Abstract:
A communication method in a gateway apparatus includes a transmission step of transmitting and receiving packets to and from a mobile station device, and transmitting and receiving packets to and from a home agent; and a setting step of establishing settings such that the packets from the mobile station device can be transmitted to at least a first and a second home agent, and the packets from at least the first and second home agents can be received.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2008-189833, filed on Jul. 23, 2008, the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0002]    The present invention relates to a communication method and a gateway apparatus. 
       BACKGROUND 
       [0003]    A WiMAX system is predicated on application of the IP protocol to a network, and combines L3 mobility technology based on mobile IP with L2 mobility technology based on the IEEE 802.16e standard to realize mobile services (see for example the “WiMAX Forum Network Specification”). 
         [0004]      FIG. 12  illustrates an example of the network configuration of a WiMAX system  1 . The WiMAX system  1  comprises a CSN (Core Service Network)  20 , an ASN (Access Service Network)  25 , and a MS (Mobile Station)  60 . 
         [0005]    The CSN  20  comprises HAs (Home Agents), as well as AAA (Authentication, Authorization, and Accounting) servers, DHCP (Dynamic Host Configuration Protocol) servers, and similar. 
         [0006]    The ASN  25  comprises the ASN-GWs (ASN-Gateways)  100 - 1 ,  100 - 02 , and the BSes  50 - 1  to  50 - 4 . The ASN-GWs  100 - 1  and  100 - 2  comprise FA (Foreign Agent), A-DP (Anchor-DP), and other functions. 
         [0007]      FIG. 13  illustrates an example of the flow of packets when packets are transmitted from the opposing node CN  10 . In the figure, the HA  21  and the FA/A-DP  140  are respectively comprised by the CSA  20  and the ASN-GW  100  in  FIG. 1 . Here, the IP address of the MS  60  is “m”, the IP address of the FA  140  is “A”, and the IP address of the BS  50  is “B”. 
         [0008]    The HA  21  receives a packet with the destination “m” from the CN  10  via the Internet. The HA  21  references a management table and decides the transfer destination (the FA/A-DP  140  with address “A”). The HA  21  encapsulates the packet with address “m” in a packet with address “A”, and transmits the packet to the FA/A-DP  140 . 
         [0009]    The FA/A-DP  140 , upon receiving the packet with destination “A”, decapsulates the packet, references a management table, and decides the transfer destination (the BS  50  with address “B”). The FA/A-DP  140  encapsulates the packet with destination “m” in a packet with destination “B”, and transmits the packet to the BS  50 . 
         [0010]    The BS  50  decapsulates the packet with destination “B”, and transmits the packet with destination “m” to the MS  60 . And, the MS  60  receives the packet with destination “m”. 
         [0011]    Further, in WiMAX, similarly to other wireless technology, network operation through roaming is also defined, but the MS  60  can only register a single HA  21  (see for example the “WiMAX Forum Network Specification”). 
         [0012]    Hence when the MS  60  performs network communications while roaming, as illustrated in  FIG. 14  and  FIG. 15  the MS  60  performs network communication by choosing either to connect to an HA operated by another enterprise (in  FIG. 14  and  FIG. 15 , a vHA (visited HA)  21 - 1 ), or be connecting to an HA operated by the contracting enterprise (in  FIG. 14  and elsewhere, a hHA (home HA)  21 - 2 ). 
       SUMMARY 
       [0013]    Hence one object of the invention is to provide a communication method, as well as a gateway apparatus, which prevent such declines in service quality. 
         [0014]    A communication method and a gateway apparatus which prevent declines in service quality can be provided. 
         [0015]    A communication method in a gateway apparatus has a transmission step of transmitting and receiving packets to and from a mobile station device, and transmitting and receiving packets to and from a home agent; and a setting step of establishing settings such that the packets from the mobile station device can be transmitted to at least a first and a second home agent, and the packets from at least the first and second home agents can be received. 
         [0016]    A gateway apparatus has 
         [0000]    a transmission unit, which transmits and receives packets to and from a mobile station device, and which transmits and receives packets to and from a home agent; and
 
a settings unit, which establishes settings such that the packets from the mobile station device can be transmitted to at least a first and a second home agent, and the packets from at least the first and second home agents can be received.
 
         [0017]    The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
         [0018]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  illustrates an example of the network configuration of a WiMAX system; 
           [0020]      FIG. 2  illustrates an example of an initial network registration sequence; 
           [0021]      FIG. 3  illustrates an example of HA connection information; 
           [0022]      FIG. 4  illustrates an example of HA connection information; 
           [0023]      FIG. 5  illustrates an example an ASN-GW configuration; 
           [0024]      FIG. 6  illustrates an example of processing to secure a communication path; 
           [0025]      FIG. 7  illustrates an example of processing to secure a communication path; 
           [0026]      FIG. 8A  illustrates an example of packet processing, and  FIG. 8B  illustrates an example of packet processing; 
           [0027]      FIG. 9A  illustrates an example of packet processing, and  FIG. 9B  illustrates an example of packet processing; 
           [0028]      FIG. 10  is a flowchart illustrating an example of packet processing; 
           [0029]      FIG. 11  is a flowchart illustrating an example of packet processing; 
           [0030]      FIG. 12  illustrates an example of the network configuration of a WiMAX system; 
           [0031]      FIG. 13  illustrates a conventional example of packet processing; 
           [0032]      FIG. 14  illustrates an example of a conventional communication path; and, 
           [0033]      FIG. 15  illustrates an example of a conventional communication path. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0034]    When the MS  60  connects with an HA  21 - 1  or  21 - 2  of one of the enterprises, depending on the service, there may be services which cannot be received without connecting to the HA  21 - 2  operated by the contracting enterprise. 
         [0035]    Further, when connecting to the HA  21 - 2  of the contracting enterprise via another enterprise, transfer packets are routed through the HA  21 - 1  of the other enterprise for transmission to the HA  21 - 2  of the contracting enterprise. Hence to this extent the number of transfers (number of hops) is increased, and delays occur. When providing highly interactive services involving voice, video and similar, such delays result in worsened service quality. 
         [0036]    Below, preferred aspects for implementation are explained, referring to the drawings. 
         [0037]    The overall configuration of a WiMAX system  1  is similar to that in  FIG. 12  explained above.  FIG. 1  illustrates the configuration example of the WiMAX system  1  and the flow of packets and similar. 
         [0038]    The WiMAX system  1  illustrated in  FIG. 1  comprises two CNs  10 - 1  and  10 - 2 , a visited CSN  20 - 1 , a home CSN  20 - 2 , an ASN-GW  30 , a BS  50 , and an MS  60 . 
         [0039]    Here, the visited CSN  20 - 1  and home CSN  20 - 2  are comprised by the CSN  20  of  FIG. 12 , and the ASN-GW  30  and BS  50  are comprised by the ASN  25 . 
         [0040]    The visited CSN  20 - 1  is the CSN which is visited (the movement destination) of the MS  60 , and is for example a CSN of another enterprise different from the contracting enterprise of the MS  60 . The visited CSN  20 - 1  comprises the vHA (visited HA 21 - 1 ) and the vAAA (visited AAA)  22 - 1 . 
         [0041]    The vHA  21 - 1  manages the addresses of FAs (ASN-GW  30 ) and similar in the visited CSN. The vAAA  22 - 1  executes control to collect authentication, permission, billing, and other information for an MS  60  in the visited CSN. 
         [0042]    The home CSN  20 - 2  is the CSN registered as the home network by the MS  60 , and is for example the CSN managed by the contracting enterprise of the MS  60 . The home CSN  20 - 2  comprises an hHA (home HA)  21 - 2  and an hAAA (home AAA)  22 - 2 . 
         [0043]    The hHA  21 - 2  manages the addresses of FAs (ASN-GW  30 ) and similar in the home CSN  20 - 2 . The hAAA  22 - 2  executes, in the home CSN  20 - 2 , control to collect authentication and other information for the MS  60 . 
         [0044]    ASN-GW  30  is a gateway apparatus, and comprises the functions of an A-DP and an FA as well as comprising an authenticator  31  which performs authentication management. 
         [0045]    BS  50  is a base station device, which converts packets from the ASN-GW  30  into wireless signals which are transmitted to the MS  60 , and converts wireless signals from the MS  60  into packets which are output to the ASN-GW  30 . 
         [0046]    MS  60  is a mobile station (or terminal) device, which receives and requests services by exchanging wireless signals with the BS  50 . 
         [0047]    The example illustrated in  FIG. 1  illustrates a state in which the MS  60  is subordinate to the visited BS  50  as a result of a handover or similar, and attempts to connect with the visited CSN  20 - 1 . 
         [0048]    At this time, the MS  60  requests authentication. When transmitting an authentication permission message, the hAAA  22 - 2  transmits the message with hHA  21 - 2  connection information. The vAAA  22 - 1  also appends vHA  21 - 1  connection information to the authentication permission message. The vAAA  22 - 1  transmits connection information for two HAs (hHA  21 - 2  and vHA  21 - 1 ) to the ASN-GW  30 . 
         [0049]    Based on connection information for the two HAs (hereafter “HA connection information”), the ASN-GW  30  transmits data packets which for example are highly interactive, such as audio and video, to the vHA  21 - 1 , and transmits packets with low interactivity such as e-mail to the hHA  21 - 2 . 
         [0050]    In this embodiment, the HA connection information is transmitted at the time of authentication of the MS  60 .  FIG. 2  illustrates an example of an initial network registration sequence. 
         [0051]    As illustrated in the figure, after each of the sequences for initial ranging and for basic function checks (SBC-REQ to SBC-RSP), a terminal authentication sequence is performed (PKM). Then, the hAAA  22 - 2  appends hHA  21 - 2  connection information when transmitting an Access Accept indicating terminal authentication permission, and transmits to the vAAA  22 - 1  (S 10 ), and the vAAA  22 - 1  further appends vHA  21 - 1  connection information and transmits (S 11 ). The ASN-GW  30  receives the HA connection information (S 12 ). 
         [0052]      FIG. 3  and  FIG. 4  illustrate examples of HA connection information. The presence of two types of HA connection information  311 ,  312  is due to the fact that in this embodiment there are two cases, one in which the MS  60  takes the initiative, and one in which the ASN-GW  30  takes the initiative. 
         [0053]    That is, in the case in which the MS  60  takes the initiative, each AAA (the hAAA  22 - 2  and the vAAA 22 - 1 ) notifies the MS  60  of two HoA (home addresses) when providing notification of the HA connection information  311 . And, the MS  60  uses the two HoAs selectively according to the service. 
         [0054]    For example, when receiving highly interactive voice services, the MS  60  uses the HoA to connect to the vHA  21 - 1  (in the example of  FIG. 3 , “10.10.10.111”), and at other times uses the HoA to connect to the hHA  21 - 2  (in the example of  FIG. 3 , “11.10.10.15”). The ASN-GW  30  holds the HA connection information  311 , and by comparing the transmission source addresses of packets from the MS  60  and the transmission source addresses of the connection information  311 , transmits the packets to the vHA  21 - 1  or to the hHA  21 - 2 . 
         [0055]    On the other hand, in the case in which the ASN-GW  30  takes the initiative, when each AAA gives notification of the HA connection information  312 , one HoA is provided (in the example of  FIG. 4 , “10.10.10.111”). The MS  60  uses this HoA. Upon receiving an IP packet from the MS  60 , the ASN-GW  30  extracts the service class (“DSCP”) assigned to the packet, references the HA connection information  312 , and transmits the packet to the vHA  21 - 1  or to the hHA  21 - 2 . 
         [0056]    For example, based on the HA connection information  312 , the ASN-GW  30  transmits voice data with high interactivity (in the example of  FIG. 4 , the DSCP “010010” indicates a voice data class) to the vHA  21 - 1 , and transmits other packets (in the example of  FIG. 4 , “not 010010”) to the hHA  21 - 2 . 
         [0057]    The HA connection information  311  and  312  both are information used in judgment in the ASN-GW  30  as to the service type and whether the interactivity is high or not, and the packet assignment destination (HA) is decided according to the result. 
         [0058]    Next, the configuration of the ASN-GW  30  which decides packet assignment destinations is explained.  FIG. 5  illustrates an example of such a configuration. 
         [0059]    The ASN-GW  30  comprises an authenticator processing portion  31 , a DP (Data Path) processing portion  32 , a classification processing portion  33 , and a FA processing portion/HA connection processing portion  34 . 
         [0060]    The authenticator processing portion  31  holds HA connection information  311 ,  312  and similar, and distributes assignment information and other information. 
         [0061]    The DP processing portion  32  sets the data path with the BS  50 , and performs processing for user packet transmission/reception with the BS  50  and similar. 
         [0062]    Based on assignment information from the authenticator processing portion  31 , the classification processing portion  33  decides the assignment destinations (hHA  21 - 2  or vHA  21 - 1 ) of user packets. 
         [0063]    The FA processing portion/HA connection processing portion  34  performs IP processing and similar of user packets, and transmits the user packets (IP packets) to the hHA  21 - 2  or to the vHA  21 - 1 . 
         [0064]    Next, operation to obtain or secure a communication path is explained. As described above, there are two cases, one in which the MS  60  takes the initiative (two HoAs) and one in which the ASN-GW  30  takes the initiative (one HoA), and so each is explained. 
         [0065]      FIG. 6  illustrates the case in which the MS  60  takes the initiative, and  FIG. 7  illustrates the case in which the ASN-GW  30  takes the initiative; both illustrate operations after the end of the initial network registration processing of  FIG. 2 . It is assumed that the ASN-GW  30  holds HA connection information, and that the MS  60  has been notified of the HoA. 
         [0066]    First, in  FIG. 6 , the ASN-GW  30  (DP processing portion  32 ) sets data paths for connection of the MS  60  to the two HAs (vHA  21 - 1  and hHA  21 - 2 ). 
         [0067]    After setting the two data paths, the MS  60  executes MIP registration with the two HAs from the two data paths. 
         [0068]    Upon receiving MIP registration from the MS  60 , the vHA  21 - 1  and hHA  21 - 2  judge whether the MIP registration is valid. At this time, the vHA  21 - 1  and hHA  21 - 2  have already transmitted authentication permission to the MS  60  (S 10  and S 11  in  FIG. 2 ), and so MIP registration is permitted. Then, packet communication paths from the MS  60  to the vHA  21 - 1  and hHA  21 - 2  are secured. Thereafter the MS  60  initiates packet transmission and reception. Packet processing after initiation of communication is described below. 
         [0069]    On the other hand,  FIG. 7  is an example of the case in which the ASN-GW  30  takes the initiative. The ASN-GW  30  (DP processing portion  32 ) sets a data path with the BS  50 . In this case the data path is a data path enabling connection to only one HA (vHA  21 - 1  or hHA  21 - 2 ). 
         [0070]    Next, the MS  60  executes MIP registration of one HA (the vHA  21 - 1  or hHA  21 - 2 ). 
         [0071]    Upon receiving the MIP registration from the MS  60 , the vHA  21 - 1  or hHA  21 - 2 , having already transmitted authentication permission to the MS  60 , permits MIP registration and transmits a message to this effect to the MS  60 . And, a communication path from the MS  60  to the HA (vHA  21 - 1  or hHA  21 - 2 ) is secured. 
         [0072]    Next, the ASN-GW  30  (for example, the FA processing portion/HA connection processing portion  34 ) executes MIP registration with the other HA (hHA  21 - 2  or vHA  21 - 1 ). 
         [0073]    Upon receiving the MIP registration, the other HA judges whether the MIP registration by the ASN-GW  30  is valid for the vAAA  22 - 1  or hAAA  22 - 2 . Because the ASN-GW  30  has already permitted connection to the hHA  21 - 2  or vHA  21 - 1  (S 10 , S 11  in  FIG. 2 ), MIP registration is permitted for the vAAA  22 - 1  or hAAA  22 - 2 . Then, packet communication paths from the MS  60  to the two HAs are secured. Thereafter the MS  60  initiates packet transmission and reception. 
         [0074]    Next, packet processing is explained for the two cases.  FIG. 8A  and  FIG. 8B  illustrate an example of packet processing for a case in which the MS  60  takes the initiative (with two HoAs), and  FIG. 9A  and  FIG. 9B  illustrate an example of packet processing for a case in which the ASN-GW  30  takes the initiative (with one HoA). 
         [0075]      FIG. 8A  illustrates an example of packet processing in the uplink direction when the MS  60  takes the initiative. 
         [0076]    The MS  60  transmits packets by means of the two HoAs, using an address “D” (in the example of  FIG. 3 , “10.10.10.111”) for a highly interactive surface, and using an address “C” (in the example of  FIG. 3 , “10.10.10.15”) for a service with low interactivity. 
         [0077]    Upon receiving a packet from the MS  60 , the BS  50  (S-DP  51  (Serving Data Path)) performs encapsulation, and transmits the packet, with its own address “a 1 ” as the transmission source and the address “a 2 ” of the ASN-GW  30  (A-DP/FA  40 ) as the transmission destination. 
         [0078]    Upon receiving this packet, the ASN-GW  30  performs decapsulation, and creates a packet which has the address “v 1 ” of the vHA  21 - 1  as the transmission destination when the transmission source address of the packet comprised by the data area is “D”, but has the address “h 1 ” of the hHA  21 - 2  as the transmission destination when the transmission source address is “C”, and transmits the packet to vHA  21 - 1  or to hHA  21 - 2  respectively. 
         [0079]    The vHA  21 - 1  and hHA  21 - 2  decapsulate received packets, and transmit packets transmitted from the MS  60  to the CN  10  via the Internet. 
         [0080]      FIG. 8B  illustrates an example of packet processing in the downlink direction, for the case in which the MS  60  takes the initiative. 
         [0081]    The vHA  21 - 1  and hHA  21 - 2  each receives from the CN  10  a packet addressed to the MS  60  (packets with address “D” and address “C”). The vHA  21 - 1  and hHA  21 - 2  encapsulate these packets, reference a management table which for example was created at the time of network entry (for example  FIG. 2 ), and transmit the packets to the ASN-GW  30  (A-DP/FA  40 ). 
         [0082]    The ASN-GW  30  (for example, the FA processing portion/HA connection processing portion  34 ) decapsulates the packets. The ASN-GW  30  (for example, the DP processing portion  32 ) then transmits the decapsulated packets to the BS  50  (S-DP  51 ). 
         [0083]    The BS  50  decapsulates packets from the ASN-GW  30 , extracts packets comprised by the data area, and transmits the packets to the MS  60 . The MS  60  receives two types of packets, having two HoAs as the transmission destinations (address “D” and address “C”). 
         [0084]      FIG. 9A  illustrates an example of packet processing in the uplink direction, for the case in which the ASN-GW  30  takes the initiative. 
         [0085]    The MS  60  transmits one packet with address “C” as the transmission source to the BS  50  (S-DP  51 ). 
         [0086]    The BS  50  encapsulates the received packet. The transmission source of the encapsulated packet is the BS  50  (address “a 1 ”), and the transmission destination is the ASN-GW  30  (A-DP/FA  40 ) (address “a 2 ”). 
         [0087]    Upon receiving the packet from the BS  50 , the ASN-GW  30  decapsulates the packet and extracts the packet transmitted by the MS  60 . At this time, the ASN-GW  30  reads assignment information from the HS connection information  312  and decides on the HA assignment destination. For example, the ASN-GW  30  reads the HA assignment information corresponding to the glass of the packet transmitted by the MS  60  (“DSCP” in  FIG. 4 ) (when the DSCP is “010010” (voice), the HA is the vHA  21 - 1 , and otherwise is the hHA  21 - 2 ), and decides the HA assignment. 
         [0088]    When the assignment destination HA is the hHA  21 - 2  (or the vHA  21 - 1 ), the ASN-GW  30  converts the transmission source address of the packet transmitted by the MS  60  (in the example of  FIG. 9A , converts the address into address “D”). Thas is, the ASN-GW  30  performs processing of the source address of the MS  60  assigned in advance by the vAAA  22 - 1  or hAAA  22 - 2 , and transmits the packet to the assignment destination HA. 
         [0089]    The ASN-GW  30  encapsulates a packet with the transmission source address converted or a packet with the transmission source address unconverted, and transmits the packet to the vHA  21 - 1  or the hHA  21 - 2 . In the example of  FIG. 9A , the ASN-GW  30  transmits a packet with an unconverted MS  60  transmission source address to the vHA  21 - 1 , and transmits a packet with a converted transmission source address to the hHA  21 - 2 . 
         [0090]    The vHA  21 - 1  or hHA  21 - 2  decapsulates a packet received from the ASN-GW  30 , and transmits the result to the Internet. 
         [0091]      FIG. 9B  illustrates an example of packet processing in the downlink direction, for the case in which the ASN-GW  30  takes the initiative. 
         [0092]    The vHA  21 - 1  and hHA  21 - 2  each receive a packet from the Internet addressed to the MS  60 . The vHA  21 - 1  and hHA  21 - 2  receive packets, each of which has a different transmission destination for the MS  60 . In the example of  FIG. 9B , the vHA  21 - 1  receives a packet the transmission destination address of which is “C”, and the hHA  21 - 2  receives a packet with a transmission destination address of “D”. Transmission source addresses for the MS  60  differ because of processing of the MS  60  addresses assigned by vAAA  22 - 1  and hAAA  22 - 2  in the vHA  21 - 1  and in the hHA  21 - 2 , as described above. 
         [0093]    Upon receiving the packets from the Internet, the vHA  21 - 1  and hHA  21 - 2  encapsulate the packets and transmit the packets to the ASN-GW  30  (A-DP/FA  40 ). 
         [0094]    The ASN-GW  30  decapsulates the packets, and based on the HA connection information  312 , confirms that the packets are addressed to the MS  60 . 
         [0095]    In the example illustrated in  FIG. 9B , the classification processing portion  33  converts the transmission source address of the packet from the hHA  21 - 2  from “D” to “C”. 
         [0096]    The ASN-GW  30  encapsulates the packet with transmission destination address converted and the packet with transmission destination address unconverted, and transmits the results to the BS  50  (S-DP  51 ). 
         [0097]    The BS  50  decapsulates packets from the ASN-GW  30 , and transmits the results to the MS  60 . 
         [0098]      FIG. 10  and  FIG. 11  are flowcharts illustrating examples of processing executed by the ASN-GW  30 , and illustrate examples of processing in the uplink direction and in the downlink direction respectively. 
         [0099]    In the uplink direction case illustrated in  FIG. 10 , when the ASN-GW  30  initiates processing (S 20 ), a packet is received from the BS  50  (S 21 ). 
         [0100]    The DP processing portion  32  decapsulates the received packet and extracts the transmission packet transmitted from the MS  60  (S 22 ). 
         [0101]    The classification processing portion  33  judges whether the transmission source address of the transmission packet extracted by the DP processing portion  32  matches a transmission source address in the HA connection information  311 ,  312  (S 23 ). 
         [0102]    In the classification processing portion  33 , if the transmission source address of the extracted transmission packet does not match an uplink-direction transmission source address of the HA connection information  311 ,  312  (“No” in S 23 ), the transmission packet is discarded (S 24 ). 
         [0103]    If on the other hand the transmission source address of the extracted transmission packet matches an uplink-direction transmission source address of the HA connection information  311 ,  312  (“Yes” in S 23 ), the classification processing portion  33  decides the assignment destination of the transmission packet, and judges whether transmission source address processing is necessary (S 25 ). 
         [0104]    The assignment destination of the transmission packet is decided for example as follows. The classification processing portion  33  accesses the connection information  311 ,  312  held by the authenticator processing portion  31 , and reads connection HAs as assignment information. 
         [0105]    For example, when the MS  60  has taken the initiative, because two addresses are allocated to the MS  60 , the connection HA corresponding to the transmission source address of the extracted packet is simply read from the HA connection information  311 . 
         [0106]    And, when the ASN-GW  30  has taken the initiative, the class information (DSCP) indicating the packet type is read from the extracted packet, and the connection HA corresponding thereto may then be read from the HA connection information  312 . For example, in the case of a packet for a highly interactive service as described above, the connection HA is vHA  21 - 1 , and for other packets the connection HA is hHA  21 - 2 . 
         [0107]    The judgment as to whether transmission source address processing is necessary is for example performed as follows. In a case in which the MS has taken the initiative in the HA connection information  311 ,  312 , the classification processing portion  33  judges that uplink direction transmission source address processing is unnecessary (“Yes” in S 25 ). 
         [0108]    On the other hand, in a case in which the ASN-GW has taken the initiative in the HA connection information  311 ,  312 , the classification processing portion  33  judges that uplink direction transmission source address processing is necessary. In this case, however, when the packet has a transmission source address which is the same as the uplink direction transmission source address, transmission source address processing is judged to be unnecessary (“Yes” in S 25 ). And, when the transmission source address is different from the address, transmission source address processing is judged to be necessary (“No” in S 25 ). 
         [0109]    Upon judging that transmission source address processing is necessary (“No” in S 25 ), the classification processing portion  33  converts the transmission source address (S 26 ). 
         [0110]    Next, the FA processing portion/HA connection processing portion  34  encapsulates a packet the transmission source address of which has been converted, or has not been converted (S 27 ), and transfers the packet to the relevant HA (S 28 ). And, the ASN-GW  30  ends the series of processing (S 29 ). 
         [0111]    In the case of the downlink direction illustrated in  FIG. 11 , the ASN-GW  30  initiates processing (S 30 ) and receives a packet from an HA (S 31 ). 
         [0112]    Next, the FA processing portion/HA connection processing portion  34  decapsulates the received packet and extracts the reception packet (S 32 ). 
         [0113]    Next, the classification processing portion  33  judges whether the transmission source address of the reception packet matches a downlink-direction “transmission source address” in the HA connection information  311 ,  312  (S 33 ). 
         [0114]    When there is no match (“No” in S 33 ), the classification processing portion  33  discards the reception packet (S 34 ). 
         [0115]    On the other hand, when there is a match (“Yes” in S 33 ), the classification processing portion  33  judges whether transmission destination address processing is necessary (S 35 ). 
         [0116]    Judgment of whether transmission destination address processing is necessary is for example performed as follows. The classification processing portion  33  accesses the HA connection information  311 ,  312  held in the authenticator processing portion  31 , and when two uplink-direction transmission source addresses are entered in the HA connection information  311 ,  312  (case in which the initiative is taken by the MS), it is judged that address conversion is not necessary (“Yes” in S 35 ). 
         [0117]    When there is only one uplink-direction transmission source address entered in the HA connection information  311 ,  312  (case in which the initiative is taken by the ASN-GW  30 ), when the transmission destination address of the packet is the uplink-direction transmission source address, the classification processing portion  33  judges that address conversion is not necessary (“Yes” in S 35 ). 
         [0118]    On the other hand, when the transmission destination address of the packet does not match the uplink-direction transmission source address, the classification processing portion  33  judges that address conversion is necessary (“No” in S 35 ). In this case, the classification processing portion  33  converts the transmission destination address (S 36 ). 
         [0119]    Next, the DP processing portion  32  encapsulates the packet with the transmission destination address converted or not converted (S 37 ), and transmits the packet to the MS  60  (S 38 ). 
         [0120]    Then, the ASN-GW  30  ends the series of processing (S 39 ). 
         [0121]    Thus in this embodiment, the ASN-GW  30  holds information for connection to a plurality of HAs during MS  60  authentication processing, and assigns and transmits transmission packets from the MS  60  to the HAs according to the service type. Hence compared with a case in which packets are transmitted to only one HA, a decline in service quality can be prevented. 
         [0122]    The above-described example explained a case of connection to two HAs. Connection to three or more HAs can be performed similarly to the above-described example. For example, information for connection to three or more HAs is registered in the HA connection information  311 ,  312 . 
         [0123]    Further, in the above-described example the packet assignment destination is judged from the transmission source addresses of the HA connection information  311 ,  312  and the DSCP. For example, in the HA connection information  311 ,  312 , the assignment destination may be decided using the “Protocol” information indicating the communication protocol, such as ftp or TCP, and the “Port” information indicating port numbers. In this case also, protocols corresponding to highly interactive services employ connection to vHA  21 - 1 , and protocols corresponding to other services can employ connection to hHA  21 - 2 . 
         [0124]    All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a illustrating of the superiority and inferiority of the invention. Although the embodiment(s) of the present inventions have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.