C.5 Handover Between Two Untrusted Non-3GPP IP Accesses Connected to the Same ePDG

23.4023GPPArchitecture enhancements for non-3GPP accessesRelease 18TS

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.

Figure C.5-1: Message flow for handover between two untrusted non-3GPP IP accesses based on MOBIKE

The following steps are performed:

1. The UE is connected via the IPSec tunnel to ePDG, from where a PMIPv6 tunnel is established to the PDN GW. The UE is utilizing a local IP address (for previous IKEv2 signalling and outer IP header address).

2. The UE disconnects on L2 from untrusted non-3GPP IP access 1.

3. UE establishes L2 connectivity to untrusted non-3GPP IP access 2.

4. Configuration of a local IP address. (In case of dual radio multihoming capability with respect to the local IP address is required).

5. MOBIKE update address message exchange (in both directions, initiated by UE).

6. MOBIKE address verification, initiated by ePDG; this step is optional as per MOBIKE, RFC 4555 [18].

7. The tunnel mapping (between PMIPv6 tunnel and IPSec tunnel) is updated.

8. The modified IPSec tunnel is now in operation.

For dual radio, step 2 is done after step 8.