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PDN GW and Protocol Selection for Chained S8/S2 of Non-3GPP Access

IP.com Disclosure Number: IPCOM000171500D
Published in the IP.com Journal: Volume 8 Issue 6B (2008-06-25)
Included in the Prior Art Database: 2008-Jun-25
Document File: 3 page(s) / 62K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

The 3GPP (3rd Generation Partnership Project) SAE (System Architecture Evolution) related specifications are in development. Basic network architecture and functions have been defined, but several detail issues are under discussion and still to be solved. One of these open issues is related to the chained S8/S2 interface which is only used in roaming scenarios of Non-3GPP access. Open questions in such scenarios are: how the PDN GW (Packet Data Network Gateway) address is sent to the Serving GW (Gateway), how the 3GPP AAA (Authentication, Authorization and Accounting) proxy knows whether to use chained S2/S8 case or not and how the S8 protocol choice is provided to the Serving GW. The relating procedure to these open issues on chained architecture has been depicted in Figure 1 and 2. A solution for the described open issues is proposed in the following and a sequenced diagram of the initial attach procedure is depicted in Figure 3.

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PDN GW and Protocol Selection for Chained S8/S2 of Non-3GPP Access

Idea: Shun Liang Zhang, CN-Beijing

The 3GPP (3rd Generation Partnership Project) SAE (System Architecture Evolution) related specifications are in development. Basic network architecture and functions have been defined, but several detail issues are under discussion and still to be solved. One of these open issues is related to the chained S8/S2 interface which is only used in roaming scenarios of Non-3GPP access. Open questions in such scenarios are: how the PDN GW (Packet Data Network Gateway) address is sent to the Serving GW (Gateway), how the 3GPP AAA (Authentication, Authorization and Accounting) proxy knows whether to use chained S2/S8 case or not and how the S8 protocol choice is provided to the Serving GW. The relating procedure to these open issues on chained architecture has been depicted in Figure 1 and 2.

A solution for the described open issues is proposed in the following and a sequenced diagram of the initial attach procedure is depicted in Figure 3.

The sequence starts with a roaming UE (User Equipment) which initiates attach to 3GPP core networks through a Non-3GPP access network and through a Non-3GPP specific procedure (Figure3, step 1). The UE completes the authentication and authorization process by interacting with the 3GPP AAA proxy and AAA server (step 2). The UE subscribed QoS (Quality of Service) profile may be provided to the serving GW during the procedure. The internal gateway of the trusted Non-3GPP IP (Internet Protocol) access network or the ePDG (Evolved Packet Data Gateway) of untrusted Non- 3GPP IP access network sends the PBU (Proxy Binding Update) message to the serving GW (step3) in the VPLMN (Visited Public Land Mobile Network) if chained S2/S8 interface is used for the roaming UE. The UE may not indicate a specific Home Agent address in the PBU message if the PDN GW address has not been determined before. Then in step 4, the serving GW knows that the chained S2/S8 interface is used. It sends an appropriate AAA request message to the 3GPP AAA server through the 3GPP AAA proxy in the VPLMN. With this message the server is informed that chained S2/S8 is used and asks the protocol selection for S8, the PDN GW address and if both protocols PMIP (Proxy Mobile IP) and GTP (GPRS Tunneling Protocol) are supported. The AAA server determines the protocol for S8 and PDN GW address based on subscription profile and responses with an appropriate AAA reply message, which indicates the selected protocol for S8 and the selected PDN GW (step 5). If GTP is the selected protocol for S8 (step 6a to 8a), the serving GW sends a create bearer request message to the selected PDN GW in HPLMN (Home Public Land Mobile Network). Then the PDN GW responses with a create bearer response to the serving GW to set up the default bearer. In...