JP2010062598A - Load sharing method and dhcp server device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a load distribution method of a service providing apparatus, using a DHCP (dynamic host configuration protocol) server which has less limitations on applicable network configurations and on the kinds of service-providing apparatuses and can be utilized for general purpose, and to provide a DHCP server device. <P>SOLUTION: A storage device 12 of the DHCP server 1 stores the addresses of a plurality of DNS (domain name system) servers. A data processor 11 for the DHCP server 1, when receiving a DHCP message for acquiring setting information, containing the addresses of self-communication terminals and the addresses of the DNS servers, uses a selection algorithm for equal selection for selecting an address to be notified to a communication terminal from among the addresses of the plurality of DNS servers, and transmits the setting information containing the selected address of the DNS server to a communication terminal which transmits the DHCP message. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a load distribution method in an IP network in which network settings of communication terminals are managed by a DHCP server, and more particularly to a load distribution method of a service providing device using a DHCP server and a DHCP server device.

  In addition to a large number of communication terminals that transmit and receive IP packets, devices that provide various services to these communication terminals are connected to an IP network such as the Internet based on TCP / IP. Typical service providing devices include a DNS (Domain Name System) server and a default router. The DNS server provides a conversion service between an IP address and a domain name. The default router is provided between the network and another network, and provides a service for relaying an IP packet of one network to the other network.

  Since such a service providing device is shared by many communication terminals, the performance of the service providing device itself may become a bottleneck. Thus, it is often performed to multiplex service providing devices for the purpose of load distribution.

  One method for distributing the load by multiplexing service providing devices is to use a network device called a load balancer. However, the processing capacity of the load balancer itself becomes a bottleneck, and network devices increase and management costs increase. Therefore, Patent Document 1 discloses a method for performing load distribution of multiplexed service providing devices without using a load balancer.

  The load distribution method (hereinafter referred to as related technology) described in Patent Document 1 uses a default router as a load distribution target, and performs load distribution of a plurality of default routers using a DHCP (Dynamic Host Configuration Protocol) server. Specifically, first, a plurality of routers connecting between networks detect the router with the lowest load by exchanging load information with each other. When the communication terminal broadcasts a DHCP message for acquiring a setting parameter including its own address and the address of the default router to the network to which the communication terminal is connected at the time of startup or reconfiguration, a predetermined one of the plurality of routers The router adds the information for identifying the detected router with the lowest load to the DHCP message and forwards it to the DHCP server. The DHCP server assigns to the communication terminal a setting parameter for setting the router with the lowest load as the default router based on the received information identifying the router with the lowest load added to the DHCP server.

Japanese Patent No. 3,896,897

  According to the related art described above, it is possible to distribute the load by distributing the default router reflecting the load of the router in the communication terminal without changing the function of the existing DHCP server.

  However, in the related technology described above, since it is assumed that the DHCP message transmitted from the communication terminal is transferred to the DHCP server via the router, the communication terminal and the DHCP server are connected to the same network. Therefore, it is difficult to apply the configuration to the network, and there are many restrictions on the applicable network configuration.

  Further, the related technique described above is a technique related to load distribution of the default router, and is difficult to apply to load distribution of service providing devices other than the default router.

  The present invention has been proposed in view of such circumstances, and its purpose is to provide a service using a DHCP server that can be used universally with few restrictions on the types of network configurations and service providing devices that can be applied. The object is to provide a load balancing method for a providing device and a DHCP server device.

  The first DHCP server device of the present invention is storage means for storing the address of a service providing device to be notified to a communication terminal, and for the same type of service providing device, storage means for storing the addresses of a plurality of service providing devices. When a DHCP message for acquiring setting information including the address of the own communication terminal and the address of the service providing device transmitted by the communication terminal is received, the same type of service providing device is stored using a selection algorithm that is selected evenly. The address of the service providing device notified to the communication terminal is selected from the addresses of the plurality of service providing devices stored in the means, and the setting information including the address of the selected service providing device is sent to the communication terminal that has transmitted the DHCP message. Data processing means for transmission.

  ADVANTAGE OF THE INVENTION According to this invention, there are few restrictions with respect to the network configuration and the kind of service provision apparatus which can be applied, and the load distribution method and DHCP server apparatus of the service provision apparatus using a DHCP server which can be used universally are obtained.

[First Embodiment]
Referring to FIG. 1, the first embodiment of the present invention provides a DNS server 1 to a DHCP server 1, communication terminals 2 and 3 using services on the network, and communication terminals 2 and 3 on the network. DNS servers 4 and 5 to be connected to each other, and a network such as a LAN 6 constituted by network devices connecting them.

  Referring to FIG. 2, the DHCP server 1 includes a data processing device 11 that executes DHCP processing, and a storage device 12 that stores DHCP setting information.

  The storage device 12 includes a notification information storage unit 121 and a DNS server address storage unit 122.

  The notification information storage unit 121 stores in advance information on an IP address assigned to the communication terminal itself. Referring to FIG. 3, an example of the terminal address management table 1210 stored in the notification information storage unit 121 includes a plurality of entries 1211, 1212,... That store different IP addresses, and each entry is assigned. It consists of a flag, an IP address assigned to the communication terminal, and a subnet mask. The assigned flag indicates whether or not the IP address in the entry has already been assigned to any communication terminal. For example, the value 0 indicates unassigned and the value 1 indicates assigned.

  The DNS server address storage unit 122 stores in advance the address of the service providing device to be notified to the communication terminal. In the present embodiment, there is one type of service providing device that notifies an address to a communication terminal, and the type is a DNS server. In this embodiment, the communication terminal is notified of a pair of a DNS server address to be used preferentially and a DNS server address to be used as an alternative when the service cannot be received from the DNS server. To do. Referring to FIG. 4, an example of the DNS server address management table 1220 stored in the DNS server address storage unit 122 includes two entries 1221 and 1222. Each entry includes a priority DNS server and an alternative DNS server. The address is stored. Specifically, one entry 1221 stores the address of the DNS server 4 as the priority DNS server and stores the address of the DNS server 5 as the alternative DNS server. In contrast to the entry 1221, the other entry 1222 stores the address of the DNS server 5 as a priority DNS server, and stores the address of the DNS server 4 as an alternative DNS server.

  Referring again to FIG. 2, the data processing apparatus 11 includes a notification information determination unit 111 and a DNS server address determination unit 112.

  The notification information determination unit 111 has a function of determining the IP address and subnet mask information set for the communication terminal itself based on the terminal address management table 1210 of FIG. 3 stored in the notification information storage unit 122. Specifically, one entry whose value is 0 and the assigned flag is not assigned is selected, and the IP address and subnet mask in the selected entry are determined as the IP address and subnet mask to be set in the communication terminal itself. Note that the notification information determination unit 111 updates the assigned flag corresponding to the assigned IP address to a value of 1.

  The DNS server address determination unit 112 has a function of determining information on the DNS server address set in the communication terminal based on the DNS server address management table 1220 in FIG. 4 of the DNS server address storage unit 122. Specifically, the entry 1221 and the entry 1222 are equally selected using a selection algorithm that selects equally, and the DNS server that sets the addresses of the priority DNS server and the alternative DNS server in the selected entry in the communication terminal Determine as an address. As the selection algorithm, for example, a round robin method, a random selection method, or the like can be used.

  The round robin method is a method in which entries to be selected are changed in order. In the case of the DNS server address management table 1220 of FIG. 4, if the entry 1221 was selected last time, the entry 1222 is selected this time, and the entry 1221 is selected again after that.

  The random selection method is a method of randomly determining entries to be selected each time. A specific example of selecting an entry at random is a method using a random number. In the case of the DNS server address management table 1220 of FIG. 4, for example, if the generated random number is an odd number, the entry 1221 is selected, and if the generated random number is an even number, the entry 1222 is selected. Further, instead of a random number, using the terminal address determined to be assigned to the communication terminal by the notification information determining means 11, the entry 1221 is selected if the terminal address is odd, for example, and the entry 1222 is selected if it is even. The entry to be selected may be determined by calculation based on the IP address to be assigned to the terminal.

  Next, the operation of the present embodiment will be described.

  When the communication terminal 2 broadcasts a DHCP request message to the LAN 6 in order to set up its own network (501 in FIG. 5), the data processing device 11 of the DHCP server 1 that has received and identified the DHCP request message starts processing the message. .

  First, the data processing device 11 of the DHCP server 1 uses the function of the notification information determination unit 111 to determine the IP address and subnet mask to be allocated to the communication terminal 2 itself from the information stored in the notification information storage unit 121. (502 in FIG. 5). Here, it is assumed that the entry 1211 on the first line in FIG. 3 is selected and (10.0.0.11) is determined as the IP address and (255.0.0.0) is determined as the subnet mask.

  Next, the data processing device 11 uses the function of the DNS server address determination means 112 to determine the DNS server address to be assigned to the communication terminal 2 from the information stored in the DNS server address storage unit 122 (FIG. 5). 503). Here, the entry 1221 in the first row in FIG. 4 is selected by the round robin method, the IP address of the DNS server 4 is determined as the IP address of the priority DNS server, and the IP address of the DNS server 5 is set as the IP address of the alternative DNS server. Assume that an address has been determined.

  Next, the data processing device 11 of the DHCP server 1 sets the IP address and subnet mask assigned to the communication terminal 2 itself determined in the processing so far, and the IP addresses of the priority DNS server and the alternative DNS server assigned to the communication terminal 2. In the DHCP reply message and transmitted to the communication terminal 2 (504 in FIG. 5).

  The communication terminal 2 receives the DHCP reply message transmitted from the DHCP server 1, and performs network setting of the own communication terminal based on this message (505 in FIG. 5). Specifically, (10.0.0.11) is set as the IP address of the own communication terminal 2, and (255.0.0.0) is set as the subnet mask. Also, the IP address of the DNS server 4 is set as the IP address of the priority DNS server used by the own communication terminal 2, and the IP of the DNS server 5 is set as the IP address of the alternative DNS server. As a result, when the communication terminal 2 uses the DNS service, the DNS server 4 set as the priority DNS server is first accessed as indicated by reference numeral 506 in FIG.

  Thereafter, when the communication terminal 3 broadcasts a DHCP request message to the LAN 6 in order to set up its own network (511 in FIG. 5), the data processing device 11 of the DHCP server 1 that has received and identified the DHCP request message performs message processing. Start again.

  First, the data processing device 11 of the DHCP server 1 uses the function of the notification information determination unit 111 to determine the IP address and subnet mask to be allocated to the communication terminal 3 itself from the information stored in the notification information storage unit 121. (512 in FIG. 5). Here, it is assumed that the entry 1212 in the second row in FIG. 3 is selected and (10.0.0.12) is determined as the IP address and (255.0.0.0) is determined as the subnet mask.

  Next, the data processing device 11 determines the DNS server address to be assigned to the communication terminal 3 from the information stored in the DNS server address storage unit 122 using the function of the DNS server address determination means 112 (FIG. 5). 513). Here, the entry 1221 in the second row in FIG. 4 is selected by the round robin method, the IP address of the DNS server 5 is determined as the IP address of the priority DNS server, and the IP address of the DNS server 4 is set as the IP address of the alternative DNS server. Assume that an address has been determined.

  Next, the data processing device 11 of the DHCP server 1 sets the IP address and subnet mask assigned to the communication terminal 3 itself determined in the processing so far, and the IP addresses of the priority DNS server and the alternative DNS server assigned to the communication terminal 3. In the DHCP reply message and transmitted to the communication terminal 3 (514 in FIG. 5).

  The communication terminal 3 receives the DHCP reply message transmitted from the DHCP server 1, and sets the network of the own communication terminal 3 based on this message (515 in FIG. 5). Specifically, (10.0.0.12) is set as the IP address of the own communication terminal 3, and (255.0.0.0) is set as the subnet mask. Further, the IP address of the DNS server 5 is set as the IP address of the priority DNS server used by the own communication terminal 3, and the IP address of the DNS server 4 is set as the IP address of the alternative DNS server. As a result, when the communication terminal 3 uses the DNS service, the DNS server 5 set as the priority DNS server is first accessed as indicated by 516 in FIG.

  As described above, when the DNS service is used, a different DNS server is used for each of the communication terminals 2 and 3, and load distribution of the DNS server is realized.

  Next, the effect of this embodiment will be described.

  According to the present embodiment, it is possible to achieve DNS server load distribution using the DHCP server 1.

  In addition, according to the present embodiment, the network configuration may be arbitrary as long as the message can be exchanged between the communication terminal and the DHCP server. Therefore, the network to which the communication terminal is connected and the network to which the DHCP server is connected are determined. The present invention can be applied universally to any network such as a network connected by a router or a network configured such that a communication terminal and a DHCP server are connected to the same network.

  In addition, according to the present embodiment, it is possible to simultaneously set the network of the IP address of the DNS server as an alternative to the priority DNS server while distributing the load of the DNS server used preferentially by each communication terminal. . However, as another embodiment, only the address of the priority DNS server may be notified to the communication terminal. In this case, a DNS server address management table 1220A as shown in FIG. 6 in which the item of the alternative DNS server is deleted from the DNS server address management table 1220 in FIG. 4 may be used.

  In the present embodiment, one type of service providing device that notifies an address to a communication terminal is one type, and the type is a DNS server. However, the present invention is not limited to the DNS server, and can be applied to load distribution of other types of service providing devices. Other types of service providing devices include NTP servers, default routers, directory servers, and devices that provide services defined as vendor options.

[Second Embodiment]
Referring to FIG. 7, in the second embodiment of the present invention, another network 8 is connected to the LAN 6 via four routers 7A to 7D, and the DNS server and the default are used by using the DHCP server 1. This is different from the first embodiment of FIG. 1 in that load distribution of two types of service providing devices of the router is performed simultaneously.

  Referring to FIG. 8, the DHCP server 1 in the second embodiment is different from the DHCP server 1 in the first embodiment in place of the DNS server address determination unit 112 and the DNS server address storage unit 123. The service providing device address determining unit 113 and the service providing device address storage unit 123 are different.

  The service providing device address storage unit 123 stores in advance the address of the service providing device notified to the communication terminal. In the present embodiment, there are two types of service providing devices for notifying addresses to communication terminals, which are a DNS server and a default router. In this embodiment, the communication terminal is notified of a pair of a DNS server address to be used preferentially and a DNS server address to be used as an alternative when the service cannot be received from the DNS server. To do.

  Referring to FIG. 9, an example of the service providing device address management table 1230 stored in the service providing device address storage unit 123 includes four entries 1231 to 1234, each of which includes a priority DNS server and an alternative DNS. The server IP address and the default router IP address are stored. Specifically, the entry 1231 on the first line stores the address of the DNS server 4 as the priority DNS server, the address of the DNS server 5 as the alternative DNS server, and the address of the router 7A as the default router. ing. The entry 1232 on the second line stores the address of the DNS server 5 as the priority DNS server, the address of the DNS server 4 as the alternative DNS server, and the address of the router 7B as the default router. The entry 1233 in the third row stores the same contents as those in the entry in the first row for the priority DNS server and the alternative DNS server, and stores the address of the router 7C as the default router. The entry 1234 in the fourth row stores the same contents as the entry in the second row with respect to the priority DNS server and the alternative DNS server, and stores the address of the router 7D as the default router.

  The service providing device address determining unit 113 has a function of determining information on the DNS server and default router addresses set in the communication terminal based on the service providing device address management table 1230 of FIG. Have. Specifically, one entry is selected from the entries 1231 to 1234 using a selection algorithm that selects equally, and the addresses of the priority DNS server and alternative DNS server and the address of the default router in the selected entry are communicated. The DNS server address and the default router address set in the terminal are determined. As a selection algorithm, a round robin method, a random selection method, or the like can be used as in the first embodiment.

  Next, the operation of the present embodiment will be described.

  When any one of the communication terminals, for example, the communication terminal 2 broadcasts a DHCP request message to the LAN 6 in order to set up its own network (1001 in FIG. 10), the data processing device 11 of the DHCP server 1 that has received and identified this DHCP request message. Starts processing the message.

  First, the data processing device 11 of the DHCP server 1 uses the function of the notification information determination unit 111 to determine the IP address and subnet mask to be allocated to the communication terminal 2 itself from the information stored in the notification information storage unit 121. (1002 in FIG. 10). Here, it is assumed that the entry 1211 on the first line in FIG. 3 is selected and (10.0.0.11) is determined as the IP address and (255.0.0.0) is determined as the subnet mask.

  Next, the data processing device 11 uses the function of the service providing device address determination unit 113 to select the addresses of the DNS server and default router to be assigned to the communication terminal 2 from the information stored in the service providing device address storage unit 123. Determine (1003 in FIG. 10). Here, it is assumed that one entry is selected from the four entries 1231 to 1234 in the service providing device address management table 1230 in FIG. 10 by the round robin method. In this case, if the entry 1231 was selected last time, the entry 1232 is selected this time. If entry 1232 was previously selected, entry 1233 is selected this time. If entry 1233 was selected last time, entry 1234 is selected this time. If entry 1234 was selected last time, entry 1231 is selected this time. Here, the entry 1231 in the first row is selected, the IP address of the DNS server 4 is determined as the IP address of the priority DNS server, the IP address of the DNS server 5 is determined as the IP address of the alternative DNS server, and the default router Assume that the IP address of the router 7A is determined as the IP address.

  Next, the data processing device 11 of the DHCP server 1 determines the IP address and subnet mask assigned to the communication terminal 2 itself determined in the above processing, the IP addresses of the priority DNS server and the alternative DNS server assigned to the communication terminal 2, and the default router. Are stored in the DHCP reply message as network setting contents and transmitted to the communication terminal 2 (1004 in FIG. 10).

  The communication terminal 2 receives the DHCP reply message transmitted from the DHCP server 1, and sets the network of the own communication terminal 2 based on this message (1005 in FIG. 10). Specifically, (10.0.0.11) is set as the IP address of the own communication terminal 2, and (255.0.0.0) is set as the subnet mask. Further, the IP address of the DNS server 4 is set as the IP address of the priority DNS server used by the own communication terminal 2, and the IP address of the DNS server 5 is set as the IP address of the alternative DNS server. Further, the IP address of the router 7A is set as a default router used by the own communication terminal 2. Thus, when the communication terminal 2 uses the DNS service, the DNS server 4 set as the priority DNS server is accessed first. When the communication terminal 2 accesses a communication terminal (not shown) connected to the network 8, the router 7A is used as a default router.

  When a communication terminal other than the communication terminal 2 broadcasts a DHCP request message to the LAN 6 in order to set its own network, the same operation as when the communication terminal 2 transmits the DHCP request message is performed. However, since the entry selection in the service providing device address management table 1230 is performed by the round robin method, the content stored in the entry 1232 in the second communication terminal is stored in the entry 1233 in the third communication terminal. The content stored in the entry 1234 is notified to the fourth communication terminal. As a result, the DNS server to be used is distributed when using the DNS service, and the default router used when communicating with the communication terminal connected to the network 8 is distributed.

  Next, the effect of this embodiment will be described.

  According to the present embodiment, it is possible to realize load distribution of the DNS server and the default router using the DHCP server 1.

  In addition, according to the present embodiment, the network configuration may be arbitrary as long as the message can be exchanged between the communication terminal and the DHCP server. Therefore, the network to which the communication terminal is connected and the network to which the DHCP server is connected are determined. The present invention can be applied universally to any network such as a network connected by a router or a network configured such that a communication terminal and a DHCP server are connected to the same network.

  In addition, according to the present embodiment, it is possible to simultaneously set the network of the IP address of the DNS server as an alternative to the priority DNS server while distributing the load of the DNS server used preferentially by each communication terminal. . However, as another embodiment, only the address of the priority DNS server may be notified to the communication terminal. In this case, a service providing device address management table 1230A as shown in FIG. 11 in which the item of the alternative DNS server is deleted from the service providing device address management table 1230 in FIG. 9 may be used.

  Furthermore, according to the present embodiment, by using the service providing device address management table 1230 as shown in FIG. 9, the processing for equally selecting the addresses of two types of service providing devices, the DNS server and the default router, is summarized. The processing efficiency in the DHCP server 1 can be increased.

  In this embodiment, there are two types of service providing devices for notifying addresses to communication terminals, and the types are a DNS server and a default router. However, two types of service providing devices for notifying addresses to communication terminals are arbitrarily selected from a DNS server, a default router, an NTP server, a default router, a directory server, a device that provides a service defined as a vendor option, and the like. Alternatively, any combination of three or more can be used. In this case, the service providing device address management table 1230 may generally be configured as follows.

  First, the number of entries in the table is equal to the least common multiple of the number of addresses of each type of service providing device. For example, if there are three types of service providing devices and the number of service providing devices of each type is two, three or four, the number of entries is twelve. Next, each entry is assigned a one-to-one area corresponding to the type of service providing device, and each type of service providing device corresponds to the type of service providing device in order from the first entry to the last entry. The addresses of a plurality of service providing devices are stored in the area to be used. At this time, for service providing devices of a type in which the number of entries is a multiple of the number of addresses of the service providing devices, the addresses of a plurality of service providing devices are stored redundantly. For example, for the service providing device having two units in the above example, the same address arrangement pattern is repeatedly stored six times.

  Although the present invention has been described with reference to some embodiments, the present invention is not limited to the above-described embodiments, and various other additions and modifications can be made. Further, the notification information determining unit 111, the DNS server address determining unit 112, and the service providing device address determining unit 113 described above can be realized by a computer and a program, as well as by hardware. . The program is provided by being recorded on a computer-readable recording medium such as a magnetic disk or a semiconductor memory, read by the computer when the computer is started up, etc., and controlling the operation of the computer, thereby notifying the computer of the notification information described above. It functions as a determination unit 111, a DNS server address determination unit 112, and a service providing device address determination unit 113.

It is a block diagram of a 1st embodiment of the present invention. It is a block diagram of the DHCP server in the 1st Embodiment of this invention. It is a block diagram of the terminal address management table used in the 1st Embodiment of this invention. It is a block diagram of the DNS server address management table used in the 1st Embodiment of this invention. It is an operation | movement sequence diagram of the 1st Embodiment of this invention. It is another block diagram of the terminal address management table used in the 1st Embodiment of this invention. It is a block diagram of the 2nd Embodiment of this invention. It is a block diagram of the DHCP server in the 2nd Embodiment of this invention. It is a block diagram of the service provision apparatus address management table used in the 2nd Embodiment of this invention. It is an operation | movement sequence diagram of the 2nd Embodiment of this invention. It is another block diagram of the service provision apparatus address management table used in the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... DHCP server 2, 3 ... Communication terminal 4, 5 ... DNS server 6 ... LAN
7A to 7D ... Router 8 ... Network 11 ... Data processing device 12 ... Storage device 111 ... Notification information determining means 112 ... DNS server address determining means 113 ... Service providing device address determining means 121 ... Notification information storage unit 122 ... DNS server address storage Unit 123 ... Service providing device address storage unit

Claims (7)

Storage means for storing addresses of service providing devices to be notified to a communication terminal, the storage means storing addresses of a plurality of service providing devices for the same type of service providing devices;
Regarding a service providing device of the same type using a selection algorithm that is selected evenly upon reception of a DHCP message for acquiring setting information including the address of the own communication terminal and the address of the service providing device transmitted by the communication terminal The address of the service providing device to be notified to the communication terminal is selected from among the addresses of the plurality of service providing devices stored in the storage means, and setting information including the address of the selected service providing device is stored in the DHCP message. A DHCP server apparatus comprising: data processing means for transmitting to the transmitted communication terminal. The storage means stores a plurality of address sets of a service providing device used preferentially and a service providing device used as an alternative for the same type of service providing device,
The data processing unit selects a set of addresses to be notified to the communication terminal from among a plurality of sets of addresses stored in the storage unit for the same type of service providing device, and setting information including the selected set of addresses The DHCP server apparatus according to claim 1, wherein the DHCP server apparatus transmits the DHCP message to the communication terminal that has transmitted the DHCP message. The storage means stores the addresses of a plurality of service providing devices for each of a plurality of types of service providing devices,
For each of a plurality of types of service providing devices, the data processing unit notifies the communication terminal of the addresses of the plurality of service providing devices stored in the storage unit for the same type of service providing device. The DHCP server apparatus according to claim 1, wherein setting information including an address of the selected service providing device is transmitted to the communication terminal that has transmitted the DHCP message. The storage means has a number of entries equal to the least common multiple of the number of addresses of service providing devices for each of a plurality of types of service providing devices, and each entry has a divided area equal to the number of types of service providing devices, For each type of service providing device, the addresses of a plurality of service providing devices are stored in the divided area corresponding to the type of the service providing device in order from the first entry to the last entry. A service providing device address management table in which addresses of a plurality of service providing devices are stored in duplicate.
4. The DHCP server device according to claim 3, wherein the data processing means selects one entry from a plurality of entries in the service providing device address management table using the selection algorithm.   The DHCP server apparatus according to any one of claims 1 to 4, wherein the service providing device includes any one of a DNS server, an NTP server, a default router, and a directory server. a) a communication terminal sending a DHCP message for acquiring setting information including its own address and the address of a service providing device to the network;
b) Service provision in which the DHCP server that has received and identified the DHCP message notifies the communication terminal from among the addresses of a plurality of service providing devices stored for the same type of service providing device, using a selection algorithm that selects equally. Selecting a device address, and transmitting setting information including the address of the selected service providing device to the communication terminal that has transmitted the DHCP message;
A load balancing method comprising: A storage unit for storing the address of a service providing device to be notified to a communication terminal, the computer constituting the DHCP server device having a storage unit for storing the addresses of a plurality of service providing devices for the same type of service providing device,
Regarding a service providing device of the same type using a selection algorithm that is selected evenly upon reception of a DHCP message for acquiring setting information including the address of the own communication terminal and the address of the service providing device transmitted by the communication terminal The address of the service providing device to be notified to the communication terminal is selected from among the addresses of the plurality of service providing devices stored in the storage means, and setting information including the address of the selected service providing device is stored in the DHCP message. A program for functioning as a data processing means for transmitting to the communication terminal that has transmitted.

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