JP2002223230A - Transfer data communication system, network address transfer device provided in the system, and foreign agent device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a transfer data communication system which can avoid the extension of a message length of an agent advertisement message so as not to waste a communication band even if a plurality of foreign agents(FAs) exist. SOLUTION: A network address transfer(NAT) device is provided in a system. The NAT device rewrites a receiving address of an outside header of a capsulated packet transmitted from a home agent(HA) controlling transfer terminals addressed to the NAT device into an address of a foreign agent(FA) device which actually carries out decapsulating treatment for transit. The FA device transfers the packet from the NAT device to the transfer terminal of the FA address.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile data communication system, and a network address transfer (NAT) device and a foreign agent (FA) device provided in the system. Including the terminal's movement support device and network,
The present invention relates to a mobile data communication system capable of continuously maintaining a network connection while a terminal moves between networks by using bileIP, and a NAT device and an FA device provided in the system.

[0002]

2. Description of the Related Art With the spread of small and light mobile terminals as seen in notebook personal computers and PDAs and the explosive spread of the Internet, there has been a demand for using terminals while going out of home or office. Is growing. Also,
Data communication using mobile phones, Internet access, use of mail services, and the like have also become popular. In a network using an IP (Internet Protocol) used as a communication protocol of the Internet, a technique called MobileIP has been proposed as a technique capable of maintaining a connection even when a terminal moves between networks. .

[0003] MobileIP is defined in the RFC (Request for Comments) 2002 of the Internet Engineering Task Force (IETF), and is proposed for the purpose of realizing mobile and transparent IP communication. MobileIP is configured by placing an HA (Home Agent) and an FA (Foreign Agent) for each subnetwork, and having a home address as an IP address of a home network, which is a network to which a terminal usually belongs. You. The FA periodically sends a control signal called an Agent Advertisement message to its own subordinate network. In this message, the IP address of the FA,
A care-of address (Care of Addr) indicating the address of the destination to which the IP packet addressed to the mobile terminal is encapsulated and transferred.
ess) is included. By receiving this message, the mobile terminal knows to which subnetwork the terminal belongs to and registers the care-of address to the HA via the FA (location registration). Hereafter, H
A realizes end-to-end IP communication by encapsulating an IP packet that has arrived at the mobile end and transferring it to the care-of address.

[0004] On the other hand, mobile communication systems such as mobile phones and wireless packet communication are considered to have a very large number of users who subscribe from external networks and use MobileIP services. Further, many users of the mobile communication system move and use the mobile terminal, so that the load on the FA device becomes extremely high due to location registration processing or the like that occurs each time the mobile terminal moves. Therefore, it is conceivable to disperse the load by arranging a plurality of FA devices in one sub-network.

[0005] Fig. 1 shows Agent Advertisement of MobileIP.
FIG. 3 is a diagram illustrating a configuration example of a message, and only a portion necessary for the present invention will be described below. This Agent Advertisem
The configuration of the ent message is specified in RFC2002, and the detailed description thereof will be omitted.

[0006] The MobileI defined in RFC2002 described above.
The technology of P is a message that the FA periodically sends to its own subordinate network, as shown in FIG.
In the ement message, a plurality of router addresses having an FA function for relaying the registration process and Preference Level 101 which is an index for selecting a router by a terminal, and
A plurality of care-of addresses (Care of Address) 102 can be included and flown. The mobile terminal receives the received Agent A
An address of one FA device is selected from a plurality of router addresses included in the dvertisement message, and through this, an arbitrary one of a plurality of Care Of Addresses can be selected to perform location registration processing in the HA device.

[0007]

According to the prior art of MobileIP defined in RFC2002, as described above, when a plurality of FA devices exist in one sub-network, as shown in FIG. , Agent Advertisement
The message length of the message becomes longer as the number of FA devices included in the subnetwork increases. For this reason, the above-mentioned prior art is based on Agent Advertisement that is periodically broadcasted when the sub-network in which the FA device exists is relatively slow, such as wireless mobile communication.
There is a problem that a communication band is wasted by the message. In addition, the above-described conventional technology is applied to a LAN environment, and a plurality of FA devices periodically perform Agent Adve
Even when the rtisement message is transmitted, there is a problem that the number of AgentAdvertisement messages transmitted according to the number of FA devices increases and the bandwidth is wasted.

[0008] An object of the present invention is to solve the above-mentioned problems of the prior art, and to improve the Agent Advertisement even when a plurality of FAs exist.
It is an object of the present invention to provide a mobile data communication system capable of preventing a message length of a vertisement message from being lengthened and preventing waste of a communication band, and a NAT device and an FA device provided in the system.

[0009]

According to the present invention, an object of the present invention is to rewrite a destination address of a header of a packet received in a subnetwork in which a plurality of FA devices exist,
This is achieved by providing a NAT device having a function of transferring a packet to the FA device having the rewritten destination address.

The present invention operates as follows. That is, the plurality of FA devices are identified by the Car in the Agent Advertisement message of the network where the FA device exists.
The mobile terminal transmits to the mobile terminal including the representative care-of address as e ofAddress, and the mobile terminal
The location registration processing is performed for the device A. The NAT device in the network to which the FA device belongs is the representative Care of
It has an interface with an address, and the representative Care of
It has a function to receive packets addressed to Address. The FA device that has relayed the location registration process from the mobile terminal returns a reply from the HA device to the mobile terminal, and if the reply from the HA device indicates that the location registration was successful, the FA device sends the reply to the NAT device. Of the home terminal and the care-of address used for the decapsulation process, or the home address of the mobile terminal, the IP address of the HA device, and the care-of address used for the decapsulation process. The NAT device that has received the notification stores the combination of the IP addresses in a table in the NAT device. After successful location registration of the mobile terminal, the HA device sends the encapsulated I-address addressed to the mobile terminal to the NAT device having the representative care-of address.
Since the P packet is sent, the representative care-of address in the destination field included in the header of the outer IP packet is rewritten to a care-of address for decapsulation processing with reference to the table of the NAT device, and is sent to the FA device. Send. The FA device that has received the encapsulated IP packet in which the IP header has been rewritten performs a process of extracting the original IP packet from the encapsulated IP packet, and transmits the original packet to the mobile terminal.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the mobile data communication system according to the present invention will be described below in detail with reference to the drawings.

FIG. 2 is a block diagram showing a configuration of a mobile data communication system according to one embodiment of the present invention. 2, 201 is an HA device, 202 to 204 are FA devices, 205 is a NAT (Network Address Transfer) device,
206 and 207 are routers, 208 is the Internet, 2
09 and 210 are mobile terminals, and 211 to 214 are networks.

The system shown in FIG. 2 has a plurality of sub-networks 212 to 214 and a network 211 for interconnecting these sub-networks, and enables a mobile terminal to move between the sub-networks and perform communication. It is configured to be possible. In the illustrated example, it is assumed that the subnetwork 212 to which the mobile terminal 209 usually belongs is the home network, and the mobile terminal 209 moves to another subnetwork 213, 214, etc., and performs communication. Further, the network 211214 may be a wireless network.

In FIG. 2, HA apparatus 201 receives a location registration request from mobile terminal 209 to support the movement of mobile terminal 209, and performs location management of the terminal.
When the mobile terminal moves and exists in another network, the mobile terminal has a function of receiving an IP packet addressed to the mobile terminal, encapsulating the IP packet, and transferring the IP packet to the care-of address included in the location registration request. FA devices 202 to 204
The address of the FA device which is arranged in the destination sub-networks 213 and 214 and provides the mobile terminal with the FA service in the visited network and the care-of address indicating the transfer of the encapsulated packet are stored in the terminals in the network. Has the function of advertising. Also, the FA device
It has the function of relaying the location registration process from the mobile terminal to the HA, and the function of extracting the original packet from the encapsulated packet sent from the HA and transmitting it to the mobile terminal. Further, when the location registration is successful, the FA device replaces the home address of the mobile terminal and the care-of address for decapsulation processing, or the home address of the terminal, the address of the home agent, and the care-of address for decapsulation processing. Notify the NAT device 205.

The NAT device 205 transmits the home address of the mobile terminal or the home address and the home address of the mobile terminal transmitted from the above-mentioned FA device which relayed the location registration of the mobile terminal.
From the combination with the agent, the encapsulated I
A function of searching for a care-of address for decapsulation processing for extracting the original packet from the P packet, and a function of the encapsulated I sent from the HA device addressed to the representative care-of address.
It has a function of receiving a P packet, rewriting the field indicating the destination IP address in the P packet with the care-of address for the decapsulation processing, and transmitting the packet to the corresponding FA device. The routers 206 and 207 respectively
It has a function of connecting the sub-network in which the A device is present and the network in which the HA device is present through the Internet 208 and transmitting and receiving IP packets.

The terminal 209 is a mobile terminal that has been in the subnetwork 212 as a home network.
9 shows that the mobile terminal is moving to the sub-network 213 where the FA devices 203 and 204 exist. Further, in FIG. 2, the mobile terminal 210 is communicable via the sub-network 214. The example shown in FIG.
Is not provided with an FA device, but is connected to the sub-network 212 in case another mobile terminal moves.
Alternatively, a plurality of FA devices may be connected. Also, for a terminal having the sub-networks 213 and 214 as home networks, these sub-networks 213 and 214
An HA device may be connected to 214.

When the mobile terminal moves from the home network, the mobile terminal receives an advertisement message from the FA device of the destination network,
The care-of address is obtained from the message, the location is registered in the HA device through the FA device, and thereafter, the packet addressed to the own mobile terminal is received through the FA device that performs decapsulation processing.

FIG. 3 is a diagram showing a sequence for performing location registration in the HA device when a mobile terminal moves to a sub-network in which a plurality of FA devices exist. This will be described below. Here, a description will be given assuming that mobile terminal 209 has moved to subnetwork 213.

(1) The mobile terminal 209 that has moved to the subnetwork 213 is transmitted from the MobileIP FA devices 203 and 204 accommodated in the subnetwork 213.
Receive AgentAdvertisement message. The FA device sends this message periodically and sends the message to the mobile terminal.
The presence or absence of the device and the capability of the FA device are advertised. When a plurality of FA devices exist in the network, the transmission time interval per device may be longer or the number of transmissions within a certain time may be reduced as compared with the case where only one FA device exists (sequence). 301, 302).

(2) The mobile terminal 209 uses the Agent Advertis
It receives the ement message and makes a location registration (Registration) request to the FA device. At that time, the terminal device 209
May make a location registration request to the FA device that first received the Agent Advertisement message, or may select a FA device from the Agent Advertisement message received within a certain period of time and make a location registration request. Good (sequence 303).

(3) The FA device that has received the location registration request from the mobile terminal 209. In the case of the example described, the FA device 203 performs location registration with the HA device 201. On the other hand, the HA device 201 returns information on the result of the location registration. The confirmation information of the location registration is stored in the FA device 203.
Is returned to the mobile terminal 209 through
4-306).

(4) FA device 203 relaying location registration
Sends to the NAT device 205 information on the mobile terminal for which the location registration was successful, and makes a registration request for the terminal-care-of address. The NAT device 205 transmits the terminal-care-of-address registration confirmation information to the FA device as a response thereto (sequences 307 and 308).

FIG. 4 is a diagram for explaining the format of an Agent Advertisement message when a representative care-of address is used according to the present invention. This will be described below.

The Agent Advertisement message shown in FIG.
IP header 401 and ICMP (Internet Control Mess
age Protocol) Router advertisement unit 402, Mobile Agent advertisement extension unit 403, and prefix length extension unit 411.

A field 404 in the IP header 401 is a field indicating a protocol of an upper layer of the IP.
Agent Advertisement is 1 because it is an extension of ICMP router advertisement. Also, 405 is the address of the FA device that is the source of this packet, and 406 is
This is the destination address of the packet, which is a broadcast address (255.255.255.255) or a multicast address (224.0.0.1).

407 in ICMP router advertisement section 402
Is the IP address of the FA device, that is, the address of the FA device that relays the location registration to the HA device when it is registered, and 408 is the selection level of the router. Also,
Reference numeral 409 denotes a valid time, and the FA device performs the next Agent Advertisement within the time set in this field.
Indicates that the message must be sent.

413 in the Mobile Agent advertisement extension unit 403
Is a sequence number field that is incremented each time an Agent Advertisement is transmitted. When this field becomes 0, it indicates that the FA device has been restarted. 414 indicates a busy bit. When this bit is set, it indicates that the FA device is busy and is not accepting a registration service. Also, 410
This is the representative care-of address, and the mobile terminal performs location registration with the HA device so as to transfer a packet to this address.

412 in prefix length extension section 411
Represents a prefix length in which the address part of the network of this address indicates the bit length of the upper mask part.

The mobile terminal receiving the Agent Advertisement message as described above calculates the network prefix by looking at the FA device address 407 and the field 412 indicating the prefix length, and the mobile terminal has moved from the home network. Then, it is determined whether or not the mobile device has moved from the previous network, and whether or not to perform location registration in the HA device is determined.

Since the embodiment of the present invention uses the Agent Advertisement message having the format described above, the FA device only needs to transmit the Agent Advertisement message containing only the representative care-of address. As in the case of the technology, when there are a plurality of FA devices, it is not necessary to include the addresses and the care-of addresses of the plurality of FA devices in the Agent Advertisement message, and the Agent Advertisement message length can be shortened.

FIG. 5 shows the sequence 30 described with reference to FIG.
FIG. 7 is a diagram illustrating a configuration example of a packet that notifies a NAT device of a mobile terminal and a care-of address for decapsulation processing at 7 and 308, which will be described below.

The illustrated packet includes an IP header 501 and a U
A DP (User Datagram Protocol) header 502, an area 503 storing information regarding a care-of address for mobile terminal-decapsulation, and an identifier 51 that associates a registration request with a confirmation by giving a unique value to each registration request.
3 and an option unit 514 for adding other information when necessary.

A field 504 in the IP header 501 is a field indicating a higher-level protocol in the IP header.
In the case of DP, it is set to 17. Reference numeral 505 denotes an IP address of a transmission source of the packet. When the mobile terminal and the care-of address for decapsulation are registered from the FA device to the NAT device, the address becomes the address of the FA device.
This is the address of the T device. Reference numeral 506 denotes an address of a reception destination.
When registering a care-of address for decapsulation processing,
It becomes the address of the NAT device, and becomes the address of the FA device at the time of confirmation. 515 in the UDP header 502 is the port number of the transmission source, and 516 is the port number of the reception destination.

A field 507 in the area 503 indicates a processing content of this packet. For example, when the value of this field is "1", a request is made, and when the value of this field is "2", a request is confirmed. , "3" means registration failure or the like. 508 indicates the length of the data portion of the packet, and 509 indicates the effective time of registration. 510 indicates the home address of the mobile terminal, and 511 indicates the HA.
The address of the device is shown, and 512 is a care-of address at which decapsulation processing is actually performed.

FIG. 6 is a block diagram showing an example of the configuration of a NAT device, which will now be described. In FIG. 6, 602 is an MPU, 603 is a memory, 604 is a network interface (I / F), 605 packet buffer, 606 is a packet bus, and 607 is a control bus.

The NAT device 205 has a network I / F
604 and a packet buffer 605 for temporarily storing packets transmitted and received between the network I / F 604
, An MPU 602, a memory 603, a packet bus 606 for connecting them, and a control bus 607. The memory 603 includes a table for storing a care-of address for mobile terminal-decapsulation processing,
If there is an encapsulated packet in the packet received from the network I / F 604, the destination address of the encapsulated packet is rewritten to a care-of address for decapsulation processing by referring to the above-mentioned table in the memory 603. .

FIG. 7 is a view for explaining an example of a table storing the care-of address for mobile terminal-decapsulation processing.
Hereinafter, this will be described.

The illustrated table shows the home address 701 of the mobile terminal and the address 702 of the home agent.
And a care-of address 703 for decapsulation and a lifetime 704 indicating an effective time of this entry as one record, and a plurality of records are stored. The lifetime 704 indicates that if there is no re-notification within the valid time indicated by the lifetime 704 from the FA device and a timeout occurs, the corresponding entry may be deleted from this table.

FIG. 8 shows the IP transmitted from the HA device 201.
FIG. 3 is a diagram illustrating a format example of a packet encapsulated by in IP, which will be described below.

The illustrated packet includes an IP header 801 of a packet encapsulated by IP in IP, an IP header 802 of an original packet, and a data portion 803 corresponding to a payload portion of the original IP packet.

The field 804 in the IP header 801 is a field indicating a protocol of an upper layer. In the case of an IP in IP packet, 804 is set to “4”. 805 indicates the IP address of the transmission source of this packet, and the HA device 20
1 IP address is set. Reference numeral 806 denotes the IP address of the destination of the IP packet, which is set as the representative care-of address by the HA device and sent to the NAT device 205.

80 in the IP header 802 of the original packet
7 is the source address of the original packet, 808
Is the IP address of the destination, and the home address of the mobile terminal is set.

The packet configured as described above has an IP header 801 whose FA device 2 performs decapsulation processing.
05 and the original packet's IP header 8
02 and a data portion 803 which is the payload of the original IP packet.
05 to the mobile terminal. Also, the NAT device 205 determines whether the home address 701 of the mobile terminal in the table described with reference to FIG.
The mobile terminal home address 808 which is the IP address of the destination of the P packet, or the mobile terminal home address 701 and home agent address 702 in the table shown in FIG. 7, the home agent address 805 of the packet shown in FIG. A care-of address for the decapsulation processing is determined from the field of the home address 808, and this care-of address is set in the field of the representative care-of address 806 of the packet shown in FIG. 8 and transmitted to the FA device performing the decapsulation processing. .

FIG. 9 shows a case where the NAT device is an IP for the NAT device.
5 is a flowchart illustrating a processing operation when a packet is received, which will be described below.

(1) Upon receiving an IP packet, the NAT device 205 performs a receiving process, and determines whether or not the received IP packet is an encapsulated IP in IP packet by checking the protocol field of the received IP packet. It is determined by looking at it (steps 901 and 902).

(2) If it is determined in step 902 that the received packet is an IP-in-IP packet,
And a destination address (home agent address) 805 of the original encapsulated packet.
A search is made as to whether or not there is a match with the source address (home agent address) of the encapsulated packet (steps 903 and 904).

(3) If a match is found in step 904, the destination address 806 of the encapsulated packet is rewritten to the found care-of address for the decapsulation process, and the FA that performs the decapsulation process on the packet is used. A process for transmitting to the device is performed and the process is terminated. If no packet is found, the received packet is discarded and the process is terminated (steps 905, 907, and 906).

(4) If it is determined in step 902 that the received IP packet is not an IP in IP packet,
It is determined whether or not the packet is a packet for requesting registration of a care-of address for mobile terminal-decapsulation processing. The processing is performed and the processing here ends (steps 908 and 91).
4).

(5) If it is determined in step 908 that the packet is a packet for requesting registration of a care-of address for mobile terminal-decapsulation processing, the home address and home agent address of the data in the received packet are as shown in FIG. Is searched for an entry that matches the entry in the table shown in FIG.

(6) As a result of the search in step 909, it is checked whether or not a match is found. If found, the items of the care-of address for decapsulation processing and the lifetime in the packet are updated. If not found, it is added to the table shown in FIG. 7 as a new entry (steps 910, 911, 913).

(7) Step 911 or step 91
After the process of step 3, a packet for confirming that the registration has been successful is transmitted to the FA device that has sent the packet for registration, and the process ends (step 912).

FIG. 10 shows a case where the mobile terminal moves and performs location registration with the HA device via a different FA device from before the movement, and
It is a figure which shows the sequence of the position registration at the time of using the same NAT device and the same care-of-address as before movement, and demonstrates it below. In FIG. 10,
The FA device of the sub-network before the movement is the FA-S device,
The FA device of the moved sub-network is shown as a FA-T device.

(1) It is assumed that the mobile terminal first performs location registration with the HA device via the FA-S device, moves to the subnetwork, and moves to the subnetwork in which the FA-T device is providing service. I do. FA-S device and FA-
T devices use a common NAT device, and Agen
The representative care-of address of the NAT device is set in the Care of Address field in the t Advertisement message and is sent. The mobile terminal uses Agent Ad from the FA-T device.
vertisement message is received, the router address 407 and the prefix length 412 in the message are checked, and the FA-S
It is detected that the device has moved from the subnetwork to which the device belongs to the subnetwork to which the FA-T device belongs (sequence 1001).

(2) The mobile terminal operates in sequence 30 of FIG.
Similarly to 2 to 306, location registration is performed in the HA device via the FA-T device, and information of the confirmation is received (sequences 1002 to 1005).

(3) Since a new mobile terminal has moved to the NAT device, the FA-T device transmits a terminal-care-of-address registration request (sequence 1006).

(4) The NAT device searches the table shown in FIG. 7 to check whether an entry corresponding to the terminal that has made the registration request exists, and if not, adds it to the table as a new entry. However, if an entry is found, the care-of address for the decapsulation process is changed from the address of the FA-S device to the address of the FA-T device or added as a new table, and the terminal-care-of-address is added to the FA-T device. Return registration confirmation information (sequence 10
07).

(5) After the sequence 1007, the NAT device may notify the original FA device, the FA-S device, that the mobile terminal has moved to the FA-T device (sequence 1011). ).

(6) The FA-S device executes the sequence 101
After the movement of the mobile terminal from the NAT device is notified in 1,
Alternatively, since the notification is not performed and the mobile terminal moves to another location and a periodic location registration request does not come, when the valid time of the location registration of the terminal times out, the corresponding terminal disappears from the NAT device. Is notified as a terminal-care-of address deletion request. The NAT device that has received this sends back the terminal-care-of-address deletion confirmation information to the FA-S device (sequence 100).
8 to 1010).

In the above-described sequence, the NAT device copies the packet addressed to the mobile terminal to both the FA-S device and the FA-T device until a request to delete the registration of the corresponding terminal comes from the FA-S device. You may make it transfer.

FIG. 11 shows a case where two FA-1 devices and an FA-2 device can provide service to a mobile terminal in the same sub-network. FIG. 8 is a diagram illustrating a processing sequence when a failure occurs in the FA-1 device while receiving service;
Hereinafter, this will be described.

(1) The NAT device periodically transmits a packet requesting the FA-1 device to report the status of operation or not, and receives a response packet of this packet from the FA-1 device. Thus, the operation of the FA-1 device is confirmed (sequences 1101 and 1102).

(2) The FA-2 device and the FA-1 device also transmit packets to each other to confirm whether or not the other party is operating (sequence 11).
03, 1104).

(3) Now, assume that a failure has occurred in the FA-1 device from the above-described state (sequence 1005).

(4) If there is no response from the FA-1 device to the status report request from the NAT device and the FA-2 device for a while, the NAT device and the FA-2 device respectively become the FA device. -1 A failure of the device is detected (sequences 1106 and 1107).

(5) In this case, the FA-2 device uses the FA-
In order to urge the FA-2 to request a registration request for the mobile terminal receiving the service by one device to receive the Mobile IP service via the FA-2, the FA-1 device is restarted and the service cannot be received. Inform that you are. For this reason, the FA-2 device is replaced by the FA-
An Agent Advertisement message to be transmitted by one device is transmitted on behalf of a certain period of time. In this message, the source IP address 405 of FIG. 4 is set to the IP address of the FA-1 device, and the address 407 of the FA device is set to the IP address of the FA-1 device.
In the address, the sequence number 413 is reset to “0” and the busy bit 414 is set. FA-
The two devices thereby prompt the mobile terminal to make a registration request to FA-1 (sequence 1108).

(6) When the mobile terminal receives the packet of sequence 1108, the sequence number has been reset to “0”, so that the FA that has received the service until now has
It detects that the device has been restarted, and attempts to perform position registration again, but recognizes that it is necessary to perform position registration via another FA device because the busy bit is set.

(7) For this reason, the mobile terminal performs location registration with the HA device via the FA-2 device, and
An Agent Advertisement message is received from the A-2 device, and a request for location registration is made to the HA device via the FA-2 device (sequences 1109 to 1111).

Note that, in the above description, the NAT device is
When the failure of the -1 device is detected, information on the terminal that has been receiving service through the FA-1 device is deleted from the transfer information table.

FIG. 12 shows a case in which the FA device can receive the service via two NAT devices. The NAT-1 device which had been receiving the service from the FA device failed and the NAT-2 device failed. FIG. 7 is a diagram showing a processing sequence when a service is received via a., Which will be described below.

(1) The FA device periodically transmits a packet requesting a report on whether or not the NAT-1 device is operating, and receives a response packet corresponding to this packet from the NAT-1 device. By doing so, the operation of the NAT-1 device is confirmed (sequences 1201 and 1201).
2).

(2) In this state, if a failure occurs in the NAT-1 device, the NAT-1 device stops responding to the status report request packet from the FA device (sequences 1203 and 1204).

(3) If there is no response from the NAT-1 device, the FA device detects that a failure has occurred in the NAT-1 device, and the Mobile IP Agent Advertisement transmitted to the mobile terminal.
The sequence number 413 in the vertisement message is reset to “0”, and the representative Care of Address 410 stores the representative Care of Ad of the NAT-2 device as a new NAT device.
A dress set is transmitted (1205).

(4) The mobile terminal has the sequence number “0” in the Agent Advertisement received from the same FA device.
, The location registration is performed again via the FA device, assuming that the FA device has been restarted. The Care of Address in this case contains the representative Ca of the NAT-2 device.
Since the one in which the re of address is set is used, the location registration request is transmitted to the HA device via the FA device and the NAT-2 device (sequences 1206 and 1206).
07).

[0074]

As described above, according to the present invention, N
By including an AT device in the system, the HA device
A single care-of address of bileIP can be seen, and a plurality of FA devices can be arranged, so that the load on the FA device can be distributed. Further, the Care of Address in the Agent Advertisement message can be suppressed to one FA instead of the number of FAs, so that a band can be prevented from being wasted even when a relatively slow line is used.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration example of a Mobile IP Agent Advertisement message.

FIG. 2 is a block diagram illustrating a configuration of a mobile data communication system according to an embodiment of the present invention.

FIG. 3 is a diagram showing a sequence of performing location registration in an HA device when a mobile terminal moves to a subnetwork in which a plurality of FA devices exist.

FIG. 4 is a diagram illustrating a format of an Agent Advertisement message when a representative care-of address is used according to the present invention.

FIG. 5 is a diagram illustrating a configuration example of a packet for notifying a NAT device of a mobile terminal and a care-of address for decapsulation processing;

FIG. 6 is a block diagram illustrating a configuration example of a NAT device.

FIG. 7 is a diagram illustrating an example of a table storing a care-of address for mobile terminal-decapsulation processing.

FIG. 8 is a diagram illustrating a format example of a packet encapsulated by IP in IP transmitted from the HA device.

FIG. 9 is a flowchart illustrating a processing operation when the NAT device receives an IP packet intended for the NAT device.

FIG. 10 shows a case where a mobile terminal moves and performs location registration with an HA apparatus via an FA apparatus different from that before the movement, and uses the same NAT apparatus as before the movement and uses the same care-of address. It is a figure which shows the sequence of.

FIG. 11 shows a case where two FA devices can provide service to mobile terminals in the same sub-network,
FIG. 9 is a diagram illustrating a processing sequence when a failure occurs in the device A.

FIG. 12 is a diagram showing a processing sequence when a FA device can receive a service via two NAT devices and a failure occurs in a NAT device that was receiving a service from the FA device. .

[Explanation of symbols]

 201 HA device 202-204 FA device 205 NAT (Network Address Transfer) device 206, 207 Router 208 Internet 209, 210 Mobile terminal 211-214 Network 602 MPU 603 Memory 604 Network interface (I / F) 605 Packet buffer 606 Packet bus 607 Control bus

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kensho Matsumoto 1099 Ozenji Temple, Aso-ku, Kawasaki City, Kanagawa Prefecture Inside Hitachi, Ltd.System Development Laboratory (72) Inventor Naoji Fukuzawa 1099 Ozenji Temple, Aso-ku, Kawasaki City, Kanagawa Prefecture F-term in Hitachi, Ltd. System Development Laboratory (Reference) 5K030 GA03 GA10 HA08 HC01 HC09 HD03 JA11 JT09 LB05 MA07 MB01 5K033 AA01 CB09 DA06 DA19 DB18 5K067 AA13 BB21 CC08 DD11 EE02 EE10 EE16 HH17 HH22 JJ66

Claims (7)

[Claims] The mobile terminal is connected to a plurality of sub-networks, a mobile terminal capable of moving between the sub-networks, and a sub-network to which the mobile terminal belongs, and manages location information of the mobile terminal belonging to its own network. A home agent device having a function of capturing a packet addressed to a terminal, encapsulating the packet, and transferring the packet to a destination subnetwork in which the mobile terminal is moving; and a home agent device connected to the subnetwork and moving from another network. An advertisement function for advertising a care-of address indicating a transfer destination address of a packet to be transferred to the mobile terminal by the home agent device for the mobile terminal performing the communication; Registration relay function that relays the process of registering the And a foreign agent device having a function of receiving the encapsulated packet addressed to the mobile terminal transferred from the agent device and relaying the packet to the mobile terminal moving from another sub-network. In a mobile data communication system, a foreign agent device that relays a packet destination address of an encapsulated packet sent to a care-of address registered in a home agent device by the mobile terminal to the mobile terminal A mobile data communication system comprising a network address transfer device that rewrites the packet to a care-of address and relays the packet. 2. A plurality of foreign agent devices are connected to the sub-network, and each of the plurality of foreign agent devices includes a representative care-of address of the network address transfer device as the care-of address. A function for setting the advertisement, a function for notifying the combination of the home address of the mobile terminal and the care-of address of the foreign agent device to the network address transfer device as transfer information, and a position registration for the home agent. 2. The apparatus according to claim 1, further comprising a function of setting the representative care-of address as a care-of address, and wherein the network address transfer device has a function of storing transfer information based on the combination in a table. Mobile data communication system. 3. The mobile terminal moves in a sub-network and uses the same representative care-of address of the network address transfer device used by the foreign agent device of the sub-network before the movement. When the location registration is performed with the home agent device via the foreign agent device, the foreign agent device used by the mobile terminal after the movement is transferred to the network address transfer device with the care-of address of the own foreign agent device, A combination of the home address of the mobile terminal, or the care-of address of its foreign agent device,
Notifying the network address transfer device of the combination of the home address of the mobile terminal and the address of the home agent as transfer information, wherein the network address transfer device stores a table of a table stored with respect to the currently registered mobile terminal. A search is made to see if any of them match the home address of the mobile terminal or the combination of the home address of the mobile terminal and the address of the home agent device. If found, the old care-of address in the table is found. The foreign agent device having the following is notified that the corresponding mobile terminal has moved, and the old care-of address in the table is rewritten to the care-of address of the foreign agent device of the destination sub-network. Item 2 Mobile data communication system. 4. The network address transfer device has means for periodically monitoring whether or not each foreign agent device is operating, and a plurality of foreign agent devices in the same sub-network are Means for periodically monitoring whether or not the other foreign agent device is operating, and when the network address transfer device detects a failure of the foreign agent device, the network address transfer device If there is a mobile terminal receiving the packet via the foreign agent device which has detected the failure by searching the transfer information table in the, the packet is received via the foreign agent which has detected the failure from the table. Delete entry for mobile terminal When the foreign agent device detects a failure of another foreign agent device belonging to the same sub-network, the foreign agent device that has detected the failure changes the source address in the advertisement message to the failure of the foreign agent device. The address of the device is set, the busy bit is set and transmitted for a certain period of time.
4. The mobile data communication system according to claim 2, wherein the mobile terminal using the agent device performs location registration via another foreign agent device. 5. A foreign agent device comprising a plurality of available network address transfer devices, wherein the foreign agent device determines whether or not the regularly used network address transfer device is operating. Means for monitoring a failure of the network address transfer device, when setting a representative care-of address of another network address transfer device as a care-of address in the advertisement message and transmitting the same. The mobile data communication system according to claim 2, 3 or 4, wherein 6. A mobile terminal that is connected to a plurality of sub-networks, a mobile terminal that can move between the sub-networks, and a sub-network to which the mobile terminal belongs, captures a packet addressed to the mobile terminal, and encapsulates the packet. A home agent device having a function of transferring to a destination sub-network in which the mobile terminal is moving; and a packet addressed to the encapsulated mobile terminal connected to the sub-network and transferred from the home agent device. Agent device having a function of relaying the packet to a mobile terminal that has moved from another sub-network, and the foreign agent device that transfers an encapsulated packet addressed to the mobile terminal transferred from the home agent device to the foreign agent device. Network address to relay to A network address transfer device provided in a mobile data communication system configured to include a transfer device, wherein the mobile terminal transmits an encapsulated packet transmitted to a care-of address registered in a home agent device. The function of rewriting the destination address to the care-of address of the foreign agent device that relays the packet to the mobile terminal, and relaying the packet; and the home address and the foreign address of the mobile terminal transferred from the foreign agent device. A network address transfer device having a function of storing in a table combination information with the care-of address of the agent device. 7. A mobile terminal connected to a plurality of sub-networks, a mobile terminal capable of moving between the sub-networks, and a sub-network to which the mobile terminal belongs, capturing a packet addressed to the mobile terminal, and encapsulating the packet. A home agent device having a function of transferring to a destination subnetwork in which a mobile terminal is moving; and a packet addressed to an encapsulated mobile terminal connected to the subnetwork and transferred from the home agent device. Agent device having a function of relaying to a mobile terminal that has moved from another subnetwork, and the foreign agent device that transfers a packet addressed to the encapsulated mobile terminal transferred from the home agent device. Network address to relay to In a foreign agent device provided in a mobile data communication system configured with a transfer device, a mobile terminal moving from another network,
An advertisement function for advertising the care-of address indicating the transfer destination address of the packet to be transferred to the mobile terminal by the home agent device, and a process for the mobile terminal to register the care-of address of the destination network with the home agent device A registration relay function of relaying a, a function of setting a representative care-of address of the network address transfer device as the care-of address in the advertisement,
A function of notifying the combination of the home address of the mobile terminal and the care-of address of the foreign agent device as transfer information to the network address transfer device, and the representative care-of address as a care-of address for location registration for the home agent. A foreign agent device having a setting function.