Abstract:
Apparatus and method for establishing call connection state in packet data communication system. The apparatus controls a Service General Packet Radio Service (GPRS) Support Node (SGSN) to avoid establishing a call connection state associated with an erroneous Gateway GPRS Support Node (GGSN). The SGSN attempts to establish a call connection state with a GGSN connected to the SGSN, and stores the attempt result information in a specific memory. In this case, the memory stores information indicating success or failure of the attempt directed to the specific GGSN, and call setup attempt time information, etc. Thereafter, if a call setup operation associated with the specific GGSN is re-attempted, then information associated with the specific GGSN is read from information pre-stored in the memory. Based on the read information, it is determined whether a call setup operation directed to the specific GGSN is reattempted, or another call setup operation directed to another GGSN is newly attempted.

Description:
PRIORITY  
         [0001]    This application claims priority to an application entitled “APPARATUS AND METHOD FOR ESTABLISHING CALL CONNECTION STATE IN PACKET DATA COMMUNICATION SYSTEM”, filed in the Korean Industrial Property Office on Aug. 16, 2002 and assigned Serial No. 2002-48472, the contents of which are incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a packet data communication system, and more particularly to an apparatus and method for establishing a call connection state for performing packet data transmission without selecting an erroneous node.  
           [0004]    2. Description of the Related Art  
           [0005]    Typically, a mobile communication system is a service system for providing users or subscribers with voice signals or data. The mobile communication system is classified into various kinds of mobile systems according to multiplexing types. A representative example of such a mobile communication system is a Code Division Multiple Access (CDMA) mobile communication system. The CDMA mobile communication system has developed from the IS-95 standard, designed for mainly performing transmission/reception of voice signals, to the next generation mobile communication standards required for transmitting not only the voice signals, but also high-speed data. The next generation mobile communication standards aim to provide users or subscribers with high-quality audio or video and moving picture data, and Internet search services, etc.  
           [0006]    A variety of switched networks have been developed for providing users with various information such as voice or data information in the aforementioned mobile communication system. Representative examples of such switched networks are a circuit switched network and a packet switched network. The circuit switched network is adapted to control circuit data including voice or audio data, and the packet switched network is adapted to control packet data. A mobile communication system for controlling such packet data in the packet switched network is called a packet data communication system.  
           [0007]    There is a need for the mobile communication system to have a network configuration for effectively transmitting voice signals and data. Particularly, this circuit configuration is more critical to the next generation mobile communication systems such as the International Mobile Telecommunications (IMT)—2000 which require large amounts of data to be transmitted for a variety of communication services. Therefore, a General Packet Radio Service (GPRS) based on a conventional circuit switched Global System for Mobile Communication (GSM) network has recently been developed. The most important purpose of a packet data service such as the GPRS is to provide users with conventional Internet application services, for example, wireless file transfer services and E-mail transmission/reception services using a Personal Computer (PC), and Internet search services through the World Wide Web (WWW).  
           [0008]    Typically, GPRS is classified into a terminal part, an access part, and a core network. The access part includes a base station, and a wireless network controller. The core network includes a Service GPRS Support Node (SGSN) and a Gateway GPRS Support Node (GGSN).  
           [0009]    [0009]FIG. 2 is a block diagram illustrating an example of a stack configuration of a conventional packet data mobile communication system.  
           [0010]    A Packet Data Protocol (PDP) context activation procedure between a Mobile Station (MS) and a GGSN will hereinafter be described with reference to FIG. 2.  
           [0011]    Firstly, a control tunnel for transmitting packet data is created between a mobile terminal and a GGSN to activate the PDP context. A user tunnel for transmitting the packet data is then created. A method for creating a control tunnel between the SGSN and GGSN from among several methods for creating control tunnels associated with embodiments of the present invention will hereinafter be described in more detail.  
           [0012]    The GPRS adapts an Access Point Name (APN) to activate the PDP context. The APN is an identifier (ID) for indicating a position of a packet data server to be connected with a user. Each packet data server provides a user with specific packet data upon receiving a request from the user, and has a Fully Qualified Domain Name(FQDN) a unique ID that varies with the APN information. The packet data servers are classified by the APN.  
           [0013]    A GMM/SM/SMS layer contained in a SGSN shown in FIG. 2 converts the APN into an FQDN, and acquires an Internet Protocol (IP) address of a GGSN connected from a Domain Name System (DNS) server to the packet data server. The DNS server manages records associated with the packet data servers and GGSN records associated with each packet data server. Therefore, if an FDQN received from the SGSN requests the DNS server to answer an IP address of a GGSN for providing a real packet data service later, the DNS server searches for an IP address of the GGSN using the FQDN. The DNS server informs the SGSN of the IP address found by the FQDN. Thus, if an IP address of the GGSN for providing the real packet data service later is acquired, an IP layer of the SGSN communicates with an IP layer of the GGSN using an IP.  
           [0014]    [0014]FIG. 3 is a block diagram illustrating an example of a procedure where creating a control tunnel between a SGSN and a GGSN fails in a general packet data mobile communication system. Specifically, if a control tunnel from a SGSN to a GGSN is not created, a method for creating a new control tunnel directed to another GGSN instead of the erroneous GGSN is shown in FIG. 3.  
           [0015]    Referring to FIG. 3, a MS requests information from a DNS server  302  concerning an IP address of a GGSN connected to a packet data server desiring packet data in a GMM/SM/SMS layer contained in the SGSN. Upon receiving the inquiry from the MS, the DNS server  302  informs the MS of the IP address of at least one GGSN connected to the packet data server. Provided that a plurality of GGSNs having the same IP APNs provide a MS with their services, a plurality of IP addresses may be transmitted to the MS. FIG. 3 shows an example where two GGSNs  308  and  310  are connected to a specific packet data server. The GGSN  308  is called a first GGSN, and the other GGSN  310  is called a second GGSN, as shown in FIG. 3. Upon receiving one IP address from the DNS server  302 , the SGSN  300  performs a communication function to create a control tunnel directed to a GGSN associated with the received IP address. However, upon receiving a plurality of IP addresses from the DNS server  302 , the SGSN  300  selects a specific IP address from among the plurality of IP addresses, and performs a communication function to create a control tunnel directed to a GGSN associated with the selected IP address. FIG. 3 shows an example for selecting an IP address associated with the first GGSN  308  from between two IP addresses. If a control tunnel is created as above, the SGSN  300  creates a user tunnel for transmitting real packet data to a corresponding GGSN.  
           [0016]    However, if a control tunnel between the SGSN  300  and the first GGSN  308  is not created, the SGSN  300  performs a communication function to create another control tunnel directed to the second GGSN  310  associated with the next IP address. Such control tunnel creation failure may occur due to internal factors of the first GGSN  308 , or may occur in a path for creating the control tunnel. If the control tunnel between the SGSN  300  and the second GGSN  310  is successfully created, the SGSN  300  attempts to create the user tunnel for transmitting the real packet data to the second GGSN  310 .  
           [0017]    When there are a plurality of GGSNs for supporting a desired packet data service in a conventional packet data communication system, the plurality of GGSNs are sequentially selected until the PDP context is activated, such that a procedure for creating a control tunnel is performed. Specifically, if the SGSN receives IP addresses corresponding to the plurality of GGSNs from the DNS server, the SGSN attempts to activate the PDP context using an IP address corresponding to one specific GGSN from among the plurality of GGSNs. In this case, there is a communication failure in the above specific GGSN attempting to activate the PDP context, the SGSN selects another GGSN from among the plurality of GGSNs, instead of selecting the erroneous specific GGSN, and then attempts to activate the PDP context. In this case, the SGSN does not additionally manage information of the erroneous specific GGSN. Therefore, it is difficult for the conventional packet data communication system to avoid attempting to create a control tunnel associated with the erroneous GGSN when activating the PDP context upon receiving a new request for the same service from a user. In other words, the conventional packet data communication system may reply to the same packet data service request from another mobile terminal using the erroneous GGSN failing to create the control tunnel, and may attempt to create a new control tunnel using the erroneous GGSN. In this case, it is expected that creating a control tunnel from the SGSN to the GGSN will inevitably fail. Due to a retry operation for creating such a control tunnel directed to the erroneous GGSN, a specific time at which a PDP context activation directed to a normal or good GGSN having no error is undesirably delayed.  
         SUMMARY OF THE INVENTION  
         [0018]    Therefore, the present invention has been developed in view of the above problems, and it is an object of the present invention to provide a method and apparatus for managing status information associated with an erroneous GGSN in a SGSN.  
           [0019]    It is another object of the present invention to provide a method and apparatus for controlling a SGSN to avoid selecting an erroneous GGSN.  
           [0020]    It is yet another object of the present invention to provide a method and apparatus for enhancing a packet call success rate by not activating a PDP context associated with an erroneous GGSN.  
           [0021]    It is yet another object of the present invention to provide a method and apparatus for reducing the amount of traffic by avoiding unnecessary retries, resulting in a reduction of internal network resources.  
           [0022]    Each SGSN has a memory. The memory stores an IP of a GGSN communicating with an external data network, a time at which the SGSN attempts to create a control tunnel directed to the GGSN, and information indicating success or failure of the attempt. The SGSN resets the time information at which creating a control tunnel directed to the GGSN is attempted and the attempt result information indicating the success or failure of the attempt at intervals of a predetermined time. The above information is reset to support the possibility of a change of network configuration information and remove a communication failure associated with a specific GGSN.  
           [0023]    In accordance with embodiments of the present invention, the above and other objects can be substantially accomplished by the provision of a method for creating a control tunnel from a Service General Support Node (SGSN) General Packet Radio Service (GPRS) to a Gateway GPRS Support Node (GGSN) when setting up a path for providing a specific packet data service between a Mobile Station (MS) and a packet data server in a mobile communication system for supporting a packet data service, comprising the steps of: a) upon receiving a specific packet data service request from the MS, enabling the SGSN to determine an Internet Protocol (IP) address corresponding to at least one GGSN connected to the packet data server for providing the specific packet data service; b) receiving control tunnel creation attempt result information managed by a memory in association with the determined IP address, and determining whether communication failure information is found in the received result information; and c) if there is no communication failure information, enabling the SGSN to attempt to create a control tunnel directed to a GGSN having the determined IP address.  
           [0024]    In accordance with embodiments of the present invention, there is also provided an apparatus for creating a control tunnel from a Service General Support Node (SGSN) to a Gateway General Packet Radio Service(GPRS) Support Node (GGSN) when setting up a path for providing a specific packet data service between a Mobile Station (MS) and a packet data server in a mobile communication system for supporting a packet data service, comprising: an Access Point Name (APN) translator for receiving a specific packet data service request from the MS, enabling the SGSN to determine an Internet Protocol (IP) address corresponding to at least one GGSN connected to the packet data server for providing the specific packet data service; a memory for storing an IP address of at least one GGSN according to individual identifiers (IDs) of packet data servers for previously providing packet data service, and managing control tunnel creation attempt result information associated with the IP address; and a control tunnel creator for receiving the control tunnel creation attempt result information managed by the memory in association with the determined IP address, determining whether communication failure information is found in the received result information, and attempting to create a control tunnel directed to a GGSN having the determined IP address if there is no communication failure information. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]    The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description of embodiments thereof taken in conjunction with the accompanying drawings, in which:  
         [0026]    [0026]FIG. 1 is a block diagram illustrating an example of a network configuration of a general CDMA mobile communication system for providing packet data;  
         [0027]    [0027]FIG. 2 is a block diagram illustrating an example of a conventional layered structure based on general protocols for use in individual components shown in FIG. 1;  
         [0028]    [0028]FIG. 3 is a block diagram illustrating an example of a conventional method for activating a Packet Data Protocol (PDP) context between a Service General Support Node (SGSN) system and a Gateway General Packet Radio Service (GPRS) Support Node (GGSN) system;  
         [0029]    [0029]FIG. 4 is a block diagram illustrating an example of activating a PDP context between a SGSN system and a GGSN system in accordance with an embodiment of the present invention; and  
         [0030]    [0030]FIG. 5 is a block diagram illustrating an example of activating a PDP context between a SGSN system and a GGSN system after performing the PDP context activation method shown in FIG. 4 in accordance with an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    Embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same or similar elements are denoted by the same reference numerals. A detailed description of known functions and configurations has been omitted for conciseness.  
         [0032]    [0032]FIG. 1 is a block diagram illustrating an example of a network configuration of a Gateway General Packet Radio Service (GPRS) in a mobile communication system for providing packet data in accordance with an embodiment of the present invention.  
         [0033]    Referring to FIG. 1, a Mobile Station (MS)  100  is connected to an (UTRAN) UMTS Terrestrial Radio Access Network (UTRAN)  102  including a plurality of Radio Network Controllers (RNCs). The UTRAN  102  is connected to a core network  110  including a plurality of Service General Support Node (SGSNs)  112   a  and  112   b  and a plurality of Gateway General Packet Radio Service (GPRS) Support Node (GGSNs)  118   a  and  118   b . The core network  110  is connected to a packet data server (i.e., Internet server) for providing specific packet data service over the Internet. Therefore, the MS  100  activates a Packet Data Protocol (PDP) context between the GGSNs  118   a  and  118   b  to transmit or receive packet data. It should be noted that activating the PDP context, establishing a packet call, and creating a control tunnel have the same meaning. Particularly, a method for activating a PDP context between the SGSNs ( 112   a ,  112   b ) and the GGSNs ( 118   a ,  118   b ) when the MS  100  activates a PDP context between the GGSNS  118   a  and  118   b  will hereinafter be described in detail.  
         [0034]    [0034]FIG. 4 is a block diagram illustrating an example of activating a PDP context between a SGSN system and a GGSN system in accordance with an embodiment of the present invention. Specifically, FIG. 4 illustrates an example for creating a control tunnel between a SGSN  400  and a plurality of GGSNs  410  and  412  in accordance with an embodiment of the present invention.  
         [0035]    As shown in FIG. 4, the control tunnel is created upon receiving a packet data service request from a MS “A”  414 .  
         [0036]    In order to allow the MS “A”  414  to perform packet data communication with a packet data server for providing a specific packet data service, the PDP context needs to be activated. For this purpose, a PDP context also needs to be activated between the SGSN  400  and either one of GGSNs  410  and  412 . In this case, the SGSN  400  exists on a path used for the specific packet data service.  
         [0037]    Upon receiving a specific packet data service request from the MS “A”  414 , an APN translator (i.e., a GMM/SM/SMS layer)  406  of the SGSN  400  converts APN information received from the MS “A”  414  into FQDN information corresponding to a packet data server for providing the specific packet data service. The APN translator  406  transmits the FQDN information to a DNS server  402 , and requests information from the DNS server  402  about an IP address of a GGSN connected to the packet data server. Upon receiving the FQDN information from the APN translator  406  of the SGSN  400 , the DNS server  402  searches for an IP address of a GGSN connected to a packet data server corresponding to the FQDN information on the basis of its own management information. If the DNS server  402  searches for at least one IP address, the searched IP address is transmitted to the APN translator  406  of the SGSN  400 . In FIG. 4, the transmitted IP addresses are equal to IP addresses associated with the first GGSN  410  and the second GGSN  412 .  
         [0038]    The SGSN  400  stores IP addresses received from the DNS server  402  in a memory  404 . Although memory  404  is shown as being located within the SGSN  400 , it should be appreciated by those skilled in the art that the present invention can be practiced with memory  404  located remotely from SGSN without departing from the scope of the present invention. An exemplary structure of the memory  404  contained in the SGSN  400  is shown in the following Table 1:  
                           TABLE 1                       APN FQDN   GGSN IP List   Failure   Last use time                   xxx.yyy.mnc111.mcc450.   10.2.20.2   No   20020522/120400       gprs   10.2.30.2   Yes   20020522/120402                  
 
         [0039]    With reference to the above Table 1, the APN FQDN indicates an address of a packet data server for providing a specific packet data service. Specifically, the APN FQDN indicates an address of a packet data server communicating with the MS “A”  414 . The GGSN IP list shown in the Table 1 indicates a storage area for storing IP addresses received from the DNS server  402 . The IP address “10.2.20.2” stored in the GGSN IP list is an IP address of the first GGSN  410 . The other IP address “10.2.30.2” stored in the GGSN IP list is an IP address of the second GGSN  412 .  
         [0040]    The SGSN  400  attempts to create a control tunnel in a predetermined order of the IP addresses received from the DNS server  402 . As shown in FIG. 4 and the Table 1, the SGSN  400  first selects a first IP address corresponding to the first GGSN  410  from among the IP addresses, and attempts to create a control tunnel using the selected first IP address. The SGSN  400  stores a prescribed time (i.e., a last attempt time) at which creating a control tunnel between the SGSN  400  and the first GGSN  410  is attempted in the memory  404 . If an attempt to create the control tunnel using a GTP-C  408  of the SGSN  400  is terminated, the result information indicating whether an erroneous node was found is stored in the memory  404 . The GTP-C  408  is considered to be a control tunnel generator. Referring to the Table 1, the SGSN  400  attempts to create a control tunnel associated with the first GGSN  410  at 12:04:00 on May 22, 2002. The SGSN  400  fails to create a control tunnel associated with the first GGSN  410 .  
         [0041]    If the GTP-C  408  fails to create a control tunnel associated with the first GGSN  410 , it attempts to create a control tunnel associated with the second GGSN  412  corresponding to the remaining IP addresses from among the plurality of IP addresses. In this case, the SGSN  400  stores a time at which creating a control tunnel associated with the second GGSN  412  is attempted and attempt result information in the memory  404 . As can be seen from the Table 1, the SGSN  400  attempts to create a control tunnel associated with the second GGSN  412  at 12:04:02 on May 22, 2002, and then successfully creates the control tunnel associated with the second GGSN  412 .  
         [0042]    According to an embodiment of the present invention, the memory  404  contained in the SGSN  400  includes an FQDN for identifying packet data servers providing specific packet data services, an IP address of at least one GGSN connected to the packet data server, a time at which creating a control tunnel is tried with respect to individual GGSNs, and the result information associated with the control tunnel creation trial, etc.  
         [0043]    An exemplary memory structure when the SGSN  400  is connected to packet data servers providing individual packet data services is shown in the following Table 2. Specifically, the SGSN  400  is connected to three packet data servers as shown in the Table 2.  
                           TABLE 2                           GGSN   Result           APN FQDN   IP List   Information   Last attempt time                   xxx.yyy.mnc111.mcc450.   10.2.20.2   No   20020522/120400       gprs       (First packet data server)   10.2.30.2   Yes   20020522/120402       xxx.yyy.mnc222.mcc460.   20.2.20.2   Yes   20020522/120357       gprs       (Second packet data server)       xxx.yyy.mnc333.mcc470.   10.2.20.2   No   20020522/120501       gprs       (Third packet data server)   20.2.20.2   Yes   20020522/120503                  
 
         [0044]    With reference to the above Table 2, the first GGSN having an IP address of 10.2.20.2 is connected to a first packet data server having an FQDN of “xxx.yyy.mnc111.mnc450.gprs” and a third packet data server having an FQDN of “xxx.yyy.mnc333.mcc470.gprs”. The second GGSN having an IP address of 10.2.30.2 is connected to the first packet data server having an FQDN of “xxx.yyy.mnc111.mnc450.gprs”. The third GGSN having an IP address of 20.2.20.2 is connected to the second packet data server having an FQDN of “xxx.yyy.mnc222.mcc460.gprs” and the third packet data server.  
         [0045]    In substantially the same manner as Table 1, Table 2 records therein a last attempt time at which the SGSN  400  attempts to create a control tunnel associated with each IP address of the GGSNs and the result information of the control tunnel creation trial. Specifically, the SGSN  400  fails to create a control tunnel associated with the first GGSN used for a PDP context activation with the first packet data server, and then successfully creates a control tunnel associated with the second GGSN, as shown in Table 2. Table 2 shows that the SGSN  400  successfully creates a control tunnel associated with the third GGSN to perform a PDP context activation with the second packet data server. Finally, the SGSN  400  fails to create a control tunnel associated with the first GGSN used for a PDP context activation with the third packet data server, and then successfully creates a control tunnel associated with the third GGSN, as shown in the Table 2.  
         [0046]    Although the aforementioned description relates to a PDP context activation among a plurality of packet data servers and one MS, it should be noted that such PDP context activation is available for a plurality of MSs.  
         [0047]    Memory structures shown in Tables 1 and 2 can be applicable to the SGSN  400 . However, memory  404  is illustrative of the memory structure shown in Table 1.  
         [0048]    [0048]FIG. 5 is a block diagram illustrating another example of activating a PDP context between a SGSN system and a CGSN system after performing the PDP context activation method shown in FIG. 4 in accordance with an embodiment of the present invention. Specifically, FIG. 5 illustrates an example of creating a control tunnel used for packet data transmission between a SGSN  400  and a plurality of GGSNs  410  and  412  in accordance with an embodiment of the present invention. More specifically, FIG. 5 illustrates a control tunnel creation method based upon receiving a packet data service request from a packet data server managed by a memory. In this case, it is assumed that information managed by the memory is the same as those of Tables 1 and 2, and the following explanation will be described on the basis of Table 1.  
         [0049]    Referring to FIG. 5, if a MS “B”  514  requests a packet data service of a specific packet data server, this request message of the MS “B”  514  is transmitted to the SGSN  400 . The SGSN  400  converts APN information corresponding to a packet data server for providing the request packet data service over an APN translator  406  into FQDN information. Then, the SGSN  400  transmits the FQDN information to the DNS server  402  to request information from the DNS server  402  concerning an IP address of a GGSN connected to the packet data server. The DNS server  402  checks an IP address of at least one GGSN connected to the packet data server using the FQDN, and informs the SGSN  400  of the checked IP address.  
         [0050]    Upon receiving information stored in the memory  404 , the SGSN  400  determines whether the received information includes communication failure information previously created in association with the FQDN information and the IP address received from the DNS server  402 . For example, this determination is performed on the assumption that the FQDN information is “xxx.yyy.mnc111.mcc450.gprs” and the DNS server  402  informs the SGSN  400  of an IP address “10.2.20.2” of the first GGSN  410  and an IP address “10.2.30.3” of the second GGSN  412 . A prescribed table stored in the memory  404  refers to the Table 1. In this case, the SGSN  400  checks the result information stored in the memory  404  which is associated with the IP address of 10.2.20.2. The result information indicates whether an erroneous node (creating communication failure information) has been created while attempting to create a control tunnel to receive the same packet data service. Based on the result information of the IP address “10.2.20.2” shown in the Table 1, a control tunnel associated with the first GGSN  410  fails to create prior to a predetermined time. If such an erroneous node (i.e., communication failure information) is found upon receiving the result information associated with a corresponding IP address, the SGSN  400  checks the result information stored in the memory  404  which is associated with the IP address of 10.2.30.2. Based on the result information of the IP address “10.2.30.2” shown in the Table 1, it can be recognized that a control tunnel associated with the second GGSN  412  is successfully created prior to a predetermined time.  
         [0051]    Because the SGSN  400  can recognize the result information previously created using the aforementioned operation, creating a control tunnel associated with the second GGSN  412  is attempted whereas creating a control tunnel associated with the first GGSN  410  is not attempted. The attempt to create such a control tunnel is performed in a GTP-C  408  contained in the SGSN  400 . As a result, the SGSN  400  avoids attempting to create unnecessary control tunnels, and firstly attempts to create a control tunnel associated with a GGSN having a high possibility of creating such a control tunnel.  
         [0052]    Information stored in the memory  404  of the SGSN  400  is reset on the basis of a predetermined time. In more detail, the last attempt time at which the SGSN  400  attempts to create a control tunnel associated with each GGSN, and its result information are reset at intervals of a predetermined time. The predetermined time is a user-defined time to be consumed for solving a communication failure generated in a specific GGSN, such that the predetermined time can be freely specified by a user. Also, the predetermined time can be differentially assigned according to individual packet data servers. Therefore, the SGSN can attempt to create a control tunnel associated with the GGSN after the lapse of the predetermined time.  
         [0053]    As apparent from the above description, one embodiment of the present invention enables SGSN to acquire an IP address of a desired GGSN from a DNS server, and then enables the SGSN to receive result information of a corresponding GGSN from a memory over the acquired IP address. Alternatively, according to another embodiment of the present invention, the SGSN does not request information from the DNS server concerning an IP address of a desired GGSN, rather the SGSN searches for the memory using the previously-known FQDN information, and thus obtains result information of the desired GGSN. Specifically, upon receiving a specific packet data service request from a MS, the SGSN creates FQDN information associated with the packet data server for providing the requested packet data service. Then, the SGSN searches for a memory using the FQDN information, and thus obtains result information corresponding to an IP address of a corresponding GGSN. However, if there is no information managed by the memory in association with the FQDN information, the present invention performs the operations shown in FIG. 4.  
         [0054]    Although embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.