Abstract:
The present invention relates to a method and system for establishing a connection via an access network ( 30 ) communicating with at least one user terminal, and at least one backbone network ( 100 ) comprising at least user terminal authentication and authorization means ( 50 ) and at least one user data processing node ( 60, 62 ), wherein the connection of a user terminal ( 10 ) is authenticated to the access network ( 30 ) and one of the at least one user data processing nodes ( 60, 62 ) is selected based on a selection information transferred in the authentication signaling. Then, a tunnel parameter information of the selected user data processing node is signaled to the access network ( 30 ) and a tunnel connection is created between the access network ( 30 ) and the selected user data processing node ( 60 ) based on the tunnel parameter information. By creating a tunnel connection based on a network signaling with both endpoints of the tunnel, the tunnel connection can be created between two network elements originally unknown to each other. Thus, cellular packet-switched services can be accessed over access networks which do not provide a context activation procedure or corresponding control plane signaling function.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a method and system for establishing a connection via an access network, for example a Wireless Local Area Network (WLAN), communicating with at least one user terminal, and at least one backbone network, for example a General Packet Radio Service (GPRS) network or a Universal Mobile Telecommunications System (UMTS) network, comprising at least user terminal authentication and authorization means and at least one user data processing node.  
         BACKGROUND OF THE INVENTION  
         [0002]    Over recent years, the market for wireless communications has enjoyed tremendous growth. Wireless technology now reaches or is capable of reaching virtually every location on the earth. With tremendous success of wireless telephony and messaging services, it is hardly surprising that wireless communication is beginning to be applied to the realm of personal and business computing. No longer bound by the harnesses of wired networks, people will be able to access and share information on a global scale nearly anywhere they venture.  
           [0003]    The major motivation and benefit from evolving WLANs is increased mobility. Network users can move about almost without restriction and access LANs from nearly everywhere. In addition to increased mobility, WLANs offer increased flexibility. Meetings can be arranged, in which employees use small computers and wireless links to share and discuss future design plans and products. Such “ad hoc” networks can be brought up and torn down in a very short time as needed, either around the conference table and/or around the world. WLANs offer the connectivity and the convenience of wired LANs without the need for expensive wiring or re-wiring.  
           [0004]    However, even with the fastest laptop, productivity while traveling can fall because of poor access to the Internet or company intranet. Despite the revolution of the Global System for Mobile communication (GSM), laptop users need faster access to download large files and to synchronize their e-mails quickly. The emerging mobile information society demands that data is available whenever and wherever. As a solution to this problem an operator WLAN (OWLAN) solution has been proposed which brings broadband access to the laptop or terminal device in specific places like airports, convention centers, hotels and meeting rooms. Thus, mobile network operators are able to offer broadband access to the internet, corporate intranets or other service machineries from virtually anywhere in the world. Thus, a public WLAN service with own WLAN roaming feature can be provided.  
           [0005]    In packet-switched cellular networks, such as the GPRS or UMTS network, the users service descriptions are specified by Access Point Names (APN). GPRS is a common packet domain core network used for both GSM and UMTS networks. This common core network provides packet-switched services and is designed to support several quality of service levels in order to allow efficient transfer of non real-time traffic and real-time traffic. A Serving GPRS Support Node (SGSN) is provided to keep track of the individual location of a mobile terminal and performs security functions and access control. Additionally, a Gateway GPRS Support Node (GGSN) provides interworking with external packet-switched networks, and is connected with SGSNs via an IP-based packet domain backbone network. In the backbone network, the APN is in practice a reference to the GGSN to be used. In addition, the APN may, in the GGSN, identify the external network and optionally a service to be offered. Further details concerning the use and structure of APNs are defined e.g. in the 3GPP specification TS 23.003.  
           [0006]    In GPRS a user can access home network services located behind access points identified by their APNs. When a user connects to a GPRS service, i.e. establishes a Packet Data Protocol (PDP) context as specified e.g. in the 3GPP specifications TS 23.060, the APN information selected by the terminal device or user equipment (UE) or the user of the terminal device is sent from the terminal device to the network in a PDP context establishment signaling. This information consists of APN and optionally username and password if required to access the service behind the selected APN. In the GPRS network, this information is used to select suitable GGSN. The information also arrives to the selected GGSN and the GGSN uses this information further to establish a connection to a network node behind the GGSN, e.g. a corporate intranet or an operator service node. If provided, the username and password are delivered to the concerned network node behind the GGSN to allow authorization of the connection.  
           [0007]    However, in the proposed public or operator WLAN systems, an operation similar to the GPRS PDP context activation is not provided. In particular, there is no dedicated signaling for setting up services between a WLAN terminal device, i.e. WLAN UE, and the WLAN network or network behind the WLAN network. Such services can be e.g. access to the user&#39;s corporate intranet, third party ISP style services, mobile operator services, So far, users have only been able to connect to the Internet directly via the local WLAN access network. Therefore, GPRS type of service selection and activation is not possible via the WLAN network, which thus forms a drawback in the proposed public or operator WLANs.  
         SUMMARY OF THE INVENTION  
         [0008]    It is therefore an object of the present invention to provide a method and system for enabling access from a WLAN network or any other access network to a broader range of services.  
           [0009]    This object is achieved by a method of establishing a connection via an access network communicating with at least one user terminal, and at least one backbone network comprising at least user terminal authentication and authorization means and at least one user data processing node, said method comprising the steps of:  
           [0010]    authenticating the connection of a user terminal to said access network;  
           [0011]    selecting one of said at least one user data processing nodes based on a selection information transferred in said authentication step;  
           [0012]    signaling a tunnel parameter information of said selected user data processing node to said access network; and creating a tunnel connection between said access network and said selected user data processing node based on said tunnel parameter information.  
           [0013]    Furthermore, the above object is achieved by an authentication server device for-providing an authentication mechanism, said authentication server device being arranged:  
           [0014]    to select a user data processing node based on a selection information received in an authentication signaling from a terminal device connected to an access network;  
           [0015]    to obtain from a signaling with said user data processing node a tunnel parameter information; and  
           [0016]    to signal said tunnel parameter information to an access server device of said access network.  
           [0017]    Additionally, the above object is achieved by access controlling device for controlling access to an access network to which a terminal device is connected, said access controlling device being arranged to obtain a tunnel parameter information from a signaling message received from an authentication server device and to create a tunnel connection to a user data processing node so as to provide a service access for said terminal device.  
           [0018]    Accordingly, a selection information is forwarded from the access network to the backbone network by using an authentication signaling. The selection information can then be used at the backbone network to select a user data processing node in order to create a tunnel connection. Thereby, access to network services of third parties is possible over the access network, e.g. the WLAN. Based on a signaling of a third element with both endpoints of the tunnel, a tunnel connection can be created between two network elements originally unknown to each other. Thus, dynamic service selection and multiple simultaneous connections to different services are enabled, and service continuity is obtained between different networks, such as WLANs and cellular packet-switched networks. Thereby, network flexibility and user mobility can be enhanced and service logics can be unified in different networks.  
           [0019]    A key advantage is that standard building blocks, as they are used in access networks like WLANs are combined in a specific way to achieve desired system level functionality. This makes it easy for network providers, e.g. WLAN providers, to adopt this solution. Moreover, the impact to the user terminals is minimized, which also maximizes interoperability. Another operator benefit is the involved saving of subscriber related operator expenditure due to a possible reuse of cellular provisioning systems for WLAN solutions. The proposed solution is advantageous in that current service description mechanisms, such as the APN mechanism in GPRS, can be used in new operator WLANs to thereby support legacy solutions.  
           [0020]    At least one signaled tunnel parameter may be used as an identifier within said created tunnel connection. This at least one tunnel parameter may be a tunnel assignment ID. Furthermore, the created tunnel connection may be of a GRE type. Then, the at least one tunnel parameter may be used as the Key parameter of the created GRE tunnel.  
           [0021]    The authentication signaling may be a signaling according to the Extensible Authentication Protocol (EAP). In particular, the authentication signaling may comprise an EAP response message. The service selection information may comprise at least one APN parameter. This at least one APN parameter may comprise an APN, a username and a password of the desired service. Furthermore, the APN parameter may be encrypted in the authentication message. The applied encryption for different APN parameters may be selected differently, so that selected APN parameters may be forwarded by the authentication server to the selected access point in encrypted format, and that the selected APN parameters are decrypted only at the access point or selected service network.  
           [0022]    The tunnel parameter information may be signaled to the access network in an AAA Access Accept message. The AAA protocol may be RADIUS or Diameter. The tunnel parameter information may comprise at least one of a tunnel type, a tunnel medium, a tunnel server address and a tunnel assignment identification.  
           [0023]    Furthermore, the user data processing node may be a WLAN gateway or a GGSN.  
           [0024]    The selection information may be resolved to an AAA realm name in the selection step. In particular, the selection information may be a service selection information.  
           [0025]    At the selected user data processing node at least one of an external server realm name, tunnel parameters and filtering parameters may be stored. Based on the selection information it may then be checked whether to signal the selection information to the external server.  
           [0026]    The authentication server may be arranged to signal the tunnel parameter information in an AAA Access Accept message. This tunnel parameter information may comprise at least one of a tunnel type, a tunnel medium, a tunnel server address and a tunnel assignment identification. For example, the tunnel type may be GRE, and/or the tunnel medium may be IPv4 or IPv6. The authentication server may be arranged to incorporate an EAP Success message into said AAA Access Accept message. This EAP Success message can then be signaled by the authentication signaling to the terminal device requesting e.g. the service connection.  
           [0027]    The access controlling device may be adapted to use the tunnel assignment identification as a flow identification of the created tunnel connection. As an example, this flow identification may then be signaled in a Key GER attribute.  
           [0028]    Further advantageous modifications are defined in the dependent claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]    In the following, the invention will be described in greater detail based on a preferred embodiment with reference to the accompanying drawings, in which:  
         [0030]    [0030]FIG. 1 shows a schematic block diagram indicating the basic principles underlying the present invention;  
         [0031]    [0031]FIG. 2 shows a schematic block diagram of a network architecture according to the preferred embodiment, where a WLAN is connected via a WLAN gateway to a GPRS network;  
         [0032]    [0032]FIG. 3 shows a signaling diagram indicating an EAP signaling according the preferred embodiment of the present invention;  
         [0033]    [0033]FIG. 4 shows the format of an enhanced EAP Response Challenge packet according to the preferred embodiment;  
         [0034]    [0034]FIG. 5 shows a signaling diagram indicating a RADIUS authentication signaling according the preferred embodiment of the present invention;  
         [0035]    [0035]FIG. 6 shows interface architectures between an authentication server and an authentication server database according the preferred embodiment of the present invention;  
         [0036]    [0036]FIG. 7 shows a signaling diagram indicating a database query signaling according the preferred embodiment of the present invention;  
         [0037]    [0037]FIG. 8 shows a signaling diagram indicating a RADIUS signaling for tunnel parameter transfer between the WLAN gateway and the authentication server according the preferred embodiment of the present invention;  
         [0038]    [0038]FIG. 9 shows a signaling diagram indicating a RADIUS signaling for tunnel parameter transfer between an external server and the WLAN gateway according the preferred embodiment of the present invention; and  
         [0039]    [0039]FIG. 10 shows a signaling diagram indicating a connection setup signaling for providing access to a service, according to the preferred embodiment. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0040]    The preferred embodiment will now be described on the basis of a network architecture as indicated in FIGS. 1 and 2, where a WLAN user is authenticated to access a WLAN network by an EAP authentication to thereby get access to a cellular packet-switched service.  
         [0041]    [0041]FIG. 1 shows a schematic block diagram of a network architecture comprising a WLAN  30  and a home network  100 , e.g. a GPRS network or any other cellular packet switched network. A terminal device or WLAN UE  10  which is subscribed to a home network service and wishes to get access to the service, first transfers a service selection information indicating at least one APN parameter and an optional username and password via the WLAN  30  to an authentication server  50  of the home network  100  by using an authentication signaling, e.g. an authorisation request message (1 st  step). Then, the authentication server  50  selects a WLAN gateway  60  arranged in the home network  100 , signals the service information to the WLAN gateway  60 , and as a response receives from the WLAN gateway  60  a connection information for establishing a connection between an access server  40  of the WLAN  30  and an application server  80  providing the requested service and being identified by the at least one APN parameter (2 nd  step). In particular, the authorisation request may be forwarded further to the application server  80  or another external AAA server together with the username and password and the WLAN gateway  60  first receives a response from there and then proxies this response to the access server  40 .  
         [0042]    [0042]FIG. 2 shows a more detailed block diagram of an OWLAN user plane architecture in which the preferred embodiment of the present invention can be implemented. In FIG. 2, a WLAN UE  10  is connected via a wireless connection, e.g. based on a IEEE 802.1×WLAN protocol, to an access point  20  of the WLAN. It is noted that the access point  20  has some similar basic functionalities as a base station in a general cellular network, such as providing the connection over the air interface towards the mobile UE. The access point  20  is not mobile and forms part of the wired network infrastructure. Further details regarding the architecture and function of the WLAN network can be gathered e.g. from the IEEE specification 802.11.  
         [0043]    Furthermore, the WLAN comprises a WLAN access server  40  for establishing a connection to external networks such as the home network  100  or another packet-switched network, e.g. the Internet or an operator or company intranet. The home network  100  may be a GPRS network or a WLAN backbone network and comprises an authentication server  50 , with an allocated authentication server database  55  in which subscriber information such as service profile information of each connected terminal device or UE are stored after retrieval of that information from a permanent subscriber database  110 , e.g. Home Location Register (HLR) or Home Subscriber Server (HSS), which can be accessed by a MAP (Media Access Protocol) signaling. It is noted that the functionality of the authentication server  50  can also be located at another network, e.g. a WLAN backbone or subsystem. The authentication signaling with the UE  10  may be based on the EAP SIM authentication protocol in case a GSM SIM card is used within the UE  10 . Alternatively, the authentication may be based on the EAP AKA (Authentication and Key Agreement) authentication protocol in case a UMTS SIM card is used within the UE  10 .  
         [0044]    The EAP protocol mechanism is used for authentication and session key distribution by means of the GSM SIM or the USIM. Authentication is based on a challenge-response mechanism, wherein the authentication algorithm which runs on the SIM or USIM card can be given a random number (RAND) as a challenge. The SIM or USIM runs an operator-specific confidential algorithm which takes the RAND and a secret key stored on the SIM or USIM as input, and produces a response (SRES) and a key as output. The key is originally intended to be used as an encryption key over the air interface. The authentication server  50  has an interface to the GSM or UMTS home network  100  of the UE  10  and operates as a gateway between the packet-switched AAA (Authentication, Authorization and Accounting) networks and the GSM or UMTS authentication infrastructure. After receiving an EAP identity response including user identification mappable to the user&#39;s International Mobile Subscriber Identity (IMSI) the authorization server  50  obtains n triplets or quintuplets from the authentication center at the home location register (HLR) or Home Subscriber Server (HSS)  110  of the user&#39;s home network  100 . From the triplets, the authentication server  50  derives the keying material based on a cryptographic algorithm.  
         [0045]    According to the preferred embodiment, the WLAN authentication signaling is used for signaling GPRS service subscription or selection information via the authentication server  50  to the home network  100 . The GPRS service information or service selection information comprises the APN of the desired service and an optional username and password required to connect to the service via the indicated APN. The authentication server  50  uses the obtained service selection information to select the WLAN gateway  60  having a similar function to a GGSN, from where the user can get access to the subscribed service. The subscribed service can be e.g. an access to a corporate intranet or to services of a mobile operator.  
         [0046]    The OWLAN user plane handling enables controlled and forced access to services provided by the home network  100  via the WLAN. This is a new feature in addition to the direct internet access service provided already. The services provided by the home network  100  can be either home operators own services or third party services like corporate intranet access. The provided service can be the same as those offered via GPRS Access points.  
         [0047]    These home network services are accessible via the OWLAN home network  100 , via the WLAN gateway  60  identified by its Access Point Names (APN). The information about home network services for a specific user are configured in a database  55 , hereinafter called authentication server database, accessible for the authentication server  50  and all other home network authentication servers. The information in the authentication server database  55  is a subset of the information in HLR GPRS profile. The authentication server database  55  may be created by copying from the HLR  110  either by a MAP Update Location procedure or via an O&amp;M (Operation &amp; Maintenance) functionality.  
         [0048]    When the home authentication server  50  is authenticating the user it checks from the authentication server database  55  whether the user is subscribed to home network services. If not then the authentication server  50  proceeds EAP authentication normally.  
         [0049]    If the user is subscribed to home network services, the authentication server  50  waits for APN information from the WLAN UE  10 . The WLAN UE  10  may inform a desired APN in the EAP-SIM Response message. APN information consists of APN, and optionally username and password for the APN. If the user doesn&#39;t include any APN information in the EAP-SIM Response message, the authentication server  50  proceeds EAP authentication normally and plain Internet access is assumed. When the user indicates by the APN parameters that he is connecting to a specific APN the authentication server  50  checks from the retrieved subscription information the user&#39;s authorisation to access the indicated APN. After successful check the authentication server  50  resolves the APN name to a WLAN gateway AAA Server realm name, e.g. a RADIUS (Remote Authentication Dial In User Service) realm name, and requests permission for the user identified by his IMSI (International Mobile Subscriber Identity) to access the WLAN gateway  60 . Further details regarding the RADIUS protocol which is used for carrying authentication, authorization and configuration information between a network access server and a shared authentication server can be gathered from the IETF (Internet Engineering Task Force) specification RFC  2138 .  
         [0050]    The authentication server  50  requests the WLAN gateway  60  (or network behind the WLAN gateway  60 ) to allocate suitable tunneling parameters and to authorise the user to access the APN. This is done by sending an AAA Access request, e.g. a RADIUS Access request, to the indicated WLAN gateway RADIUS server. Depending on the utilised AAA realm name, the WLAN gateway  60  detects the requested service.  
         [0051]    If the service is a mobile operator (MO) service provided by a home network server  120 , a respective WLAN gateway  62  selects appropriate tunneling and filtering parameters from an internal database for the service, assigns a tunnel assignment ID and sends an AAA Access Accept message back to the authentication server  50 .  
         [0052]    If the service is a third party service, the WLAN gateway  60  selects a respective external AAA server, e.g. a RADIUS server  130 , based on the utilized AAA realm name and forwards the AAA Access request, e.g. with username and password, there. After reception of the AAA Access Accept message and establishment of the indicated tunnel to the external network, the WLAN gateway  60  selects tunneling parameters towards the WLAN access server  40 , assigns a tunnel assignment ID and sends a RADIUS Access Accept message to the authentication server  50 . The authentication server  50  adds the EAP Success message and the keying material to the AAA Access Accept message and forwards it to the WLAN access server  40 .  
         [0053]    If the WLAN UE  10  supports IP multihoming and thus simultaneous connections with different IP addresses it is possible to establish multiple connections in parallel to already existing ones in the same way as described here. Each connection would have its own WLAN UE IP address, its own WLAN gateway and its own tunnel between the respective WLAN gateway and the WLAN access server  40 . An accounting function may then be used to detect the existence of a user plane tunnel.  
         [0054]    [0054]FIG. 3 shows a signaling diagram indicating an EAP-SIM authentication signaling between the UE  10  and the authentication server  50 . The first EAP request (not shown) issued by the network is an EAP Identity Request. The client or UE  10  responds with an EAP Identity Response (step 1) comprising a pseudonym or IMSI. The pseudonym is used when an identity privacy support is being used by the UE  10 . In response to the EAP Identity Response message or packet, the authentication server  50  sends an EAP challenge request comprising the n random numbers RAND among other parameters (step 2). In response thereto, the UE  10  issues an EAP Challenge Response including the calculated response value SRES. Furthermore, according to the preferred embodiment of the present invention, the EAP Challenge Response also includes at least one encrypted APN parameter specifying the desired GPRS service to be accessed. The encrypted APN parameters my comprise the APN of the desired service and an optional username and password for getting access to the service (step 3). The applied encryption for different APN parameters may be selected differently. I.e., the APN itself may be the only APN parameter which is required for AP selection, and therefore only this parameter has to be in a format which is to be decrypted and/or read by the access server. The username and password parameters may be forwarded by the authentication server to the selected access point in encrypted format, and these parameters are decrypted only at the access point or selected service network. It is thus not possible to access them while transferred via the first network. If the authentication procedure was successful, the authentication server  50  responds with an EAP Success message (step 4).  
         [0055]    The above authentication signaling procedure enables a signaling of service selection parameters to the authentication server  50  without requiring any additional context activation function as would be required in a conventional GPRS network without WLAN functionality. To achieve this enhanced functionality of the authentication signaling, the client software at the UE  10  is modified or programmed to add the respective service selection information to the EAP Challenge Response message. In particular, if a user has selected to connect to a specific service identified by its APN, the service information or service selection information is configured in the client software at the UE  10 . For each service the following settings may be performed. Firstly, a free text entry identifying the service for the user may be set. Secondly, the APN, i.e. the identification of the Public Land Mobile Network (PLMN) plus the Domain Name Server (DNS) name assigned by the Mobile Operator (MO) may be set to point to the specific service, and, thirdly, a setting indicating whether the username and password are required (e.g. a Yes/No setting) can be made in the client software. The third setting may comprise a setting indicating either a predefined or a dynamic username or/and password setting.  
         [0056]    At the latest after reception of the EAP request message, the UE  10  gets the required service selection related information from the user and encrypts it as specified by the utilized signaling protocol such as EAP-SIM. The UE  10  then inserts the APN parameter information to the EAP Challenge Response message and sends it to the authentication server  50 .  
         [0057]    [0057]FIG. 4 shows a format of the enhanced EAP SIM Challenge Response message according to the preferred embodiment as generated at the SIM. A “code” field is used to identify the message as a response message. An “identifier” field is one octet and aids in matching replies to responses. In particular, the “identifier” field must match the “identifier” field of the message to which it is sent in response. The “length” field indicates the length of the EAP message or packet. The “type” and “sub-type” fields are set to specific values specifying the EAP SIM Challenge Response message. The “reserved” fields are set to zero upon sending and ignored on reception. The “AT_SRES” field indicates an attribute value and is followed by an additional “length” field indicating the length of the following SRES value and by a “reserved” field. Finally, the proposed APN parameters specifying the requested service may be added e.g. as encrypted values.  
         [0058]    [0058]FIG. 5 shows a signaling diagram indicating a RADIUS authentication signaling according the preferred embodiment of the present invention. When the WLAN access server  50  receives a RADIUS Access Accept message it examines the parameters related to tunneling settings. If the Tunnel Type Attribute defined in the IETF specification RFC  2868  is present, tunneling shall be applied for the user. In particular, the Tunnel-Type Attribute  9  (GRE) can be utilised by the WLAN access server  40 , while an IP (Internet Protocol) address can be added as one optional field. Then, the WLAN access server  40  may act either as Boot Protocol relay, if the IP address is not delivered in the RADIUS signaling, or as a DHCP (Dynamic Host Configuration Protocol) server allocating IP addresses given by the RADIUS signaling.  
         [0059]    The tunnel medium type can be indicated by the Tunnel-Medium-Type attribute defined in RFC  2868 . The supported medium types are IPv4 (IP version 4) and IPv6 (IP version 6).  
         [0060]    The tunnel is then established towards the indicated Tunnel server end point address. This information is given in the Tunnel-Server-Endpoint Attribute, defined in RFC  2868 , in the RADIUS Access Accept.  
         [0061]    The end point address can be either a FQDN or an IP address with dotted notation. Depending on the Tunneling base protocol (IPv4 or IPv6) the end point address is also of format IPv4 or IPv6.  
         [0062]    The RADIUS Tunnel-Assignment-ID can be used by the WLAN access server  40  as a flow ID of the GRE tunnel to be established towards the indicated tunnel server endpoint address. In GRE, the flow ID is provided by the Key GRE attribute.  
         [0063]    After GRE tunnel establishment, the WLAN access server  40  maps all user data received from the WLAN UE  10  to the tunnel towards the tunnel server. This includes any DHCP requests.  
         [0064]    In case no tunneling parameters are set in the RADIUS Access Accept message, the WLAN access server  40  may utilize an internal DHCP server for IP address allocation and route the forthcoming user data directly to the Internet according to a local routing policy.  
         [0065]    In the following, the service subscription retrieval signaling between the authentication server  50  and the authentication server database  55  is described.  
         [0066]    [0066]FIG. 6 shows interface architectures between the authentication server  50  and the authentication server database  55 . The interface between the authentication server  50  and the authentication database  55  may support a many-to-one connection, i.e. multiple authentication servers may be able to use the same authentication server database. Specifically, the authentication server database functionality may correspond to the forthcoming WLAN specific functionality of the HSS as defined in the corresponding 3GPP release  6  specification. The interface between the authentication server  50  and the authentication server database  55  may thus resemble the forthcoming Wx interface being specified by 3GPP. The Wx application may be used on top of the RADIUS connection between authentication servers and the authentication server database  55 . Also the MAP interface towards the HLR  110  could logically be between the authentication database  55  and the HLR  110 .  
         [0067]    [0067]FIG. 7 shows a signaling diagram indicating a signaling for a query at the authentication server database query  55 . At latest when the user provides APN information within the EAP-SIM Response message, the authentication server  50  queries the authentication server database  55  for the subscriber&#39;s service subscription information. The subscription Information may be requested by the RADIUS application message WLAN Subscriber Profile Request. This message contains the IMSI of the subscriber. The authentication server database  55  responds with the RADIUS application message WLAN Subscriber Profile. This message contains a list of subscribed services for the indicated subscriber. For each subscribed service following information is included:  
         [0068]    Access Point Name (APN)  
         [0069]    MSISDN number (for MCD)  
         [0070]    SIM authentication, or extra username and password authentication  
         [0071]    If no subscribed services exist, the authentication server database  55  may return an empty message.  
         [0072]    In the following, the tunnel parameter transfer from the external RADIUS server  130  via the WLAN gateway  60  to the authentication server  50  is described.  
         [0073]    [0073]FIG. 8 shows a signaling diagram indicating a RADIUS signaling for tunnel parameter transfer between the WLAN gateway  60  and the authentication server  50 , and FIG. 9 shows a signaling diagram indicating a RADIUS signaling for tunnel parameter transfer between the external RADIUS server  130  and the WLAN gateway  60 . There is one to one mapping between an APN and the RADIUS Server  130  authorising the user&#39;s access to the service. Typically, the RADIUS server  130  or RADIUS proxy towards the server locates within a WLAN gateway. The authentication server  50  resolves the RADIUS Server name associated with the indicated APN from an internal database, i.e. not from the authentication server database  55  which contains only subscriber specific entries.  
         [0074]    In particular, the authentication server  50  sends a RADIUS Access Request message towards the resolved RADIUS server  130 .  
         [0075]    If the service relies on SIM authentication, the authentication server  50  may use the authenticated IMSI as user&#39;s identity in the RADIUS Access Request message.  
         [0076]    If the service has its own additional authentication, the authentication server  50  may use the username and password provided within the APN parameters in the EAP SIM Response within the RADIUS Access Request message.  
         [0077]    Upon reception of RADIUS Access Request, the WLAN gateway  60  checks from its internal database the service associated to the utilized realm name. There shall be one to one mapping between each realm name and service available via the WLAN gateway  60 .  
         [0078]    For each service, the following information can be stored in WLAN gateway  60 :  
         [0079]    External RADIUS server realm name (if any)  
         [0080]    Appropriate tunneling parameters  
         [0081]    Appropriate filtering parameters  
         [0082]    The WLAN gateway  60  checks whether the RADIUS Access Request message is to be proxied to the external RADIUS server  130  or not. If yes, the WLAN gateway  60  forwards the message to the external RADIUS server  130  using the realm name resolved from its internal database.  
         [0083]    In unsuccessful cases, the authentication server  50  receives a RADIUS Access Reject message as a reply and the authentication server  50  rejects the connection from the WLAN UE  10  with an appropriate reason code.  
         [0084]    In successful cases, the authentication server  50  receives a RADIUS Access Accept message from the RADIUS server  130 . This message includes appropriate tunneling and filtering attributes to be utilized between external network and the WLAN gateway  60 .  
         [0085]    The tunneling parameters may include:  
         [0086]    Tunneling type (GRE)  
         [0087]    Tunneling medium (IPv4 or IPv6)  
         [0088]    Tunnel Server Address (Address allocated by WLAN gateway  60 )  
         [0089]    Framed IP Address attribute (optional)  
         [0090]    Tunnel Assignment ID (unique identifier allocated by WLAN gateway  60 )  
         [0091]    Also, pre-configured L2TP (Layer 2 Tunnel Protocol) tunnels can be supported between the WLAN gateway  60  and external networks can be supported.  
         [0092]    Then, the WLAN gateway  60  forwards the RADIUS Access Accept message to the authentication server  50 . The authentication server  50  adds the EAP Success message and session keying material to the RADIUS Access Accept message and forwards it to the WLAN access server  40 .  
         [0093]    [0093]FIG. 10 shows a detailed signaling diagram indicating a service access to a GPRS service via the WLAN  30 . Initially, the EAP Identity Response is transmitted from the UE  10  to the access point  20  which generates a RADIUS Access Request message and forwards this message via the WLAN access server  40  to the authentication server  50 . The authentication server  50  performs a processing for restoring subscriber data at the HLR  110  of the home network  100  of the WLAN UE  10  and the HLR  110  responds with the subscriber data of the WLAN UE  10 . Then, the authentication server  50  issues a Send Authorization Info Request message to the HRL  110  which responds with a Send Authorization Info Response message which includes the required authorization information. Then, the authorization server  50  requests a service profile information from the authorization database  55  by using the IMSI of the subscriber of the UE  10  and receives from the database  55  a service profile including a list of APNs indicating the subscribed services of the subscriber. Then, the authentication server  50  issues an EAP Challenge Request message, e.g. EAP SIM Request, to the UE  10  and receives the enhanced EAP Challenge Response message, e.g. EAP SIM Response, specified in FIG. 4.  
         [0094]    Based on the APN parameter information and the optional username and password, the authentication server  50  selects the WLAN gateway  60  and forwards a RADIUS Access Request message including username and password to the WLAN gateway  60  which routes the RADIUS Access Request to the concerned APN, e.g. the external RADIUS server  130 . The RADIUS server  130  responds with a RADIUS Access Accept message comprising tunnel and filter parameters required for establishing a tunnel connection in order to provide the requested service. The WLAN gateway  60  generates tunnel and filter parameters, required for the tunnel connection between an access controller functionality of the WLAN access server  40  and the WLAN gateway  60 , and a tunnel assignment ID and forwards the RADIUS Access Accept message to the authentication server  50 . The authentication server  50  adds to the RADIUS Access Accept message an EAP Success message and session keys, and forwards the RADIUS Access Accept message to the WLAN access server  40 . In response thereto, the WLAN access server  40  forwards a RADIUS Access Accept message comprising the EAP Success message to the WLAN access point  20  which extracts the EAP Success message and forwards it to the WLAN UE  10 . Finally, based on the information received from the authentication server  50  in the RADIUS Access Accept message, the WLAN access server  40  establishes a tunnel connection to the WLAN gateway  60  using the tunnel assignment ID as a flow ID or key.  
         [0095]    In summary, the service access is achieved by incorporating or including a packet-switched domain type service selection information as a new encrypted attribute in the EAP SIM or EAP AKA authentication signaling. When a user desires to connect to a specific service identified by an APN, user or client software in the WLAN UE  10  sets the desired APN and optional username and password to the concerned EAP message, and the WLAN  30  uses this information for selecting a suitable user plane network element as well as tunneling and filtering policies.  
         [0096]    It is noted that the present invention is not restricted to the described WLAN and GPRS service and can be used in any network architecture where a control plane signaling required for accessing a packet-switched service is not provided in the access network. The functionalities of the authentication server  50  and the gateway  60  not necessarily have to be GPRS functionalities, but can be located in any backbone network or subsystem of the WLAN or any other network accessible by the WLAN  30 . They may be provided in standalone server devices or in GPRS GGSN or SGSN functionalities, respectively. Also, the accessed service does not have to be a GPRS service. Thus, the WLAN UE  10  can be a single-mode WLAN terminal without GPRS functionality but with a functionality to access external services via an authentication signaling, e.g. by a similar mechanism as the GPRS service selection mechanism. Furthermore, any given authentication message can be used for transferring the service selection information. The preferred embodiments may thus vary within the scope of the attached claims.