JPH05327720A - Lan node and lan system - Google Patents

Abstract

PURPOSE:To attain the communication with no change of a terminal address table by relaying the frame to a mobile terminal and adding and changing the address information on the relayed frame with use of the LAN nodes of the relaying devices set between the mobile terminal and a router. CONSTITUTION:The LAN 1, 2, 4, etc., are connected together by a router 6, a bridge 7, etc. When a terminal 4a, etc., of a communication area 13a moves, this movement is detected by the LAN nodes of the relaying devices S1, S2, etc., which are set between the terminal 4a and the router 7. When the terminal 4a passes over the router 6, the frame addressed to the mobile terminal is relayed and the address information on the relayed frame are added and changed by the LAN node of a relaying device S3 of a router 8. Thus the communication is possible without changing the contents of a host address table of the terminal even if the terminal passes over a router.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a LAN system,
More specifically, the present invention relates to a LAN system suitable for moving terminals and a LAN node constituting the LAN system.

[0002]

2. Description of the Related Art In a conventional LAN system, each terminal is
LA directly connected in a bus or ring by a wire transmission line such as a twisted wire pair, a coaxial wire, or an optical fiber.
Had formed N. In addition, each LAN is interconnected with other LANs by a relay device such as a "repeater" that relays physical layer signals, a "bridge" that relays MAC layer frames, or a "router" that relays network layer packets. Was connected to. Although individual terminals may be connected to a backbone LAN via a LAN node, in this case, the LAN node includes one LAN system existing between the terminal and the LAN node and a plurality of LAN nodes. It can be regarded as a device interconnecting the formed basic LAN system, and is functionally classified as any of the above-mentioned repeater, bridge, or router.

Generally, the frame relay function of the bridge is applied as the function of the LAN node. However, in the case of connecting LANs or in a large-scale network, it is possible to relay communication information with different protocols below the MAC layer, and the whole network can be divided into a plurality of sub-networks for management. The connection by is common.

On the other hand, many LAN terminals and end systems (hereinafter, these devices are generically referred to as “hosts” in the present specification) have an internet protocol (IP) in the network layer, and therefore, are not available in the prior art. In networks, most routers are configured to route incoming packets based on IP address.

The IP address has a length of 32 bits, for example, and is composed of a network number (Net-ID) for identifying a network and a host number (Host-ID) for identifying individual terminals and the like. It

The router uses the Net included in the received packet.
-It is determined whether or not the ID matches the Net-ID of its own, and if these IDs are different, the received packet is addressed to a host belonging to a network different from the network to which it is connected. It is determined that
In this case, the IP address of the first router (hereinafter, referred to as “forwarding destination router”) on the route through which the received packet should be relayed is obtained from the IP table stored in the router, and then the host The MAC address corresponding to the IP address of the transfer destination router is obtained from the address table, a MAC frame having this MAC address in the destination address field and its own MAC address in the source address field is assembled, and this is used as the transmission path. Output.

On the other hand, the received packet and its Net-ID
, The MAC address of the host corresponding to the IP address of the received packet is obtained from the host address table, and this MAC address is used as the destination address field and the MAC frame having its own MAC address as the source address field. Is assembled and transferred to the transmission line.

[0008]

In a LAN system in which a plurality of LANs are interconnected by routers, a host belonging to one of the LANs crosses the routers to another LAN.
Net-of the IP address that was valid until then, that is, when connected to another network
N is the ID assigned to the network at the destination
Since the packet does not match the et-ID, the packet addressed to the host will not reach the host after transfer. This problem is caused by a new Net-I for the destination host, for example.
This can be solved by adding D and changing the host address table of all routers involved in the communication with the moved host. For example, in a network system such as a wireless LAN in which the host moves frequently, It is not easy to change and manage the above-mentioned IP address and host address table each time the host is moved.

An object of the present invention is to allow a host to move over a router to another LAN in a network in which a plurality of LANs are connected via a router.
It is to provide an AN system.

Another object of the present invention is to provide a LAN system in which the contents of the host address table provided in each router need not be changed each time even when the host is allowed to move over the router to another LAN. To provide.

Another object of the present invention is to provide a LAN node and a LAN system which allow each host to move to another LAN in an existing router environment.

[0012]

In order to achieve the above object, in the present invention, a relay device is arranged between a movable host and a router that manages a Net-ID assigned to the host, and each relay is arranged. The device has the function of detecting the movement of the host, and the host connected to one LAN is transferred to another LA.
When moving to N, the relay device (source relay device) that has detected the movement of the host sends the received frame addressed to the moved host (destination host) to each router located on the relay route to the destination host. Ne handled correctly by the destination host
The t-ID is used for relaying toward the destination host.

In order to successfully relay a frame addressed to a host that has moved to another LAN, if the destination host does not change the Net-ID at the destination, the source relay device relays it to the destination host. In the packet of the OSI layer 3 to be transmitted, the Net-ID of the relay device to which the destination host is moved
Is added and transmitted to the destination relay device. The destination relay device that has received the packet removes the Net-ID from the received packet, reassembles the MAC layer frame, and delivers it to the destination host.

If the Net-ID is changed so that the destination host can adapt to the destination network, a new Net is sent to the destination host via the destination relay device.
-Notify the source relay device of the ID so that the source relay device stores the ID. The source relay device is
When a packet addressed to the host whose Net-ID has been changed is received, the Net-ID of the received packet is changed to the new Net-ID and relayed toward the destination host.

[0015]

According to the above configuration of the present invention, when the host moves to another network beyond the router, the transfer source relay device is provided with the OSI first packet which is the relay information of the router for the MAC frame addressed to the moved host. It suffices to add or change the three-layer address and relay it to the movement destination. In the LAN connection environment by the existing router, each host can freely communicate without being aware of the movement of the destination host. In addition, it is not necessary for each router to change the host address table when the host is moved.

[0016]

1 shows an example of the overall configuration of a network system according to the present invention. In the figure, each individual LAN 1
5 are bridges (B1) 7 and routers (R1, R
2) Interconnected via 6 and 8. Since the function of each router has already been described, the function of each bridge will be described here.

The bridge 7 is a device for controlling relay of communication information between LANs in units of MAC layer frames, and is a destination M of MAC frames received from one LAN.
Based on the AC address, it is determined whether to discard the received MAC frame or relay it to the other LAN.
That is, if the destination terminal (destination host) specified by the destination address of the received MAC frame belongs to the LAN on the input side of the frame, the received frame is discarded, and if it belongs to the LAN on the other side. For example, the received frame is relayed to the LAN on the opposite side. Which LAN of the bridge accommodates the destination terminal is determined by referring to a table called a "filtering database" managed by each bridge.

In the network of FIG. 1, LAN 1 and LA
Each of the N3s is connected to the wide area network 18 via the gateway. However, this structure is not essential to the present invention, and therefore the detailed description is omitted here.

In this embodiment, each individual LAN 1-5 is
It has an Ethernet structure with a coaxial line as a transmission line, the terminal (T0) 1a is directly connected to the LAN 1 by a wire, and the LAN 4 has a coverage area 9a and 10a (hereinafter referred to as "cell"). LAN node (S
1, S2) 9 and 10 are connected, and a terminal device (T
1, T2) 4a, 4b are housed. The LAN nodes 9 and 10 serve as the above-mentioned "relay device", and the terminals 4a,
4b corresponds to the above-mentioned "host".

A LAN node (S4) 11 for accommodating a wired terminal is also connected to the LAN 4. For the wireless terminal devices 4a and 4b, replace the LAN board,
Alternatively, by using a wired interface prepared in advance, it is possible to use it as a wired terminal at the position 11a.

Like the LAN 4, the individual LAN 5 also has a LAN node (S3) 12 having a cell 12a and can accommodate a wireless terminal. Here, the following operations will be described assuming that the terminals (T0 to T2) 1a, 4a, and 4b adopt the TCP / IP protocol in the third and fourth layers of the OSI reference model.

FIG. 2 shows an address structure adopted in the IP protocol. The IP address is in format 21
As shown in FIG. 2, it has a length of 32 bits, for example, and is composed of a network unit 21a and a host unit 21b. Depending on the system, as shown in format 22, the host unit 21b may include a subnet unit 22a and a host unit 22b.
It is divided into

Each router (R1 to R2) shown in FIG.
IP address of the received packet, especially the network unit 21
a, in some cases, the network part 21a plus the subnet part 22a is used as an identifier (Net-ID), and is designed to determine the packet relay route of the OSI third layer. Therefore, in the network system shown in FIG. 1, for example, each device located in the communication area (area indicated by the broken line 13a) connected to the interface 13 of the router (R1) 6 has “n” as the Net-ID.
1 ”is commonly given, while a device located in the communication area 14b connected to the interface 14 of the router (R2) 8 is given“ n2 ”as the Net-ID.

Here, the terminal (T1) 4a, which was in the communication area 13a, is moved to the communication area 14 as shown by an arrow 15.
After moving to the connection position 5a in b, the terminal (T0) 1a
The communication procedure according to the present invention will be described by taking as an example the case where communication from the terminal (T1) 4a to the terminal (T1) 4a occurs.

In FIG. 3, the destination terminal before moving and the destination terminal after moving are denoted by T1 and T1 ', respectively, and the originating terminal T0 and the destination terminal T are shown.
FIG. 3 is a diagram showing operations of LAN nodes S1 and S3 located between 1 and T1 ′. When the terminal T1 moves from the position 4a to the position 5a (becomes the terminal T1 ′), the LA of the movement destination
The N node S3 is notified 31 that it has newly joined. The subscription notification 31 includes at least the MAC address of the terminal T1 ′ (= T1) as notification information. At this time, the terminal T1 ′ may notify the LAN node S3 of the IP address together with the MAC address.
As shown in the figure, the LAN node S3 that has received the join notification 31 makes an inquiry about the IP address to the terminal T1 'using the TCP / IP protocol ARP 32, and sends the IP address in the response frame 32'. The address may be notified.

In the LAN node S3, if the terminal T1 'is I
If the P address is not changed, the IP of the terminal T1 '
The network to which the user belongs before the move is specified based on the Net-ID included in the address, and the communication of the broadcast frame or the individual frame is repeated with respect to the LAN node in the network, so that the terminal T1 is in its own cell. Notification that it has moved to (T1 move notification 33).

The LAN node S which has received the movement notice 33
1 relays the frame 34 sent from the terminal T0 to the terminal T1 to the LAN node S3 as a relay frame 35. The LAN node S3 delivers the received frame addressed to T1 to the terminal T1 '(data delivery 36). In addition,
A method of generating a relay frame performed by the LAN node S1 will be described later with reference to FIG.

In the above communication procedure, the terminal T1 is the LAN
During the period from when the LAN node S1 receives the movement notification 33 after leaving the cell under the control of the node S1, the frame addressed to the terminal T1 is forwarded into the cell of the LAN node S1 and consequently the received frame is discarded. Will be done.

FIG. 4 shows state transitions of terminal devices managed by the LAN nodes 9 to 12. Each LAN node has the same Net-I as the Net-ID assigned to its own node.
When a terminal having D newly joins, the state of the terminal is stored as a "primary connection state" 42. That is, when the terminal moves its position within the same network, the terminal device is managed as a terminal in the primary connection state by the LAN node of the movement destination. In this state, if the departure of the terminal is confirmed,
Transition to the "moving state" 43.

With respect to the terminal in the primary connection state or the moving state, the LAN node searches the filtering database using the destination address of the received MAC frame as a key and relays the received MAC frame as it is or discards it. Functioning as a bridge, and as a result, the frame addressed to the mobile terminal is discarded.

Regarding the terminal in the moving state, the destination LAN
Upon receiving the movement notification 48 from the node, the state of the corresponding mobile terminal transits to the "relay state" 44 which is responsible for relaying the received frame. When the movement notification cannot be received within the predetermined time after the movement state (when the movement notification waiting time-out 47 is reached), the “departure state” 41 is set.

If the Net-ID of the newly joined terminal is different from the Net-ID of its own node, "secondary connection state"
Transition to 45. As for the terminal in the secondary connection state, each node has L
It is obligated to output a movement notification to the AN node (source LAN node) informing that the terminal has moved into the cell of the own node. It is also obliged to deliver the MAC frame addressed to the mobile terminal, which is relayed from the source LAN node to the own node, to the destination terminal.

To detect that a new terminal has joined, for example, each LAN node periodically sends out the MAC address assigned to itself by a predetermined time interval t,
Each terminal receiving the address compares the MAC address (T-t) received and stored immediately before with the newly received MAC address (T), and when these do not match, the LAN It suffices to transmit a specially defined “new joining notification frame” whose source MAC address is the MAC address of the terminal itself to the node. At the LAN node that manages the state of the source terminal of the "new subscription notification frame" as "primary connection", the Net node of its own node
Since the ID matches the NetID of the transmission source network layer address in the received new subscription notification frame,
By broadcasting the movement notification within the own network, the movement of the terminal can be notified to the movement source LAN node.

In the above-described embodiment, when the non-communication state of the terminal exceeds the predetermined time, it is considered that the terminal has left. Therefore, the transition from the primary connection state to the disconnection state occurs relatively frequently, and the terminal state is monitored by frequently activating two types of timers for the disconnection confirmation 46 and the movement notification waiting 47.

In order to avoid such complicated timer monitoring, for example, as shown in FIG. 5, the "moving state" is eliminated from the state of the terminals, and all the terminals are "primarily connected" until the movement notification 48 is received. It can be managed as "state". In the state transition of FIG. 5, the received frame is discarded even though it is apparently in the primary connection state. This is the “frame discard in the moving state” in FIG.
Since it corresponds to, it does not become a practical problem.

FIG. 6 shows a processing flowchart executed by each LAN node for the above-mentioned terminal status management.
When the MAC frame is received (step 61), the destination address of the received frame is compared with the MAC address of its own node (62a), and if the addresses match, the destination IP address is further compared (62b). If the IP addresses match, it is determined to be an inter-node communication frame addressed to the own node, and the information of the received MAC frame is transferred to the upper layer (62c). If the destination IP addresses do not match, it is determined whether the destination terminal is in the secondary connection state in its own node (62d). If the destination terminal is in the secondary connection state, the received MAC frame is a relay frame from the LAN node that manages the destination terminal in the primary connection state. In this case, the MA of the received frame
After changing the C address and the IP address, the received frame is delivered to the corresponding terminal (62e).

If the MAC address of the received frame does not match its own address in step 62a, the filtering database (FDB) is searched using the destination address of the received frame as a key.

The FDB, as shown in FIG. 7, corresponds to the MAC address 71 and the accommodation direction information 72 and the connection state 73.
And a plurality of records including timer information 74,
From the accommodation direction information 72 of the record corresponding to the destination address (MAC address) of the received frame, it is determined whether the destination terminal having the address is accommodated in the own LAN node (63a). If the destination terminal is not accommodated (outer accommodation), the received frame is discarded (63b).

When the destination terminal is accommodated, the above F
If the destination terminal is in the primary connection state by referring to the connection state 72 stored in the corresponding record in the DB (64a),
Forward the received frame to the destination terminal (64
b) In the moving state (65a), the received frame is discarded (65b). If the destination terminal is in the relay state (66a), the received frame is relayed to the destination LAN node (66b). Other received frames are regarded as frames addressed to the terminal in the leaving state and are discarded (6
8).

In step 66b, the received frame is moved to the destination L
When relaying to the AN node, the IP table 7 shown in FIG.
5 and the host address table 80 shown in FIG.

The IP table 75 has a NetID 76 and
I of the router in the network to which the NetID is assigned
It is composed of a P address 78 and route information 77 indicating the distance to the router. On the other hand, the host address table 80 is composed of an IP address 81 of a terminal or a LAN node and a MAC address 82.

The NetID of the destination LAN node of the terminal in the relay state can be known from the movement notification.
By storing the etID in a table format in association with the MAC address, first, the IP table 75
From the IP address 78 of the router connected to the network to which the destination LAN node belongs, and from the host address table 80, I
The MAC address 82 corresponding to the P address is obtained, and the received frame is transmitted in the form of setting it in the destination MAC address area of the received frame. It should be noted that the IP table 75 and the host address table 80 are tables already provided in each router in the conventional network, and the information settings in these tables are respectively RI.
P (Routing Information Protocol) and ARP (Addre
ss Resolution Protocol).

FIG. 10A shows that when the terminal T1 moves in the system of FIG.
The MAC address and IP address of the movement notification frame transmitted to the node S1 are shown. The LAN node S3 sets the MAC address of the router R2 as the destination MAC address (DA) and the MAC address of its own node as the source MAC address (SA). Also,
LAN node S is set to the IP address (SIA) of the transmission source.
The NetID (= n2) and the host address (= s3), which are the IP addresses of No. 3, are set, and the IP address of the LAN node S1 is set as the destination IP address (DIA). The MAC address of this frame is sequentially rewritten by the router located on the relay path, and finally, the router R1 sets DA = S1, SA = R1 and is transferred to the destination LAN node S1.

FIG. 10B shows the format of the broadcast frame transmitted when the LAN node S1 cannot be identified. In the DIA field, a code indicating that broadcasting should be performed within NetID = n1 is set.

FIG. 11 shows the address of the frame relayed by the LAN node S3 to the terminal T1 in the "relay state". The MAC field of the first router R1 on the communication path of the destination terminal T1 is set in the DA field of the frame 90 sent by the source terminal T0, and the IP address of the destination terminal T1 is set in the DIA field. There is. The frame 90 is rewritten by DA = T1 by the router R1 and reaches the source LAN node S1 in the state of the frame 91.

Source LAN that received the frame 91
Since the terminal T1 is in the relay state, the node S1 newly generates a spontaneous frame 94 and transmits it to the first router (R1) on the relay route. The frame 94
Is the IP address (SIA
92, DIA93).

The destination LAN node S3 rewrites the MAC address of the received frame 95 to the destination terminal T1 for DA, and the own address S3 for SA.
The IP addresses 92 and 93 added by the source LAN node S1 are deleted and delivered to the destination terminal T1 (= T1 ′) as the format of the frame 96.

FIG. 12 is a functional block diagram showing the structure of a LAN node having the above-mentioned functions. The MAC frame received from the LAN is subjected to address area extraction and error detection in the reception processing unit 100. 101
Is a state management unit, which performs an FDB search for the MAC address of the received frame and a comparison between the network layer address of the received frame and the network layer address of the own node to perform the state transition of the terminal described in FIG. Realize management. In addition, along with these operations, deregistration control of the table group such as the IP table and the host address table stored in the memory 102, and the relay processing unit 10 are performed.
3 and the delivery processing unit 104 are controlled.

The relay processing unit 103 executes the frame discarding processing 63b and 65b and the relay processing 66b of the received frame to the destination node described with reference to FIG.

The delivery processing unit 104 executes each processing of transfer 62c to the upper layer, delivery 62e to the destination terminal, and forwarding 64b described in FIG.

The transmission processing unit 105 transmits the transmission frame from the terminal received via the terminal interface 106 and the relay frame received from the relay processing unit 103 to the wired LAN.
According to this access method, the data is selectively transmitted on the LAN transmission path.

FIG. 13 is a block diagram schematically showing the configuration of the switch unit of the terminal interface 106 shown in FIG. In the example shown here, the terminal interface 1
As a physical layer connectable to 06, a wireless physical layer interface 110 and a wired physical layer interface 111 are provided.
Various types are prepared, and either one of them can be connected to the MAC layer interface 112 by selecting from an input from a keyboard or a dedicated changeover switch 120. Instead of providing the above two types of physical layer interfaces independently, the MAC layer interface 1
12 is mounted on the interface board of each physical layer as a common interface, a slot for connecting the interface board is provided on the terminal side, and either the wired interface board or the wireless interface board is provided in the slot. You may make it possible to insert or. Next, as a second embodiment of the present invention, communication control when the terminal has a plurality of IP addresses in advance will be described.

In the present embodiment, when the terminal moves over the router to another LAN, an IP address suitable for the destination network is selected, and the subsequent communication is performed by this IP address. In this case, when the mobile terminal joins the network, it communicates with the destination LAN node using the IP address before the movement to notify that the terminal is in the secondary connection state and join the network. Using the information area of the notification frame, a new IP address that becomes valid at the destination is registered.

Destination LA that has received the subscription notification from the mobile terminal
The N node registers the state of the terminal as the secondary connection state and the primary connection state at the same time. By performing the processing in this way, it is possible to directly receive the frame addressed to itself from the source LAN node without performing processing such as changing the IP address by the destination LAN node, and by the communication after the movement, the new IP address of the mobile terminal is received. It is possible to directly receive the information transmitted by another terminal that has been able to recognize, without passing through the LAN node of the movement source.

According to this embodiment, the LAN node accommodating the terminal in the secondary connection state is the LAN from which the terminal moves.
By issuing a movement notification to the node, the movement source LAN node can be made to update the relay table, so that the terminal can be allowed to move in multiple stages.

Further, for example, the LAN node (S
4) A LAN node accommodating a wired terminal such as 11 has the same function as a LAN node to which a wireless terminal is connected. Therefore, by changing the physical layer interface, the terminal used in the wireless connection can be changed. It is possible to change the terminal to a wired connection type and to use it in a fixed position.

[0057]

As is apparent from the above description, according to the present invention, in a network environment in which LANs are connected by routers, when a host (or a terminal) moves beyond a router to another LAN, By performing the relay operation of the frame addressed to the mobile host and the operation of adding and changing the address information of the relay frame in the LAN node, the host address table managing the address information corresponding to each host is not changed and Can communicate. In addition, communication with a moved terminal is possible without changing the existing router, bridge, and communication OS of each terminal in the network.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of a network system according to the present invention.

FIG. 2 is a diagram showing an address configuration used in an IP protocol.

FIG. 3 is a diagram showing an embodiment of a communication procedure in the present invention.

FIG. 4 is a diagram showing a state transition of a terminal managed by a LAN node.

FIG. 5 is a diagram showing another embodiment of terminal state transition managed by a LAN node.

FIG. 6 is a flowchart showing an operation of a LAN node executed when a frame is received.

FIG. 7 is a diagram showing a configuration of a filtering database included in a LAN node.

FIG. 8 is a diagram showing a configuration of an IP table included in a LAN node.

FIG. 9 is a diagram showing a configuration of a host address table included in a LAN node.

FIG. 10 is a diagram for explaining changes in a movement notification frame.

FIG. 11 is a diagram for explaining changes in a relay frame.

FIG. 12 is a block diagram showing a configuration of a main part of a LAN node.

13 is a diagram showing a configuration of a switch unit of the terminal interface 106 of FIG.

[Explanation of symbols]

 4a: wireless LAN terminal 9: wireless LAN node 31: terminal joining notification 33: terminal moving notification 35: relay of data addressed to mobile terminal 41: leaving state 42: primary connection state 43: moving state 44: relay state 45: secondary connection Status

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideya Suzuki 1-280, Higashi Koigokubo, Kokubunji, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (5)

[Claims] 1. A LAN system having a plurality of LAN nodes for accommodating wired or wireless terminals, wherein L
The AN node detects the MAC address of the terminal by the notification from the terminal newly placed in the coverage area of the own node or the terminal newly connected by wire, and the detected MAC is detected.
A means for obtaining the network layer address of the OSI7 layer reference model layer 3 from the terminal by transmitting an inquiry frame including the address in the destination address field, and the network layer address of the terminal and the own node are assigned. To compare with the network layer address, and if the addresses do not match, to notify the other LAN node from which the terminal has moved to notify that the terminal has moved to its own node A LAN system having means. 2. The LAN system according to claim 1, wherein any one of the terminals has an interface that can be selectively connected to the wireless LAN node and the wired LAN node. 3. A LAN node, which accommodates at least one wired or wireless terminal and is connected to each other to form one sub-network, when a new terminal joins the jurisdiction of its own node, Means for notifying the other LAN node, which is the movement source of the terminal, of the movement of the terminal to its own node, and means for storing the state information indicating the connection state with the own node for each terminal When a frame addressed to a terminal that has moved outside the area covered by its own node is received, the received frame is transferred outside the OSI Layer 3 packet of the received frame with the network layer address of the destination of the terminal added. A LAN node having means for relaying to a destination node. 4. In a LAN node that accommodates at least one wired or wireless terminal and is connected to each other to form one sub-network, the terminal in the area covered by another LAN node is its own node. Means for notifying the other LAN node of the information on the subscribed terminal when joining the jurisdiction area, and storing the information on the connection state between the terminal and the own node and the moving state of the terminal. And a means for relaying a frame addressed to a terminal that has moved to the jurisdiction area of another LAN node after modifying at least part of the address of the OSI layer 3 packet. A LAN node characterized in that 5. A LAN terminal which is wired or wirelessly connected to an arbitrary LAN node connected to a network, and which stores a plurality of network layer addresses.
When moving from the jurisdiction area of one LAN node to the jurisdiction area of another LAN node, in response to the inquiry of the address from the movement destination LAN node, the movement is made from the network layer addresses stored in advance in the storage means. Select one network layer address according to the destination network,
The selected network layer address is used as the destination LAN.
LA having means for notifying a node
N terminals.