Abstract:
A control system includes a user management server or server group, a Service Policy Decision Function (SPDF) server, an Access-Resource and Admission Control Function (A-RACF) server, and a control interface location between the user management server or server group and the SPDF n server for transmitting the information. In addition, a control method using the control system above and a control device are provided. By the technical solutions above, when there are many access network operators connecting to the uniform network operation operator, the problem that the SPDF server searches the A-RACF server is solved, and the user information is acquired by setting the interface between the SPDF server and the user management server or server group.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of International Patent application No. PCT/CN2007/070529, filed Aug. 21, 2007, which claims priority to Chinese Patent Application No. 200610121795.7, filed Aug. 22, 2006, both of which are hereby incorporated by reference in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to the field of telecommunications and in particular to a control system, a control method and a control device. 
       BACKGROUND OF THE INVENTION 
       [0003]    The ETSI Telecommunications and Internet converged Services and Protocols for Advanced Networking (TISPAN) works on creating requirements, network architecture and related protocols of the Next Generation Networks (NGN). Logically the NGN includes three layers: data bearing layer, bearer control layer, and service control layer. Generally there are two systems in the bearer control layer: Network Attachment Subsystem (NASS) and Resource and Admission Control Subsystem (RACS). The NASS carries out address and authentication management for users, and provides user location information for the service control layer and the RACS. The RACS manages bearer network resources, and performs admission control for Quality of Service (QoS) requests of the service control layer. A brief introduction of this is as follows. 
         [0004]    The structure of a TISPAN RACS is illustrated in  FIG. 1 . The Session Policy Decision Function (SPDF) is a service-based policy decision function module, providing a Gq&#39; interface for the service control layer and providing a bearer service for an application function (AF). The interface receives service-based QoS requests from the service control layer. When a user requests a service, a session is established with the AF. The AF extracts required QoS parameters according to the service request in the session, and requests the SPDF for bearer service. The request includes type of service, bandwidth, quintuple information of flow, user representation, flow operation instruction and so forth. That is, the service control layer requests the bearer control layer to set a QoS channel for a particular service. Policy rules are stored at the SPDF to make service-based decisions. The SPDF locates an access gateway, related resources and a control entity A-RACF of the user, and transfers the QoS request to the A-RACF via Rq interface. The A-RACF carries out admission control of QoS. The A-RACF receives the QoS request for an access network managed by the A-RACF via the Rq interface, acquires user profile data and location information (which are provided by the NASS, detailed description will not be given herein.) via an e 4  interface, and determines whether the network can provide QoS for the user. A clear response of admission/non-admission is given to the SPDF by bandwidth reservation or after implementing QoS to a bearer layer entity. 
         [0005]    If the QoS request can be implemented, the A-RACF sends a command to a RCEF and an Access Node (AN) through RE and RA interface operations, according to flow status as indicated in the request. Located in an edge device of the access network, the RCEF carries out QoS implementation. 
         [0006]    In addition, the SPDF instructs a C-BGF to implement QoS via Ia interface, which also performs NAT. 
         [0007]    The functionality architecture of the RACS can support management, control and implementation of user end-to-end QoS, provide reference function decomposition and interfaces for operators such as network operators and service providers, and provide authentication and accounting capabilities between different providers. The NASS stores user profile information and performs access authentication and accounting, address allocation, user network parameter configuration, user end device management, etc. The RACS carries out QoS control and management. With the RACS, the bearer control layer can control each network element of the service control layer, which makes the network manageable and operable. Also, the bearer control layer provides a uniform access interface, covering the differences of different networks. The service control layer performs service-related control and provides management of a variety of services for users. 
         [0008]      FIG. 2  illustrates the structure of an NASS. As illustrated in  FIG. 2 , the NASS includes (1) an Access Management Function (AMF) entity, adapted to coordinate and forward network access requests initiated by a user terminal device, request a Network Access Configuration Function (NACF) entity to assign an IP address and other network parameters to the user terminal device, and interact with a User Access Authorization Function (UAAF) entity for user authentication, authorization, access denial and so forth; (2) an NACF entity, adapted to assign an IP address to a user terminal device, and distribute other network parameters to the user terminal device, such as a Domain Name Server (DNS) address and a session signaling proxy address; (3) a Connectivity Session Location Function (CLF) entity, adapted to associate the identity of a user with physical/geographical location information, IP address and other location information when a user uses a particular connectivity session service, provide a query interface between the service control layer an the bearer control layer, and provide related information of the user bear network required by the service control layer for the service control layer, such as a user ID and user location information; (4) a User Access Authorization Function (UAAF) entity, adapted to perform authentication and authorization of a user accessing the network, and send activation and profile information of the user to the CLF via a 4  interface; and (5) a Profile Data Base Function (PDBF) entity, adapted to store subscriber authentication information, user identity authentication methods, additional important data, etc. 
         [0009]    The NASS also includes the following system interfaces (1) an e 1  interface, between an AMF and a user terminal device, through which a user terminal device initiates an access request to a network, in which an Access Relay Function (ARF) entity can implement relay function of the access request and insert location information of the network that the user terminal device accesses; (2) an e 2  interface, between a CLF and a service control and application subsystem, through which the NASS provides for the service control and application subsystem user access location information (e.g., an access device identifier, a route identifier), access authentication result, etc; and (3) an e 4  interface, between a CLF and a RACS, through which the NASS provides user access location and QoS subscription information for the RACS, and by which the RACS determines resource allocation and whether resource allocation meets a service requirement according to an access device and an accessing method of the user. 
         [0010]    Seen as part of a network model, the SPDF belongs to a Network Service Provider (NSP) which provides Internet access services, normally providing a core network, and provides IP addresses for users. The A-RACF belongs to a Network Access Provider (NAP) operating a network access device with which a user can access the core network. Normally the A-RACF is embodied as an access resource management and admission control server managing access network resources and performing admission control of QoS requests. Different NAPs handle network accesses in different areas. When multiple NAPs of different areas access the core network of one NSP, functionally, there is one SPDF connected with multiple A-RACFs. Furthermore, as illustrated in  FIG. 3 , the AMF belongs to an NAP, and the NACF, the CLF and the UAAF belong to an NSP. 
         [0011]    In  FIG. 3 , two NAP 1  and NAP 2  are connected to an NSP (user management server). User management is carried out at the NSP. Each NAP includes an AMF and an A-RACF. 
         [0012]    This issue is briefly discussed in the draft standards of RACS at present. An SPDF finds an A-RACF based on local configuration. Practically, information that can be used by the SPDF is merely user identifier and IP address information from an AF. Home domain information can be carried in the user identifier. However, if a user visits another network, a correct A-RACF cannot be found based on the home domain information. As illustrated in  FIG. 3  about user IP address space, because IP addresses are assigned collectively at an NSP, if different IP address spaces are assigned to different NSPs, corresponding A-RACFs can be found based on a corresponding relationship between the IP address spaces and A-RACF addresses configured at the SPDF. However this limits the network. For example, a correct A-RACF can not be found when a user changes his access location carrying his IP address with him. In practice, multiple access resource management and admission control servers may be cascaded, which results in the problem in the existing systems for an upper-level access resource management and admission control server to find a lower-level access resource management and admission control function server. 
       SUMMARY OF THE INVENTION 
       [0013]    In view of the above problems, the present invention intends to solve one or more of the problems in the existing systems as stated above. An object of the present invention is to provide a control system and a control method and a control device capable of finding an access resource management and admission control server. 
         [0014]    Embodiments of the invention are implemented by the technical solutions as follows. 
         [0015]    An embodiment of the invention provides a control system including (1) a user management server or server group, a policy decision server and an access resource management and admission control server; and (2) a control interface, between the user management server or server group and the policy decision server, adapted to transfer information. The user management server or server group sends location identifier information of the access resource management and admission control server or location information of a user access point to the policy decision server via the control interface, wherein the policy decision server locates the access resource management and admission control server according to the location identifier information or the location information. 
         [0016]    An embodiment of the invention provides a control method for finding an access resource management and admission control servers, including (1) acquiring location information of a user access point; (2) determining for a pre-configured corresponding relationship between the location information of the user access point and location identifier information of an access resource management and admission control server according to the acquired location information of the user access point, to determine the location identifier information; and (3) locating the access resource management and admission control server based on the location identifier information. 
         [0017]    The above technical solutions of the present invention have the following advantages. The problem for an SPDF to find an A-RACF is solved when a plurality of access network operators connect to a uniform network service provider. And user information can be acquired via an interface configured between the SPDF and an NASS (user management server or server group). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0018]    Figures, which constitute part of this application, are provided for a better understanding of the present invention. Provided for interpretation of the invention, embodiments of the invention and the descriptions thereof do not limit the invention. In the figures: 
           [0019]      FIG. 1  illustrates network architecture of a TISPAN RACS; 
           [0020]      FIG. 2  is structural diagram of an NASS; 
           [0021]      FIG. 3  is a structural diagram of mapping NASS RACS to NAP NSP; 
           [0022]      FIG. 4  is a block diagram of a control system according to a first embodiment of the invention; 
           [0023]      FIG. 5  is a logical diagram of a control system according to the first embodiment of the invention; 
           [0024]      FIG. 6  illustrates a control system according to one embodiment of the invention; 
           [0025]      FIG. 7  illustrates a user management server or server group according to one embodiment of the invention; 
           [0026]      FIG. 8  is a flow chart of a control method according to another embodiment of the invention; 
           [0027]      FIG. 9  is a flow chart of a control method according to another embodiment of the invention; 
           [0028]      FIG. 10  is a flow chart of a control method according to another embodiment of the invention; 
           [0029]      FIG. 11  illustrates the process of a control method according to an embodiment of the invention; 
           [0030]      FIG. 12  is a block diagram of a control device according to another embodiment of the invention; 
           [0031]      FIG. 13  illustrates network architecture of another embodiment of the invention; and 
           [0032]      FIG. 14  is a flow chart of a control method according to another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0033]    Exemplary embodiments of the invention are described in detail hereinafter by reference to the drawings constituting part of the application and are intended to interpret the principle of the invention together with the embodiments of the invention. 
       Embodiment 1 
       [0034]    A control system is provided in the first embodiment of the invention which is described hereinafter by reference to  FIGS. 4 to 7 .  FIG. 4  is a block diagram of a control system according to the first embodiment of the invention. 
         [0035]    As illustrated in  FIG. 4 , a control system  400  according to this embodiment includes: a user management server or server group  402 , a policy decision server  404 , an access resource management and admission control server  406 , and a control interface  408  between the user management server or server group  402  and the policy decision server  404  for transferring information. The user management server or server group  402  sends location identifier information of the access resource management and admission control server  406  or location information of a user access point to the policy decision server  404  via the control interface  408 . 
         [0036]    The control system  400  according to this embodiment further includes: a network access management server  410  adapted to send the location identifier information and/or location information of the user access point to the user management server or server group  402  while a user is being attached to network.  FIG. 6  illustrates an example of the control system. As illustrated in  FIG. 6 , the user management server or server group is connected with the policy decision server via the control interface, the network access management server is connected with the user management server or server group, and the access resource management and admission control server is connected with the policy decision server. 
         [0037]    As illustrated in  FIG. 5 , the policy decision server  404  (an SPDF) and the user management server or server group  402  (an NSP-NASS) are in a same NSP domain. Via the control interface  408  (E 6 ) configured between them, the policy decision server  404  (an SPDF) can acquire user-related information, e.g., location information of a user access point, through the user management server or server group  402  (an NSP-NASS), or directly acquire address information of the access resource management and admission control server of a user, so that the access resource management and admission control server  406  (an A-RACF) can be easily found. A same procedure can be used in the case of roaming. 
         [0038]    The user management server or server group  402  performs user authentication, user address distribution, user location information collection and storage, etc. As illustrated in  FIG. 7 , which illustrates an example of the user management server or server group, the user management server or server group  402  can include a user location server adapted to collect and store user location information; a user address configuration server used for user address distribution; or an authentication server used for authentication. The policy decision server  404  implements user-based policy decision functions or service-based policy decision functions. The access resource management and admission control server  406  carries out resource management at the network managed by the access resource management and admission control server, and admission control of QoS requests. 
         [0039]    Further, the user location information can include location identifier information and location information of a user access point. Particularly, the location identifier information includes an IP address and a name of the access resource management and admission control server  406 , and location information by which the access resource management and admission control server  406  can be uniquely determined. The location information includes a network domain identifier. The location information of a user access point includes an identifier of an access device of the user access point, or a physical port number and/or a logic port number of the user access point. The logic port number includes a Virtual Path (VP), permanent Virtual Circuit (VC), Virtual LAN (VLAN) or user Medium Access Control (MAC) address of a user access line. 
         [0040]    In addition, the e 4  interface used in the related art as illustrated in  FIG. 1  and  FIG. 2  can be replaced with the control interface in the first embodiment of the invention. 
       Embodiment 2 
       [0041]    A control method using the control system according to the first embodiment is provided by a second embodiment of the present invention. The second embodiment of the invention is described hereinafter with reference to  FIG. 8  which is a flow chart of the control method according to the second embodiment of the invention. 
         [0042]    As illustrated in  FIG. 8 , a control method according to the second embodiment of the invention includes as follows. 
         [0043]    Step S 802 : While a user is being attached to network, the network access management server sends location identifier information of the access resource management and admission control server to the user management server or server group. 
         [0044]    Step S 804 : The policy decision server acquires the location identifier information via the control interface between the user management server or server group and the policy decision server. 
         [0045]    Step S 806 : The policy decision server locates the access resource management and admission control server by using the location identifier information acquired at step S 804 . 
         [0046]    Particularly, in different cases the step S 804  can include different steps as follows. 
       Example 1 
       [0047]    The step S 804  includes. 
         [0048]    Step S 804 - 1 : The user management server or server group sends the location identifier information and user identifier information with a corresponding relationship via the control interface. 
         [0049]    Step S 804 - 2 : The policy decision server receives the location identifier information via the control interface. 
       Example 2 
       [0050]    The step S 804  includes. 
         [0051]    Step S 804 - 1 ′: The policy decision server sends a request message with user identifier information to the user management server or server group via the control interface. 
         [0052]    Step S 804 - 2 ′: The user management server or server group returns the location identifier information corresponding to the user identifier information to the policy decision server in response to the request message. 
         [0053]    Particularly, the user management server or server group can include any one or a combination of: a user location server adapted to collect and store user location information, a user authentication server adapted to authenticate users, a user address configuration server adapted to distribute user addresses, or a database server adapted to store user data. 
         [0054]    The location identifier information includes an IP address and a name of the access resource management and admission control server, and location information by which the access resource management and admission control server can be uniquely determined. The location information includes a network domain identifier. 
         [0055]    When a network domain identifier is used as the location information, the policy decision server performs service-based DNS lookup at step S 806  based on the network domain identifier (in accordance with RFC2782), thereby completing the operation of location. 
         [0056]    The location information of a user access point includes an identifier of an access device of the user access point, or a physical port number and/or a logic port number of the user access point. The logic port number includes a VP, VC, VLAN or user MAC address of a user access line. 
       Embodiment 3 
       [0057]    A control method using the control system according to the first embodiment is provided by a third embodiment of the invention. The third embodiment of the invention is described hereinafter with reference to  FIG. 9  which is a flow chart of the control method according to the third embodiment of the invention. 
         [0058]    As illustrated in  FIG. 9 , a control method according to the third embodiment of the invention includes as follows. 
         [0059]    Step S 902 : A corresponding relationship between location information of a user access point and location identifier information of the access resource management and admission control server is pre-configured at the user management server or server group. 
         [0060]    Step S 904 : While a user is being attached to network, a network access management server sends user identifier information and the location information of the user access point to the user management server or server group. 
         [0061]    Step S 906 : The user management server or server group searches for the location identifier information by using the location information of the user access point based on the corresponding relationship. 
         [0062]    Step S 908 : The policy decision server acquires the location identifier information via the control interface between the user management server or server group and the policy decision server. 
         [0063]    Step S 910 : The policy decision server locates the access resource management and admission control server by using the location identifier information acquired at step S 908 . 
         [0064]    Particularly, in different cases, the step S 908  can include different steps as follows. 
       Example 1 
       [0065]    The step S 908  includes. 
         [0066]    Step S 908 - 1 : The user management server or server group sends the location identifier information and the user identifier information with the corresponding relationship via the control interface. 
         [0067]    Step S 908 - 2 : The policy decision server receives the location identifier information via the control interface. 
       Example 2 
       [0068]    The step S 908  includes: 
         [0069]    Step S 908 - 1 ′: The policy decision server sends a request message with the user identifier information to the user management server or server group via the control interface. 
         [0070]    Step S 908 - 2 ′: The user management server or server group returns the location identifier information corresponding to the user identifier information to the policy decision server in response to the request message. 
         [0071]    The user management server or server group can include any one or a combination of: a user location server adapted to collect and store user location information, a user authentication server adapted to authenticate users, a user address configuration server adapted to distribute user addresses, or a database server adapted to store user data. 
         [0072]    The location identifier information includes an IP address and a name of the access resource management and admission control server and location information by which the access resource management and admission control server can be uniquely determined. The location information includes a network domain identifier. When a network domain identifier is used as the location information, at step S 910 , the policy decision server performs service-based DNS lookup based on the network domain identifier, thereby completing the operation of location. 
         [0073]    The location information of a user access point includes an identifier of an access device of the user access point, or a physical port number and/or a logic port number of the user access point. The logic port number includes VP, VC, VLAN or user MAC address of a user access line. 
       Embodiment 4 
       [0074]    A control method using the control system according to the first embodiment is provided in a fourth embodiment of the invention. The third embodiment of the invention is described hereinafter with reference to  FIG. 10  is a flow chart of the control method according to the fourth embodiment of the invention. 
         [0075]    As illustrated in  FIG. 10 , the control method according to the fourth embodiment of the invention includes as follows. 
         [0076]    Step S 1002 : A corresponding relationship between location information of a user access point and location identifier information of the access resource management and admission control server is pre-configured at the policy decision server. 
         [0077]    Step S 1004 : While a user is being attached to network, a network access management server sends user identifier information and the location information of the user access point to the user management server or server group. 
         [0078]    Step S 1006 : The policy decision server acquires the location information of the user access point via a control interface. 
         [0079]    Step S 1008 : The policy decision server acquires the location identifier information by using the location information of the user access point acquired at step  1006  based on the corresponding relationship. 
         [0080]    Step S 1010 : The policy decision server locates the access resource management and admission control server by using the location identifier information acquired at step S 1008 . 
         [0081]    Particularly, in different cases, the step S 1006  can include different steps as follows. 
       Example 1 
       [0082]    The step S 1006  includes. 
         [0083]    Step S 1006 - 1 : The user management server or server group sends the user identifier information and the location information of the user access point with the corresponding relationship via the control interface between the user management server or server group and the policy decision server. 
         [0084]    Step S 1006 - 2 : The policy decision server receives the location identifier information via the control interface. 
       Example 2 
       [0085]    The step S 1006  includes. 
         [0086]    Step S 1006 - 1 ′: The policy decision server sends a request message with the user identifier information to the user management server or server group via the control interface, requesting for the location information of the user access point. 
         [0087]    step S 1006 - 2 ′: The user management server or server group returns the location information of the user access point corresponding to the user identifier information to the policy decision server in response to the request message. 
         [0088]    Particularly, the user management server or server group can include any one or a combination of: a user location server adapted to collect and store the user location information, a user authentication server adapted to authenticate users, a user address configuration server adapted to distribute user addresses, or a database server adapted to store user data. 
         [0089]    The location identifier information includes an IP address and a name of the access resource management and admission control server, and location information by which the access resource management and admission control server can be uniquely determined. The location information includes a network domain identifier. When a network domain identifier is used as the location information, at step S 1010  the policy decision server performs service-based DNS lookup based on the network domain identifier (in accordance with RFC2782), thereby completing the operation of location. The location information of a user access point includes an identifier of an access device of the user access point, or a physical port number and/or a logic port number of the user access point. The logic port number includes a VP, VC, VLAN or user MAC address of a user access line. 
         [0090]    Further, the interface e 4  used in the related art as illustrated in  FIG. 1  and  FIG. 2  can be replaced with the control interface in the first embodiment of the invention. In this case, the process of resource control is as illustrated as  FIG. 11 . 
         [0091]    Refer to  FIG. 11 . With the introduction of the control interface according to the invention, QoS control flow is as follows: (1) an AF sends a QoS request with a user identifier (user IP address, or user name) to an SPDF; (2) the SPDF makes a service-based policy decision, and if the request is accepted, go to step (3), otherwise the request is rejected and the AF is informed; (3) the SPDF requests an NASS for user profile information and location information of a user access point; (4) the NASS returns the user profile information and the location information of a user access point to the SPDF in response to the request; (5) the SPDF makes a user-based policy decision if the request is accepted, go to step (6), otherwise the request is rejected and the AF is informed; (6) the SPDF requests a C-BGF for resources; (7) the C-BGF responds to the resource request; (8) the SPDF requests a A-RACF for access network resources; (9) the A-RACF performs admission control according to current condition of network resources; (10) the A-RACF responds to the resource request; and (11) the SPDF responds to the AF. 
       Embodiment 5 
       [0092]    A control device provided in a fifth embodiment of the invention is described hereinafter with reference to  FIG. 12 , a block diagram of the control device according to the fifth embodiment of the invention. 
         [0093]    As illustrated in  FIG. 12 , a control device  1200  according to the fifth embodiment of the invention includes: a control interface module  1202  between a user management server or server group and a policy decision server, adapted to transfer location identifier information or location information of a user access point; a user management server or server group, and a policy decision server (not shown in the figures). 
         [0094]    The user management server or server group sends the location identifier information of the access resource management and admission control server or the location information of the user access point to the policy decision server via the control interface module. 
         [0095]    The location identifier information includes an IP address and a name of the access resource management and admission control server and location information by which the access resource management and admission control server can be uniquely determined. The location information includes a network domain identifier. The location information of a user access point includes an identifier of an access device of the user access point, or a physical port number and/or a logic port number of the user access point. The logic port number includes a VP, VC, VLAN or user MAC address of a user access line. 
       Embodiment 6 
       [0096]    In a large regional network, a single access resource management and admission control server cannot handle all admission control requests. Therefore, a hierarchal network structure of resource management is provided by an embodiment of the present invention, as illustrated in  FIG. 13 . This embodiment is not based on the first embodiment of the invention, including a user management server or server group  1303 , a policy and resource controller  1301 , and at least one lower-level access resource management and admission control server, i.e., access resource management and admission control servers  1304  and  1305  as illustrated in  FIG. 13 . 
         [0097]    The SPDF 1  belongs to a local access operator and the SPDF 1  belongs to a network connection service operator, both of which implements operator-established policies. The policy and resource controller  1301  implements functions of two function entities SPDF and A-RACF. The policy and resource controller  1301  provides a unique control connection point to the outside, receives requests from a policy and decision controller (the physical entity SPDF 0 ) of the network connection service operator, and carries out policy control of requested services and admission control of resources in a network domain managed by the policy and resource controller (typically the core part of a metropolitan area network). The lower-level access resource management and admission control servers  1304  and  1305  manages part of the resources in the network domain (typically one or more access convergence networks of a metropolitan area network) respectively. The policy and resource controller  1301  is connected with the lower-level access resource management and admission control servers  1304  and  1305  via a control interface  2  to transfer resource requests and responsive signaling messages. The policy and resource controller  1301  is connected with the user management server or server group  1303  via a standard control interface  1 , i.e., E 4  interface. This embodiment describes a preferred control implementation structure. Alternatively, the policy and resource controller  1301  can be implemented by a separate policy decision server (to implement the function entity SPDF 1 ) and a separate access resource management and admission control server (to implement the function entity A-RACF 1 ) with a connection relation same as this embodiment. 
         [0098]    In the case as illustrated in  FIG. 13 , there is still a problem for a policy and resource controller  1301  to find a lower-level access resource management and admission control server on receipt of a QoS request. A method to solve the problem is provided according to a seventh embodiment of the invention. 
       Embodiment 7 
       [0099]    A control method using the system according to the sixth embodiment is provided by this embodiment, for a policy and resource controller (corresponding to the case where an SPDF and a top-level A-RACF are implemented in a same physical entity) or an access resource management and admission control server (corresponding to the case where a top-level A-RACF is separately implemented in a physical entity) to find a lower-level access resource management and admission control server. 
         [0100]    As illustrated in  FIG. 14 , the control method according to the seventh embodiment of the invention includes. 
         [0101]    Step S 1401 : A corresponding relationship between location information of a user access point and location identifier information of the lower-level access resource management and admission control server (e.g.,  1304  in  FIG. 13 ) are pre-configured at the policy and resource server. 
         [0102]    Step S 1402 : A network access management server sends user identifier information and the location information of the user access point to the user management server or server group. 
         [0103]    Step S 1403 : The policy and resource server acquires the location information of the user access point via interface e 4 . 
         [0104]    Step S 1404 : The policy and resource server acquires location identifier information based on the corresponding relationship by using the location information of the user access point acquired at step S 1403 . 
         [0105]    Step S 1405 : The policy and resource server locates the access resource management and admission control server by using the location identifier information acquired at step S 1404 . 
         [0106]    This method is also applicable when the function entity A-RACF 1  is implemented by a separate physical entity as illustrated in  FIG. 13 , replacing the policy and recourse server in the above steps with an access resource management and admission control server. 
         [0107]    The location identifier information includes an IP address and a name of the lower-level access resource management and admission control server and location information by which the lower-level access resource management and admission control server can be uniquely determined. The location information includes a network domain identifier. When a network domain identifier is used as the location information, at step S 1405  the policy decision server performs service-based DNS lookup based on the network domain identifier (in accordance with RFC2782), thereby completing the operation of location. The location information of a user access point includes an identifier of an access device of the user access point, or a physical port number and/or a logic port number of the user access point, where the logic port number includes a VP, VC, VLAN or user MAC address of a user access line. 
         [0108]    Exemplary embodiments of the invention are described as above, which are not intended to limit the present invention. It should be noted that those skilled in the art can make various changes or modifications without departing from the spirit and principle of the invention. These changes, equivalent alternations and modifications should be included within the scope of the invention.