JP2000022708A - Mobile terminal for mobile ip system and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a mobile IP function without revising an existing IP protocol processing section when communication is made to a mobile destination network by using the mobile IP protocol. SOLUTION: A mobile terminal 2 used for a mobile IP system conducting processing corresponding to a mobile IP protocol is provided with a mobile IP processing section 15 that realizes the mobile IP protocol and the mobile IP processing section 15 is placed at a lower layer of an IP processing section 14 that conducts processing of the IP protocol to eliminate the need for a mobile IP protocol processing function in the IP processing section, in the mobile terminal of the mobile IP system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile terminal and a recording medium of a mobile IP system, and more particularly, to a mobile terminal for realizing a mobile IP protocol from a client destination.
The present invention relates to a mobile terminal and a recording medium of the P system.

[0002]

2. Description of the Related Art In recent years, batteries (computers, PCs, WSs) are driven by batteries that are smaller and lighter, and communication infrastructures are being developed with the development of the Internet. Thus, for example, a computer (mobile terminal) used in a certain network (home network) can be moved to another network, and connected to the home network via the Internet or the like, and used.

Here, even if the connection location of a mobile terminal changes, the mobile terminal can be accessed from another computer as if it were connected to a home network, and the same computer environment can be used for other computers. A mobile IP protocol has been developed in order to make it accessible on the Internet.

[0004] The mobile IP protocol conforms to the IETF, and a system that implements the mobile IP protocol is called a mobile IP system. In the mobile IP system,
When the mobile terminal moves, the home agent server performs proxy reception of a packet addressed to the mobile terminal from a communication partner that is sent to the home network. The environment is realized by transferring the packet from the home agent to the destination of the mobile terminal.

[0005] By the way, various forms are conceivable for a system configuration when the mobile IP protocol is realized.
Among them, there is an NCG (network crypto gate) system. Taking this NCG system as an example, a mobile IP system will be specifically described.

In the NCG system, when a terminal first moves, the mobile terminal notifies the home agent existing on the home network that it has moved and the care-of address newly acquired at the destination. By registering the movement in the home agent in this way, the proxy reception and the packet transfer to the movement destination are performed.

Here, if there is a communication partner who wants to transmit a packet to the mobile terminal after moving, the communication partner does not know where the mobile terminal has moved. To send a communication packet. This packet is once delivered to the home network, and the home agent intercepts the packet and transfers it to the destination.

At the time of this transfer, a new IP header from the home agent to the mobile terminal is added to the outside of the packet from the communication partner. The encapsulated packet is transmitted. On the mobile terminal side, the added I
After removing the P header, the original packet is processed.

A packet from a destination terminal to a communication partner is directly transmitted using a home address as a source address. As a result, communication between a mobile terminal and an arbitrary communication partner in the NCG system is always performed on a triangular route via a home agent. In this case, the communication partner to the home agent, the home agent to the destination terminal, the destination terminal to the communication partner are each side of the triangle.

[0010]

By the way, in order for a mobile terminal to realize a mobile IP protocol so as to be compatible with the mobile IP system, for example, a conventional IP protocol processing unit (also referred to as an IP processing unit) is used. Make changes to
It is necessary to change the terminal to recognize and process the mobile IP function.

However, if a change is made to the existing IP protocol processing unit, it may be difficult to maintain consistency with other parts of the system. Also, for example, mobile IP
When attempting to convert a computer that does not support the protocol into a mobile terminal for a mobile IP system, the conventional method of changing the IP protocol processing unit itself is not a simple method.

Therefore, there is a need for a more efficient and flexible means of realizing a mobile IP protocol. On the other hand, when the mobile terminal moves using the mobile IP protocol, a problem may occur because the communication route is always a redundant triangular route via the home agent.

That is, in the mobile IP protocol, instead of providing the convenience of being able to access the destination even as if it is connected to the home network, the overhead is increased due to the redundant triangular route. .

Here, when the mobile terminal communicates with the communication partner as described above, it can be said that the mobile IP function is fully utilized and the convenience is superior to the increase in overhead.

However, for example, when accessing local resources such as a printer connected to a destination network, communication efficiency becomes extremely poor. In this case, communication must always go through the home network, even though they are physically connected to the same network. Therefore, the increase in the communication overhead cannot be ignored.

Further, since the mobile terminal accesses another computer using the address of the home network, various services such as a name service may not be available depending on the system environment of the destination.

In order to avoid such a problem and directly access local resources such as a computer and a printer at the destination, the mobile terminal uses a client belonging to the destination network without using the mobile IP protocol at the destination. It should just be. However, for that purpose, the IP address of the mobile terminal itself needs to be changed, and the terminal computer must be restarted. Further, if the IP address of the terminal is changed, access in the environment before the movement becomes impossible.

The present invention has been made in view of such circumstances, and a first object of the present invention is to provide a communication system in a destination network using a mobile IP protocol.
It is an object of the present invention to provide a mobile terminal and a recording medium of a mobile IP system that can realize a mobile IP function without changing a P protocol processing unit.

A second object is to enable direct communication without going through a home agent when accessing local resources of a destination network while securing a mobile IP function, thereby enabling overhead of a triangular route. Another object of the present invention is to provide a mobile terminal and a recording medium of a mobile IP system that can reduce the number of mobile terminals.

[0020]

Means for Solving the Problems To solve the above problems, the invention corresponding to claim 1 has been made for a mobile terminal used in a mobile IP system that performs processing corresponding to a mobile IP protocol.

In this terminal, a mobile IP processing unit for realizing the mobile IP protocol is provided, and the mobile IP processing unit is arranged below the IP processing unit for performing the processing of the IP protocol.

Therefore, the mobile IP in the IP processing unit
In the case where a protocol processing function is not required and communication is performed on a destination network using a mobile IP protocol, a mobile IP can be used without changing an existing IP protocol processing unit.
Function can be realized.

Next, a second aspect of the present invention is directed to a moving I
This is for a mobile terminal used in a mobile IP system that performs processing corresponding to the P protocol. The mobile terminal includes a first processing unit for performing processing corresponding to a mobile IP protocol on a transmission / reception packet, replacing a source address of the transmission packet with an address obtained in a destination network, and transmitting a reception packet. A second processing unit is provided for replacing the destination address with the home address before the movement, so that the lower processing part appears to be a terminal belonging to the network of the movement destination.

The processing for the transmission / reception packet is as follows:
It is configured to be switchable between the first and second processing units. Therefore, when accessing the local resources of the destination network while securing the mobile IP function, it is possible to perform direct communication without going through the home agent, thereby reducing the overhead of the triangular route.

Next, according to a third aspect of the present invention, in the mobile terminal of the mobile IP system of the first aspect, the first processing unit and the second processing unit of the second aspect are provided in the mobile IP processing unit. Things.

[0026] Further, regarding which of the first and second processing units processes the transmission / reception packet, switching control is performed from a higher level than the mobile IP processing unit, so that packet processing can be selected.

Therefore, the functions and effects of the invention corresponding to claims 1 and 2 can be combined. Next, an invention corresponding to claim 4 is a recording medium on which a program for causing a computer to realize the invention corresponding to claim 1 is recorded.

The computer controlled by the program read from the recording medium functions as the mobile terminal of the first aspect. Next, an invention corresponding to claim 5 is a recording medium that records a program for causing a computer to implement the invention corresponding to claim 1. The computer controlled by the program read from the recording medium functions as the mobile terminal according to the second aspect.

[0029]

Embodiments of the present invention will be described below. (First Embodiment of the Invention) FIG. 1 is a configuration diagram showing an example of a mobile IP system to which a mobile terminal according to an embodiment of the present invention is applied.

The mobile IP system is configured as an NCG system. A home agent server 1, a mobile terminal 2 as a client belonging to the network A, a management server (not shown), and the like are connected to a network A as a home network. It is connected.
This network A is connected to the Internet 4 via a router 3 and further to other networks such as networks B and C.

Here, the network C is provided with a client 5 with which the mobile terminal 2 communicates. The network B is the mobile terminal 2 in the present embodiment.
Is a visiting network in which the printer 6 and the DH
The hardware resources such as the CP server 7 are provided.

The mobile terminal 2 is a system for an IP network having an IP processing unit for processing an IP protocol, and includes a portable personal computer, a workstation, and the like. The mobile terminal 2 has a unique IP address N belonging to the network A (hereinafter, also simply referred to as a home address).

The IP address N is an IP address corresponding to the network A, and is not changed after the terminal moves. In other words, the IP processing unit always has
It operates as if the address N was assigned. Further, the mobile terminal 2 includes a processing unit corresponding to the mobile IP protocol, so that communication via the home agent server 1 is possible even when the mobile terminal 2 moves from the network A to the network B.

As shown in FIG. 1, the home agent server 1 has an IP address HA, the mobile terminal 2 after moving to the network B has a care-of IP address (hereinafter, also simply referred to as a care-of address) CoA, and the client 5 has a care-of address. Is assigned an IP address CH, and the printer 6 is assigned an IP address P.

Here, one of the points in the present embodiment is how to realize the mobile IP protocol in the mobile terminal 2, and the method is shown in FIG. FIG. 2 is a diagram illustrating a system configuration example of the mobile terminal according to the present embodiment.

As shown in FIGS. 3A and 3B, the mobile terminal system includes an upper processing unit 11 composed of an application and an OS (operating system), a socket I / F 12, TCP / I
P processing unit 13, IP processing unit 14, mobile IP processing unit 15,
It is configured by providing a device driver 16 and hardware 17.

The feature of the mobile terminal 2 is that the IP processing unit 14
The mobile IP processing unit 15 is inserted between the mobile IP processing unit 15 and the general device driver 16 to realize the mobile IP protocol. That is, no change corresponding to the mobile IP protocol is made to the IP processing unit 14 itself.

The IP processing unit 14 always holds the IP address N obtained in the home network regardless of the movement of the mobile terminal 2 and processes a normal IP protocol. Thus, at a level higher than the IP processing unit 14, the IP
All processes related to the protocol are executed using the home address N.

When the mobile terminal 2 moves to a network other than the home network, the mobile IP processing unit 15 holds the destination network information and implements processing relating to the mobile IP protocol, that is, the mobile IP function. Further, processing such as conversion of an IP address is performed to absorb all state changes associated with the movement of the network, so that the IP processing unit 14 is not made aware of the state change (terminal movement).

FIG. 2A shows UNIX as an OS.
FIG. 2B is an example of a configuration using Windows or the like as the OS. Here, in the mobile IP processing unit 15 shown in FIG. 2B, the output of the IP processing unit 14 is once received by the pseudo device driver 15a, and the pseudo device driver 15a delivers the output to the mobile IP processing main unit 15b to perform the actual processing.

Next, a more specific configuration of the mobile IP processing unit 15 will be described. FIG. 3 is a block diagram illustrating an example of the mobile terminal according to the present embodiment. As shown in the figure, the mobile IP processing unit 15 includes an input switch 21, an encapsulation processing unit 22, an address conversion unit 23, an output switch 24, and a mobile IP management unit 25.

Here, first, the input switch 21 is
The encapsulation processing unit 22 or the address conversion unit 23 is selected as the processing unit that should process the transmission packet in accordance with the instruction from the management unit 25.

The encapsulation processing unit 22 acquires a care-of address from the mobile IP management unit 25 and performs encapsulation processing (decapsulation processing) of the mobile IP protocol.
The address conversion unit 23 acquires the care-of address from the mobile IP management unit 25, and uses this to change the address and reconfigure the packet when directly transmitting a packet to a destination computer or the like.

The output switch 24 is a mobile IP management unit 25
As a processing unit that should process the received packet in accordance with the instruction from
Select

FIG. 4 is a block diagram showing a configuration example of the mobile IP management unit according to the present embodiment. The mobile IP management unit 25 manages the state of the mobile IP processing, and manages default route information and the like. Specifically, as shown in FIG. 4, it comprises a care-of address etc. acquiring unit 31, a care-of address etc. storage unit 32, a mobile IP registration unit 33, a distribution setting information storage unit 34, and an input switch switching instruction unit 35. .

With these configurations, the mobile IP management unit 2
In 5, a care-of IP address CoA, a required MAC address, and other necessary information at the destination are acquired, and the input switch 21, the encapsulation processing unit 22, the address conversion unit 2
3 and a function to be provided to the output switch 24, and a function to perform mobile registration in the home agent server 1 based on the acquired information and the information of the home network.

Here, first, the care-of address etc. obtaining unit 31
Request to DHCP server 7 or DNS server, etc.
The P address is stored in the care-of address storage unit 32. The care-of address storage section 32 stores information necessary for the destination, such as a care-of IP address, and information at the source, such as an IP address in a home network.

When the mobile terminal 2 moves to a network other than the home network, the mobile IP registration unit 33
Using the information stored in the storage unit 32 such as the care-of address, the movement registration to the home agent server 1 is performed.

The distribution setting information storage section 34 stores distribution setting information of outgoing packets via the instruction interface 18 shown in FIG. This packet distribution setting information is information that serves as a criterion for determining whether to add a care-of address or a home address to the source address of the transmission packet when the mobile terminal 2 moves to another network. This information is set in the distribution setting information storage unit 34 at the discretion of the user after moving the terminal or automatically based on the acquired information on the local resources.

The input switch switching instructing section 35 supplies the distribution setting information to the input switch main body 36 and causes the input switch main body 36 to execute the distribution of the transmission packet. In FIG. 4, the distribution setting information storage unit 34 and the input switch switching instruction unit 35 are shown as a configuration common to both the input switch 21 and the mobile IP management unit 25. This indicates that the setting information from the instruction interface 18 passes through the mobile IP management unit 25 as a management unit, and the actual configuration may belong to any of them.
Alternatively, the distribution setting information storage unit 34 and the input switch switching instruction unit 35 may be configured to completely belong only to the mobile IP management unit 25, and the input switch 21 may be configured to inquire necessary setting information.

Next, the operation of the mobile terminal of the mobile IP system configured as described above according to the present embodiment will be described. In FIG. 1, for example, it is assumed that the network A is installed at a branch office of a certain company, and the network B is installed at the head office of the company.

It is assumed that the owner of the mobile terminal 2 goes to the head office on a business trip or the like and connects the terminal 2 to the network B. When the mobile terminal 2 detects the movement or is notified by the user that the mobile terminal 2 has moved, the care-of-address etc. obtaining unit 31
Output a DHCP packet from the network B
Is obtained.

The care-of IP address is stored in the mobile IP management unit 2
5 is set in the storage unit 32 such as a care-of address, and is used for transfer registration transmission to the home agent server 1 and encapsulation processing. In the care-of address storage unit 32 of the mobile IP management unit 32, not only the care-of address but also a default gateway address, a server address of a default name service, and the like are set. These pieces of information are automatically or manually acquired and registered by the care-of address etc. acquiring unit 31.

When various necessary information is obtained in the network B, the care-of address CoA is sent to the home agent server 1 of the network A by the mobile IP registration unit 33 of the mobile IP management unit 25, and the mobile registration is performed. You.

After the mobile registration, the packet transmission / reception at the mobile terminal 2 is usually performed by the encapsulation processor 22.
Operates to perform processing of the mobile IP protocol. At this time, when viewed from the IP processing unit 14, the mobile IP processing unit 15 operates as a pseudo default gateway, and it is not recognized that the mobile terminal 2 has moved above the IP processing unit 14.

For example, when a packet is transmitted to the client 5 of the network C, or when a packet from the client 5 is transferred by proxy reception at the home agent server 1, the encapsulation processing unit 2
In step 2, processing corresponding to the mobile IP protocol is performed.
Thereby, a triangular communication path in the NCG system is secured.

When direct access to the destination computer is requested by an instruction from the host (instruction interface 18), the input switch 21 is switched, and the packet processing is performed by the address translation unit 23. This instruction information is used as distribution setting information in the distribution setting information storage unit 3.
3 At this time, the address conversion unit 23 changes the source address of the transmission packet from the home address of the terminal to the care-of address, and recalculates the checksum and the like.

The processing of the received packet is normally in a mode corresponding to the mobile IP protocol which is processed by the encapsulation processing unit 22. However, when there is a designation from the upper level (instruction interface 18), an automatic distribution mode in which the packet is distributed to the encapsulation processing unit 22 or the address translation unit 23 depending on the state of the received packet is set.

In this case, if the received packet has been encapsulated by the home agent, the packet is transferred to the encapsulation processing unit 22 and the normal mobile IP packet is processed.

On the other hand, if encapsulation has not been performed and the destination address is the care-of address, the destination address is converted from the care-of address to the home address N and passed to the IP processing unit 14. At this time, a transmission packet from a local computer or the like at the destination directly arrives at the mobile terminal 2 without passing through a redundant triangular route.

The above processing will be specifically described with reference to FIGS. 1, 3 and 5. FIG. 5 is a diagram for explaining communication between a mobile terminal after movement and a communication partner on another network and communication between the mobile terminal and local resources on the mobile network.

First, as shown in FIG.
Will be described from the client to the client 5 on the network C. First, the IP processing unit 14 outputs a packet in which the home address N of the mobile terminal 2 is set as the source address and the IP address CH of the client 5 is set as the destination address (FIG. 5: a1).

This packet is sent by the input switch 21 to the encapsulation processing unit 22, and the encapsulation processing unit 22 sends the packet to the network
Is transmitted to the client 5 (FIG. 5: a2). The client 5 sees the source address of the received packet and recognizes that the packet has been received from the mobile terminal 2 of the network A.

Next, as shown in FIG. 5B, a case where the client 5 sends a reply to the mobile terminal 2 will be considered. In this case, a packet with the home address N of the mobile terminal 2 as the destination address is transmitted from the client 5, and the packet arrives at the network A (FIG. 5B).
1).

The packet transmitted on the transmission line of the network A is received by the home agent server 1 by proxy. Further, a packet is created and transmitted with the source address HA as the home agent and the destination address CoA as the care-of address of the mobile terminal B on the network B (FIG. 5: b2). Note that the packet portion that has been previously received by proxy is encapsulated and encrypted.

The packet transmitted from the home agent to network B is received by mobile terminal 2 and detected as a transfer packet from the home agent. As a result, the output is switched from the output switch 24 to the encapsulation processing unit 22. Then, the original packet (the packet before proxy reception) encapsulated by the encapsulation processing unit 22 is extracted and delivered to the IP processing unit 14.

Therefore, from the viewpoint of the IP processing unit 14,
Packets in the same state as when connected to network A will be received. The above is the processing when the mobile IP protocol is realized. Next, the case where communication with the printer 6 on the network B is performed will be described with reference to FIG.
This will be described with reference to FIGS.

First, the IP processing unit 14 outputs a transmission packet with the home address N as the transmission source and the IP address P of the printer 6 as the transmission destination (FIG. 5: c1).

In this case, it is assumed that information is set in the distribution setting information storage unit 34 so that address conversion is performed when transmitting to the printer 6. Based on the setting information, the packet is distributed to the address conversion unit 23 by the input switch 21.

The packet is reconfigured by the address conversion unit 23 so that the source address is set to CoA, and transmitted to the printer 6 (FIG. 5: c2). The printer 6 that has received this packet transmits the packet to the mobile terminal 2 as necessary. The printer 6 sets the source address to CoA
, The address CoA
Reply to Therefore, the packet is created and transmitted such that the source address is P and the destination address is CoA (FIG. 5: d1).

This packet is directly received by the mobile terminal 2 on the transmission path of the network B. Then, it is determined by the output switch 24 that the transmission is not from the home agent based on the source and destination addresses, and is assigned to the address conversion unit 23.

The allocated packet is reconstructed by the address translator 23 so that its destination address becomes N, and is delivered to the IP processor 14 (FIG. 5: d).
2). Thus, the IP processing unit 14 can execute processing in the same environment as that connected to the network A.

As described above, the mobile terminal of the mobile IP system according to the embodiment of the present invention
Is provided separately from the IP processing unit 14.
And implements the mobile IP protocol by inserting it between the device driver 16 and the device driver 16, so that when communicating on the destination network using the mobile IP protocol, the existing IP protocol processing part can be easily modified without any change. Can realize a mobile IP function.

The mobile terminal according to the present embodiment has a mobile IP
Since the processing unit 15 is provided with a capsulation processing unit 22 for executing mobile IP processing by encapsulation and an address conversion unit 23 for executing processing for directly accessing a destination resource by address conversion, these processings are switched. Even if the mobile terminal 2 is moved, take the redundant triangular route for the local resource at the destination while maintaining the advantage of the mobile IP that other computers can be accessed in the same environment as before the movement. And direct communication can be performed without the need. Therefore, an increase in communication overhead in such a case can be reduced.

The present invention is not limited to the above embodiments, but can be variously modified without departing from the gist thereof. For example, in the embodiment, the movement I
Although the P processing is realized by software processing on the mobile terminal body, the present invention is not limited to such a case. For example, the mobile IP function of the mobile IP processing unit 15 may be realized by hardware such as a LAN board or a LAN card.

The method described in the embodiment can be implemented by a computer (computer) as a program (software means) such as a magnetic disk (floppy disk, hard disk, etc.), an optical disk (CD-ROM, DVD, etc.). ), Stored in a storage medium such as a semiconductor memory, or transmitted and distributed via a communication medium. The programs stored on the medium side include
A software program (including not only an execution program but also a table and a data structure) to be executed by the computer includes a setting program for configuring the computer. A computer that realizes the present apparatus reads a program recorded in a storage medium, and in some cases, constructs software means by using a setting program, and executes the above-described processing by controlling the operation of the software means.

[0077]

As described above in detail, according to the present invention, when communication is performed on a destination network using a mobile IP protocol, a mobile IP function can be realized without changing the existing IP protocol processing unit. A mobile terminal and a recording medium of a mobile IP system can be provided.

Further, according to the present invention, when accessing a local resource of a destination network while securing a mobile IP function, it is possible to directly communicate without using a home agent, thereby enabling a triangular route. It is possible to provide a mobile terminal and a recording medium of a mobile IP system that can reduce overhead.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of a mobile IP system to which a mobile terminal according to an embodiment of the present invention is applied.

FIG. 2 is an exemplary view showing an example of the system configuration of the mobile terminal according to the embodiment.

FIG. 3 is a block diagram showing an example of the mobile terminal according to the embodiment;

FIG. 4 is an exemplary block diagram showing a configuration example of a mobile IP management unit according to the embodiment;

FIG. 5 is a diagram for explaining communication between a mobile terminal after movement and a communication partner on another network and communication between the mobile terminal and local resources on the mobile network.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Home agent server 2 ... Mobile terminal 3 ... Router 4 ... Internet 5 ... Client 6 ... Printer 7 ... DHCP server 11 ... Upper processing part 12 ... Socket I / F 13 ... TCP / IP processing part 14 ... IP processing part 15 ... Mobile IP processing unit 16 Device driver 17 Hardware 18 Instruction interface 21 Input switch 22 Encapsulation processing unit 23 Address conversion unit 24 Output switch 25 Mobile IP management unit 31 Care-of address etc. acquisition unit 32 Care Address etc. storage unit 33 Mobile IP registration unit 34 Distribution setting information storage unit 35 Input switch switching instruction unit 36 Input switch body A, B, C Network

Claims (5)

[Claims] 1. A mobile terminal used in a mobile IP system that performs processing corresponding to a mobile IP protocol, comprising: a mobile IP processing unit that implements the mobile IP protocol; A mobile terminal of a mobile IP system, wherein the mobile terminal is disposed below an IP processing unit that performs processing and does not require a mobile IP protocol processing function in the IP processing unit. 2. A mobile terminal used in a mobile IP system that performs processing corresponding to a mobile IP protocol, comprising: a first processing unit that performs processing corresponding to the mobile IP protocol on transmission / reception packets; By replacing the source address of the received packet with the address obtained in the destination network and replacing the destination address of the received packet with the home address before the transfer, the terminal belonging to the destination network for the lower processing part A mobile terminal of a mobile IP system, comprising: a second processing unit that pretends to be as described above; and configured to be able to switch processing for transmission / reception packets between the first and second processing units. 3. The mobile terminal of the mobile IP system according to claim 1, wherein the first processing unit and the second processing unit according to claim 2 are provided in the mobile IP processing unit, and a transmission / reception packet is transmitted to the mobile IP processing unit. A mobile terminal of a mobile IP system in which packet processing can be selected by performing switching control on which of a first processing unit and a second processing unit to perform processing from above the mobile IP processing unit. 4. A program for controlling a mobile terminal used in a mobile IP system that performs processing corresponding to a mobile IP protocol, wherein the program does not have a processing function corresponding to the mobile IP protocol.
IP processing means for performing only the processing of the IP protocol, and realizing the mobile IP protocol,
A computer-readable recording medium in which a program for causing a computer to function as mobile IP processing means provided below the processing means is recorded. 5. A program for controlling a mobile terminal used in a mobile IP system that performs processing corresponding to a mobile IP protocol, wherein the first processing means performs processing corresponding to the mobile IP protocol with respect to transmitted / received packets. By replacing the source address of the transmitted packet with the address obtained on the destination network, and replacing the destination address of the received packet with the home address before the move, the lower-order processing part is connected to the destination network. A second processing unit that makes the computer appear to belong to the terminal, and a computer-readable recording that stores a program for causing a computer to function as a switching unit that switches processing of transmission / reception packets between the first and second processing units. Medium.