WO2013117102A1

WO2013117102A1 - Broadband access interworking (bbai) gateway control session proper termination for untrusted-s2c roaming traffic over gxb*

Info

Publication number: WO2013117102A1
Application number: PCT/CN2012/086454
Authority: WO
Inventors: Yifeng Bi; Zaifeng Zong; Xiaoyun Zhou; Tricci So
Original assignee: Zte Corporation; Zte (Usa) Inc.
Priority date: 2012-02-10
Filing date: 2012-12-12
Publication date: 2013-08-15

Abstract

Systems and methods for terminating an established session of a user equipment (UE), between a gateway and a visiting policy charging rule function (vPCRF) of the UE, are disclosed. A home policy charging rule function (hPCRF) associated with a home network of the UE, initiates termination of the established session between the hPCRF and a fixed broadband access network element. The vPCRF detects the termination initiated by the hPCRF. The vPCRF initiates the termination with the gateway.

Description

Broadband Access Interworking (BBAI)

Gateway Control Session Proper Termination For Untrusted-S2c Roaming Traffic Over Gxb* Aspects of this invention propose a solution to resolve an issue during the BBAI interworking scenario between the 3 GPP Evolved Packet Core (EPC) and the Fixed Broadband network over WiFi access. The invention is designed to provide the proper termination for the neglected orphan Gateway Control Session (GCS) for the untrusted S2c interworking session that was established between the Evolved Packet Data Gateway (ePDG) and the visiting Policy and Charging Rule Function (vPCRF). During the untrusted S2c interworking session is terminated, such GCS between the ePDG and vPCRF is not properly terminated.

This invention proposed the UE's serving vPCRF, which is operating as a proxy for the UE's serving ePDG and home PCRF (hPCRF), to monitor and to intercept the GCS termination signaling between the UE's serving hPCRF and the fixed Broadband access network elements (i.e. Broadband Policy Control Function (BPCF) or Broadband Network Gateway (BNG)). Once the vPCRF detects such GCS termination signal, it will then also initiate the GCS termination signal to the ePDG to clean up the corresponding GCS.

The present invention relates to a method to support the BBAI interworking between the 3 GPP Evolved Packet Core (EPC) and the Fixed Broadband Access Network for both the non- converged and converged network architectures to enable the 3 GPP device to interconnect to the 3GPP EPC over WiFi access interface during the 3GPP User Entity (UE) roaming scenario.

BACKGROUND

During the BBAI interworking between the 3 GPP EPC and Fixed Broadband networks, there is an untrusted S2c interworking scenario while the 3 GPP UE is roaming, a GCS is established over Gxb* interface (see Figure- 1 and Figure-2 below for two different architectures). In both the roaming and non-roaming operations, the function of the the GCS over Gxb* is to convey the Local network information(UE local IP address, UDP port number, BBF FQDN and so on) to hPCRF (non-roaming) or to vPCRF (roaming) at the home Public Land Mobile Network (hPLMN) and vPLMN respectively.

SUMMARY OF THE INVENTION

In the case of roaming, after the UE's serving vPCRF receives these local network information, the serving vPCRF will initiate a GCS establishment trigger to UE's serving BPCF over S9a (in the case of non-converged 3 GPP and Fixed Broadband networks) or to UE's serving BNG over Gxd (in the case of converged 3 GPP and Fixed Broadband network). The BPCF or BNG will then initiate the establishment of a GCS with the hPCRF via vPCRF as a proxy.

After the UE performs the Dual Stack Mobile IP (DSMIP) binding with UE's serving 3 GPP Packet Data Network Gateway (PDN-GW or P-GW), there is a Gx session setup between P- GW and hPCRF. The hPCRF will associate the Gx session with the GCS over S9a and S9 interface (in the case of non-converged 3 GPP and Fixed Broadband networks) or over Gxd and S9 interface (in the case of converged 3 GPP and Fixed Broadband network).

It is important to point out that, during the roaming situation, the vPCRF selects the UE's serving hPCRF based on the UE's ID and the Care-of-address (Co A) without the consideration of the Packet Data Network's ID (PDN-ID). Hence, the same hPCRF will always be selected for all the roaming UEs' attaching to the same BPCF or BNG that serves such UEs.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 : S2c Interworking Roaming Scenario for "Non-converged" 3GPP and Fixed

Broadband Networks

Figure 2: S2c Interworking Roaming Scenario for "Converged" 3 GPP and Fixed Broadband

Network

Figure 3 : S2c Interworking Roaming Control Flows for PCC Establishment & Termination

Figure 4: Additional GCS termination procedures between UE's Serving ePDG and vPCRF from this Invention

DETAILED DESCRIPTION

In order to explain the problem so that the solution proposed by this invention is justified, let's first examining the procedures on the Policy Charging Control (PCC) establishment procedures for the untrusted S2c between the EPC and the Fixed Broadband networks as captured in today draft release 11 3 GPP TS 23.139 [1].

The following Figure 3 describes the step-1 to 5 for the PCC session establishment procedures in non-converged 3 GPP and Fixed Broadband networks of which the procedures are extracted from today draft 3 GPP TS 23.139 [1]. In order to provide better understanding for the given procedures that are shown as below, an additional explanation may also be provided by this invention to articulate the corresponding step.

Step 1 : UE attaches to EPC via Broadband Forum (BBF) network, IP sec tunnel setup between UE and UE' s serving ePDG.

Step 2: UE's serving ePDG initiates GCS establishment with UE's serving vPCRF.

(After this step, there will be a GCS over Gxb * interface between the ePDG and vPCRF)

Step 3 : This step is triggered by step 2, the UE's serving vPCRF will initiate a GCS session establishment trigger to UE's serving BPCF. Subsequently, the UE's serving BPCF initiates the GCS establishment procedure by sending GCS establishment message towards UE's serving hPCRF via vPCRF which proxies this message to hPCRF as a result.

The hPCRF responses the GCS establishment Ack message to vPCRF which will then proxy this message to feedback to the UE's serving BPCF.

(After this step, there will be a GCS between BPCF and hPCRF with the support from vPCRF which is operating as a proxy server between the BPCF and hPCRF.) Step 4: DSMIP tunnel between the UE and the UE's serving P-GW is setup for the PDN connection establishment.

Step 5 : UE's serving P-GW initiates Gx session setup with UE's serving hPCRF.

(After this step, there will be a Gx session between P-GW and hPCRF.)

After the Step-1 to Step-5 are completed as shown above, the outcomes of the PCC session are: • A GCS over Gxb* interface between UE"s serving ePDG and vPCRF, however, the UE's serving hPCRF would have no awareness or control over such session.

· A GCS between UE's serving BPCF and hPCRF with the support of vPCRF operated as the proxy server

Note that, the similar interworking roaming procedures as described in Figure 3 above for the non-converged 3 GPP and Fixed Broadband network architecture apply also to the procedures for the converged network architecture by simply replacing (a) BPCF by BNG, and (b) S9a by Gxd, as shown in the procedures Figure-3 above.

Given the understanding as described above that the hPCRF's is unaware of the GCS over Gxb* between ePDG and vPCRF, the problem arises during the UE PDN disconnection procedures.

The current roaming design according to the TS 23.402 [2] for the UE PDN disconnection, it relies on the hPCRF to initiate the GCS setup over Gxx interface for the Host-based mobility scenario (S2c-DSMIP case) (refer to section 6.5 of TS 23.402 for the trusted S2c case).

The history of the design described above that BBAI is referring is coming from the legacy 3 GPP design for the trusted S2c interworking handling. The reason for the UE's serving PCRF to initiate the GCS termination rather than having the trusted access network gateway (trusted S2c scenario) or ePDG (untrusted S2c scenario) to initiate the GCS termination because the trusted access network gateway/ePDG, which is between the UE and the P-GW, would not be aware of the UE's detachment to the Fixed Broadband Network as there is no signaling protocol for the trusted access network gateway/ePDG to intercept such termination notification. As a result, when the UE terminated its DSMIP tunnel with its serving P-GW by sending the Mobile IP's Binding Update (BU with Lifetime=0), the trusted access network's gateway cannot detect such event. Hence, the trusted access gateway/ePDG would not aware of the termination of the GCS between trusted access gateway/ePDG and UE's serving PCRF. As a result, it was decided that it is the UE's serving PCRF's responsibility to terminate the corresponding GCS between its serving truseted access gateway and the UE's serving PCRF (e.g. vPCRF). The following procedures as shown in Figure 3 above for the UE's PDN disconnection from

Step-6 to Step-8 are captured from 3GPP TS 23.139 [1]. These procedures explain the problem when the UE's serving hPCRF is not aware of the GCS over Gxb* between its corresponding serving vPCRF and ePDG. After these steps, the GCS over Gxb* interface will become an orphan session even though all the PDN connections have been disconnected.

Step 6: UE's PDN disconnection.

Step 7: UE's serving P-GW starts the Gx session release between itself and the UE's serving hPCRF. Step 8: UE's serving hPCRF initiates GCS termination between itself and the UE's serving BPCF/BNG with the support of vPCRF operating as the proxy.

At this point the UE's Gx session and the corresponding GCS between BPCF and hPCRF have been released, while the corresponding GCS over Gxb* interface between the ePDG and the vPCRF becomes an orphan session even though all the PDN connections are terminated.

To resolve the issue as described above, this invention propose to have the UE's serving vPCRF which is operating as the proxy to monitor and to intercept the GCS termination signaling between the UE's serving hPCRF and BPCF/BNG as described in Step 8 above. Once the UE's serving vPCRF detects the GCS termination signaling for the given UE, the vPCRF will then initiate the GCS termination procedure over the Gxb* with its corresponding ePDG that serves the UE. Figure 4 illustrates an embodiment of the present invention. Additional steps 9 and 10 are described as follows:

Step-8: UE's serving hPCRF initiates GCS termination between itself and the UE's serving BPCF/BNG with the support of vPCRF operating as the proxy.

Step-9: UE's serving vPCRF detects the operation of step-8 above.

(Internal behavior of vPCRF according to this invention) Step- 10: UE's serving vPCRF initiates the GCS termination procedure with ePDG.

( External behavior according to this invention).

As a result, the GCS session between the UE's serving ePDG and the vPCRF will be terminated properly when all the PDN connection are terminated.

The solution proposed by this invention applies to both the non-converged and converged architecture for 3 GPP and Fixed Broadband networks as shown in Figure 1 and Figure 2.

Claims

1 . A method for terminating an established session of a user equipment (UE), between a gateway and a visiting policy charging rule function (vPCRF) of the UE, the method comprising:

initiating, by a home policy charging rule function (hPCRF) associated with a home network of the UE, termination of the established session between the hPCRF and a fixed broadband access network element;

detecting, by the vPCRF, the termination initiated by the hPCRF; and initiating, by the vPCRF, the termination with the gateway.

2. The method of claim 1 further comprising terminating the established session.

3. The method of claim 2, wherein the gateway comprises an enhanced packet data gateway.

4. The method of claim 2, wherein the fixed broadband access network element is a broadband policy control function.

5. The method of claim 2, wherein the fixed broadband access network element is a broadband network gateway.

6. A system for terminating an established session of a user equipment (UE), between a gateway and a visiting policy charging rule function (vPCRF) of the UE, the system comprising:

a home policy charging rule function (hPCRF)associated with a home network of the UE, configured to initiate termination of the established session between the hPCRF and a fixed broadband access network element;

a vPCRF configured to:

detect the termination initiated by the hPCRF; and

initiate the termination with the gateway.

7. The system of claim 6, wherein the gateway comprises an enhanced packet data gateway.

8. The system of claim 6, wherein the fixed broadband access network element is a broadband policy control function.

9. The system of claim 6, wherein the fixed broadband access network element is a broadband network gateway.

10. An apparatus for terminating an established session of a user equipment (UE), between a gateway and a visiting policy charging rule function (vPCRF) of the UE, the apparatus comprising:

means for initiating termination of the established session between the hPCRF and a fixed broadband access network element.

means for detecting the termination initiated by the hPCRF; and

means for initiating the termination with the gateway.

1 1 . The apparatus of claim 10 further comprising means for terminating the established session.

12. The apparatus of claim 1 1 , wherein the gateway comprises an enhanced packet data gateway.

13. The apparatus of claim 1 1 , wherein the fixed broadband access network element is a broadband policy control function.

14. The apparatus of claim 1 1 , wherein the fixed broadband access network element is a broadband network gateway.