JP2911431B2 - Local area network system and address translator in local area network system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a local area network (LAN) system and, more particularly, to an address translator for switching an access destination to a different computer without changing the designation of the access destination on the access source computer.

[0002]

2. Description of the Related Art For example, in a duplex system or a cluster system employing a communication protocol such as TCP / IP, a logical address given to each computer on a network is added to a packet to specify a destination. Data communication is realized. In TCP / IP, I
The P address corresponds to the above logical address, where
The IP address will be described in detail.

When constructing a network system using the TCP / IP communication protocol, a unique IP address is assigned to each computer in the network system. This IP address is uniquely assigned all over the world, and the user can use an IP address whose registration has been permitted by application. IP
An address is a permitted net ID (network address) and a host ID (host address) that can be uniquely assigned in a network system.
Are 32-bit logical addresses for network communication. The net ID has a length of 8, 16, or 24 bits depending on the registered class, and the host ID has a length of 24, 16, or 8 bits correspondingly. The first 1 to 4 bits of the net ID include bits for identifying the class. The IP address is represented by four sequences separated by three dots. Each computer to which an IP address is assigned according to such a rule can perform data communication by designating the IP address of a communication partner, but the computer cannot directly access a computer having a different net ID. This is because different network systems are constructed if the net IDs are different. However, usually, a relay device such as a router existing on a communication path converts a destination address added to a transmission packet, thereby enabling access between computers configuring different network systems.

Incidentally, in a dual system or a cluster system, even if a computer providing a service is stopped due to a failure or the like, a substitute computer can continuously provide the service. The switching operation of the computer from the active system to the standby system will be described.

FIG. 12 is an overall configuration diagram showing an example of a conventional network system. This system comprises two server computers 1 and 2 for providing a service and one client computer 3 for using the service.
And a name server 4 that converts the received computer name into an IP address and returns it to the LAN 5, and is configured to perform data communication based on TCP / IP. In this system, usually, the server computer 1
Are always running and provide services to the client computer 3, and the server computer 2 is on standby as a substitute for the failure of the server computer 1. The client computer 3 having the name “PC1” has the IP address “1.3”, the name server 4 has the IP address “1.4”, and the server computer 1 having the name “SVR1” has the IP address “1. 5 "is assigned to the server computer 2 having the name" SVR2 ", respectively. Note that I
The P address is usually represented by four numerical sequences separated by three dots. Here, the P address is described as a description divided into a net ID “1” portion and host ID “3” to “6” portions. Has been simplified.

Next, an operation of the conventional system when a service is provided will be described.

[0007] When using the service, the client computer 3 becomes a target server computer 1.
The name server 4 is queried to obtain an IP address from the name “SVR1”. Note that the client computer 3 has the name “SVR1” of the server computer 1.
Is assumed to be known in advance. The name server 4 has an IP address corresponding to the name "SVR1" of the server computer 1.
The address is registered in advance, and in response to an inquiry from the client computer 3, the I
Returns P address "1.5". The client computer 3 can access the server computer 1 by specifying the received IP address in the transmission packet. At this time, the standby server computer 2 is on standby while constantly monitoring the operation state of the server computer 1.

Here, the standby server computer 2
Detects the failure of the server computer 1, and sends the name “SVR” of the server computer 1 to the name server 4.
1 "and an instruction to change the IP address of the server computer 2 to the IP address of the server computer 2. The name server 4 notifies the IP address" 1.6 "of the server computer 2 to the name" SVR ".
The IP address corresponding to “1.” is changed from “1.5” to “1.
6 ".

Thereafter, the name server 4 sends the name “SV” of the server computer 1 from the client computer 3.
When an inquiry about the IP address corresponding to R1 "is received, the I
The P address "1.6" will be returned.

As described above, the name server 4 operates to return the IP address of the standby server computer 2 instead of the server computer 1 in response to the inquiry to the server computer 1 when the server computer 1 fails. . Thus, the client computer 3 actually receives the service from the server computer 2 even though the client computer 3 intends to access the server computer 1, but can continuously use the same service.

FIG. 13 is a diagram showing the configuration of Japanese Patent Laid-Open No. 5-120188.
FIG. 1 is a block diagram of a communication system disclosed in Japanese Patent Laid-Open Publication No. H10-26095. The communication system includes a workstation 6 that receives a service, a business server 7 that provides a service to the workstation 6, and an address management server 8 that manages a unique address of the business server 7 in association with a virtual address. Are connected. In this system, the address management server 8 refers to the address management information 9 based on a virtual address request from the workstation 6 in which the unique address of the business server 7 is specified, and assigns a virtual address that can be assigned to the business server 7. return. After that, the workstation 6 receives the service by designating the received virtual address. However, even if the designated business server 7 has been stopped, the address management server 8 can execute the other business server. 7
The workstation 6 can receive the service from the business server 7 other than the designated virtual address by designating the received virtual address. The address management server 8 in this example
Corresponds to the above-described name server, the workstation 6 corresponds to a client computer, and the business server 7 corresponds to a server computer.

[0012]

However, in the prior art, the client computer can switch the access destination to the standby server computer because of the following reason.
This is because when the client computer makes an inquiry to the name server, the name server notifies the IP address of the server computer of the switching destination. Therefore, when the client computer has its own correspondence table between the name of the server computer and the IP address, when executing an application that directly specifies the IP address without inquiring about the IP address, when caching the query result from the name server, etc. Does not make an inquiry to the name server every time, the change of the association between the name of the server computer and the IP address is not reflected, and as a result, the server computer cannot be switched to the standby server computer.

In the above-described conventional example, since the same net ID is assigned to each computer, the client computer can directly access the standby server computer. However, if the standby server computer is assigned a different net ID than the client computer or the active server computer, even if the active and standby server computers are physically connected to the same LAN,
The client computer cannot directly access the standby server computer. For this reason,
The client computer cannot continue to use the service provided by the server computer.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to make it possible to switch a computer to be used without performing an operation of associating a computer name with a logical address. And an address translation device in the LAN system.

[0015]

In order to achieve the above object, an address translation device in a local area network system according to a first aspect of the present invention includes a first server computer for providing a service, and a first server computer for providing a service . The sir
A logical address different from that of the first computer, a second server computer providing the same service as the first server computer, and a client computer utilizing the service provided by the server computer. Is an operation of the first server computer in a local area network system connected to the same local area network and performing packet communication by designating a destination logical address.
Server monitoring means for monitoring a state, client-to-client communication processing means for receiving a packet transmitted by the client computer on behalf of the first server computer by taking over a logical address of the stopped first server computer, Address translation means for translating the destination of the packet received by the inter-client communication processing means to the second server computer, and inter-server communication for transmitting the packet translated by the address translation means to the second server computer have a processing means provided separately and each server computer,
During normal operation of the first server computer,
Do not relay the packet transmitted by the computer,
Only when the server computer is stopped, the client
To the first server computer transmitted by the computer
Of the packet .

According to a second aspect of the present invention, in the local area network system according to the first aspect, the server-to-server communication processing means is configured to transmit the transmitted
The second server computer receives, in response to the translated packet, a packet transmitted to the client computer from the second server computer for relaying, and the address translation unit transmits the packet received by the server-to-server communication processing unit. Into the first server computer,
The client-to-client communication processing means transmits a packet whose address has been converted by the address conversion means to the client computer.

According to a third aspect of the present invention, in the first or second aspect, the address translation device in the local area network system corresponds to a logical address of a computer connected to the local area network based on the received inquiry packet. It has address resolution means for returning a physical address.

A local area network system according to a fourth aspect of the present invention is a local area network system which performs a packet communication via the same local area network by designating a logical address of a destination. , The first
A logical address different from the server computer is set,
An alternative second server computer that provides the same service as the first server computer, a client computer that uses a service provided by the server computer, and a separate server computer
An address translation device that relays packets transmitted and received between the client computer and the server computer only when the first server computer is stopped , and provides the same service. First and
At least one set of the second server computer is formed.
And wherein the address translation device is the first server
When the computer is stopped, the first stopped computer is stopped .
By taking over the logical address of the server computer
The first and the client communication processing means for said on behalf of the server computer the client computer receives the transmitted packets, the client inter-communication processing means the first to the destination of the packet received in server configuration
Yes address conversion means for converting the second server computer forming a computer and set, and a server communication processing means for transmitting the address conversion packet to the second server computer by said address translation means
The first server computer is shut down,
Change the logical address of the server computer
Service to the client computer
It is provided continuously .

According to a fifth aspect of the present invention, in the local area network system according to the fourth aspect, the server-to-server communication processing means transmits the transmitted address-converted packet.
Depending on the preparative received for relaying a packet to the second server the client computer the computer is sent, the address conversion means, wherein the source of said received server communication processing unit packets second No
The first server computer forming a pair with the server computer, and the client-to-client communication processing means transmits the packet whose address has been converted by the address conversion means to the client computer.

A local area network system according to a sixth aspect of the present invention is the local area network system according to the fourth or fifth aspect of the present invention, wherein the alternative address translator is provided .

A local area network system according to a seventh aspect of the present invention is the local area network system according to the fourth or fifth aspect, wherein
Local area network has a network address
Different network systems divided by
The first server computers, which are mixed and form a set,
Data and the second server computer have respective
Different network addresses are assigned to logical addresses
Belonging to different network systems
Is what it is.

According to an eighth aspect of the present invention, in the local area network system according to the seventh aspect, the address translator is provided corresponding to each of the sets.

A local area network system according to a ninth invention is the local area network system according to the fourth or fifth invention, wherein the address translation device has a function as a gateway.

[0024]

Preferred embodiments of the present invention will be described below with reference to the drawings. The same components as those in the conventional example are denoted by the same reference numerals.

Embodiment 1 FIG. 1 is a functional block diagram showing Embodiment 1 of an address translation device according to the present invention, and shows a configuration of a LAN system using the address translation device according to the present embodiment. The LAN system shown in FIG. 1 is configured by connecting a client computer 3, two server computers 1 and 2, and an address translator 10 to the same LAN 5,
Data communication is performed based on CP / IP. This L
In the AN system, usually, the server computer 1 is always running and providing a service to the client computer 3, and the server computer 2 is on standby as a substitute when the server computer 1 fails.

The address translator 10 has a client-to-client communication processor 11, a server-to-server communication processor 12, an address converter 13, an address resolution unit 14, and a server monitoring unit 15. The client-to-client communication processing unit 11
5 is a communication interface that enables communication with another computer based on TCP / IP via the client computer 5. In the present embodiment, packet communication is performed with the client computer 3. Specifically, by taking over the logical address of the stopped first server computer 1, the packet transmitted from the client computer 3 on behalf of the server computer 1 is received, and the packet from the second server computer 2 whose address is converted is transferred. Is transmitted to the client computer 3. Inter-server communication processing unit 1
Reference numeral 2 denotes a communication interface having the same function as that of the inter-client communication processing unit 11, and in the present embodiment, performs packet communication with the server computers 1 and 2. Specifically, it transmits the address-translated packet from the client computer 3 to the server computer 2 and receives the packet transmitted from the server computer 2 to the client computer 3 for relaying. The address conversion unit 13 converts the address of the received packet. Specifically, the destination of the packet received by the inter-client communication processing unit 11 is
And the source of the packet received by the server-to-server communication processing unit 12 is converted to the server computer 1. The address resolving unit 14 has a function of returning a physical address (MAC address) corresponding to a logical address (IP address) included in the received inquiry packet. AR to use
P (Address Resolution Prot)
ocol). The server monitoring unit 15 detects the stop of the operation of the server computer 1 in real time. In the present embodiment, since the server computer 2 constantly monitors the operation of the server computer 1, the LAN
5, the server computer 1 receives the notification from the server computer 2 received from the server-to-server communication processing unit 12
Stop is detected. Of course, the server monitoring unit 15 directly monitors the operation of the server computer 1 or uses a dedicated line separate from the LAN 5
2 may be connected. The address translator 10 can be realized by a normal computer,
In the present embodiment, data communication can be performed based on TCP / IP.

FIG. 2 is a block diagram of a LAN according to the present embodiment, which corresponds to FIG. 12 of a conventional example. Also in the present embodiment, the server computer 1 is similar to the conventional example.
Are always running and provide services to the client computer 3, and the server computer 2 is on standby as a substitute for the failure of the server computer 1. The client computer 3 with the name “PC1” has an IP address “1.3” as a logical address and a MAC address “1” as a physical address, and a name “S1”.
The IP address “1.5” and the MAC address “4” are assigned to the server computer 1 of “VR1” by the name “SVR”.
2 is assigned to the IP address "2.
In addition, the IP address “2.1” and the MAC address “3” are assigned to the server-to-server communication processing unit 12 of the address translator 10 in the client-to-client communication. The processing unit 11 includes:
MAC address “2” is assigned to each. When it is not necessary for the address translation device 10 to relay a packet, data communication can be performed via the LAN 5 by operating only one of the communication interfaces of the address translation device 10. Therefore, in the present embodiment, since data communication is performed via the network interface of the server-to-server communication processing unit 12, the initial setting of the IP address to the client-to-client communication processing unit 11 is unnecessary. The expression of the IP address is simplified by showing only the net ID and the host ID as in the conventional example.

As apparent from FIG. 2, the client computer 3 belongs to the same network system because the same net ID “1” is assigned to the server computer 1, but the client computer 3 has the net ID “2”. It can be understood that the server computer 2 belongs to a different network system even though it is physically connected to the same LAN 5. That is, the client computer 3 and the server computer 2 cannot directly transmit and receive packets.

FIG. 3 is a diagram showing the flow of IP packets and their address information when the server computer 1 is operating normally in FIG. 2, and FIGS. 4 and 5 show the server computer 1 in FIG. FIG. 3 is a diagram showing a flow of an IP packet and address information of the IP packet when a failure occurs. Next, the operation in the LAN system when the client computer 3 uses the service provided by the server computers 1 and 2 will be described with reference to these drawings. First, the operation when the server computer 1 is operating normally will be described.

The client computer 3 knows in advance the name "SVR1" of the server computer 1 to receive the service and, based on this name, obtains the IP address of the server computer 1 from the name server shown in the conventional example or a host file held by itself. “1.5” is acquired. Further, the client computer 3 acquires the MAC address “4” of the server computer 1 based on the acquired IP address. Since the ARP is also implemented in each of the computers 1, 2, and 3, the client computer 3 sends out an inquiry packet specifying the IP address "1.5", so that the ARP of the server computer 1 , The MAC address “4” can be obtained. And the client computer 3
As shown in FIG. 3, the server adds the IP address and MAC address of the source client computer 3 and the IP address and MAC address of the destination server computer 1 to the request IP packet 21 for using the service. Send to computer 1.

When the server computer 1 recognizes that the IP packet 21 is addressed to itself by referring to the destination address information of the received IP packet 21, the server computer 1 executes an application based on the contents of the IP packet 21 and obtains a predetermined result. obtain. Then, the processing result is set in the providing IP packet 22 for providing the service. Furthermore,
Based on the IP address “1.3” included in the received IP packet 21, the MA of the client computer 3
Acquire the C address "1". Server computer 1
Sends an inquiry packet designating the IP address “1.3”, so that the client computer 3
The MAC address “1” can be obtained by the response from P. Then, the server computer 1 adds the IP address and MAC address of the source server computer 1 and the IP address and MAC address of the destination client computer 3 to the IP packet 22 as shown in FIG. Send.

The client computer 3 receives the IP packet 22 by referring to the destination address information of the IP packet 22 and recognizing that the IP packet 22 is addressed to itself. As a result, the client computer 3
The service provided by the server computer 1 can be used.

As described above, the address translator 10
When the server computer 1 is operating normally, it is not used for inter-computer communication at all. Next, the operation of the LAN system according to the present embodiment when the server computer 1 stops due to a failure will be described with reference to the flowchart shown in FIG.

When the server computer 2 detects a stop due to a failure of the server computer 1 or the like, the server computer 2 stores the IP address “1.
5 ”and the MAC address“ 4 ”are transmitted to the address translator 10.

The address converting apparatus 10, upon detecting the stop server computer 1 by receiving the notification from the server computer 2 (step 101), the server computer 1 included in the notification as shown in FIG. 4
Update each address of the client-to-client communication processing unit 11 with the IP address and the MAC address (step 10).
2). Then, the setting is made effective by restarting the inter-client communication processing unit 11. The IP addresses of the server computer 2 and the server-to-server communication processing unit 12 are as follows:
Since the same network ID “2” and the same network system are configured, the address translation device 10 and the server computer 2 can communicate directly via the LAN 5.

After the above-described settings in the address translation device 10 have been completed, the client computer 3 receives the service from the server computer 1.
As in the normal operation of the server computer 1, the IP address "1.5" of the server computer 1 is obtained based on the name "SVR1" of the server computer 1, and the M of the server computer 1 is further determined based on the obtained IP address.
A request for acquiring an AC address is issued. At this time, the IP address “1.5” is set to the address
0, the address resolution unit 14 of the address translator 10 responds to this acquisition request by using the MA instead of the server computer 1.
C address "4" is returned. Since the client computer 3 is not informed of the stop of the server computer 1, the client computer 3
Performs the same processing as in the normal operation of the server computer 1. Then, the client computer 3 adds the address information to the request IP packet 23 and transmits the request to the server computer 1. The designation of the address information of the created IP packet 23 is exactly the same as that of the IP packet 21 created under normal conditions. Becomes As described above, according to the present embodiment, it is possible to cause the client computer 3 to create a request IP packet without being conscious of the operation status of the server computer 1.

The I sent by the client computer 3
Destination IP address “1.5” of P packet 23 and MA
Since the C address “4” is set in the inter-client communication processing unit 11 of the address translation device 10, the address translation device 10 receives the IP packet 23 (step 103). The address translation unit 13 of the address translation device 10 performs the following address translation process based on the IP packet 23 and the notification from the substitute server computer 2 received when the server computer 1 fails (step 104).

First, the address conversion unit 13 checks the source IP
The address is kept at “1.3” set in the received IP packet 23, and the destination IP address is converted from “1.5” to the IP address “2.5” of the server computer 2 based on the notification. The address conversion unit 13
Converts the source MAC address from “4” set in the IP packet 23 to the MAC address “3” of the inter-server communication processing unit 12 that transmits the packet. The address conversion unit 13 changes the destination MAC address from “3” set in the IP packet 23 to the IP address “2.5”.
Is converted to “5” obtained from the server computer 2 based on The MAC address of the server computer 2 is responded to by the ARP of the server computer 2 by transmitting an inquiry packet. The server-to-server communication processing unit 12 transmits the IP packet 24 created in this way (step 105).

The server computer 2 receives the IP packet 2
The IP packet 24 is received by recognizing that the packet is addressed to itself by referring to the destination address information of No. 4.
The server computer 2 includes an inter-server communication processing unit 1
Since the same net ID “2” as “2” is set, it can be directly received from the server-to-server communication processing unit 12 of the address translation device 10. As described above, since the net IDs of the client computer 3 and the server computer 2 are different, the server computer 2 cannot directly receive the IP packet 23 transmitted to the server computer 1 by the client computer 3 instead of the server computer 1. Can not. However, the address translator 10
Since the address information of the IP packet 23 is translated to the server computer 2, the server computer 2 can receive the request IP packet transmitted by the client computer 3 via the address translator 10.

Upon receiving the requesting IP packet, the server computer 2 creates and returns a providing IP packet 25 to which the following address information is added in order to provide a service on behalf of the server computer 1.

First, the server computer 2 sets its own IP addresses “2.5” and “5” as the source IP address and MAC address, respectively. Also, the IP address “1.3” obtained from the received IP packet 24 is set as it is for the destination IP address. Then, the server computer 2 sends out an inquiry packet based on the IP address “1.3” to obtain the destination MAC address. However, the server computer 2
It is not possible to directly access the client computer 3 having the IP address “1.3”. Therefore, the server-to-server communication processing unit 12 of the address translator 10 in which the same net ID as the server computer 2 is set receives the inquiry packet, and the address resolution unit 14 transmits its own MA.
The C address "3" is returned. As a result, the destination MAC address of the providing IP packet 25 includes
“3” is set. Server computer 2
Sends the IP packet 25 with the address information set as described above. Note that the processing executed in the server computer 2 is processing at the time of packet transmission generally performed based on TCP / IP.

Since the server computer 2 and the client computer 3 belong to different network systems, the server computer 2 sends an IP address to the client computer 3 having the IP address “1.3”.
Packet 25 cannot be transmitted directly. Therefore,
The server computer 2 will look for a gateway. Here, the IP address of the server-to-server communication processing unit 12 of the address translation device 10 is registered as a default gateway in the server computer 2 or the IP address of the client computer 3 is set in advance in the address translation device 10. IP packet to address translation device 10
To be relayed.

The address translator 10 transmits the IP packet 2
Since “3” is set in the destination MAC address of No. 5, the IP packet 25 can be received (step 106). Then, the address translator 13 of the address translator 10 performs the following address translation process based on the IP packet 25 (Step 107).

First, the address conversion unit 13 checks the source IP
Address is set to “2.5” set in IP packet 25
Is converted to the IP address “1.5” of the inter-client communication processing unit 11 that sends out the IP packet 26 after the conversion. Similarly, the source MAC address is converted from “5” to “4”. As a result, the IP address “1.5” and the MAC address “4” originally assigned to the server computer 1 are set as the source IP address and the MAC address. In addition, the address conversion unit 13 keeps the destination IP address at “1.3” set in the received IP packet 25 and changes the destination MAC address from “5” set in the IP packet 25 to the IP address. It is converted to “1” obtained from the client computer 3 based on the address “1.3”. The MAC address of the client computer 3 is responded to by the ARP of the client computer 3 by transmitting an inquiry packet. The client-to-client communication processing unit 11 transmits the IP packet 2
6 is transmitted (step 108).

As a result, the client computer 3
Can receive the IP packet 26 sent from the address translator 10, so that the services provided by the server computers 1 and 2 can be used.

Here, as can be understood from a comparison between the IP packet 22 shown in FIG. 3 and the IP packet 26 shown in FIG.
The packet has the same content irrespective of whether or not the server computer 1 has a failure or the like. That is, as long as the client computer 3 only requests the server computer 1 to provide a service irrespective of the operating status of the server computer 1, the client computer 3 apparently uses the service of the server computer 1. From the viewpoint of the client computer 3, there is no problem because the service can be reliably used as a result even if the server computer 2 actually provides the service.

As described above, according to the present embodiment, even if the client computer 3 always designates the use destination of the service as the server computer 1, the client computer 3 can use the service. Therefore, no problem occurs even if the client computer 3 holds the correspondence between the name of the server computer 1 and the IP address, or caches the query result of the IP address and uses it every time. .

Further, according to the present embodiment, the service can be used without making the client computer 3 aware of the service providing destination. Of course, even if the server computer 1 recovers and resumes providing services, the client computer 3
There is no need to let the system recognize that resumption.

Further, in the present embodiment, even if the server computer 1 breaks down and the service destination is switched, there is no need to update the IP address or MAC address of the substitute server computer 2. In addition, the server computer 2 does not need to put an extra burden due to the switching.

Further, the client computer 3 cannot directly receive the service from the server computer 2 because the network ID is different. However, according to the present embodiment, the client computer 3 performs the address conversion processing as described above. Can receive a service from the server computer 2 belonging to a different network system. Therefore, it is possible to provide a common standby server computer in different network systems without preparing a substitute server computer for each network system. The “standby system” used in the embodiment means that the system is in standby for a service that is normally provided, and is made to wait without using the server computer for another purpose. It does not mean to keep. of course,
If it is a dual system, it may be interpreted as a standby system for a normal operating system.

The address translator 10 according to the present embodiment can be realized by installing an application for executing the above-described processing in a general-purpose computer capable of performing network communication based on TCP / IP. It is not necessary to use a device having a relay function between networks, such as a router.

In the above description, the address translation device 10 according to the present embodiment uses one client computer 3 as a computer using a service, and the server computer 1 as a computer providing a service, and the server computer 1 as an alternative. Although the example of the network configuration in which one server computer 2 is connected to the LAN 5 is used, it is needless to say that the present invention can be applied to a LAN system having another connection form such as a plurality of client computers being connected.

Embodiment 2 FIG. 7 shows the LA according to the present invention.
FIG. 1 is an overall configuration diagram showing Embodiment 2 of an N system.
In the first embodiment, one address translation device 10 is connected to the LAN 5, but in the present embodiment,
Further, it is characterized in that a substitute address translator 27 is connected to the LAN 5. If the LAN system is composed of only one address translation device 10, and the address translation device 10 becomes inoperable due to a failure or the like, the client computer 3 must be aware of the service use destination, and Therefore, data communication with the server computer 2 belonging to a different network system cannot be performed. Therefore, in the present embodiment, by providing the substitute address translation device 27, even if the address translation device 10 fails, the client computer 3 can continue to use the service provided by the server computer. I made it.

The configuration of the address translator 27 may be exactly the same as that of the address translator 10;
The setting contents of the IP address and the MAC address for the client-to-client communication processing unit and the server-to-server communication processing unit are L
The address conversion device 27 is notified via the AN 5 or a dedicated line (not shown). When the address translator 27 detects that the address translator 10 has stopped, the address translator 27 uses its IP address and MAC address set in each communication processing unit of the address translator 10 to control its own I / O.
Update the P address and the MAC address.

Thus, the address translator 27 allows the client computer 3 to use the service provided by the server computer 2 instead of the address translator 10, so that the reliability in the LAN system can be improved.

In the present embodiment, an example has been described in which only one substitute address translation device is provided, but a plurality of substitute address translation devices may be provided with priority.

Embodiment 3 FIG. 8 shows the LA according to the present invention.
FIG. 9 is an overall configuration diagram showing a third embodiment of the N system.
In the first embodiment, the active server computer 1 that normally provides a service to the client computer 3
In the present embodiment, two sets of the active system and the standby system are provided in the same LAN 5 (the server computers 1 and 2 and the server computers 28 and 29). ) Are connected. And even in such a configuration, only one address translation device 10 in the present embodiment can be applied. The operation in the address translator 10 is basically the same as in the first embodiment.

For example, each of the computers 1, 2, 3, 2
8, 29 and the address translator 10
If the address is set and the server computer 1 fails, the IP address “1.5” of the server computer 1 is set in the inter-client communication processing unit 11 of the address translator 10. Thus, even if the client computer 3 transmits a request packet for using the service to the server computer 1, the service is actually provided from the server computer 2 by the address translation function and the relay function of the address translation device 10. Can receive. The process of converting the address information of the packet and the process of relaying the packet in the address translator 10 are the same as those in the first embodiment, and a description thereof will be omitted.

If the server computer 28 breaks down, the IP address “1.6” of the server computer 28 is set in the inter-client communication processing section 11 of the address translator 10. Thereby, even if the client computer 3 transmits a request packet for using the service to the server computer 28, the client computer 3 actually provides the service from the server computer 29 by the address translation function and the relay function by the address translation device 10. Can receive. In this process, the process executed only by changing the set value of the IP address is exactly the same as described above.

Although the present embodiment has been described with reference to an example in which two sets of active and standby server computers are connected to the LAN 5, the present invention can be applied to a case where a plurality of sets are connected.

Further, in the present embodiment, the description regarding the MAC address which is the physical address is omitted, but it is actually the same as the first embodiment.

Embodiment 4 FIG. 9 shows the LA according to the present invention.
FIG. 13 is an overall configuration diagram showing Embodiment 4 of the N system.
The LAN system according to the present embodiment is characterized in that address translation devices 10 and 30 are provided so as to correspond to sets of active and standby server computers, respectively.

In the third embodiment, it is not possible to cope with simultaneous failure of the active server computers 1 and 28. Therefore, in the present embodiment, the address translators 10 and 30 are provided in correspondence with each set of server computers, that is, each set of the server computers 1 and 2 and the server computers 28 and 29. Thus, even when the server computer 1 and the server computer 28 stop at the same time, the client computer 3 can receive the service from the substitute server computers 2 and 29.
In this example, one client computer 3
Although only the LAN 5 is connected to the LAN 5 but a plurality of client computers are connected, the address translators 10 and 30 may process request packets simultaneously transmitted from the plurality of client computers in parallel. become able to.

Further, according to the present embodiment, as shown in FIG. 9, the active server computers 1 and 28, the standby server computer 2 and the standby server computer 29 are different from each other in the network system 1. ,
Even in the case where the address conversion device belongs to
The IP address of the same network system 2 as the server computer 2 is set in the server-to-server communication processing unit 12 and the IP address of the same network system 3 as the server computer 29 is set in the server-to-server communication processing unit 32 of the address translator 30. By doing so, it is possible to cope with a case where three different network systems are configured.

More specifically, when the server computer 1 fails, the address translation device 10 operates in the same manner as in the first embodiment and takes over the IP address “1.5” of the server computer 1 so as to take over the network system 1. Between the client computer 3 belonging to the network system 2 and the server computer 2 belonging to the network system 2.

When the server computer 28 breaks down, the address translator 30 operates in the same manner as in the first embodiment to operate the IP address “1.
By taking over 6 ″, communication can be performed between the client computer 3 belonging to the network system 1 and the server computer 29 belonging to the network system 3.

From the above, it can be said that this embodiment has a structure in which the structure shown in Embodiment 1 is superimposed. In the present embodiment, the case where two address translators 10 and 30 are connected to the LAN 5 is taken as an example, so that three different network systems can be handled. By connecting a set with a conversion device, it is possible to cope with even more network systems.

It is to be noted that not only the IP address setting processing but also the processing such as address conversion and packet relay performed by the address conversion apparatuses 10 and 30 are the same as the processing based on FIG. 6 described in the first embodiment. The description will be omitted because it may be executed.

Embodiment 5 In this embodiment, packet communication between computers having different classes of IP addresses will be described.

FIG. 10 is an overall configuration diagram of a LAN system according to the present embodiment. FIG. 10 shows the same LAN.
(Not shown) and two client computers 33 and 34 and two server computers 35 and 36
And an address translation device 37 are shown. In this configuration, the server computer 35 is the first computer according to the present invention.
And provides a service to the client computer 33 during operation. The server computer 36 corresponds to the second computer according to the present invention, and provides a service to the client computer 33 when the server computer 35 is stopped. Each of the computers 33 to 36 has “5.5.5.3”,
“5.5.4.3”, “5.5.5.5”, “5.5.
The IP address “4.5” is set.
By setting the subnet mask to the P address,
The net IDs of the client computers 33 and 34 are “5.5”, the net ID of the server computer 35 is “5.5.
D is recognized as “5.5.4”. The server-to-server communication processing unit 39 of the address translator 37 includes:
An IP address “5.5.4.6” is set, and its net ID is “5.5.4”. Further, in the present embodiment, even when the active server computer 35 is not stopped, communication between the client computer 33 and the standby server computer 36 is enabled so that the address translator 37 can be used. An IP address “5.5.5.6” is set in the server communication processing unit 39. This net ID is “5.5”.

In FIG. 10, arrows indicate the flow of IP packets when the server computer 35 which normally provides services to the client computer 33 is operating normally.

In the LAN system having the above configuration, when the server computer 35 is operating normally, the IP packet transmitted when the client computer 33 uses the service of the server computer 35 is transmitted to the upper two Byte "5.5"
Is the net ID “5.
5 ”is transmitted directly to the server computer 35. On the other hand, in the IP packet returned from the server computer 35 to the client computer 33, the upper three bytes“ 5.5.5 ”of the IP address of the client computer 31 are the same. Net ID of server computer 35
Since it is the same as “5.5.5”, it is transmitted directly to the client computer 33. Similarly, the client computer 34 and the server computer 36
IP packets can be transmitted and received directly to each other.

In the IP packet transmitted when the client computer 33 uses the service of the server computer 36, the upper two bytes “5.5” of the server computer 36 have the net ID “5.5” of the client computer 33. Since they are the same, they are transmitted directly to the server computer 36. On the other hand, the server computer 36
Returns the upper three bytes “5.5.5” of the IP address of the client computer 33 to the client computer 33.
And is not directly transmitted to the client computer 33 because it is not the same as the net ID “5.5. Therefore, the address translation device 37
Instead of the net ID “5.
The IP packet is received from the server-to-server communication processing unit 39 which is the same as “5.4”, and the IP address of the IP packet is converted to “5.5.5.6”. The address is the address set in the processing unit 38, and the net ID is “5.5.” The client computer 33 transmits the address from the server computer 36 via the address translation device 37 that performs such address translation. An IP packet can be received.

As described above, when the server computer 35 is operating normally, the address translator 37 of this embodiment is used.
Can also function as a gateway.

Next, the operation of the LAN system according to the present embodiment when the server computer 35 stops due to a failure or the like will be described. The operation described here is
This embodiment is basically the same as the first embodiment except that packet communication between computers having different classes of IP addresses is taken as an example.

When the address translation device 37 detects a failure of the server computer 35 based on the notification from the server computer 36, the address translation device 37 transmits the IP address "5.5.5.5" The IP address of the communication processing unit 38 is changed. At this time, the I set in the inter-client communication processing unit 38
The net ID of the P address is “5.5” depending on the setting of the subnet mask.

Thereafter, the client computer 33
Sends out a service request IP packet designating the server computer 35,
The address translator 37, which has succeeded the IP address of the above, receives the IP packet on behalf of the server computer 35. At this time, both the client computer 33 and the inter-client communication processing unit 38 have the net ID “5.
5 ", the address translation device 37 can directly receive the IP packet from the client computer 33. Then, the destination translation IP address is translated into the IP address" 5.5.4.5 "of the server computer 36. And send it out.

The server computer 36 receives the IP packet from the client computer 33 via the address translator 37. The server-to-server communication processing unit 39
Since the server computer 36 and the net ID of the server computer 36 are both “5.5.4”, the server computer 36 can directly receive the IP packet from the address translation device 37. The server computer 36 returns an IP packet in response to the service request, and the IP address of the server computer 36 is added to the source IP address of the IP packet.
The P address “5.5.4.5” is set to “5.5.5.3” of the client computer 33 as the destination IP address.
Are set respectively.

The address translator 37 transmits the I data transmitted from the server computer 36 to the client computer 33.
When the P packet is received from the server-to-server communication processing unit 39 in the same manner as in the first embodiment, the source IP address of the IP packet is changed to the IP address of the client-to-client communication processing unit 38, that is, the IP address of the server computer 35 "5. 5.5.5 "and send.

Thus, the client computer 3
3 is the IP for the request sent to the server computer 35
In response to the packet, the server computer 3
6 can receive the service provided.

As described above, according to the present embodiment, the same effects as in the first embodiment can be obtained between computers having different classes of IP addresses.

In the present embodiment, the client computer 33 can receive the service provided by the server computer 36 independently by the function of the address translator 37 as a gateway. However, when the server computer 36 is operating as a substitute for the stopped server computer 35, the server computer 36 cannot provide its own service to the client computer 33. This is because the server computer 36 automatically translates the source IP address of the IP packet sent to the client computer 33 into the IP address of the server computer 35 by the address translation function of the address translation device 37. However, IP
The problem can be solved by taking measures such as adding other identification information to the packet.

In each of the above embodiments, the TCP / I
Although a LAN system that performs communication based on P has been described as an example, the present invention can also be applied to a communication protocol that specifies a logical address as a destination of a packet, similarly to TCP / IP.

[0084]

According to the present invention, even if a client computer always sends a packet specifying a service use destination as a first server computer, the first server computer is stopped when the first server computer is stopped. Since the packet is received on behalf of the server computer and its destination is translated to the second server computer, the packet sent by the client computer can be delivered to the second server computer for substitution. In addition, since the packet transmitted by the second server computer is relayed and the packet is subjected to the address translation, the service can be used by the client computer regardless of the operation state of the first server computer. . Therefore, even if the client computer holds the correspondence between the name of the first server computer and the logical address, or caches the query result of the logical address and uses it every time, the client computer is , The service can be reliably used.

Although the client computer cannot directly receive the service from the second server computer belonging to a different network system, the client computer performs an address conversion process on the packet transmitted by the client computer as in the present invention. Therefore, the client computer can use the service provided by the second server computer belonging to a different network system. this is,
For example, in a LAN system based on TCP / IP,
Computers with IP addresses of different classes are in the same LA
It is possible even when connected to N.

Further, since the address resolution means is provided, a physical address can be returned in response to an inquiry from another computer in place of the first server computer.

Further, by providing a substitute address translator, even when the operating address translator is stopped due to a failure or the like, the same processing performed by the stopped address translator can be continuously performed. LA
The reliability in the N system can be improved.

Also, by providing the address translation device with a function as a gateway, when the first server computer is operating normally, the client computer can provide services independently provided by the second server computer belonging to a different network system. Can receive.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a first embodiment of an address translation device according to the present invention.

FIG. 2 is an overall configuration diagram of a LAN system according to the first embodiment.

FIG. 3 is a diagram showing a flow of an IP packet and address information thereof when an active server computer is operating normally in the LAN configuration shown in FIG. 2;

4 is a diagram showing a flow of IP packets and address information when an active server computer has failed in the LAN configuration shown in FIG. 2;

5 is a diagram showing a flow of IP packets and address information thereof when a server computer has failed in the LAN configuration shown in FIG. 2;

FIG. 6 is a flowchart showing processing of the address translation device according to the first embodiment.

FIG. 7 is an overall configuration diagram of a LAN system according to a second embodiment.

FIG. 8 is an overall configuration diagram of a LAN system according to a third embodiment.

FIG. 9 is an overall configuration diagram of a LAN system according to a fourth embodiment.

FIG. 10 is a diagram showing an overall configuration of a LAN system according to a fifth embodiment together with a flow of an IP packet during a normal operation of an active server computer.

FIG. 11 is a diagram showing an entire configuration of a LAN system according to a fifth embodiment together with a flow of IP packets when an active server computer is stopped.

FIG. 12 is an overall configuration diagram showing an example of a conventional network system.

FIG. 13 is a block diagram of a conventional communication system.

[Explanation of symbols]

1, 2, 28, 29, 35, 36 server computer, 3, 33, 34 client computer, 5
LAN, 10, 27, 30, 37 address translator,
11, 31, 38 inter-client communication processing unit, 12,
32, 39 inter-server communication processing unit, 13 address conversion unit, 14 address resolution unit, 15 server monitoring unit, 21
~ 26 IP packets.

Continuation of the front page (56) References JP-A-62-198238 (JP, A) JP-A-4-27239 (JP, A) JP-A-6-318946 (JP, A) JP-A-8-235084 (JP) JP-A-8-335198 (JP, A) JP-A-9-224048 (JP, A) JP-A-9-326810 (JP, A) JP-A-10-23074 (JP, A) RFC826: Request For Comments 826, An Ethernet Address Resolution Protocol Converting Network Talk Protocol Addresses to 48. bit Ethernet address for Transaction on Ethernet Hardware, David C. et al. P, Nov, 1982 (58) Fields investigated (Int. Cl. ⁶ , DB name) H04L 12/28 G06F 13/00 355 INSPEC (DIALOG) JICST file (JOIS) WPI (DIALOG)

Claims (9)

(57) [Claims] A first server computer for providing a service and a logical address different from the first server computer are provided.
A second server computer configured to provide the same service as the first server computer, and a client computer using a service provided by the server computer, wherein each computer has the same local area network In a local area network system connected to the network and performing packet communication by designating a destination logical address, a server for monitoring an operation state of the first server computer.
Server monitoring means, client-to-client communication processing means for receiving a packet transmitted by the client computer on behalf of the first server computer by taking over the logical address of the stopped first server computer, Address conversion means for converting the destination of the packet received by the communication processing means to the second server computer, and server-to-server communication processing means for transmitting the packet whose address has been converted by the address conversion means to the second server computer; , it has a separately provided with the respective server computer,
During normal operation of the first server computer,
Do not relay the packet transmitted by the computer,
Only when the server computer is stopped, the client
To the first server computer transmitted by the computer
An address translation device in a local area network system, which performs address translation of a packet . 2. The server-to-server communication processing means transmits
Receiving the packet transmitted from the second server computer to the client computer in accordance with the address-translated packet, to relay the packet received by the server-to-server communication processing unit; 2. The apparatus according to claim 1, wherein the first server computer converts the packet to the first server computer, and wherein the client-to-client communication processing unit transmits the packet whose address has been converted by the address conversion unit to the client computer.
An address translation device in a local area network system as described in the above. 3. An apparatus according to claim 1, further comprising address resolution means for returning a physical address corresponding to a logical address of a computer connected to the local area network based on the received inquiry packet. Address translation device in a local area network system. 4. In a local area network system for performing packet communication via the same local area network by designating a destination logical address, a first server computer for providing a service, and a logic different from the first server computer. Address is
A second server computer that is set and provides the same service as the first server computer, a client computer that uses a service provided by the server computer, and is provided separately from each of the server computers. The first
An address translation device that relays a packet transmitted / received between the client computer and the server computer only when the server computer is stopped, wherein the first and second servers provide the same service.
Ba computer has at least one pair formed, said address translation unit, wherein when the first server computer is down, it in the first to take over the logical address of the first server computer that has stopped server A client-to-client communication processing unit for receiving a packet transmitted by the client computer on behalf of a computer; and a destination of the packet received by the client-to-client communication processing unit before forming a pair with the first server computer. possess a serial second server into a computer address conversion means, and the inter-server communication processing means for transmitting the address conversion packet to the second server computer by said address converting means, wherein the first server Before computer shutdown
Change the logical address of the second server computer
Service to the client computer
A local area network system characterized by continuously providing services . 5. The server-to-server communication processing means transmits
Receiving the packet transmitted from the second server computer to the client computer in accordance with the address-translated packet, to relay the packet received by the server-to-server communication processing unit; Source to the second server computer
5. The method according to claim 4, wherein the first server computer forms a pair with the data, and the client-to-client communication processing unit transmits the packet whose address has been converted by the address conversion unit to the client computer.
The local area network system as described. 6. Local area network system according to claim 4 or 5, characterized in that <br/> provided with the address translator for substitution. 7. The local area network includes:
Different nets divided by network address
A plurality of work systems are mixed, and the first server computer and the
The two server computers have their own logical addresses
By assigning different network addresses
6. The local area network system according to claim 4, wherein the local area network system belongs to different network systems. 8. The local area network system according to claim 7, wherein said address translator is provided corresponding to each of said sets. 9. The address translation device according to claim 4, wherein said address translation device has a function as a gateway.
The local area network system according to any one of the above.