This clause describes non-exhaustive examples of flows for handover between non-3GPP accesses connected to the EPC. The handover scenarios are based on the mechanisms defined in clause 8 of this document.

In this scenario, the session starts in (source) trusted non3GPP access using DSMIPv6 over S2c. The session hands over to another (target) trusted non-3GPP access system. The UE subsequently initiates DSMIPv6 with the same PDN-GW to maintain the IP session. In the non-roaming case, none of the optional entities in Figure C.2-1 are involved.

This clause shows a call flow for a handover when UE moves from an untrusted non-3GPP IP access network to the trusted non-3GPP access network. PMIPv6 is assumed to be used on S2a and S2b interfaces.

This procedure supports the non-roaming (Figure 4.2.2-1), home-routed roaming (Figure 4.2.3-1) and roaming with Local breakout (Figure 4.2.3-4) case. The PCRF in the HPLMN is informed of the change of access and any change in the policy that results is signalled to the Trusted non-3GPP IP Access. The signalling takes place through the vPCRF in the VPLMN. In the case of roaming with Local Breakout, the PDN-GW in the VPLMN exchanges messages with the vPCRF. The optional interaction steps between the gateways and the PCRF in the above figure only occur if dynamic policy provisioning is deployed. Otherwise policy may be statically configured with the gateways.

This clause shows a call flow for a handover when UE moves from a source trusted/untrusted non-3GPP IP access network to a target trusted non-3GPP access network. PMIPv6 is assumed to be used on S2a and DSMIPv6 is assumed to be used on source trusted/untrusted access network.

This procedure supports the non-roaming (Figure 4.2.2-1), home routed roaming (Figure 4.2.3-1) and roaming with Local breakout (Figure 4.2.3-4) case. The PCRF in the HPLMN is informed of the change of access and any change in the policy that results is signalled to the Trusted non-3GPP IP Access. The signalling takes place through the vPCRF in the VPLMN. In the case of roaming with Local Breakout, the PDN-GW in the VPLMN exchanges messages with the vPCRF. The optional interaction steps between the gateways and the PCRF in the above Figure only occur if dynamic policy provisioning is deployed. Otherwise policy may be statically configured with the gateways. In case of connectivity to multiple PDNs, step 8 is repeated for each PDN the UE is connected to. This step can occur in parallel for each PDN. Other impacts related to the handover for multiple PDNs are described in clause 8.1. Alternatively, if supported by non-3GPP access technology and if the UE does not provide any APN upon handover attach in the trusted non-3GPP IP access, Step 5 is repeated for each PDN the UE is connected to, instead of Step 8. DSMIPv6 de-registration in step 9 will be performed for each PDN connection. These steps can occur in parallel for each PDN.

This handover case is handled by MOBIKE, RFC 4555 [18], i.e. the existing IPSec tunnel, via the first untrusted non-3GPP IP access, is only modified for the use with the second untrusted non-3GPP access (and not torn down and re-created from scratch). It is assumed that the MOBIKE support indication has been sent by UE to ePDG in the initial attach.

The following steps are performed: For dual radio, step 2 is done after step 8.

No specific mechanisms are defined to support AP-to-AP handover with and without TWAG relocation. However, this does not preclude the support of IP address preservation in handovers without TWAG relocation when supported by procedures out of 3GPP scope.