7.2 Initial Attach

23.1393GPP3GPP system - fixed broadband access network interworkingRelease 17Stage 2TS

This clause specifies the additional procedures at the UE’s initial attachment to a Fixed Broadband access network via PMIPv6 or GTPv2 based S2b interface, for the UE to establish the first PDN connection over the Fixed Broadband Access with S2b, and/or for the UE to have offloaded traffic via Fixed Broadband Access.

NOTE 1: It is up to stage 3 to optimize S9a procedures for Non-Seamless WLAN offloaded traffic and EPC routed traffic handled by the same PCRF.

This procedure establishes a session between the BPCF and the PCRF to provision policy decisions for NS-WLAN offloaded traffic and/or to provision policy decisions for EPC routed traffic.

Figure 7.2-1: Initial attachment

NOTE 2 In the roaming case, step 7 terminates at the V-PCRF.

If dynamic policy provisioning over S9a is not deployed, the optional steps 3, 4, 5, 7 and 8 do not occur. Instead, the Fixed Broadband Access Network may employ local policies.

For NS-WLAN offloaded traffic, the local IP session for the UE in Fixed Broadband Access is handled as an IP-CAN session by the PCRF. For EPC-routed traffic, the IP-CAN session for the PDN Connection in the PDN GW is created via Gx procedures. In addition, a Gateway Control Session is established between the BPCF and the PCRF corresponding to the EPC-routed IP-CAN session in the PCRF.

The Fixed Broadband Access domain has local policies that indicate as part of the inter-operator agreements, both if policy control for NSWO is provided and the NSWO-APN for subscribers for a given HPLMN.

NOTE 3: Dynamic provisioning from the HPLMN of either an indication of policy control for NS-WLAN traffic and what the NSWO-APN is for the subscriber of a certain PLMN is out of the scope of this Release.

1. The UE may perform the 3GPP based (EAP) access authentication procedure involving the Fixed Broadband Access network as specified in TS 23 402 [3] clause 7.2.1 step 1. As part of this step, the permanent user identity (IMSI) is provided from the 3GPP AAA Server to the Fixed Broadband Access network and an indication to apply Reflective QoS is provided to the UE..

2. The UE receives a local IP address from the Fixed Broadband Access Network. How this is done is out of 3GPP scope, but it may involve IP address assignment by an RG or a BNG.

The steps in 3, 4 and 5 describe PCC signalling to provision policies for NS-WLAN offloaded traffic and are only triggered when 3GPP access authentication is performed and the BPCF receives the IMSI and the Fixed Broadband Access allocated UE local IP address.

3. Triggered by steps 1 and 2, the BPCF is informed about the UE accessing over Fixed Broadband Access. How this is done is out of 3GPP scope.

4. When the BPCF receives the trigger and policy interworking with PCRF is supported, if local policies indicate that policy control for NS-WLAN offloaded traffic is provided for subscribers from that PLMN, the BPCF sends an indication of IP-CAN session establishment for NS-WLAN offloaded traffic as specified in TS 23.203 [4]. The BPCF includes the IMSI, IP-CAN type, UE local IP address and the NSWO-APN in the message to the PCRF. The PCRF acknowledges the IP-CAN session establishment if HPLMN operator policies enable policy control for NS-WLAN offloaded traffic for this user as specified in TS 23.203 [4]..

5. Triggered by the successful establishment of the IP-CAN session for the UE local IP address in step A2, the V-PCRF (roaming) and the PCRF (non-roaming) may establish a session with the TDF to provision ADC Rules for that UE local IP address (if applicable and when solicited application reporting mode applies).

The steps in 6, 7 and 8 describe PCC signalling to provision policies for EPC routed traffic. Step 7 is only applicable when S2b PMIPv6 is used.

6. The description of the PDN connection setup procedure is the same as for steps 2-9 in TS 23 402 [3], clause 7.2.1 or for steps A.1-E.1 in TS 23 402 [3] clause 7.2.4, with the following additions when S2b-GTP is used: The UE local IP address and optionally UDP source port number (if NAT is detected) are also included in the Create Session Request message. The UE local IP address and optionally UDP source port number (if NAT is detected) are forwarded to the PCRF in IP-CAN Session Establishment procedure, an indication to apply Reflective QoS is provided to the UE as part of the IKEv2 tunnel establishment.

7. Triggered by the IKEv2 tunnel establishment in step 3 and by the indication that the UE is connected via a WLAN connected to fixed broadband access from 3GPP AAA, the ePDG initiates Gxb* session establishment with the PCRF by using Gateway Control Session establishment procedure as specified in TS 23.203 [4]. The ePDG includes the IMSI, APN, IP-CAN type, UE IP address allocated by EPC, the UE local IP address and optionally UDP source port number (if NAT is detected).

NOTE 4: The 3GPP AAA determines if the UE is connected via a WLAN connected to a fixed broadband access on UE Local IP address received in EAP-AKA signalling over SWm.

8. This step may be triggered by step 6 or step 7.

When triggered by step 6, the PCRF (for non-roaming case), the V-PCRF (for visited access) or the H-PCRF (for home routed) initiates Gateway Control Session establishment with the BPCF. The V-PCRF (for home routed) proxies the Gateway Control Session Establishment request to the BPCF: IMSI and UE local IP address and port needs to be included in the Gateway Control Session Establishment request message.

When triggered by step 7, the PCRF (for non-roaming case) and the V-PCRF (for home routed and visited access roaming case) initiates Gateway Control Session establishment request over S9a with the BPCF. IMSI and UE local IP address and port needs to be included in the Gateway Control Session Establishment request message over S9a.

9. The BPCF may interact with the BNG, e.g. to download policies, as defined by Fixed Broadband Access Policy Framework specifications BBF TR-134 [11] and BBF TR-203 [6]. This step is out of 3GPP scope.