Mobile IP network system

A home agent provides mobility transparent communications to a mobile node temporarily connected to a second network as a mobile destination different from a first network normally utilized. The home agent includes a module receiving a new registration request from the mobile node via the second network, a module detecting, when receiving the new registration request, that lease addresses of a DHCP server and addresses pooled beforehand are all occupied, and a module searching for, when detecting that all the addresses are occupied, an address on the basis of self-managed information and allocating the searched address to the mobile node.

BACKGROUND OF THE INVENTION

The present invention relates to a mobile IP network system having an address allocation management function of dynamically allocating an address to a mobile node in accordance with the mobile Internet Protocol (mobile IP).

There have increased over the recent years communication modes of utilizing handheld information terminals such as PDAs (Personal Digital Assistants), notebook type personal computers and so on as communication terminals and connecting these terminals to the IP network from a variety of places different from those usual.

The present Internet Protocol technology and mobile IP (strictly, mobile IPv4) technology enable mobility transparent communications to be actualized in a mobile IP network system, wherein a node connected normally to specified network (that may be called a home network as a base network to a mobile target node (mobile communication terminal)) is temporarily connected as a mobile node to a different network (a foreign network utilized in a local area to which the mobile node moves), and receives an IP packet originally addressed (transmitted) to a fixed IP address (home address) of this mobile node from a sender node in the home network, and namely the IP packets are forwarded to anywhere the mobile node moves to.

A method of allocating the IP address fixedly to the mobile node concerned and a method of temporarily allocating (leasing) IP address on the basis of DHCP (Dynamic Host Configuration Protocol) are provided as methods of allocating the IP address as a home address to the mobile node.

According to this DHCP, a DHCP server batchwise manages the IP addresses. For example, if the mobile node as an information device is newly connected to the home network and operated, this information device functions as a DHCP client (client terminal).

The DHCP client normally connected to the home network broadcasts an IP address allocation requests to the DHCP server on the home network immediately after the DHCP client has been operated. The DHCP server detecting this IP address allocation request provides the DHCP client with an IP address that can be allocated at that point of time.

In the case of the mobile node, this mobile node, when accessing the home network via the foreign network, sends a registration request to the home agent. If the IP address (home address) of the mobile node is not yet set at this registration request time, it is a rule that the home agent as a proxy of the mobile node obtains the IP address from the DHCP server and notifies the mobile node connected to the foreign network of this obtained IP address. It does not happen that the mobile node requests directly the DHCP server to allocate the IP address.

An up-to-date and popular way of utilizing the mobile node is that the user of the mobile node establishes a contract with a provider such as ISP (Internet Service Provider) for providing a certain category of information communication service and receives this service.

The number of the mobile nodes (contract user count) receiving this service is larger than the number of the IP address held by the provider, and it is therefore impossible for all the mobile nodes to receive the services at the same timing. Consequently, there appear the users who desire to use the mobile nodes any time in a way that corresponds to a content of the contract.

Further, if a registration request is given from the mobile node, the DHCP server must allocate the IP address to the mobile node. When used as by an e-mail and if accessed from a multiplicity of mobile nodes all day though short in time, the DHCP server allocates the IP address each time, a rise in load upon the home network is inevitable.

According to the conventional mobile IP network system, if the mobile node is unable to obtain the IP address from the DHCP server, or if unable to obtain the IP address from a reserve pool held by the home agent, the mobile node cannot be provided with the mobility transparent communication service.

FIGS.21(A) and21(B) show an outline of a process for dynamically allocating the IP address to the mobile node in the conventional mobile IP network system.

The conventional mobile IP network system, though an illustration of this system architecture is herein omitted, includes a home network system and a foreign network system. The home network system is connected to the foreign network system via an IP (IPv4) network such as the Internet or Intranet.

The home network system is configured by a home network, a home agent connected to this home network and serving to administer a connection from the foreign network, and a general terminal (a mobile node as a mobile target).

Further, the foreign network system is configured by a foreign network, a mobile node connected to the foreign network, making a request for an access to the home network and forwarding/receiving IP packets, and a foreign agent that administers a connection to the home network from the mobile node via the foreign network.

The home agent in the home network system has an address allocation management function of dynamically allocating the IP address (home address) to a device connected afresh via the foreign network.

As indicated by processing steps SA01to SA05shown in FIG.21(A) and processing steps SB01to SB05shown in FIG.21(B), when the home agent receives a new registration request from the mobile node connected to the foreign network via the foreign agent, the home agent, based on the address allocation management function, obtains an IP address to be temporarily allocated to the mobile node out of the DHCP server or a reserve pool, and continues the registration process for the mobile node with the IP address obtained.

The home agent, if unable to obtain the IP address to be temporarily allocated to the mobile node out of the DHCP server or the reserve pool, sends to the mobile node a reply that the address cannot be obtained. Herein, the DHCP server is normally connected to the home network, and the reserve pool is configured on a memory of the home agent.

Note that if the home agent dynamically allocates the IP address to the mobile node, a method of obtaining a free address from the DHCP server or the reserve pool maybe used in combination.

An address allocation to a specified user (who desires for an ever-use of the mobile node) corresponding to the mobile node can be attained by fixing the IP address to the specified user or reserving beforehand the IP address presumed to be necessary in consideration of a node activity ratio by the specified user and allocating the reserved IP address to the specified user.

The number of the addresses usable for the mobile nodes is, however, a finite number, and it follows that the addresses left after allocating the IP addresses to the specified users are allocated to general users corresponding to the mobile nodes. Hence, the number of the general users allowed to receive the services is limited.

Further, queries of the DHCP server for obtaining the IP addresses lead to a traffic load on the home network.

SUMMARY OF THE INVENTION

It is a primary object of the present invention to provide an address allocation management method capable of relieving, though impossible of avoiding that there might appear some users unable to receive services because of a finite number of IP addresses for mobile nodes, en exhaustion of the IP addresses by using the IP addresses as effectively as possible, and of reducing a traffic on a home network.

To accomplish the above object, according to one aspect of the present invention, a first home agent that provides mobility transparent communications to a mobile node temporarily connected to a second network as a mobile destination different from a first network normally utilized, comprises a module receiving a new registration request from the mobile node via the second network, a module detecting, when receiving the new registration request, that lease addresses of a DHCP server and addresses pooled beforehand are all occupied, and a module searching for, when detecting that all the addresses are occupied, an address on the basis of self-managed information and allocating the searched address to the mobile node.

A second home agent according to the present invention may further comprise a module temporarily pooling the address requested to be open by the mobile node without immediately returning the address to the DHCP server.

A third home agent according to the present invention may further comprise a module allocating the temporarily pooled address to the mobile node making the new registration request.

A fourth home agent according to the present invention may further comprise a module extracting an address just before time-out of a life time and allocating this extracted address to the mobile node making the new registration request. Herein, the address just before the time-out of the life time may be extracted from a mobile binding list.

A fifth home agent according to the present invention may further comprise a module administering address allocation priorities of users corresponding to the mobile nodes.

A sixth home agent according to the present invention may further comprise a module, when the new registration request is given from the mobile node used by a higher priority user, extracting a lower priority user, stopping providing a mobile service to the extracted user, and allocating an address used by the extracted user to the mobile node making the new registration request.

A seventh home agent according to the present invention may further comprise a module extracting, when the new registration request is given from the mobile node used by a higher priority user, all lower priority users, and stopping providing mobile services to all the lower priority users extracted.

An eighth home agent according to the present invention may further comprise a module temporarily pooling the address used by the user stopped from receiving the mobile service without immediately returning the same address to the DHCP server.

According to the present invention, the address requested to be open by the mobile node is not immediately returned to the DHCP server but is temporarily pooled in the home agent, thereby making it possible to decrease both of the access count to the DHCP server and the home network traffic.

Further, according to the present invention, the address temporarily pooled is allocated to the mobile node making the new registration request, thereby making it possible to decrease both of the access count to the DHCP server and the hone network traffic.

Moreover, according to the present invention, the address just before the time-out of the life time is extracted from the mobile binding list, whereby the address extracted can be allocated to the mobile node as the new registration requester without waiting for the time-out.

Furthermore, according to the present invention, the address allocation priorities of the registered users are administered, whereby the services differentiated based on the priorities can be provided.

According to the present invention, when the registration request is given from the mobile node used by the higher priority user, the lower priority user is extracted from the mobile binding list and stopped from receiving the mobile service, thereby making it feasible to enhance the service provided to the higher priority user.

According to the present invention, the address used by the user stopped from receiving the mobile service is not immediately returned to the DHCP server but is temporarily pooled in the home agent, thereby making it possible to decrease both of the access count to the DHCP server and the home network traffic.

Still further, a scheme according to the present invention is that the address is, as if seemingly usable any time without allocating the address to the single specified user, allocated to the general user when the specified user does not use the mobile node, the number of the addresses usable at the same timing can be increased.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[Architecture of Mobile IP Network System]

FIGS. 1 and 2show an architecture of a mobile IP network system in one embodiment of the present invention. Referring toFIGS. 1 and 2, this mobile IP network system SYS includes a home network system HNM and a foreign network system FNW. The home network system HNM is connected to the foreign network system FNW via an IP (IPv4) network700such as the Internet or Intranet.

The home network system HNW is configured by a home network500such as a wireless LAN, a home agent (HA)100connected to the home network500and serving to administer a connection from the foreign network, a DHCP server200as a lender of an IP address (that might be simply called an address), i.e., a home address, and a general terminal (a mobile node as a mobile target)520.

Further, the foreign network system FNW is configured by a foreign network600such as the wireless LAN, a mobile node (MN)400connected to the foreign network600, making a request for an access to the home network500and forwarding/receiving IP packets, and a foreign agent (FA)300that administers a connection to the home network500from the mobile node400via the foreign network600.

The home agent100in the home network system HNW has an address allocation management function of dynamically allocating the IP address as a home address to the mobile node400connected afresh via the foreign network600.

To give a more detailed description, the home agent100and the foreign agent300are categorized as routers. In the home agent100, an address management module110has a function of managing a user information database150, a priority address database160and an open address database170, and a function of referring to a mobile binding list180. The address management module110administers address-related control processes (allocation/open).

A mobile management module120administers mobile-related processes and, if the address-related control process occurs, entrusts the address management module110with this process. The home agent100further includes a mobile data transmitting/receiving module130connected via an IP network700to the foreign agent300, and a data transmitting/receiving module140connected to the DHCP server200via the home network

The DHCP server200includes an address management module210, a data transmitting/receiving module240, and an address information database250. The address management module210, based on the DHCP defined as a server/client type protocol, dynamically allocates (leases) the IP address to each mobile node400when booted and collects the lease IP addresses when ended.

The foreign agent300includes a mobile management module320, a mobile data transmitting/receiving module330, and a data transmitting/receiving module340. The mobile management module320administers mobile-related processes between the home agent100and the mobile node400.

The mobile node400includes a data transmitting/receiving module440and a connection request issuing module460. The connection request issuing module460issues a registration request message or an open request message as a connection request.

Note that each of the general terminals520and the mobile nodes400as the mobile terminals (mobile communication terminals) may be, if structured to implement a communication function, and information display function and an information specifying function, a single or composite unit of any one category of mobile phone terminals of i-mode, EZweb, J-sky and so on, and mobile information terminals such as PDAs (Personal Digital Assistants), notebook type personal computers and so forth.

[Various Categories of Databases]

Next, various categories of databases possessed by each of the home agent100and the DHCP server200in the home network system HNW described above, will be explained.

FIGS.3(A),3(B),3(C) and3(D) through FIGS.14(A),14(B),14(C) and14(D) show one examples of data stored in the user information database150, the priority address database160, the open address database170and the mobile binding list180that constitute the home agent100.

FIG. 15shows one example of data stored in the address information database250constituting the DHCP server200.

Herein, a user priority of using the mobile node is categorized into three levels for simplifying the description, however, much more levels may also be set. Further, a priority rank is set such as a priority A>a priority B>a priority C in this example.

Namely, the implication is that the user given the priority A is a specified user having the top priority, the user given the priority B is a general user having a middle priority, and the user given the priority C is a user (allowed to access, e.g., free of charge as a trial) having the lowest priority. Moreover, it is assumed that an active user count (the number of users using the mobile nodes) be based on a relationship such as the priority A<the priority B>the priority C.

In the discussion made herein, categories of the data stored in the respective databases and transitions of the data stored in the databases that correspond to variations in mobile node oriented users' activities, will be explained.

(1) FIGS.3(A),3(B),3(C) and3(D) show states of the databases when none of users are active, i.e. when none of the mobile nodes400are connected to the foreign network600in the foreign network system FNW.

As illustrated in FIG.3(A), when none of the users are active, the user information database150is registered beforehand with mappings of mobile node (connection) oriented user identifiers (MN-NAI: Mobile Node-Network Access Identifiers) to users' priorities.

In this example, totally 15 users, i.e., five users (user identifiers: aaa1to aaa5) given the priority A and ten users (user identifiers: bbb1to bbb10) given the priority B, are registered beforehand in the user information database150.

Further, as illustrated inFIG. 3(B), n-pieces of addresses (home agent HA acquisition addresses) allowing for a priority-A user count and an activity ratio, are obtained from the DHCP server200, and registered beforehand in the priority address database160.

In this example, five users with the priority A are registered in the user information database150, and hence IP addresses aaa.aaa.aaa.aa1through aaa.aaa.aaa.aa3for three users given the priority A are acquired and previously registered in consideration of the activity ratios.

As shown in FIG.3(C), an IP address, an open time and a forced delete rank are stored in the open address database170.

The address registered in the open address database170is an address (a lease IP address) leased by the home agent100from the DHCP server200.

The [forced delete rank[ in the open address database170is defined as a sub-item to the address forcibly acquired from the priority-B user (general user) or the priority-C user (the lowest priority user). The data entered in this [forced delete rank] field indicate which user, the priority-A user or priority-B user or others, the forcibly acquired address is allocated to.

Further, the [open time] in the open address database170represents a time (effective time t) for pooling for a certain period of time, and a time (protection time z) that permits the forcibly acquired address to be allocated to the higher priority user.

Namely, when the open time expires, the address is returned to the DHCP server200. If the open time is within a time (a protection time: z1) for which the address can not be allocated to the priority-B user, the address allocation to the priority-B user is rejected, and if within a time (a protection time: z2) for which the address can not be allocated to the priority-C user, the address allocation to the priority-C user is rejected. Herein, a relationship between the protection times z1and z2is that the priority B (z1) is to be longer than the priority C (z2).

Further, as shown in FIG.3(D), the mobile binding list180is stored with an active user identifier, an active address, an active user priority and a life time LT.

(2) FIGS.4(A),4(B),4(C) and4(D) show statuses in the databases when only the user aaa1is active, i.e., when the mobile node400used by the user aaa1is connected to the foreign network600in the foreign network system FNW.

As shown in FIG.4(B), the user aaa1is given the priority A and is therefore is allowed to use the IP address aaa.aaa.aaa.aa1registered beforehand in the priority address database160, and this status can be administered based on contents stored in the priority address database160.

Further, as shown in FIG.4(D), it is possible to administer the status that the user aaa1uses the IP address aaa.aaa.aaa.aa1on the basis of the contents stored in the mobile binding list180.

(3) FIGS.5(A),5(B),5(C) and5(D) show statuses in the databases when the users aaa1and bbb1are active, i.e., when the mobile bodes400used by the users aaa1and bbb1are connected to the foreign network600in the foreign network system FNW.

As shown in FIG.5(B), the user aaa1is given the priority A and is therefore is allowed to use the IP address aaa.aaa.aaa.aa1registered beforehand in the priority address database160, and this status can be administered based on contents stored in the priority address database160.

The user bbb1is, however, given the priority B and therefore needs to obtain an IP address bbb.bbb.bbb.bb1from the DHCP server200. If the user bbb1obtains the IP address bbb.bbb.bbb.bb1from the DHCP server200, as shown inFIG. 15, [bbb.bbb.bbb.bb1] as a lease IP address and [abc1(an identifier of the home agent100)] as a client identifier are stored together with a lease time [1] in the address information database250of the DHCP server200.

As shown in FIG.5(D), it is possible to administer the status that the users aaa1and bbb1use the IP addresses aaa.aaa.aaa.aa1and bbb.bbb.bbb.bb1on the basis of the contents stored in the mobile binding list180. Moreover, a residual time x1of the life time LT of the lease IP address allocated to the user bbb1can be administered.

(4) FIGS.6(A),6(B),6(C) and6(D) show statuses in the databases when the user bbb1finishes using the mobile mode.

As shown in FIG.6(D), when the user bbb1finishes the use, a record corresponding thereto is deleted from the contents stored in the mobile binding list180. Further, as shown in FIG.6(C), the IP address bbb.bbb.bbb.bb1used so far by the user bbb1is stored within the open time (effective time) t in the open address database170and administered therein. This open time t is shorter than the lease time [1].

(5) FIGS.7(A),7(B),7(C) and7(D) show statuses in the databases when the user bbb2starts using the mobile mode from the status shown in the process (4).

As shown in FIG.7(D), when the user bbb2starts the use, a record corresponding thereto is added to the mobile binding list180. Based on the contents stored in the mobile binding list180, it is feasible to administer the status that the users aaa1, bbb2use the IP addresses aaa.aaa.aaa.aa1and bbb.bbb.bbb.bb1, respectively.

Further, as shown in FIG.7(C), the IP address bbb.bbb.bbb.bb1used by the user bbb1is reused by the user bbb2(the IP address bbb.bbb.bbb.bb1is obtained not from the DHCP server200but from the open address database170), and hence this is deleted from the contents stored in the open address database170.

(6) FIGS.8(A),8(B),8(C) and8(D) show statuses in the databases when a new user does not occur within the open time t from the state in the process (4).

As shown in FIG. (C), if the new user does not occur within the open time t, the IP address bbb.bbb.bbb.bb1is deleted from the open address database170.

(7) FIGS.9(A),9(B),9(C) and9(D) show statuses in the databases when the users aaa1through aaa5are active, i.e., when the mobile nodes400used by the users aaa1through aaa5are respectively connected to the foreign network600in the foreign network system FNW.

As shown in FIG.9(B), it is feasible to administer, based on the contents stored in the priority address database160, the priority-A users aaa1, aaa5and aaa4using the IP addresses aaa.aaa.aaa.aa1through aaa.aaa.aaa.aa3registered beforehand in the priority address database160.

The users aaa2and aaa3are given the priority A, however, all the IP addresses registered previously in the priority address database160are occupied, and hence there is a necessity of obtaining the IP addresses bbb.bbb.bbb.bb1and bbb.bbb.bbb.bb2from the DHCP server200.

If the users aaa2and aaa3acquire the IP addresses bbb.bbb.bbb.bb1and bbb.bbb.bbb.bb2from the DHCP server200through the home agent100as the proxy, the lease IP addresses [bbb.bbb.bbb.bb1andbbb.bbb.bbb.bb2] and the client identifier [abc1] are stored together with each lease time in the address information database250of the DHCP server200shown in FIG.15.

As shown in FIG.9(D), the status that the users aaa1through aaa5respectively use the IP addresses can be administered based on the contents store din the mobile binding list180.

(8) FIGS.10(A),10(B),10(C) and10(D) show statuses in the databases when none of the users are active from the status in the process (7).

As shown in FIG.10(B), the active user identifiers and the priority data of the active users are deleted from the contents stored in the priority address database160. As shown in FIG.10(D), all the corresponding records are deleted from the contents stored in the mobile binding list180.

Further, as shown in FIG.10(C), the IP addresses bbb.bbb.bbb.bb1and bbb.bbb.bbb.bb2obtained from the DHCP server200are stored in the open address database170and administered up to the open time t.

(9) FIGS.11(A),11(B),11(C) and11(D) show statuses in the databases when the user given the priority B leases the IP address for the priority-A user.

As shown in FIG.11(B), it is possible to administer, based on the contents stored in the priority address database160, a status that the priority-A user aaa3uses the IP address aaa.aaa.aaa.aa1registered beforehand in the priority address database160, and a status that the priority-B user bbb10uses (leases) the IP address aaa.aaa.aaa.aa2.

As shown in FIG.11(D), the status that the priority-B user bbb10uses the IP address aaa.aaa.aaa.aa2for the priority-A user, can be administered based on the contents stored in the mobile binding list180.

Note that if the users bbb1to bbb5acquire the IP addresses bbb.bbb.bbb.bb1to bbb.bbb.bbb.bb5from the DHCP server200through the home agent100as the proxy, the lease IP addresses [bbb.bbb.bbb.bb1to bbb.bbb.bbb.bb5] and the client identifier [abc1] are stored together with each lease time in the address information database250of the DHCP server200shown in FIG.15.

(10) FIGS.12(A),12(B),12(C) and12(D) show statuses in the databases when the users given the priorities A, B and C are active one after another.

As shown in FIG.12(B), a status that the priority-A users aaa1to aaa3use the IP addresses aaa.aaa.aaa.aa1to aaa.aaa.aaa.aa3registered in beforehand in the priority address database160, can be administered based on the contents stored in the priority address database160.

The users bbb1to bbb7and ccc1to ccc4are given the priorities B and C and therefore need to acquire the IP addresses bbb.bbb.bbb.bb1to bbb.bbb.bbb.bb7and ccc.ccc.cc1to ccc.ccc.ccc.cc4from the DHCP server200.

As shown in FIG.12(D), a status that the users aaa1to aaa3, bbb1to bbb7and ccc1to ccc4respectively use the IP addresses, can be administered based on the contents stored in the mobile binding list180.

(11) FIGS.13(A),13(B),13(C) and13(D) show statuses in the databases when forcibly deleting all the priority-C users with a service request made by the priority-A user in the status shown in the process (10) and providing the priority A-user with the service.

As shown in FIG.13(D), all the records corresponding to the priority-C users ccc1to ccc4are forcibly deleted from the contents stored in the mobile binding list180. Then, the IP address ccc.ccc.ccc.cc1used so far by the priority-C user ccc1is allocated to the priority-A user aaa4, and this status is administered.

Further, as shown in FIG.13(C), the IP addresses ccc.ccc.ccc.cc2to ccc.ccc.ccc.cc4used so far by the priority-C users ccc2to ccc4are stored in the open address database170. These IP addresses are inhibited from being allocated to the users other than the priority-A users up to the open time (protection time) z in accordance with the contents stored in the [forced delete rank] field.

(12) FIGS.14(A),14(B),14(C) and14(D) show statuses in the databases after an elapse of the protection time z of the IP address forcibly deleted in the status in the process (11).

FIG.14(C) shows that a preferential allocation mode to the priority-A user is switched over to a general allocation mode by clearing the forced delete rank after the elapse of the protection time z of the forcibly deleted IP address and rewriting the storage contents at the open time t, and that the IP address obtained is returned to the DHCP server200after the open time t has elapsed.

If the priority-A, -B and -C users make registration requests in this status, the IP addresses ccc.ccc.ccc.cc2through ccc.ccc.ccc.cc4stored in the open address database170can be allocated.

Next, an address allocation management method in the mobile IP network system SYS in one embodiment of the present invention shown inFIGS. 1 and 2, will be described.

FIGS. 16,17and18are flowcharts showing procedures of an address allocation management process in the home agent100.

Herein, the user priority is categorized into the three levels for simplifying the description, however, muchmore levels may also be set. Further, the priority rank is set such as the priority A>the priority B>the priority C in this example.

Namely, the implication is that the user given the priority A is a specified user (the specified user) having the top priority, the user given the priority B is the general user having the middle priority, and the user given the priority C is the user (allowed to access, e.g., free of charge as a trial) having the lowest priority. Moreover, it is assumed that the active user count be based on the relationship such as the priority A<the priority B>the priority C.

Referring first toFIGS. 1,2and16, the home agent100in the home network system HNW in this mobile IP network system SYS previously registers the user information database150with mappings of the mobile node oriented user identifiers (MN-NAI) to the user priorities as a pre-preparation (processing step S1601) for executing the address allocation management process which will hereinafter be described.

Herein, as FIG.3(A) shows the specific example, totally 15 users, i.e., five users (user identifiers: aaa1to aaa5) given the priority A and ten users (user identifiers: bbb1to bbb10) given the priority B, are registered beforehand in the user information database150.

Further, the home agent100, as the pre-preparation (S1601) obtains n-pieces of addresses (home agent HA acquisition addresses) allowing for a priority-A user count and an activity ratio from the DHCP server200, and registers them beforehand in the priority address database160.

Herein, five priority-A users are registered in the user information database150, and hence, as FIG.3(B) shows the specific example, IP addresses (aaa.aaa.aaa.aa1through aaa.aaa.aaa.aa3) for three priority-A users are acquired and previously registered.

Each registration in this pre-preparation can be executed in such a way that an administrator of, e.g., the home network system HNW accesses the address management module110via the data transmitting/receiving module140from a maintenance terminal (unillustrated) connected to the home network500.

The address management module110in the home agent100in the home network system HNW receives an address request (registration request) transmitted by the mobile data transmitting/receiving module130from the mobile node400, then refers to the user information database150, this reference being triggered by the registration request given from the mobile management module120notified of this receipt status from the mobile transmitting/receiving module130, and makes a judgement about a mobile node oriented user priority of the user making the same registration request (S1602, S1603).

As a result of this judgement, in the case of the registration request given from the priority-A user (the specified user), the address management module110extracts the IP address (the HA acquisition address) from the priority address database160that has been previously reserved for the priority-A user, and notifies the mobile management module120of this extracted IP address (S1604).

If unable to extract the address in S1604(S1605), the address management module110extracts the address from the open address database170, and notifies the mobile management module120of this extracted address (S1606).

If unable to extract the address in S1606(S1607), the address management module110extracts the address from the HDCP server200, and notifies the mobile management module120of this extracted address (S1608).

If unable to extract the address in S1608(S1609), the address management module110extracts the address that is on the verge of time-out of the life time LT from the mobile binding list180, and notifies the mobile management module120of this extracted address (S1610). Note that a residual time obtained by a subtraction of the address management module110is always set in the “life time (LT)” field in the mobile binding list180. The address just before the time-out of the life time (LT) has a high possibility of its being not what is normally disconnected but what is left as a residual.

If unable to extract the address in S1601(S1611), the address management module110lists up the priority-C users (mobile nodes) receiving the mobile services on the basis of the mobile binding list180(see FIG.12(D)), and notifies the mobile management module120of this list.

The mobile management module120rejects an update request of the mobile node400receiving a registration update among the mobile nodes400listed up in the notified list, and notifies the address management module110for the forcible acquisition. Further, the mobile management module120stops tunneling (forwarding of encapsulated IP packets) to the notified address.

The address management module110notifies the mobile management module120that the address notified from the mobile management module120is to be allocated to the priority-A user. At this time, an update request reject count is adjusted depending on how much a registration request queue count is. This adjusting method may involve a one-by-one adjustment or a (queue count+n-pieces) suite adjustment or an overall adjustment (S1612).

If unable to extract the address in S1612, i.e., if there is no priority-C user (S1613), the address management module110lists up addresses to be allocated to the priority-A users from the addresses for the priority-B users with reference to the mobile binding list180, and notifies the mobile management module120of this list.

The mobile management module120rejects the update request of the mobile node400receiving the registration update among the mobile nodes400listed up in the notified list, and notifies the address management module110of an address of the rejected mobile node. Further, the mobile management module120stops tunneling to the notified address.

The address management module110notifies the mobile management module120that the address notified from the mobile management module120is to be allocated to the priority-A user (S1614).

If unable to extract the address in S1614(S1615), the address management module110lists up the priority-B users (mobile nodes) receiving the mobile services on the basis of the mobile binding list180, and notifies the mobile management module120of this list.

The mobile management module120rejects the update request of the mobile node400receiving the registration update among the mobile nodes400listed up in the notified list, and notifies the address management module110of an address of the rejected mobile node. Further, the mobile management module120stops tunneling to the notified address.

The address management module110notifies the mobile management module120that the address notified from the mobile management module120is to be allocated to the priority-A user. At this time, the update request reject count is adjusted depending on how much the registration request queue count is. This adjusting method may involve the one-by-one adjustment or the (queue count+n-pieces) suite adjustment or the overall adjustment (S1616).

If unable to extract the address in S1616(S1617), it implies that all the addresses are used up for the allocations to priority-A users, and at this time the registration request for the mobile service is not rejected till it comes to this status. Namely, the home agent100gives the mobile node400a reply that the address can not be acquired via the foreign agent300and the foreign network600in the foreign network system FNW (S1618).

If able to extract the address in each of S1604, S1606, S1608, S1610, S1612, S1614and S1616, the address management module110continues the registration request process with respect to the mobile node400on the basis of the address obtained (S1619).

Referring next toFIGS. 1,2and17, as a result of the judgement about the registration requester mobile node oriented user priority (S1603in FIG.16), in the case of the registration request given from the priority-B user (the general user), the address management module110extracts the address from the open address database170, and notifies the mobile management module120of this extracted address (S1701).

If unable to extract the address in S1701(S1702), the address management module110extracts the address from the DHCP server200, and notifies the mobile management module120of the extracted address (S1703).

If unable to extract the address in S1703(S1704), the address management module110extracts the address just before the time-out of the life time LT from the mobile binding list180, and notifies the mobile management module120of this extracted address (S1705).

If unable to extract the address in S1705(S1706), the address management module110extracts the address (the HA acquisition address registered beforehand in the priority address database160in the pre-preparation) from the priority address database160, i.e., leases the address for the priority-A user for the priority-B user, and notifies the mobile management module120of this extracted address (S1707).

If unable to extract the address in S1707(S1708), the address management module110lists up the addresses of the priority-C users (mobile modes) receiving the mobile services on the basis of the mobile binding list180, and notifies the mobile management module120of this list.

The mobile management module120rejects the update request of the mobile node receiving the registration update among the mobile nodes listed up in the notified list, and notifies the address management module110of an address of the rejected mobile node. Further,the mobile management module120stops tunneling to the notified address.

The address management module110notifies the mobile management module120that the address notified from the mobile management module120is to be allocated to the priority-B user. At this time, the update request reject count is adjusted in the same way as described above depending on how much the registration request queue count is (S1709).

If unable to extract the address in S1709(S1710), it implies that all the addresses are used up for the allocations to priority-B users, and at this time the registration request for the mobile service is not rejected till it comes to this status. Namely, the home agent100gives the mobile node400a reply that the address can not be acquired via the foreign agent300and the foreign network600in the foreign network system FNW (S1711).

If able to extract the address in each of S1701, S1703, S1705, S1707and S1709, the address management module110continues the registration request process with respect to the mobile node400on the basis of the address obtained (S1712).

Referring next toFIGS. 1,2and18, as a result of the judgement about the registration requester mobile node oriented user priority (S1603in FIG.16),in the case of the registration request given from the priority-C user (the lowest priority user) the address management module110extracts the address from the open address database170, and notifies the mobile management module120of this extracted address (S1801).

If unable to extract the address in S1801(S1802), the address management module110extracts the address from the DHCP server200, and notifies the mobile management module120of the extracted address (S1803).

If unable to extract the address in S1803(S1804), the address management module110extracts the address just before the time-out of the life time LT from the mobile binding list180, and notifies the mobile management module120of this extracted address (S1805).

If unable to extract the address in S1805(S1806), it implies that all the addresses are used up for the allocations to priority-A and -B users, and at this time the registration request for the mobile service is not rejected till it comes to this status. Namely, the home agent100gives the mobile node400a reply that the address can not be acquired via the foreign agent300and the foreign network600in the foreign network system FNW (S1807).

If able to extract the address in each of S1801, S1803and S1805, the address management module110continues the registration request process with respect to the mobile node400on the basis of the address obtained (S1808).

FIGS.19(A) and19(B) show one example of processing steps for temporarily pooling the addresses to be open in the address allocation management process described above, i.e., the addresses that must be returned to the HDCP server200. Herein, the priority rank count and the processes (services to be provided can be set and carried out in multiple variations depending on how these elements are combined.

With respect to the addresses registered in the open address database170, the addresses leased by the home agent100from the DHCP server200are administered.

If the address to be open is the priority address, the address management module110of the home agent100returns this address to the priority address database160. This open address return process serves to reduce the access count to the DHCP server200and to relieve the IP traffic on the home network500, and makes it possible to differentiate the priority-based address allocations.

As shown in FIG.19(A), in the database registration process (S1901through S1903), the address management module110of the home agent100registers the open address database170with the address used so far by the user corresponding to the open-requester mobile node, this registration being triggered by the address open (request) via the mobile management module120.

At this time, an allowable value (limit value) of the registerable address count is set in the open address database170. If over the limit value, the address management module110returns the address concerned to the DHCP server200.

Further, the address management module110, when registering the open request address in the open address database170, sets the open time (the effective time) and the forced delete ranks.

As shown in FIG.19(B), in the database delete process (S1904to S1906), the address management module110of the home agent100periodically manages the address open time registered in the open address database170on the basis of the allowable value. The address management module110, when the open time expires, returns the address concerned to the DHCP server200.

As shown inFIG. 20, in the address extraction process, the address management module110refers to the user information database150, this reference being triggered by the address request given from the mobile management module120, and makes a judgement about the priority of the user as a registration requester (S2001).

As a result of the priority judgement, in the case of the registration request given from the priority-A user, the address management module110extracts the address from the open address database170(S2002).

The address management module110deletes this extracted address from the database170, and sets the extracted address in the “extraction result”, i.e., outputs the extracted address (S2003to S2005). If unable to extract the address in S2002, the address management module110sets [unextractable] in the “extraction result” (S2006).

As a result of the priority judgement in S2001, in the case of the registration request given from the priority-B user, the address management module110extracts the address from the open address database170(S2007).

The address management module110detects a forced delete rank of the extracted address, and judges whether the address is an address forcibly acquired for the allocation to the priority-A user. The address management module110, when judging that the address is the forcibly acquired address, deletes this address from the database170if its open time detected proves over the protection time, and sets the extracted address in the “extraction result” (S2008to S2012). If unable to extract the address in S2007, the address management module110sets [unextractable] in the “extraction result” (S2013).

Further, as a result of the priority judgement in S2001, in the case of the registration request given from the priority-C user, the address management module110extracts the address from the open address database170(S2014).

The address management module110detects a forced delete rank of the extracted address, and judges whether the address is an address forcibly acquired for the allocation to the priority-A or -C user. The address management module110, when judging that the address is the forcibly acquired address, deletes this address from the database170if its open time detected proves over the protection time, and sets the extracted address in the “extraction result” (S2015to S2019). If unable to extract the address in S2014, the address management module110sets [unextractable] in the “extraction result” (S2013)

The processes in one embodiment discussed above can be actualized as a program executable by a computer, and this program can be recorded on recording mediums such as a CD-ROM, a floppy disk and so on and further can be distributed via a communication line.

Moreover, an arbitrary plurality of or all the processes in one embodiment may be selectively combined and thus executed.

Although only a few embodiments of the present invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the preferred embodiments without departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of the present invention as defined by the following claims.