Abstract:
System and method for resource admission and control is disclosed. The system for resource admission and control includes an interface unit for application function unit configured to receive service request sent from the application function unit; a policy decision function unit configured to identify the type of an access network according to the service request received by the interface unit for the application function unit and select corresponding service logic for resource admission and control according to the identified type of access network. According to the technical solutions, no matter the request for resource is made to a fixed access network defined in TISPAN, or to a wireless access network defined in the 3GPP, the policy decision function unit xPDF may identify the type of the access network and select corresponding service logic to perform resource admission and control. The xPDF conceals the details of the access network from the AF such that the solution for network construction can be simplified and the system maintenance may become simple and convenient.

Description:
CROSS REFERENCE 
       [0001]    The application claims the priority of CN application No. 200610135846.1, filed on Oct. 10, 2006 with the State Intellectual Property Office of the People&#39;s Republic of China, entitled “SYSTEM AND METHOD FOR RESOURCE ADMISSION AND CONTROL”, the entire contents of all of which are incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to communication fields, more specifically, to a system and method for resource admission and control. 
       BACKGROUND 
       [0003]    The resource admission and control sub-system proposed by ETSI TISPAN relates to bearer control layer. It implements policy control, resource reservation, admission control as well as accessing, convergence, and translation of network address port/protocol of the core network. The framework of resource admission and control subsystem is illustrated in  FIG. 1 . 
         [0004]    In  FIG. 1 , RACS refers to resource admission and control sub-system which includes RACS-related function units such as a service-based policy decision function (SPDF) unit, an access-unction (A-RACF) unit, an application function (AF) unit, a network attachment sub-system (NASS), an access node (AN), a resource control enforcement function (RCEF) unit, and a border gateway function (BGF) unit, etc. 
         [0005]    The RACS is a subsystem for implementing policy control, resource reservation, and admission control. The RACS further provides supports for the control of Network Address Translation (NAT) in the BGF. The RACS provides a policy-based transmission control service for the application layer. With the RACS, the application layer accomplishes admission control, application, and reservation of the bearer resources within the coverage of the application layer. 
         [0006]    The SPDF provides below functions: 
         [0007]    checking to see if the information in the request from the AF is consistent with the local policy rules defined by the SPDF; 
         [0008]    authorizing the resources requested by the AF session. The SPDF utilizes the information in the request from the AF to compute appropriate authorization. (e.g., compute the number of media components which need to be authorized); 
         [0009]    determining the location of BGF and/or A-RACF according to the requested transmission capability; 
         [0010]    requesting A-RACF resource; 
         [0011]    requesting services from the BGF. These services include opening/closing gate control, marking the packet, allocating resource based on flow, NAT, hosted NAT transversal, setting up uplink and downlink service policy, measuring service, etc.; 
         [0012]    concealing internal details of RACS from the AF; 
         [0013]    concealing details of transport layer from the AF; 
         [0014]    mapping the resource request of AF to the request for the A-RACF and/or BGF. 
         [0015]    The A-RACF includes below functions of: admission control; and network layer policy assembly. 
         [0016]    In 3GPP R7, the service based local policy (SBLP) and flow based charging (FBC) in 3GPP R6 are combined into a policy and charging control (PCC) scheme, as illustrated in  FIG. 2 , in which: 
         [0017]    The functions related to the policy control in PCC include: 
         [0018]    “gate control” function: enable or disable the packet passing capability of service data flows (SDF). No matter the charging control and policy control functions have or have not been applied, the “gate control” function can be applied to a session. 
         [0019]    Session event: The capability of notifying the application layer events and reacting to the application layer events may trigger new user level behavior. The session events capability is a necessity for the application of gate control function. For instance, in the gate control function, the session termination event may trigger a corresponding packet disable behavior. 
         [0020]    Quality of Service (QoS) authorization function: Authorized QoS refers to a maximum QoS authorization for some IP flows. When multiple IP flows exist in one bearer, the authorized QoS for these flows may be combined together as the authorized QoS for the bearer. Subscription information relating to QoS may be used to assist the specific QoS authorization operation, including acceptation, rejection or modification. 
         [0021]    QoS execution function: The QoS execution function of policy and charging control (PCC) must be consistent with the function of PEP in the service based local policy (SBLP). The QoS execution function includes degrading processing of the requested bearer QoS performed by the gateway (GW) when establishing the bearer. The policy and charging rules function (PCRF) may also actively provide authorized QoS information for the GW through Gx+ reference point according to some triggering condition and enable the GW for execution. 
         [0022]    The Charging related functions include: 
         [0023]    charging association: support for charging association between the application layer charging and the bearer layer charging. 
         [0024]    charging control: IP flow is identified in accordance with the charging rule and a corresponding charging operation is performed. Related subscription information should also be taken into consideration in the process. The charging rule in the new PCC may be provided by PCRF dynamically or may be pre-configured in the GW. 
         [0025]    According to prior art, the implementation of SPDF function entity relating to TISPAN RACS specification and the implementation of PCRF function entity relating to 3GPP PCC specification have already been provided. Both the implementations of SPDF and PCRF need to provide interfaces for the application layer function AF. The AF requests resources from the bearer control layer through the interfaces. 
         [0026]    In RACS specification, the interface between SPDF and AF is Gq′ interface. The message type relating to the interface includes: Authorization Authentication Request, AA-Request (AAR)/Authorization Authentication Answer, AA-Answer (AAA), re-authentication and/or re-authorization Request (RAR)/re-authentication and/or authorization answer (RAA), Session-Termination-Request (STR)/Session-Termination-Answer (STA), Abort-Session-Request (ASR)/Abort-Session-Answer (ASA). All the messages for one session have a same &lt;Session-Id&gt;,&lt;Session-Id&gt; to identify the same session. 
         [0027]    For the Gq′ interface, the format of AAR message is defined as (ETSI TS 183 017): 
         [0000]    
       
         
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 &lt;AA-Request&gt; ::= &lt; Diameter Header: 265, REQ, PXY &gt; 
               
               
                   
                         &lt; Session-Id &gt; 
               
               
                   
                         { Auth-Application-Id } 
               
               
                   
                         { Origin-Host } (origin host) 
               
               
                   
                         { Origin-Realm } 
               
               
                   
                         { Destination-Realm } 
               
               
                   
                         *[ Media-Component-Description ] 
               
               
                   
                          *[ Flow-Grouping ] 
               
               
                   
                         [ AF-Charging-Identifier ] 
               
               
                   
                         [ SIP-Forking-Indication ] 
               
               
                   
                         *[ Specific-Action ] 
               
               
                   
                         [ User-Name ] 
               
               
                   
                         [ Binding-Information ] 
               
               
                   
                         [ Latching-Indication ] 
               
               
                   
                         [ Reservation-Priority ] 
               
               
                   
                         [ Globally-Unique-Address ] 
               
               
                   
                         [ Authorization-Lifetime ] 
               
               
                   
                         *[ Proxy-Info ] 
               
               
                   
                         *[ Route-Record ] 
               
               
                   
                         *[ AVP ]  ( other attribute-value pair) 
               
               
                   
                   
               
             
          
         
       
     
         [0028]    In PCC scheme, the interface between PCRF and AF is Rx interface. The message type relating to the interface includes: AAR/AAA, RAR/RAA, STR/STA, ASR/ASA.All the messages for one session have a same &lt;Session-Id&gt;, ,&lt;Session-Id&gt; to identify the same session. 
         [0029]    The message format for Rx interface is defined as (3GPP TS 29.214): 
         [0000]    
       
         
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 &lt;AA-Request&gt; ::= &lt; Diameter Header: 265, REQ, PXY &gt; 
               
               
                   
                         &lt; Session-Id &gt; 
               
               
                   
                         { Auth-Application-Id } 
               
               
                   
                         { Origin-Host } 
               
               
                   
                         { Origin-Realm } 
               
               
                   
                         { Destination-Realm } 
               
               
                   
                         *[ Media-Component-Description ] 
               
               
                   
                          *[ Flow-Grouping ] 
               
               
                   
                         [ AF-Charging-Identifier ] 
               
               
                   
                         [ SIP-Forking-Indication ] 
               
               
                   
                         *[ Specific-Action ] 
               
               
                   
                         *[ Subscription-ID ] 
               
               
                   
                         *[ Proxy-Info ] 
               
               
                   
                         *[ Route-Record ] 
               
               
                   
                         *[ AVP ]  ( other attribute-value pair ) 
               
               
                   
                   
               
             
          
         
       
     
         [0030]    The fixed-mobile convergence (FMC) application includes xDSL fixed access as well as a variety of mobile access schemes such as UMTS RAN access, WiMAX access, W-LAN access. According to the existing ways of implementation, SPDF function entity is needed to support the resource admission and control in fixed access mode. PCRF is also needed to support the resource admission and control in mobile access mode. However, using two sets of bearer control layer entities is not conducive to the construction and maintenance of the network, and not conducive for the AF to implement bearer control, neither. 
       SUMMARY 
       [0031]    Systems and methods for resource admission and control are provided according to embodiments of the present invention. The systems and methods can be used to tackle the problem of complicated network construction and maintenance due to two sets of bearer control layer entities in the prior art. 
         [0032]    A resource admission and control system includes: 
         [0033]    an interface unit for application function unit, configured to receive a service request sent from the application function unit; 
         [0034]    a policy decision function unit, configured to identify the type of an access network according to the service request received by the interface unit for the application function unit and select corresponding service logic for resource admission and control according to the identified type of access network. 
         [0035]    A method for resource admission and control includes: 
         [0036]    receiving, by a policy decision function unit, a service request sent from an application function unit; 
         [0037]    identifying, by the policy decision function unit, the type of an access network according to the service request and selecting a corresponding service logic for resource admission and control according to the type of the access network. 
         [0038]    Advantageously, according to the technical solutions provided by the embodiments of the present invention, no matter the request for resource is made to a fixed access network defined in TISPAN, or to a wireless access network defined in the 3GPP, the policy decision function unit xPDF may identify the type of the access network and select corresponding service logic to perform resource admission and control. The xPDF conceals the details of the access network from the AF such that the solution for network construction can be simplified and the system maintenance may become simple and convenient. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING(S) 
         [0039]      FIG. 1  is a conventional framework of a resource admission and control subsystem based on a fixed network access type and the network environment thereof, 
           [0040]      FIG. 2  is a conventional framework of a resource admission and control subsystem based on a mobile network access type and the network environment thereof, 
           [0041]      FIG. 3  is an illustration of connection of a resource admission and control system in a network according to one embodiment of the present invention; 
           [0042]      FIG. 4  is a block diagram of xPDF according to one embodiment of the present invention; 
           [0043]      FIG. 5  is a detailed block diagram of xPDF according to one embodiment of the present invention; 
           [0044]      FIG. 6  is a detailed block diagram of a service control function unit according to one embodiment of the present invention; 
           [0045]      FIG. 7  is a schematic flowchart according to one embodiment of the present invention; 
           [0046]      FIG. 8  is an illustration of session setup procedure initiated by the AF in PCRF; 
           [0047]      FIG. 9  is an illustration of resource request procedure initiated by the AF in SPDF; and 
           [0048]      FIG. 10  is an illustration of resource request procedure initiated by the AF in xPDF according to one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0049]    Detailed description according to the present invention is made below in conjunction with the accompanying drawing. 
         [0050]    In a fixed-mobile convergence (FMC) scenario, the service layer needs to employ bearer control to control a fixed access network and a mobile access network at the same time. Therefore, support for the convergence of fixed access scheme and the mobile access scheme is required such that the bearer control layer may offer a unified interface for the application layer and block the difference of various access schemes, the difference of control schemes for each access scheme, and the difference between the fixed access scheme and the mobile access scheme in terms of resource control, admission control, charging for the application function, and may provide compatibility with conventional resource admission and control schemes. As such, the issue of a complicated network construction and maintenance due to the deployment of two sets of bearer control function entities in FMC application can be solved. 
         [0051]      FIG. 3  illustrates a system framework of a solution in application according to one embodiment of the present invention. The solution combines the SPDF and PCRF. The combined resource admission and control system provides resource admission and control interface for the application layer function via a unified Rx+ interface. 
         [0052]    For ease of illustration, in one embodiment, xPDF is used to indicate a policy decision function unit which implements SPDF and PRCF functions. For compatibility with the existing solutions, the interfaces between the xPDF and service layer AF is Rx+ which employs a diameter protocol. 
         [0053]    The AAR message for Rx+ interface is defined as below: 
         [0000]    
       
         
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 &lt;AA-Request&gt; ::= &lt; Diameter Header: 265, REQ, PXY &gt; 
               
               
                   
                         &lt; Session-Id &gt; 
               
               
                   
                         { Auth-Application-Id } 
               
               
                   
                         { Origin-Host } 
               
               
                   
                         { Origin-Realm } 
               
               
                   
                         { Destination-Realm } 
               
               
                   
                         [ Access-Id ] 
               
               
                   
                         [ Tran-Control-Mode ] 
               
               
                   
                         *[ Media-Component-Description ] 
               
               
                   
                          *[ Flow-Grouping ] 
               
               
                   
                         [ AF-Charging-Identifier ] 
               
               
                   
                         [ SIP-Forking-Indication ] 
               
               
                   
                         *[ Specific-Action ] 
               
               
                   
                         [ User-Name ] 
               
               
                   
                         [ Binding-Information ] 
               
               
                   
                         [ Latching-Indication ] 
               
               
                   
                         [ Reservation-Priority ] 
               
               
                   
                         [ Globally-Unique-Address ] 
               
               
                   
                         [ Authorization-Lifetime ] 
               
               
                   
                         *[ Proxy-Info ] 
               
               
                   
                         *[ Route-Record ] 
               
               
                   
                         *[ AVP ] (other attribute-value pair ) 
               
               
                   
                   
               
             
          
         
       
     
         [0054]    Similar to the prior art, the messages relating to the same session uses the same Session-Id. According to one embodiment of the present invention, the xPDF needs to identify if it is intended to control a fixed access network or to control a mobile access network from the first message, namely, AAR message, at the very beginning of the session. The subsequent xPDF may make a correction selection of SPDF or PCRF procedure for implementing resource reservation, admission control and policy control according to the Session-Id information in the subsequent messages. Accordingly, apart from AAR message, the definitions for interfacing with Gq′ and Rx interfaces for other messages such as AAA, RAR/RAA, STR/STA, ASR/ASA remain unchanged. 
         [0055]    The Access-Id field may be defined as an AVP of enumeration type (AVP type code is to be assigned). The Access-Id may be used to identify and recognize the type of the access network. It can be defined as follow. 
         [0056]    xDSL access, with a value of 0; 
         [0057]    GGSN mobile access network, with a value of 1; 
         [0058]    WLAN fixed access network, with a value of 2; 
         [0059]    WLAN mobile access network, with a value of 3; 
         [0060]    WiMAX fixed access network, with a value of 4; 
         [0061]    WiMAX mobile access network, with a value of 5. 
         [0062]    By expanding the enumeration value, other types of access networks may also be defined. The purpose of adding attribute value of Access-Id in the Rx+ is that the xPDF may identify if the current service is directed to control a fixed access network or a mobile access network at the very beginning of each session according to the assigned value of Access-Id field. 
         [0063]    According to one embodiment of the present invention, a Tran-Control-Mode field may also be defined as an AVP of enumeration type (AVP type code is to be assigned). The Tran-Control-Mode field is used to indicate the bearer control scheme. The bearer control scheme is used to indicate which manner the xPDF employs to implement bearer control, e.g., push manner or pull manner, on-path manner or off-path manner. 
         [0064]    In a specific scenario, the attribute values for User-Name field, Subscription-ID field, Globally-Unique-Address field in AAR can also be used to identify the type of the access networks. For instance, the range of the value for the aforementioned fields and the relationship between the range and the type of the access networks may be used to identify the type of the access networks. If different types of access networks can be recognized by the attribute values for User-Name, Subscription-ID, or Globally-Unique-Address, the relationship between the range of values for the aforementioned fields and the type of the access networks may be given as shown in below table. 
         [0000]    
       
         
               
               
             
               
               
               
             
           
               
                   
                 TABLE ONE 
               
               
                   
                   
               
               
                   
                 Type of Access Network 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 User-Name 
                   
               
               
                   
                 Zhang San 
                 xDSL 
               
               
                   
                 Li Si 
                 WiMAX 
               
               
                   
                 Subscription-ID 
               
               
                   
                 139xxxxxxxx 
                 GGSN 
               
               
                   
                 2887xxxx 
                 xDSL 
               
               
                   
                 Globally-Unique-Address 
               
               
                   
                 10.20.x.x 
                 xDSL 
               
               
                   
                 20.20.x.x 
                 GGSN 
               
               
                   
                   
               
             
          
         
       
     
         [0065]    The first column in Table ONE is the specific value for the corresponding field whereas the second column is the type of the access networks to which the specified value corresponds. In practice, xPDF looks up the above table with the above specific value of each field in the AAR messages relating to the Rx+ interface. If the type of the access network is located, then an associated manner can be determined for resource control for the access network. 
         [0066]      FIG. 4  illustrates one implementation of the xPDF. The implementation mainly includes a service control function unit  401 , policy and resource management function unit  402 , and a protocol processing function unit  403 . 
         [0067]    In the implementation, after the service control function unit  401  receives a message from AF from the protocol processing function unit  403 . The service control function unit  401  initially checks if the message is an AAR message and check the AAR message if it includes an Access-Id attribute. If it includes the Access-Id attribute, the type of the access network can be determined according to Access-Id and corresponding service logic is thus selected for resource admission and control. 
         [0068]    If the above message does not include Access-Id attribute, the service control function unit  401  proceeds to check the existence of attribute value of User-Name, Subscription-ID, Globally-Unique-Address. If the message includes such attribute values, corresponding type of access network can be determined by looking up Table ONE according to the configuration data, and corresponding service logic is thus selected for resource admission and control. If the type of the access network cannot be found, the processing will be done according to a default control manner, including returning an error message to the AF. 
         [0069]    If the above message includes a Tran-Control-Mode field, the xPDF may implement resource admission and control according to the bearer control mode associated with the content of the field. 
         [0070]    During the foregoing process, the policy and resource management function unit  402  may provide policy and resource information for the service control function unit  401 . 
         [0071]      FIG. 5  is a detailed diagram of xPDF. As can be seen from the figure, the protocol processing function unit  403  further includes: 
         [0072]    a Diameter protocol (new generation of AAA protocol) interfacing and adaption unit  4031 , configured to process Diameter protocol; 
         [0073]    a Common Open Policy Service (COPS) protocol interfacing and adaption unit  4032 , configured to process COPS protocol; 
         [0074]    an H.248 protocol interfacing and adaption unit  4033 , configured to process H. 248 protocol; and 
         [0075]    a Simple Object Access Protocol (SOAP) protocol interfacing and adaption unit  4034 , configured to process SOAP protocol. 
         [0076]    The above service control function unit  401  further includes a service control data block generation unit  4011 , configured to generate service control data block after receiving a service request processed by the protocol processing unit. The service control data block is identified by the identifier &lt;session-id&gt;. The service control data block records the service request processing. The state of the service control data block is managed by a state management unit  4013 . 
         [0077]    In the above scheme, the service control function unit  401  may further include: 
         [0078]    a service logic storage unit  4012  configured to store service logic; 
         [0079]    a state management unit  4013  configured to manage the state of service; and 
         [0080]    a service selection and control unit  4014  configured to select and control service request according to the policy and resource information provided by the policy and resource management function unit. 
         [0081]    As illustrated in  FIG. 6 , the foregoing service logic storage unit  4012  further includes: 
         [0082]    a PCRF service logic storage unit  40121  configured to store PCRF service logic; 
         [0083]    an SPDF service logic storage unit  40122  configured to store SPDF service logic; 
         [0084]    a policy decision function(PDF) service logic storage unit  40123  configured to store PDF service logic; and 
         [0085]    an A-RACF service logic storage unit  40124  configured to store A-RACF service logic. 
         [0086]    The above state management unit  4013  further includes: 
         [0087]    a state machine management unit  40131  configured to manage the state of service control data block; 
         [0088]    a binding state management unit  40132  configured to manage the binding relation between the service and the rule; 
         [0089]    a session connection management unit  40133  configured to manage service session connection; and 
         [0090]    a routing management unit  40134  configured to manage the routing between the bearer entities. 
         [0091]    The above policy and resource management function unit  402  further includes: 
         [0092]    a service policy database  4021  configured to store service policies; 
         [0093]    a network policy database  4022  configured to store network policies; 
         [0094]    an access control policy database  4023  configured to store access control policy; 
         [0095]    a user subscription rule database  4024  configured to store user subscription rules; 
         [0096]    a bearer control routing list unit  4025  configured to store routing information relating to the bearer control; and 
         [0097]    a bearer network topology and resource unit  4026  configured to store network topology and resource information. 
         [0098]    The policies or resource information stored in the above units may be provided to the service control function unit  401  according to the actual requirements. 
         [0099]    In the above scheme, the xPDF further includes: 
         [0100]    an A-RACF interface unit  4041  configured to provide an interface for interacting with the A-RACF; 
         [0101]    a Core-Border Gateway Function(C-BGF) interface unit  4042  configured to provide an interface for interacting with the C-BGF; 
         [0102]    a Policy and Charging Enforcement Function (PCEF) interface unit  4043  configured to provide an interface for interacting with the PCEF; and 
         [0103]    an Interconnection-Border Gateway Function (I-BGF) interface unit  4044  configured to provide an interface for interacting with the I-BGF. 
         [0104]    In the above scheme, with respect to AF, an AF interface unit  405  may further be provided in the xPDF. The AF interface unit may include different configuration schemes. 
         [0105]    If the xPDF employs the Session-Id information or Tran-Control-Mode field information carried in the service request transmitted by the AF to recognize the type of the access network, the AF interface unit can be set as a unified interface unit. 
         [0106]    If the AF may recognize the type of the access network by itself, different AF interface units for different types of access networks can be set in the xPDF. The AF interface unit  405  may be set according to different types of access network such that the AF may determines the type of the access network and may send service requests to different AF interface units according to different types of access network. The identification of the type of the access network can be done without the help of service request information. Rather, the xPDF may identify the type of the access network directly by virtue of different port numbers. 
         [0107]    In the above scheme, the service request from the AF is processed as follow. 
         [0108]    The service control data block generation unit  4011  generates a service control data block after receiving the AAR message processed by the protocol processing function unit. The service control data block is identified by session-id. The state of service control data block is managed by a station machine management unit  40131 . The binding relation between the service and the rule is managed by a binding state management unit  40132 . The service session is managed by a session connection management unit  40133 . The routing between the bearer control entities is managed by a routing management unit  40134 . 
         [0109]    If the above service request message is not an AAR message, and if the respective dedicated service procedure of SPDF and PCRF can be identified according to the message, the service selection and control selection unit may operate according to the respective procedure. Otherwise, the service selection and control selection unit locates a corresponding service control data block according to the session-id in the message and implements bearer control according to a corresponding state machine and received information. 
         [0110]    The policy rule, bearer topology resource, bearer control routing data required during service control process can be found by the service selection and control unit  4014  looking up in the policy and resource management function unit  403 . 
         [0111]    As can be seen, compared with prior art, the conventional SPDF and PCRF may simply implement the SPDF and PCRF function separately with no needs for implementing service selection and control function or the like. However, the embodiments of the present invention combine the SPDF and PCRF functions and overcome the deficiency of having various frameworks and solutions for resource admission and bearer control due to various access types. 
         [0112]      FIG. 7  is a schematic flowchart according to one embodiment of the present invention where the following main steps are included, as illustrated in this figure. 
         [0113]    At step  701 , the application function unit sends a service request to the policy decision function unit. 
         [0114]    At step  702 , the policy decision function unit identifies the type of the access network according to the service request and selects corresponding service logic for resource admission and control according to the type of the access network. 
         [0115]    At step  703 , if the type of the access network is a fixed network access, the resource admission and control is performed according to the service-based policy and decision function(SPDF) procedure. 
         [0116]    At step  704 , if the type of the access network is a mobile network access, the resource admission and control is performed according to the (PCRF) procedure. 
         [0117]    The foregoing service request includes an access identifier (Access-Id) field. The information of the type of the access network is carried in the Access-Id. 
         [0118]    The foregoing service request further includes a User-Name field, a User Subscription-ID field, or a Globally-Unique-Address field. The policy decision function unit may identify the type of the access network according to the value range of the field. 
         [0119]    In the foregoing scheme, if the service request further carries a bearer control mode, then the procedure may further includes identifying, by the policy decision function unit, the bearer control mode according to the service request and selecting corresponding service logic for resource admission and control according to the bearer control mode. 
         [0120]    The control mode information can be included in the service request. The bearer control mode information can be carried in the bearer control mode field, i.e., Tran-Control-Mode. 
         [0121]    In the foregoing scheme, the application function unit may also be used to identify the type of the access network and to send the service request to different AF interface units according to the identified type of access network. The xPDF may operate according to the identified type of access network. As such, the type of the access network can be identified with no need for service request information. Rather, the type of the access network can be identified directly according to the port number. 
         [0122]    In practice, there are lots of PCRF related procedures which can be classified into types of IP-CAN session setup, an IP-CAN session termination and an IP-CAN session modification. Each type may include lots of procedures according to different cases and scenarios. Some may be a PCRF-specific procedure which can be identified by a first message initiated. Some may be similar to the service control procedure in the SPDF, which can be identified according to the method provided by the embodiments of the present invention. SPDF is the same. Some may be a SPDF-specific procedure which can be identified by a first message initiated. Some may be similar to the service control procedure in the PCRF, which can be identified according to the method provided by the embodiments of the present invention. 
         [0123]      FIG. 8  is a session setup procedure initiated by AF in the PCRF. The procedure includes the following steps. 
         [0124]    At step  801 , the service on the AF requires to trigger a policy and charging control. 
         [0125]    At step  802 , the AF generates service information related to bearer control according to the applied context. 
         [0126]    At step  803 , the request is sent via an AAR message to the PCRF. 
         [0127]    At step  804 , the service related information is stored in the PCRF. 
         [0128]    At step  805 , if the subscription-related user information is required, send a request to SPR. 
         [0129]    At step  806 , the SPR responds to the request and returns the subscription-related user information. 
         [0130]    At step  807 , the sessions which influence the IP-CAN are identified. 
         [0131]    At step  808 , the locally configured policy is used. A decision is made according to the service related information and the subscription-related user information. 
         [0132]    At step  809 , the control policy and charging rule are delivered to GW via a RAR message. 
         [0133]    At step  810 , the GW installs/modifies/deletes the PCC rule and executes the policy. 
         [0134]    At step  811 , the GW makes a response via an RAA message. 
         [0135]    At step  812 , if QoS authorization or timer needs to be updated, the GW initiates to update PDP context. 
         [0136]    At step  813 , the PCRF sends a AAA message to AF. 
         [0137]      FIG. 9  is a resource request procedure initiated by AF in the SPDF. The procedure includes the following steps. 
         [0138]    At step  901 , the AF triggers the bearer control as required. 
         [0139]    At step  902 , an AAR message is used to request the resource admission and control from the SPDF. 
         [0140]    At step  903 , the SPDF checks authorization and determines the policy. 
         [0141]    At step  904 , a request is made to A-RACF for access resource control. 
         [0142]    At step  905 , the A-RACF employs the local policy and determines if to issue the policy to RCEF. 
         [0143]    At step  906 , if the A-RACF needs to issue the policy to the RCEF, it issue the policy to the RCEF via an AAR message. 
         [0144]    At step  907 , the RCEF responds to the policy installment state. 
         [0145]    At step  908 , the A-RACF sends a respond of the result of access resource request to the SPDF. 
         [0146]    At step  909 , the SPDF issues a gateway control policy to the BGF (such as gate control, address conversion, etc). 
         [0147]    At step  910 , the BGF responds to the request. 
         [0148]    At step  911 , the SPDF responds to the request. 
         [0149]      FIG. 10  is an illustration of resource request procedure initiated by the AF in xPDF according to one embodiment of the present invention. 
         [0150]    At step  1001 , the AF triggers a resource control request upon service request. 
         [0151]    At step  1002 , the AF delivers a resource control request to the xPDF via an AAR message. 
         [0152]    At step  1003 , the xPDF determines which access resource control procedure to take according to the information in the AAR message. 
         [0153]    At step  1004 , if it is a PCRF procedure, the bearer control is implemented according to the service procedure illustrated in  FIG. 8 . 
         [0154]    At step  1005 , if it is an SPDF procedure, the bearer control is implemented according to the service procedure illustrated in  FIG. 9 . 
         [0155]    Apparently, various modifications and variations may be made by those skilled in the art without departing from the spirit and scope of the present invention. Accordingly, the present invention is intended to cover these modifications and variations if these modification and variation according to the present invention fall within the scope of the claims of the present invention and equivalent thereof.