter-RAT 3GPP handover, after receiving the Handover Command the UE can adopt an implementation dependent mechanism to trigger the handover of one or more PDN connections or mobility of one or more IP flows to WLAN (e.g. taking into account policies obtained from ANDSF).