16.2.2 Initial Attach in WLAN on PMIP S2a

23.4023GPPArchitecture enhancements for non-3GPP accessesRelease 18TS

Figure 16.2.2-1: Initial attachment in WLAN on PMIP S2a for roaming, LBO and non-roaming scenarios

The home routed roaming, LBO and non-roaming scenarios are depicted in the figure 16.2.2-1:

– In the LBO case, the 3GPP AAA Proxy acts as an intermediary, forwarding messages from the 3GPP AAA Server in the HPLMN to the PDN GW in the VPLMN and vice versa. Messages between the PDN GW in the VPLMN and the hPCRF in the HPLMN are forwarded by the vPCRF in the VPLMN.

– In the home routed roaming and non-roaming cases, the vPCRF is not involved. In the non-roaming cases, the 3GPP AAA Proxy is not involved. In home routed roaming case, the 3GPP AAA Proxy is not involved in steps 5 and 12.

This procedure is also used to establish the first PDN connection over a trusted WLAN with S2a when the UE already has active PDN connections only over a 3GPP access and wishes to establish simultaneous PDN connections to different APNs over multiple accesses.

This procedure is based on clause 16.2.1 with the following key differences:

– In step 3 and 10 the TWAN selects S2a protocol variant, PMIPv6. The TWAN sends a Proxy Binding Update message. The details of the Proxy Binding Update message are described in step 5 in clause 6.2.1. Additionally, Proxy Binding Update includes the current TWAN Identifier as described in clause 16.1.7 and the UE Time Zone. The TWAN shall also provide also the IMEI(SV) in Proxy Binding Update when it has received this information from the AAA server

– Step 5 and 12 is the same as described in step 7 in clause 6.2.1, except that the Proxy Binding Update message shall contain the Serving Network parameter, which identifies the selected PLMN used for 3GPP-based access authentication i.e. the VPLMN in roaming case, and the HPLMN in non-roaming case.

– In step 6 and 13 the PDN GW sends a Proxy Binding Acknowledgement message. The details of the Proxy Binding Acknowledgement message are described in step 8 in clause 6.2.1.

– In step 7 and 14 the established tunnel between the TWAN and PDN GW is a PMIPv6 tunnel.

NOTE 1: For transparent single-connection mode, the UE may request to get some IP configuration parameters (e.g. DNS server) by means of DHCP. These parameters sent by TWAN (acting as a DHCP server) to the UE in a DHCP reply. These parameters are retrieved by the TWAN from the PDN GW within Proxy Binding Ack.