JP2003348130A - Address providing system and consecutive communication system to mobile terminal - Google Patents

Abstract

(57) [Summary] [PROBLEMS] When a terminal connected to a subnet connected by using an Internet protocol by a short-range wireless communication is mounted on an automobile or the like and is expected to move, an instantaneous operation is performed. To provide a terminal with an address and continue communication when moving between base stations and subnets. A method according to the present invention lends an address to a base station in advance in order to instantaneously assign an address to a terminal. Furthermore, gateways in each subnet manage addresses leased by all gateways so that communication can be continued even if the terminal moves between subnets. Furthermore, dynamic D
In order to prevent duplicate registration in the NS, when registering the IP address and the host name, the record deletion is resent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a short-range wireless communication (DSR) for subnets connected to each other using the Internet Protocol (IP).
If the terminal connected by C: Dedicated ShortRange Communications) is mounted on a car or the like and is expected to move,
A method for dynamically assigning an address to a terminal entering the subnet and associating the address with the host name of the terminal. Address management and route change for continuing communication even if the terminal moves between subnets. The method is further applied to a communication method in a case where a moving terminal and a plurality of base stations for wireless communication exist in the same subnet so as to cover a moving area of the terminal, and the terminal moves between the base stations. And effective technology.

[0002]

2. Description of the Related Art In recent years, intelligent transportation systems (ITS: Inte
lligent Transport Systems).
Literature ITS HANDBOOK 2000-2001-5
According to the description on page 0, in the intelligent transportation system, an automatic toll collection system (ETC: Electric Toll Collection System) in which a terminal for performing DSRC is mounted on a vehicle and payment is automatically made without stopping the vehicle. )
Etc. are being put to practical use.

In the above-mentioned intelligent transportation system, a plurality of base stations are installed on a road, and a terminal mounted on a moving vehicle is connected to a network such as the Internet via a nearest base station and a gateway to connect to a network. It is also considered to perform communication between the vehicle and an external network.

In the highway traffic system as described above, in order to communicate between the vehicle and an external network, it is necessary to dynamically assign an address to the vehicle. Further, in order to perform communication between vehicles, it is necessary to associate dynamically allocated addresses with host names of vehicles. In addition, when configuring and operating a network to which base stations and gateways are connected, it is necessary to perform a method of continuing communication even when a terminal moves between base stations or between subnets, that is, perform handover.

As a technique for dynamically allocating addresses,
There are DHCP (Dynamic Host Configuration Protocol) and PPP (Point to Point Protocol). DHCP
Is a protocol for dynamically assigning an IP address to each host on a TCP / IP network.
1533, 1534, 1541, and 1542. The one that performs this address assignment work is DHC
P server, DHC gets address from server
Become a P client.

Further, IPCP (IP Control Pro
tocol) is NCP (netw) when using TCP / IP.
This is used when assigning IP addresses to be used by two parties when connecting and communicating data between two points using an ork control protocol, and is defined by RFC 1332.

As a technique for associating a dynamically assigned address with a host name, the DHCP and the dynamic D
There is a technology for combining NS. RF for DNS
C1034 and 1035.

One of the techniques developed for the purpose of handover is to provide a means for continuing communication of a terminal moving between subnets in Mobile I.
There is P technology, which is used in combination with Mobile IP technology and provides a means for a mobile to communicate with a base station by radio and to provide a means for continuing communication of terminals when moving between base stations. There is technology. Mo
The bile IP technology is described in document RFC2002,
Cellular IP technology is described in INTERNET D
It is described in RAFT Cellular IP.

[0009]

In the DSRC, when a vehicle moving at a maximum speed of 180 km / h enters a wireless zone, the address must be dynamically allocated in a short time when the wireless zone is as narrow as 30 m. In addition, even when moving between subnets, once assigned addresses must be able to be used continuously so that communication can be continued.

In DHCP and PPP, complicated procedures are required until addresses are assigned, and it is difficult to assign addresses in a short time. In addition, when moving between subnets, it is necessary to assign addresses again, and communication cannot be continued.

In the technology of DHCP and dynamic DNS for dynamically associating dynamically assigned addresses with host names,
Since the registration or deletion of a record may not always be performed correctly depending on the state of the communication path, there is a problem that the same host name is registered twice at different addresses.

[0012] In Mobile IP technology, a terminal is usually
A home network is defined as a home network (Home Network), and a node called a home agent (Home Agent; hereinafter, referred to as HA) for supporting a terminal is provided in the home network. Subnet to external network (Foreign Networ
k) and external agents (Forei
gn Agent; hereafter referred to as FA), a node that relays data exists, and even if the terminal moves on the subnet, the terminal receives data through the HA, so if the terminal is not connected to the home network, Then, the data is transferred to the FA after passing through the home network, and the data reaches the terminal. This technology is mainly
It has been developed on the assumption that the terminal is temporarily moved from the place where it is originally used for use.

However, in consideration of communication of a terminal mounted on an automobile or the like in which almost all terminals under the subnet move, when almost all terminals under the subnet move, data is concentrated on the HA. However, even if the gateways existing in the respective subnets have room to process data, if there is no room in the data transfer capability of the HA, the use efficiency of the network is reduced.

Further, the DSRC has a feature that the radio zone is as small as 30 m and the radio zones do not overlap each other, so that the position can be easily specified. However, while the conventional handover technique performs a handover while the terminal is passing through the range where the respective wireless zones overlap, in DSRC there is no range where the respective wireless zones overlap, so the handover is performed. It is necessary to provide a service in a short time to complete the overtime in a short time.

In the Cellular IP technology,
The route is established by the terminal receiving a beacon signal periodically transmitted by the node, and the terminal receiving the beacon signal and responding to it with a message. In other words, once a message is exchanged between the node and the terminal, a route is established, and communication cannot be performed unless a route is established in a gateway higher than the base station, which is not suitable for providing services in a short time. There is a problem that.

According to the present invention, when a user enters an area where a service can be provided, addresses are dynamically allocated in a short period of time, and a plurality of subnets are provided without the need for a node for data transfer such as an HA. Interface to a network that allows other gateways to communicate with each other,
In addition to providing a means for allowing terminals to continue communication while moving between subnets by adding them to gateways that make up an ordinary IP network and communicating with each other, nodes and base stations are the same. When a terminal moves between base stations, a message is sent from the in-vehicle terminal without waiting for a signal from the node, and the route of the base station is changed without changing the route information of the gateway. An object of the present invention is to provide a method for establishing a route only by changing information, thereby enabling handover in a short time.

[0017]

In order to solve the above-mentioned problems, according to the present invention, a gateway belonging to each of a plurality of subnets to which a mobile terminal can be connected is connected between gateways capable of communicating with each other. The network is connected to a connection network, and the subnet is connected to an intra-subnet connection network that enables a gateway and a plurality of base stations to communicate with each other.

The gateway has a plurality of identification addresses to be lent to the terminal, and each gateway belonging to all subnets manages all the identification addresses lent to the terminal. In addition, the gateway lends an address to a base station in advance in order to quickly assign an address when a terminal newly enters a subnet. The base station manages the identification addresses of all terminals connected in the subnet. When the terminal newly enters the subnet, the base station that has confirmed the connection of the terminal assigns an identification address to the terminal and notifies the gateway of the subnet of the assignment. The gateway enables communication within the subnet by adding route information.

Further, the gateway of the subnet notifies the gateways of all the subnets to which the terminals are to be connected that the new terminal has been connected to its own subnet via the inter-gateway network. . The gateway of the notified subnet
Add address information. When the terminal moves between subnets, the gateway of the subnet that has newly confirmed the connection of the terminal adds route information and enables communication within the subnet. Further, the gateway of the previous subnet notifies the gateways of all the subnets to which the terminal is expected to be connected via the inter-gateway connection network that the terminal has moved to its own subnet, and recognizes the terminal before moving. The gateway of the subnet that has changed the route information about the terminal.

In the gateway-to-gateway connection network for interconnecting the gateways, only a message for notifying the connection of the terminal is sent, and normal data is not sent. A message notifying the connection of the terminal can be promptly delivered to the gateway without being affected by the traffic of the terminal.
In an intra-subnet connection network, packets are transmitted by broadcast from the gateway or base station. If a terminal moves between base stations in the same subnet, the route information of the gateway is not changed. , Only the route information of the base station is changed.

Specifically, in order to realize the method of the present invention,
The gateway of each subnet has its own gateway lending address table for lending, another gateway lending address table, and a routing table, a function to lend an identification address to the base station in advance, and when a new terminal enters the subnet In addition, the function that confirms that the base station has assigned an identification address to the terminal and sends a message to all gateways existing in the subnet where the connection of the terminal is assumed, and the function when the mobile terminal enters the subnet or another subnet Function to update the routing table when a mobile terminal entry message is received from the gateway, look at the destination information included in the data, sort the data to that destination, and rent the address and host name of the vehicle to the terminal To notify the DNS server to register or delete A.

The base station has a base station rental address table for lending and an address table of mobile terminals existing in the subnet, and assigns an identification address when a mobile terminal to which no identification address is assigned enters. When the mobile terminal enters the subnet, or when moving between base stations, has a function of notifying the gateway and other base stations by broadcasting, and a function of updating the terminal address table under the subnet of the base station at that time .

By this series of operations, communication is enabled by instantly assigning an identification address to a mobile terminal newly entering the subnet, and communication is performed without moving through the source subnet when moving between subnets. By doing so, it is possible to prevent a decrease in network use efficiency, and to enable handover in a short time when a mobile terminal moves between base stations in the same subnet.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the system of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an example of a current ITS road-to-vehicle system. In FIG. 1, a car 100 moves on a road,
The base stations 101-1, 101-2, and 101-3 each have a wireless zone 102 that is a range in which wireless communication can be performed on a road.
-1, 102-2, and 102-3, and when the vehicle 100 exists in each wireless zone, ETC or the like is performed by communicating between the vehicle 100 and each base station.

FIG. 2 is a diagram showing the configuration of a network constituted by a plurality of subnets to which the method of the present invention is applied. In the system shown in FIG. 1, a car is connected to an IP network such as the Internet. FIG. In the network of FIG. 2, a car 2 having a unique terminal number 200 and a car name AAA
Reference numeral 00 denotes a vehicle that is assumed to move with a terminal connected to the Internet or the like. The subnet a210, the subnet b211 and the subnet c212 are subnets in which the connection of the moving in-vehicle terminal is assumed, and the MOBILE
The IP network 220 is a normal IP network.
When a packet is sent to a network other than the network indicated by (1), the packet reaches the destination by Mobile IP.

Gateway address 210.1.1.1
Gateway a 230, gateway address 21
1.1.1.1 gateway b231, gateway address 212.1.1.1 gateway c232
Can access MOBILE I via a normal IP network.
P network 220.
The connection is also made via the inter-gateway connection network 221 which is a network other than the P network, and all control data is transferred by broadcast. Gateway a 230 and base station 24
0-1 to 240-n are connected in the subnet a210, and the gateway a230 and the base stations 240-1 to 240-2 are connected.
All data between 40-n is transferred by broadcast.

The gateway b 231 and the base station 241-1
241-n are connected within the subnet b211 and the gateway b231 and the base stations 241-1 to 241 are connected.
All data between -n is transferred by broadcast. The gateway c232 and the base stations 242-1 to 242-n are connected within the subnet c212, and all data between the gateway c232 and the base stations 242-1 to 242-n are transferred by broadcast.

As will be described later in detail, the gateway a 230, the gateway b 231 and the gateway c 232 of the present invention have their own gateway lending address table, another gateway lending address table, a packet transfer routing table, and the base station 240-1.
To 240-n and 241-1 to 241-n and 24
2-1 to 242-n have a base station lending address table and a packet transfer routing table. The gateway lends an identification address to the base station in advance from its own gateway lending address table. Register the address in the base station rental address table. When a terminal without an assigned address enters, the base station assigns an address to the terminal from the base station lending address table and notifies the gateway and the base station within the same subnet to the base station without assigning an address from the gateway. , It is possible to instantaneously assign an address to a terminal.

When a terminal moves between subnets and detects a terminal in the destination subnet, the gateway of the subnet checks the terminal number and the address of the terminal.
Rewrite the own gateway or other gateway lending address table and the routing table for packet transfer, and send the inter-gateway movement notification message to the gateways of all the subnets. Rewrite the gateway lending address table and the packet transfer routing table. With this operation, the route information is changed, and communication can be continued even if the terminal moves between subnets.

FIG. 3 shows the gateway a 230 of the present invention.
It is a block block diagram which shows the structure of b231 and c232. Taking the gateway a230 as an example, the gateway a230 is a mobile IP network interface 300.
-1, a base station interface 300-2, an inter-gateway connection network interface 300-3, a routing unit 301, a message processing unit 302, and a control unit 303. The control unit 303 includes the processor 32
0, a program storage memory 321, an own gateway lending address table 322, another gateway lending address table 323, and a packet transfer routing table 324.

MOBILE IP network interface 30
0-1 is composed of an input interface from the MOBILE IP network 220 and an output interface to the MOBILE IP network 220.
00-2 is composed of an input interface from the base station and an output interface to the base station, and the inter-gateway connection network interface 300-3 is an input interface from the inter-gateway connection network 221 and an output to the inter-gateway connection network 221. Consists of an interface. MOBILE IP Network Interface 300-1
The packet 310 received by the input interface is subjected to routing processing by the routing unit 301 with reference to the packet transfer routing table 323, and is output to the output interface of the base station interface 300-2 or is discarded. When output to the output interface of the base station interface 300-2, all the base stations 240-1 to 240-2 in the subnet a210
The broadcast is output so that the packet reaches 40-n.

If the packet 310 received by the input interface of the base station interface 300-2 is user data, the routing unit 301 performs routing processing by referring to the packet transfer routing table 323, and performs MOBILE IP. It is output to the output interface of the network interface 300-1. In the case of control data, a packet 311 including a message is input to the message processing unit 302. The message processing unit 302 expands the packet 311 including the received message into a message format, sends the message 312 to the control unit 303, and assembles the message 312 received from the control unit 303 into a packet 311 including the message. .

The function of the message processing unit 302 may be realized by storing a program for performing message processing in the program storage memory 321 and executing the program by the processor 320. Further, the packet 311 including the message is sent to the routing unit 301 and routed, and is output from the output interface of the base station interface 300-2 or the output interface of the inter-gateway connection network interface 300-3. The packet including the message from the gateway of the other subnet input from the input interface of the inter-gateway connection network interface 300-3 is processed in the same manner as the control data input to the base station interface, and is processed by the base station interface or the inter-gateway interface. Output from the output interface. In the gateway of the present invention, the processor 320 analyzes the message received from the message processing unit 302 and rewrites the own gateway lending address table 322, the other gateway lending address table 323, and the packet transfer routing table 324, so that the route information is rewritten. To change.

When a new terminal is detected, the processor 320 creates a message and sends the message to the gateways belonging to all other subnets through the inter-gateway connection network 221. Also,
The own gateway lending address table 322 and the other gateway lending address table 323 are used to save the state when an address is assigned to a terminal or the terminal moves and the state of the identification address changes. The program storage memory 321 includes a processor 32
0 stores a processing program such as table rewriting to be executed.

FIG. 4 shows base stations 240-1 to 240 of the present invention.
FIG. 2 is a block diagram showing a configuration of 2-n. Base station 24
0-1 to 242-n are a gateway, a base station interface 400-1, and a terminal interface 40, respectively.
0-2, a routing unit 401, a message processing unit 402, and a control unit 403. The control unit 403 includes a processor 420, a program storage memory 421, a base station rental address table 422, and a terminal address table 423 under the subnet.

Gateway, base station interface 40
0-1 is composed of an input interface from the gateway and the base station, and an output interface to the gateway and the base station, and the terminal interface 400-2 is composed of an input interface from the in-vehicle terminal and an output interface to the in-vehicle terminal. I have. If the packet 410 received at the input interface of the gateway / base station interface 400-1 is user data, the routing unit 401 performs routing processing by referring to the terminal address table 423 under the subnet. The packet reaches the vehicle-mounted terminal by being output to the second output interface.

In the case of control data, a packet 411 including a message is input to the message processing unit 402.
The message processing unit 402 expands the packet 411 including the received message into a message format,
Sent to the control unit 403 as a message 412, and
The message 412 received from the control unit 403 is assembled into a packet 411 including the message. The function of the message processing unit 402 is as follows.
May be realized by storing a program for performing message processing in the processor 420 and the processor 420 executing the program.

Packet 411 further including a message
Are sent to the routing unit 401, are routed, and are output from the output interface of the gateway / base station interface 400-1. The packet 410 received at the input interface of the terminal interface 400-2 is subjected to routing processing by the routing unit 401 by referring to the terminal address table 423 under the subnet, and is output to the output interface of the gateway / base station interface 400-1. Is output. In the case of a base station belonging to the subnet a, the packet is output to the gateway and, if output to the output interface of the base station interface 400-1, to the gateway a 230 so that the packet reaches all the other base stations.

In the base station of the present invention, the processor 420
Analyzes the message received from the message processing unit 402 and finds the terminal address table 42
The route information is changed by rewriting 3. When a new terminal is detected, the processor creates a message and sends the message to the gateway a230. Further, the program storage memory 421 stores processing programs such as table rewriting executed by the processor 420.

FIG. 5 is a diagram showing the configuration of the own gateway lending address table provided in each of the gateway a230, the gateway b231, and the gateway c232 of the present invention. In the own gateway lending address table 322, the identification address 50 to be rented and managed by the own gateway is displayed.
1 and state 5 of whether the identification address is available for lending, lending to a base station, or being assigned to a mobile terminal
02, the node number 503 of the lending base station when the identification address is being lent to the base station, and the mobile terminal number 504 of the mobile terminal when the identification address is assigned to the mobile terminal. 505, the lending expiration date 506 of the identification address, and the vehicle name 507 of the mobile terminal when the identification address is assigned to the mobile terminal.

FIG. 6 is a configuration diagram of another gateway lending address table provided in the gateway a230, the gateway b231, and the gateway c232 of the present invention. Other gateway rental address table 323
Is the address 60 of a gateway belonging to another subnet.
1 and the identification address 602 lent by the other gateway
And a state 603 as to whether the identification address exists under the own gateway or under another gateway,
The mobile terminal number 6 of the mobile terminal to which the address is assigned
04.

FIG. 7 is a configuration diagram of a routing table for packet transfer provided in each of the gateway a230, the gateway b231, and the gateway c232 of the present invention. The routing table 324 includes a destination address 701 and an interface 702 for outputting a packet. When the gateway receives the packet, the destination address of the packet matches the destination address 701 of the packet transfer routing table. Sometimes, the packet is output to the interface indicated by the interface 702 that outputs the packet. If the interface is a base station interface, the packet is output by broadcast.

FIG. 8 shows base stations 240-1 to 240 of the present invention.
-N, base stations 241-1 to 241-n and base station 242
It is a block diagram of the base station lending address table which -1 to 242-n has respectively. The base station lending address table 422 contains an identification address 801 that the base station can lend.
And an address 802 of the gateway that leased the identification address. The identification address leased from the gateway is registered in advance, and when the identification address is assigned to the mobile terminal, it is deleted from the table. When the identification address is exhausted or becomes smaller than a predetermined threshold, the gateway requests the gateway to lend the identification address again.

FIG. 9 shows base stations 240-1 to 240 of the present invention.
-N, base stations 241-1 to 241-n and base station 242
FIG. 14 is a configuration diagram of a terminal address table under a subnet provided for each of -1 to 242-n. Table 423
Is the identification address 901 assigned to all mobile stations existing under the subnet, the address 902 of the gateway that leased the address, and whether the mobile terminal is under its own base station or under another base station. State 9 of existence
03 and a packet output interface 904.

FIG. 10 is a configuration diagram of mobile terminal information provided in the mobile terminal 200 of the present invention. Mobile terminal information 1000
Is the mobile terminal number 1001, the identification address 1002 assigned to the mobile terminal, the address of the gateway that leased the identification address, and the vehicle name 1004 of the mobile terminal.
Consists of

FIG. 11 shows the format of a message used within a subnet or between gateways. The message 1100 includes a message header section 1101 and message-specific data 1102. The message header section 1101 further includes a message identifier 1111 indicating a type of the message, a transmission source node number 1112 indicating a transmission source of the message, and transmission of the message. It is composed of a destination node number 1113 indicating the destination and a message length 1114. The transmission destination node number 1113 is set with the node number of the transmission destination when performing individual communication, and is set with the number indicating the broadcasting when performing the broadcast notification.

FIG. 12 shows a case where the base station requests the gateway to lend the identification address to the gateway when the identification address given to the mobile terminal by the base station is exhausted or becomes smaller than a certain threshold. It is a format of an address lending request message. The address lending request message 1200 includes a message header section 1101 and the number of address lending requests 1201. The destination node number 1113 of the address lending request message 1200 is set with the node number of a gateway in the same subnet and transmitted.

FIG. 13 shows the format of an address lending response message transmitted by the gateway when lending an identification address to the base station in response to an address lending request message 1200 from the base station. The address lending response message 1300 includes a message header 110
1, address lending number 1301, lending address 130
2 and a gateway address 1303 for renting an address. The lending address 1302 and the gateway address 1303 are repeated for the number of address lending. The node number of the base station is set as the destination node number 1113 of the address lending response message 1300 and transmitted.

FIG. 14 shows a case where the gateway refuses to lend an identification address to the base station in response to the address lending request message 1200 from the base station when the lending identification address of the gateway is exhausted.
This is the format of the address lending rejection message. The address lending rejection message 1400 includes a message header section 1101. The node number of the base station is set as the transmission destination node number 1113 of the address lending rejection message 1400 and transmitted.

FIG. 15 shows a format of an address assignment notification message transmitted from the base station to the gateway when the base station assigns an identification address to the mobile terminal. The address assignment notification message 1500 includes a message header section 1101, a mobile terminal number 1501, an identification address 1502 assigned to the mobile terminal, and a vehicle name 1503 of the mobile terminal. The address assignment notification message 1500 is broadcast to other base stations and gateways in the same subnet.

FIG. 16 shows a format of an address lending notification message transmitted to a gateway on another subnet when the gateway receives an address assignment message from the base station. Address lending notification message 1
Reference numeral 600 denotes a message header section 1101, a mobile terminal number 1601, and an identification address 160 lent to the mobile terminal.
2 and the address 1603 of the gateway that leased the identification address. The address lending notification message 1600 is transmitted by broadcast to a gateway on another subnet.

FIG. 17 shows a format of an address confirmation notification message transmitted when a mobile terminal moves between base stations in the same subnet or when moving between subnets. Address confirmation notification message 170
0 is the message header 1101 and the mobile terminal number 1
701 and the identification address 17 assigned to the mobile terminal
02. Address confirmation notification message 17
00 is broadcast to other base stations and gateways in the same subnet.

FIG. 18 shows the case where the mobile terminal has moved between subnets, or the address assigned to the mobile terminal exists in the identification address table 423 of the terminal under the base station of the base station that received the inspection request from the mobile terminal. If not,
It is a format of an address check request message transmitted from the base station to the gateway. The address check request message 1800 includes a message header 1101
, The mobile terminal number 1801, the identification address 1802 assigned to the mobile terminal, the address 1803 of the gateway that leased the identification address, and the vehicle name 1804. The destination node number 1113 of the address check request message 1800 is set with the node number of a gateway in the same subnet and transmitted.

FIG. 19 shows, in response to the address check request message 1801 from the base station, whether the check address 1801 exists in the own gateway lending identification address table 322 or the other gateway lending identification address table 323, and checks the identification address. Is a format of an address check response message transmitted from the gateway to the base station when it is determined whether or not it can be continuously used and a check response is made. The address check response message 1900 is
Message header section 1101, mobile terminal number 1901
, Inspection address 1902, lending gateway address 1903, vehicle name 1904, and inspection result 1905. The node number of the base station is set as the destination node number 1113 of the address check response message and transmitted.

FIG. 20 shows an inter-gateway movement notification transmitted from a gateway to a gateway in another subnet when the mobile terminal moves between subnets and the identification address assigned to the mobile terminal is an address that can be used continuously. The format of the message. The inter-gateway movement notification message 2000 includes a message header section 1101, a mobile terminal number 2001, and an identification address 2
002 and a destination gateway address 2003. Gateway movement notification message 2000
Is broadcast to the gateway connection network.

FIG. 21 shows a case where a ping is transmitted to the identification address given to the mobile terminal and there is no response,
Address release notification message sent when a gateway notifies release to a gateway on another subnet (gateway → gateway on another subnet)
Format. The address release notification message 2100 for the other gateway includes a message header section 1101, a terminal number 2101, an identification address 2102 to be released, and an address 2102 of the gateway that leased the identification address. The address release notification message 2100 for the other gateway is transmitted by broadcast to the inter-gateway connection network.

FIG. 22 shows a case where a ping is transmitted to the identification address given to the mobile terminal and there is no response,
This is a (gateway → base station) format of an address release notification message transmitted when notifying release to a base station in the own subnet. The address release notification message 2200 for the base station includes a message header section 1101, a mobile terminal number 2201, and an identification address 2202 to be released. The address release notification message 2200 for the base station is broadcast to base stations in the same subnet.

FIG. 23 shows a vehicle inspection request message transmitted to a base station when the vehicle moves between base stations or between subnets. Vehicle inspection request message 23
00 is the mobile terminal number 2301 and the inspection request address 2
302, the address 2303 of the gateway that leased the address, and the vehicle name 2304.

FIG. 24 shows a vehicle inspection response message transmitted from the base station to the vehicle when responding to the vehicle inspection request message from the vehicle. The vehicle inspection response message 2400 includes a mobile terminal number 2401, an assigned address 2402, an address 2403 of a gateway that leased the address, and a vehicle name.

FIGS. 25 to 32 are flowcharts showing the operation of the gateway. When a message from a base station or another gateway is received (2501), the message type is determined (2502), and processing for each message type is performed. Message type is address lending request 1200 (A)
In the case of (2), it is determined whether or not there is an identification address that can be rented in the own gateway lending address table 322 (26).
01) If there is no rentable address, an address lending rejection message 1400 is transmitted (2602).
If there is an address that can be borrowed, an address lending response message 1300 is transmitted (2603), the state 502 of the borrowed address is set to lending the base station, and the source node number 1112 of the message is set to the node number 503 of the base station. (2604).

If the message type is the address assignment notification 1500 (B) in the message type determination (2502),
The state 502 of the corresponding address in the own gateway lending address table 322 is set under the own gateway (27
01), sends an address lending notification message 1600 to the other gateway (2702), and starts an address lending timer (2703). Judgment of message type (250
In 2), the message type is the address check request 1800
In the case of (C), own gateway lending address table 3
22 and the other gateway lending address table 323 are searched (2801). If the corresponding address does not exist in the table, the inspection result 1904 is transmitted to the base station as an NG address inspection response message 1900 (28).
02).

If the corresponding address exists in the table, the state 502 of the corresponding address in the rental address table
Alternatively, 603 is set under the own gateway (280
3) The inspection result 1904 sends an OK address inspection response message 1900 (2804), and sends an inter-gateway movement notification message 2000 to another gateway (2805). Judgment of message type (250
If the message type is the address release notification (gateway → other gateway) 2100 (D) in 2), the corresponding address is deleted from the other gateway lending address table 323 (2901), and the address is sent to the base station under its own gateway. Release notification message (Gateway →
Base station) 2200 (2902).

In the message type determination (2502), the message type is the address lending notification message 1600.
In the case of (E), it is registered in the other gateway lending address table 323 (3001). When the message type is determined to be the inter-gateway movement notification message 2000 (F) in the message type determination (2502), the own gateway lending address table 322 or the other gateway lending address table 323 is searched (3101).
The state 502 or 603 of the corresponding address is changed to another gateway (3102), and an address release notification message (gateway → base station) 2200 is transmitted to the base station under the own gateway (3103).

When the lending timer expires (3201), an ICMP echo command is executed for the corresponding address (3202). If there is no ICMP echo response,
An address release notification message (gateway → base station) 2100 is transmitted to a gateway in another subnet (gateway → other gateway) (3204), and an address release notification message (gateway → base station) 2200 is transmitted to a base station in the same subnet (3205). . If there is a response to the ICMP echo, the lending timer is started again (3206).

FIG. 33 to FIG. 38 are operation flowcharts of the base station. When a message from the gateway or the vehicle is received (3301), the message type is determined (3).
302), a process for each message type is performed. When the message type is the address lending response message 1300 (A), the identification address 1302 and the gateway address 1303 in the message are stored in the lending identification address table 422.
(3401). Judgment of message type (33
02), if the message type is a vehicle inspection request message 2300 (B) from a vehicle, if there is no address in the inspection request address 2301 of the message, an address is assigned from the rental address table 422, and the vehicle inspection response message 2400 is assigned to the vehicle. Is transmitted (3502),
An address assignment notification message 1500 is transmitted to a gateway and another base station in the same subnet (3503).

The assigned address is deleted from the rental address table 422 (3504). After deletion, if the loan address is exhausted or less than the threshold (35
At 05), an address lending request message 1200 is transmitted to the gateway (3506). If there is an address in the inspection request address of the message, the terminal address table 423 under the subnet is searched, and if there is no inspection request address, an address inspection request message 1800 is transmitted to the gateway (350).
8). When the terminal number and the address exist in the terminal address table 423 under the subnet, the mobile terminal number 2301 and the inspection request address 2302 of the vehicle inspection request message 2300 are added to the mobile terminal number 2401 and the assigned address 2402 of the vehicle inspection response message 2400. And sends it to the vehicle (3509), changes the state of the corresponding address in the terminal address table under the subnet to the one under its own base station (3510), and sends an address confirmation notification message to the gateway and other base stations in the same subnet. 17
00 is transmitted (3511).

In the determination of the message type (3302), the message type is the address check response message 1900.
In the case of (C), when the inspection result 1904 of the message is NG, an address is assigned from the lending address table 422, a vehicle inspection response message 2400 is transmitted to the vehicle (3602), and the address is transmitted to the gateway and another base station in the same subnet. An assignment notification message 1500 is transmitted (3603), and the assigned address is deleted from the lease address table 422 (3604). If the inspection result 1904 of the message is OK, the mobile terminal number 2301 of the vehicle inspection request message 2300 is replaced with the mobile terminal number 2301. The inspection request address 2302 is set to the mobile terminal number 2401 and the assigned address 2402 of the vehicle inspection response message 2400, transmitted to the vehicle (3605), the corresponding address is added to the terminal address table under the subnet, and the state is set to the own base station. (3606), same It sends an address acknowledgment message 1700 to the gateway and the other base stations in the subnet (3607).

In the message type determination (3302), if the message type is an address release notification message (gateway → base station) 2200 (D), the corresponding address is deleted from the terminal address table 423 under the subnet (3701). Determination of message type (3302)
And the message type is the address confirmation notification message 17
In the case of 00 (E), if the corresponding address does not exist in the terminal address table 423 under the subnet, the address is added to the table 423 and the state is set under the control of another base station (3802). If the corresponding address exists in the table 423, the state of the corresponding address is set under the control of another base station (3803).

FIG. 39 shows an address lending sequence to the base station. The base station transmits an address lending request message 1200 to the gateway when there is no lending address in the lending address table or when the lending address is smaller than the threshold value when the address is periodically or when the address is assigned to the mobile terminal (3901). . Address lending request message 1
The gateway receiving the 200 transmits an address lending response message 1300 to the corresponding base station (39).
02).

The own gateway lending address table and the routing table of the gateway a 230 before lending the identification address to the base station 240-1 are shown in FIGS. 5 and 7, the other gateway lending address table of the gateway b 231 is shown in FIG. When the rented address table of the station 240-1 and the terminal address table under the subnet are shown in FIGS. 8 and 9, the tables after renting out two identification addresses to the base station 240-1 are shown in FIGS. 44 and 45.

FIG. 44 is an own gateway lending address table of the gateway a 230 after lending the address to the base station 240-1, and the identification address 210.1.1.1.1.
01 and 210.1.1.102 are lent, and the base station node number is set to “240-1”.

FIG. 45 is a base station rental address table of the base station 240-1 whose identification address has been leased from the gateway a230. The address 210.1.1.10.
1 and 210.1.1.1.12 are added, and a gateway address 210.1.1.1.1 is set.

FIG. 40 shows a sequence when a mobile terminal newly enters. The newly entered mobile terminal sets the inspection request address 2302 to “Null” and transmits a vehicle inspection request message 2300 to the base station (400).
1). The base station assigns an address, sets the assigned address 2402 to the vehicle, and sends a vehicle inspection response message 2400
(4002), and an address assignment notification message 15 is sent to the gateway and other base stations in the same subnet.
00 is transmitted (4003). The gateway that has received the address assignment notification message 1500 sends an address lending notification message 1 to a gateway in another subnet.
600 is transmitted (4004), a registration request is made to the Mobile IP network (4005), and a registration request is made to the DNS server (4006).

When the vehicle 200 to which no address is assigned enters the base station 240-1 of the subnet a210, the address tables after the address assignment are shown in FIG. 46 to FIG.

FIG. 46 is the own gateway lending address table of the gateway a230 after the address is assigned. The state of the address 210.1.1.1.11 is under the own gateway, and "200" is set as the mobile station terminal number.

FIG. 47 is a gateway routing table of the gateway a230 after the address is assigned.
The destination address 201.1.1.101 is added, and the base station interface is set as the packet output interface.

FIG. 48 shows base station 240 after address assignment.
-1 is a base station lending address table, address 2
01.1.1.101 is deleted.

FIG. 49 shows base station 240 after address assignment.
-1 is a terminal address table under the subnet of -1,
The address 201.1.1.101 is added, and the state of the address is set under the control of the own base station.

FIG. 50 shows base station 240 after address assignment.
2 is a terminal address table under the subnet of the base station 240-n from the base station -2, and the address 210.1.1.1.11.
Is added, and the state of the corresponding address is set under the control of another base station.

FIG. 51 shows the mobile terminal information of the vehicle having the mobile terminal number “200” to which the address has been assigned.
10.1.1.101 is set and 2100.1.1.1 is set as the gateway address.

FIG. 52 shows another gateway lending address table of the gateways b231 and c232 after the addresses are assigned.
An identification address 210.1.101 of 0.1.1.1 is added, the status of the address is set under the control of another gateway, and "200" is set as the mobile terminal number.

FIG. 41 shows a sequence when a mobile terminal moves between base stations. The mobile terminal that has moved between the base stations transmits a vehicle inspection request message 2300 to the base station (4101). The base station searches the terminal address table 423 under the subnet, and if there is a matching address, transmits a vehicle inspection response message 2400 (41).
02), an address confirmation notification message 1700 is transmitted to the gateway and another base station on the same subnet (4103).

The vehicle 200 given the address 210.1.1.1.11 is moved from the base station 240-1 to the base station 240-
2, each table after movement between base stations is shown in FIG.
FIG. 54 from FIG.

FIG. 53 is a terminal address table under the subnet of the base stations 240-1 and 240-3 to 240-n after the vehicle moves between base stations. The state is set to another base station.

FIG. 54 shows base station 2 after the vehicle has moved between base stations.
This is a terminal address table under the subnet 40-2, in which the state of the address 210.1.1.1.11 is set in the own base station.

FIG. 42 shows a sequence when a mobile terminal moves between gateways. The mobile terminal that has moved between the gateways sends a vehicle inspection request message 2300 to the base station.
Is transmitted (4201). Vehicle inspection request message 23
The base station that has received 00 performs a search in the terminal address table under the subnet, and if there is no matching address and mobile terminal number, transmits an address check request message 1800 to the gateway (4202). The gateway that has received the address check request message 1800 searches the own gateway lending address table 322 and the other gateway lending address table 323, and if there is a matching address and mobile terminal number, the check result 1904 is OK.
Is transmitted (4203).

Further, the inter-gateway movement notification message 2000 is transmitted to the gateway on the other subnet (4205), and the change of the route is notified to the Mobile IP network (4207). The base station that has received the address inspection response message 1900 in which the inspection result 1904 is set to OK sets the address set in the inspection request address 2302 of the vehicle inspection request message 2300 as the assigned address 2402 of the vehicle inspection response message 2400. And transmits it to the vehicle (4204), and transmits an address confirmation notification message 1700 to the gateway and another base station on the same subnet (4208). Further, the gateway of another subnet that has received the inter-gateway movement notification message 2000 transmits an address release notification message 2200 to the base station in its own subnet (420).
6).

The vehicle 200 given the address 210.1.1.1.11 is moved from the subnet a210 to the subnet b.
In the case of moving to 211, each table after the movement between the gateways is as shown in FIG. 55 to FIG.

FIG. 55 is an own gateway lending address table of the gateway a230 after the vehicle has moved between the gateways, and the state of the address 210.101 is set under the other gateway.

FIG. 56 is a gateway routing table of the gateway a230 after the vehicle has moved between the gateways, and the destination address 210.1.1.1.11 is deleted.

FIG. 57 shows base stations 240-1 to 240-n of subnet a210 after the vehicle has moved between gateways.
Is a terminal address table under the subnet of, and the destination address 210.1.1.1.11 is deleted.

FIG. 58 is another gateway lending address table of the gateway b231 after the vehicle has moved between the gateways, and the state of the address 210.101 is set under the own gateway.

FIG. 59 is a gateway routing table of the gateway b231 after the vehicle moves between the gateways, and a destination address 210.1.1.1.11 is added.

FIG. 60 is a terminal address table under the base station 241-1 subnet of the subnet b211 after the vehicle moves between the gateways.
1.1.101 is added, and the state is set under the control of the own base station.

FIG. 61 shows a case where the vehicle moves from the base station 241-2 to the base station 24 on the subnet b211 after the vehicle moves between the gateways.
1 is a terminal address table under the subnet of 1-n, where a destination address 210.1.1.1.11 is added;
The state is set under the control of another base station.

FIG. 43 shows a sequence at the time of address release. When the lending timer expires at the gateway that has leased the address (4301), P
ing is transmitted (4302). If there is no ping response (4303), the base station in its own subnet is
An address release notification message is transmitted (4304), and an address release notification message is also transmitted to a gateway in another subnet (4305). Also Mobil
e transmits a route deletion request to the IP network (430).
7), also sends a delete request to the DNS server (4)
308). The gateway of another subnet that has received the address release notification message transmits an address release notification message to the base station in its own subnet (43).
06).

Each table after address release returns from FIG. 5 to FIG.

FIG. 62 shows a dynamic DNS registration sequence. When a new vehicle enters the subnet, the gateway transmits an IP address acquisition packet (forward DNS packet) to the dynamic DNS with the added domain name (6).
201). Dynamic DNS receiving the packet responds (1)
Is returned (6202). Upon receiving the response (1), the gateway transmits a domain acquisition packet (reverse DNS packet) to the dynamic DNS with the IP address to be added (6).
203). Dynamic DNS which received the packet responds (2)
Is returned (6204). The gateway that has received the response (2) determines the response (1) (6205), and if there is an IP address, deletes the PTR record of the acquired IP address (conditional PTR record deletion Dynamic).
DNS packet) to the dynamic DNS (620)
6).

The dynamic DNS having received the packet returns a response (3) (6207). The gateway that has received the response (3) determines the response (3) (6208), and if there is an IP address, determines the response (2) (6209). If there is no IP address in the determination of response (1) (6205), determination of response (2) (6209) is performed. In the determination (6209) of the response (2), if there is an IP address,
An A record deletion packet of the acquired domain name (conditional A record deletion Dynamic DNS packet) is transmitted to the dynamic DNS (6210). The dynamic DNS having received the packet returns a response (4) (6211). The gateway that has received the response (4) determines the response (4) (6212), and if the response is correct, deletes the A record deletion packet of the domain name to be added (the unconditional A record deletion D).
dynamic DNS packet) to the dynamic DNS (6213).

In the determination (6209) of response (2), I
Even if there is no P address, the A record deletion packet of the domain name to be added (A record deletion Dyna without conditions)
micDNS packet) to the dynamic DNS (62).
13). The dynamic DNS having received the packet returns a response (5) (6214). The gateway that has received the response (5) determines the response (5) (6215). If the response (5) is correct, the gateway deletes the PTR record of the IP address to be added (the PTR record deletion with no condition Dynami).
cDNS packet) (6216). The dynamic DNS receiving the packet returns a response (6) (621).
7). The gateway that has received the response (6) determines the response (6) (6218), and if the response (6) is correct, the A record addition packet (A record addition Dyna).
micDNS packet) (6219). The dynamic DNS receiving the packet returns a response (7) (62).
20).

The gateway receiving the response (7) judges the response (7) (6221), and if the response (7) is correct, transmits a PTR record addition packet (PTR record addition DynamicDNS packet) (622).
2). The dynamic DNS that has received the packet returns a response (8) (6223). The gateway that has received the response (8) determines the response (8) (6224), and terminates normally if the response (8) is correct.

If the determinations (1) to (8) are not correct, the retransmission timer is started, and when the retransmission timer times out, the process is performed again from the place where NG is determined in this processing.

FIG. 63 shows a dynamic DNS deletion sequence. When the identification address assigned to the vehicle is released, the gateway transmits an A record deletion packet (conditional A record deletion DynamicDNS packet) to the dynamic DNS (6301). The dynamic DNS that has received the packet returns a response (6302). Upon receiving the response, the gateway deletes the PTR record packet (PTR record delete Dynamic DNS packet with conditions).
Is transmitted to the dynamic DNS (6303). The dynamic DNS that has received the packet returns a response (6304). On this occasion,
Even if the response is NG, the packet is not retransmitted.

[0105]

As described above, according to the present invention,
When a new terminal is connected, it is possible to instantaneously assign an address to the terminal without making an inquiry to the gateway, and without using a node such as an HA for data transfer, a plurality of addresses can be provided. An interface to a network connected so that the subnets can communicate with each other is added to the gateway that constitutes a normal IP network, and by communicating with each other, even if a terminal moves between subnets, the source Because communication can be continued without passing through subnets, many terminals can communicate while moving between subnets without lowering network usage efficiency. A message is sent from the in-vehicle terminal without waiting for the signal of the base station, without changing the routing information of the gateway. It provides a method of route is established by changing the computing information enables handover in a short time.

Further, the IP address and the host name are not registered redundantly in the dynamic DNS, and the IP address and the host name can be surely associated with each other. For example, by lending a recognition address to a base station in advance, an address can be instantaneously assigned to a connected terminal, and an interface to a network connected so that a plurality of subnets can communicate with each other can be used as a normal interface. By adding the gateway to the IP network and communicating with each other, even if the terminal moves between subnets, communication can be continued without passing through the source network, thereby reducing network use efficiency. Many terminals can communicate while moving between subnets, without waiting for signals from nodes when terminals move between base stations. Sends out a message from the on-board terminal,
Since a method for establishing a route is provided by changing the routing information of the base station without changing the routing information of the gateway, a handover can be performed in a short time.

Further, when registering the IP address and the host name in the dynamic DNS, the record of the IP address and the host name is repeatedly transmitted until the record of the IP address and the host name can be surely deleted. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a configuration example of a current road-to-vehicle system of ITS.

FIG. 2 is a diagram illustrating a network configuration to which the method of the present invention is applied.

FIG. 3 is a block diagram of a gateway.

FIG. 4 is a block diagram of a base station.

FIG. 5 is a configuration diagram of an own gateway lending address table.

FIG. 6 is a configuration diagram of another gateway lending address table.

FIG. 7 is a configuration diagram of a gateway routing table.

FIG. 8 is a configuration diagram of a base station rental address table.

FIG. 9 is a configuration diagram of a terminal address table under a subnet.

FIG. 10 is a diagram showing the configuration of mobile station terminal information.

FIG. 11 is a diagram showing a message format configuration.

FIG. 12 is a diagram showing a format of an address lending request message.

FIG. 13 is a diagram showing the format of an address lending response message.

FIG. 14 is a diagram showing an address lending rejection message format.

FIG. 15 is a configuration diagram of an address assignment notification message format.

FIG. 16 is a diagram showing the configuration of an address lending notification message format.

FIG. 17 is a diagram showing the format of an address confirmation notification message format.

FIG. 18 is a diagram showing the format of an address check request message format.

FIG. 19 is a diagram showing the format of an address check response message format.

FIG. 20 is a diagram showing the format of a movement notification message between gateways.

FIG. 21 is a format configuration diagram of an address release notification message (gateway → other gateway).

FIG. 22 is a diagram showing the format of an address release notification message (gateway → base station).

FIG. 23 is a diagram showing a format of a vehicle inspection request message.

FIG. 24 is a diagram showing the format of a vehicle inspection response message format.

FIG. 25 is a flowchart of a gateway process.

FIG. 26 is a flowchart of a gateway process.

FIG. 27 is a flowchart of a gateway process.

FIG. 28 is a flowchart of a gateway process.

FIG. 29 is a flowchart of a gateway process.

FIG. 30 is a flowchart of a gateway process.

FIG. 31 is a flowchart of a gateway process.

FIG. 32 is a flowchart of a gateway process.

FIG. 33 is a flowchart of a base station process.

FIG. 34 is a flowchart of a base station process.

FIG. 35 is a flowchart of a base station process.

FIG. 36 is a flowchart of a base station process.

FIG. 37 is a flowchart of a base station process.

FIG. 38 is a flowchart of a base station process.

FIG. 39 is a sequence diagram at the time of address lending.

FIG. 40 is a sequence diagram at the time of new entry.

FIG. 41 is a sequence diagram at the time of movement between base stations.

FIG. 42 is a sequence diagram when moving between gateways.

FIG. 43 is a sequence diagram at the time of address release.

FIG. 44 is a table configuration diagram after address lending.

FIG. 45 is a diagram showing the configuration of each table after address lending.

FIG. 46 is a diagram showing the configuration of each table after an address is assigned.

FIG. 47 is a diagram showing the configuration of each table after an address is assigned.

FIG. 48 is a diagram showing the configuration of each table after an address is assigned.

FIG. 49 is a diagram showing the configuration of each table after an address is assigned.

FIG. 50 is a diagram showing the configuration of each table after an address is assigned.

FIG. 51 is a diagram showing the configuration of each table after an address is assigned.

FIG. 52 is a diagram showing the configuration of each table after an address is assigned.

FIG. 53 is a diagram showing the configuration of each table after movement between base stations.

FIG. 54 is a diagram showing the configuration of each table after movement between base stations.

FIG. 55 is a diagram showing the configuration of each table after movement between gateways.

FIG. 56 is a diagram showing the configuration of each table after movement between gateways.

FIG. 57 is a diagram showing the configuration of each table after movement between gateways.

FIG. 58 is a diagram showing the configuration of each table after movement between gateways.

FIG. 59 is a diagram showing the configuration of each table after movement between gateways.

FIG. 60 is a diagram showing the configuration of each table after movement between gateways.

FIG. 61 is a diagram showing the configuration of each table after movement between gateways.

FIG. 62 is a sequence diagram at the time of dynamic DNS registration.

FIG. 63 is a sequence diagram at the time of dynamic DNS deletion.

[Explanation of symbols]

100: car, 101-1: base station, 101-2: base station, 101-3: base station, 102-1: wireless zone, 1
02-2: Wireless zone, 102-3: Wireless zone, 20
0: Car, 210: Subnet a, 211: Subnet b, 212: Subnet c, 220: MOBILE I
P network, 221: gateway connection network, 230: gateway a, 231: gateway b, 232: gateway c, 240-1 to 240-n: base station, 241-1
241 to n: base station, 242-1 to 242-n: base station, 300-1: MOBILE IP network interface, 300-2: base station interface, 300-3:
Gateway connection network interface, 301: routing unit, 302: message processing unit, 303: control unit, 310: packet, 311: message packet,
312: message, 320: processor, 321: program storage memory, 322: own gateway lending address table, 323: other gateway lending address table, 324: packet transfer routing table, 400-1: gateway, base station interface, 400- 2: terminal interface, 401: routing unit, 402 message processing unit, 403: control unit,
410: packet, 411: message packet, 41
2: message, 420: processor, 421: program storage memory, 422: base station rental address table, 423: terminal address table under the subnet,
1000: mobile terminal information, 1100: message format, 1111: message identifier, 1112: source node number, 1113: destination node number, 111
4: message length, 1200: address lending request message, 1300: address lending response message, 140
0: Address lending rejection message, 1500: Address assignment notification message, 1600: Address lending notification message, 1700: Address confirmation message, 180
0: Address check request message, 1900: Address check response message, 2000: Gateway movement notification message, 2100: Address release notification message (gateway → other gateway), 2200: Address release message (gateway → base station), 230
0: Vehicle inspection request message, 2400: Vehicle inspection response message.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Toshimichi Nome             890 Kashimada, Saiwai-ku, Kawasaki-shi, Kanagawa Stock             Hitachi, Ltd. Network Solutions             In the business division (72) Inventor Hiroshi Isono             890 Kashimada, Saiwai-ku, Kawasaki-shi, Kanagawa Stock             Hitachi, Ltd. Network Solutions             In the business division F term (reference) 5K030 HC09 HD03 HD05 JL01 JT09                 5K033 DA05 DA17 EC03                 5K067 AA14 DD17 DD57 EE02 EE10                       EE16 HH11 HH23 JJ39

Claims (6)

[Claims] 1. A network system comprising a network in which a plurality of subnets are communicably connected to each other and a plurality of terminals movable between the subnets, wherein each of the plurality of subnets includes a gateway and a gateway in each of the subnets. One or more base stations, wherein the gateways in the plurality of subnets are connected by a mutually communicable medium, and the gateway and the one or more base stations are communicable with each other; In the network system connected by a medium, the gateway manages a recognition address to be lent to a terminal and rents a recognition address to the base station in advance. 2. The gateway manages a recognition address to be lent to a terminal, rents a recognition address to the base station in advance, and the base station recognizes that a terminal to which no identification address is assigned is connected. Then, an address assignment method is provided, in which the terminal is given an identification address that has been rented in advance, and that the identification address has been assigned to the base station other than the gateway and the base station is broadcast. 3. When a recognition address is given to a terminal connected to one of the plurality of subnets (subnet 1), route information of a gateway (gateway 1) of the subnet 1 is added and the gateway is added. The gateway other than the gateway 1 notifies the gateway other than the gateway 1 of the identification address assigned to the terminal by broadcast, and the gateway other than the gateway 1 that has received the notification registers the identification address in the other gateway lending address table. The communication continuation method is characterized in that the identification address is managed by the above-mentioned method, and the other base station that has received the notification adds path information of the base station. 4. When a terminal moves between base stations in the same subnet, the base station that has detected the terminal notifies other base stations in the same subnet of the detection of the terminal. A communication continuation method characterized by updating the following. 5. When a terminal moves between subnets, a base station that has detected the terminal notifies the gateway in the same subnet and another base station of the detection of the terminal, so that the gateway adds route information, and A communication continuation method in which a gateway is notified by a broadcast that a terminal has moved, and another base station updates route information. 6. When the terminal is newly connected to the subnet, the gateway checks whether the address and the host name to be added are registered, and if there is, repeats the deletion request until the terminal is deleted. The host name and address correspondence method is characterized by registering the address and the host name after confirming the deletion.