JP2010226665A - Load distribution system, apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a load distribution system maintaining identicalness between a port number included in a request packet received from a client and a port number included in a response packet to be transmitted to the client. <P>SOLUTION: A load distribution system includes: a plurality of servers; a load distribution unit which selects a transfer destination server from among the plurality of servers, generates a transfer request packet by rewriting header information of a request packet received from a client into header information indicative of the transfer destination server, and transmits the transfer request packet to the transfer destination server; and a relay conversion unit for transferring a response packet from the transfer destination server to a client terminal. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a load distribution system.

  A load distribution device (load balancer) is a device that distributes traffic to each of a plurality of servers and distributes the load on each server in a server system including a plurality of servers having the same function.

  For example, consider a server system that includes a plurality of DHCP (Dynamic Host Configuration Protocol) servers and a load balancer. First, the client transmits a request packet to the load balancer. When receiving the request packet, the load balancer selects one DHCP server from a plurality of DHCP servers based on a predetermined process, and transfers the request packet. The selected DHCP server performs a predetermined process to generate a response packet and transmits it to the load balancer. When receiving the response packet, the load balancer transfers the response packet to the client. In this way, the load balancer reduces the processing load on each DHCP server by distributing requests from clients to a plurality of DHCP servers.

  Here, when transferring the request packet from the client to the selected DHCP server, the load balancer dynamically sets the destination IP (Internet Protocol) address and the destination port number of the request packet by a NAT (Network Address Translation) function. Assign to. However, the load balancer does not convert the source port number for the response packet from the DHCP server. For this reason, when the client receives the response packet, the destination port number of the request packet does not match the source port number of the response packet. There is a problem that the client cannot recognize that the received response packet is a packet from the DHCP server, and rejects reception by regarding the response packet as an invalid packet. The following technologies are disclosed as related technologies for converting IP addresses and port numbers.

  Patent Document 1 discloses an address translation device that dynamically acquires and assigns a global port number to a server on a local network in response to a port assignment request. The address translation device disclosed in Patent Document 1 is an address translation device that connects a first network and a second network, and is a second port number of a second network that is exchanged in a protocol higher than the transport layer. Is replaced with the first port number of the first network. According to the address translation device of Patent Document 1, it is possible to obtain an effect of dynamically acquiring and assigning a global port number in response to a port assignment request to a server on a local network.

  Patent Document 2 discloses a packet relay device capable of performing IP address conversion of IP packets transmitted and received between a plurality of different IP packet networks while not knowing where the address conversion information is. . The packet relay device of Patent Document 2 does not have an IP address, and the presence of the packet relay device is hidden from other viewpoints. The packet relay device connects the IP packet networks while concealing the presence from others, has an IP address conversion condition list for performing IP address conversion based on a predetermined condition, and includes packets that pass through the own packet relay device. For both IP packets or DNS (Domain Name System) packets that satisfy a predetermined condition, IP address conversion is performed according to the predetermined condition, and the output destination of the predetermined condition is a VLAN (Virtual Local Area Network) or a VC (Virtual Connection). Output. According to the packet relay device of Patent Document 2, it is possible to perform IP address conversion of IP packets transmitted and received between a plurality of different IP packet networks without knowing where the address conversion information is.

JP 2004-072291 A JP 2007-251374 A

  An object of the present invention is to provide a load distribution system capable of maintaining the identity of a port number included in a request packet received from a client and a port number included in a response packet transmitted to the client.

  The load distribution system of the present invention selects a transfer destination server from a plurality of servers and a plurality of servers, and rewrites the header information of the request packet received from the client into header information indicating the transfer destination server. A load distribution unit that transmits the transfer request packet to the transfer destination server, and a relay conversion unit that transfers the response packet from the transfer destination server to the client terminal. The load distribution unit includes a header of the transfer request packet The information is stored in the first address table, and the relay conversion unit acquires the header information of the transfer request packet from the first address table and records it in the second address table. Packet inspection to determine whether or not the header information matches the header information recorded in the second address table If, If they match, the header information of the response packet, the converted response packet generated by rewriting the predetermined header information, including a, a conversion unit that transmits the converted response packet to the client.

  The load distribution apparatus of the present invention includes a load distribution unit and a relay conversion unit that are used in the load distribution system described above.

  The load distribution method of the present invention is a transfer request packet in which a transfer destination server is selected from a plurality of servers and a plurality of servers, and header information of a request packet received from a client is rewritten to header information indicating the transfer destination server. Header information of the transfer request packet in a load distribution system comprising: a load distribution unit that generates a transfer request packet to the transfer destination server; and a relay conversion unit that transfers the response packet from the transfer destination server to the client terminal. Is stored in the first address table, the header information of the transfer request packet is acquired from the first address table, and is recorded in the second address table. When the response packet is received, the header information of the response packet is A step for determining whether or not the header information recorded in the second address table matches. If the flop, matches, the header information of the response packet, and generates the converted response packet rewrites the predetermined header information, comprising the steps of: transmitting the converted response packet to the client.

  ADVANTAGE OF THE INVENTION According to this invention, the load distribution system which can maintain the identity with the port number contained in the request packet received from a client and the port number contained in the response packet transmitted to a client can be provided. Therefore, it can be prevented that the response packet received by the client is regarded as an illegal packet and reception is rejected.

It is a figure which shows the structure of the load distribution system in this embodiment. It is a functional block diagram which shows the structure of the load distribution apparatus 3 in this embodiment. It is a figure which shows address table A311 in this embodiment. It is a figure which shows address table B324 in this embodiment. It is a figure which shows the flow of the packet transmitted / received in the load distribution system of this embodiment, and header information. It is an operation | movement flow of the load distribution apparatus which received the request packet from the client 1 in this embodiment. It is an operation | movement flow of the synchronization process of the address table by the load distribution apparatus 3 in this embodiment. It is an operation | movement flow when the load distribution apparatus 3 in this embodiment receives a response packet from the transfer destination DHCP server.

  A load distribution system according to an embodiment of the present invention will be described below with reference to the accompanying drawings. The load distribution system according to the present embodiment will be described on the assumption that load distribution processing is performed on a DHCP (Dynamic Host Configuration Protocol) server.

[Description of configuration]
First, the configuration of the load distribution system in the present embodiment will be described. FIG. 1 is a diagram illustrating a configuration of a load distribution system according to the present embodiment. The load distribution system of this embodiment includes a client 1, the Internet 2, a load distribution device 3, and a DHCP server group 4.

  The client 1 is an information terminal such as a personal computer (hereinafter, PC). The client 1 is connected to the Internet 2 and can communicate on the Internet using a network protocol such as TCP / IP (Transmission Control Protocol / Internet Protocol). Note that the client 1 may be connected to the Internet 2 via a proxy (proxy) server having a DHCP relay agent function or a network router. In this case, the proxy server or the network router transfers communication from the subordinate client 1 to the Internet 2. The client 1 transmits a request packet to the DHCP server group 4. The request packet includes a destination IP address, a source IP address, a destination port number, and a source port number.

  The Internet 2 connects the client 1 and the load balancer 3. The Internet 2 transfers communication between the client 1 and the load balancer 3. In the present embodiment, the client 1 and the load balancer 2 are connected by the Internet 2. However, the network that connects the client 1 and the load balancer 2 is not limited to the Internet 2 and may be connected using another alternative network.

  The DHCP server group 4 includes DHCP servers 41 to 43. In the present embodiment, there are three DHCP servers, but this is an example, and the number of DHCP servers is not limited to three. When receiving the request packet from the client 1, the DHCP servers 41 to 43 perform predetermined processing to generate a response packet and transmit the response packet to the client 1. Here, the predetermined process is a process of assigning an arbitrary IP address to the client 1 in response to a request from the client 1. Since such an IP address assignment process by the DHCP server is a well-known technique, a detailed description thereof will be omitted. Communication between the load balancer 3 and the DHCP servers 41 to 43 of the DHCP server group 4 is transferred by a network switch (not shown). In addition, arbitrary private addresses are set in advance in the DHCP servers 41 to 43.

  The load distribution device 3 performs load distribution processing for communication performed between the client 1 and the DHCP server group 4. When the load distribution device 3 receives a request packet from the client 1 via the Internet 2, an arbitrary one of the DHCP servers 41 to 43 of the DHCP server group 4 is referred to as a transfer destination (hereinafter referred to as a transfer destination DHCP server). And select to forward the request packet. When receiving a response packet for the request packet from the transfer destination DHCP server, the load balancer 3 transfers the response packet to the client 1.

  The configuration of the load distribution apparatus 3 in this embodiment will be described with reference to FIG. FIG. 2 is a functional block diagram showing the configuration of the load distribution device 3 in the present embodiment. The load distribution apparatus 3 includes a load distribution unit 31, a relay conversion unit 32, a communication unit A33, and a communication unit B34.

  The load distribution unit 31 receives a request packet from the client 1 and performs load distribution processing. When receiving the request packet from the client, the load distribution unit 31 selects one transfer destination DHCP server from among the DHCP servers 41 to 43 of the DHCP server group 4 by a predetermined method. The predetermined method for the load balancer 31 to select the transfer destination DHCP server from the DHCPs 41 to 43 is based on a well-known technique, and thus the description thereof is omitted here. When selecting the transfer destination DHCP server, the load distribution unit 31 rewrites the header of the request packet by using a NAT (Network Address Translation) function. The load distribution unit 31 rewrites the destination IP address of the request packet with the IP address of the transfer destination DHCP server, sets a port number arbitrarily assigned to the destination port number of the request packet, and transmits the port number to the transfer destination DHCP server. The load distribution unit 31 determines port numbers corresponding to the DHCP servers 41 to 43 in advance, and sets a port number corresponding to the transfer destination DHCP server selected from the DHCP servers 41 to 43 in the request packet. There is a case. In the following, for the purpose of distinction, a request packet whose header has been rewritten by the load distribution unit 31 is referred to as a transfer request packet.

  The load distribution unit 31 includes an address table A311. When transferring the transfer request packet to the transfer destination DHCP server, the load distribution unit 31 records the header information of the transfer request packet in the address table A311. FIG. 3 is a diagram showing the address table A311 in the present embodiment. The load distribution unit 31 records the destination IP address, source IP address, destination port number, and source port number of the transfer request packet in the address table A311. Hereinafter, the destination IP address, the source IP address, the destination port number, and the source port number may be collectively referred to as header information.

  The relay conversion unit 32 receives the response packet from the DHCP servers 41 to 43, converts the header information of the response packet, and transfers the converted response packet (hereinafter referred to as “converted response packet”) to the client 1. The relay conversion unit 32 includes a synchronization unit 322, a packet inspection unit 321, and a conversion unit 323.

  The synchronization unit 322 includes an address table B324. FIG. 4 is a diagram showing the address table B324 in the present embodiment. The synchronization unit 322 acquires the header information of the transfer request packet recorded in the address table A311 of the load distribution unit 31, and records it in the address table B324. When the header information of the transfer request packet is recorded in the address table B324, the synchronization unit 322 switches the destination and the transmission source and records them. That is, the synchronization unit 322 records the destination IP address and destination port number of the transfer request packet recorded in the address table A311 as the source IP address and source port number in the address table B324. In addition, the synchronization unit 322 records the transmission source IP address and the transmission source port number of the transfer request packet recorded in the address table A311 as the destination IP address and the destination port number in the address table B324.

  The packet inspection unit 321 performs a match determination on the response packet. The packet inspection unit 321 inputs a response packet from the DHCP servers 41 to 43 of the DHCP server group 4 via the communication unit 34. The packet inspection unit 321 refers to the header information of the response packet and the header information of the transfer request packet recorded in the address table B 324 of the synchronization unit 322, and sets the header information of the transfer request packet recorded in the address table B 324. Then, it is determined whether there is information that matches the header information of the response packet. Specifically, the packet inspection unit 321 refers to the transmission source IP address and transmission source port number included in the header of the response packet, and refers to the transmission source IP address of the header information of the transfer request packet recorded in the address table B324. Then, it is determined whether there is information that matches the source port number.

  When the packet inspection unit 321 determines that there is information that matches the header information of the response packet in the information recorded in the address table B 324 in the match determination, the conversion unit 323 performs a conversion process of the header information of the response packet. . Specifically, the conversion unit 323 converts the transmission source IP address and the transmission source port number included in the header of the response packet into the IP address of the load balancer and the port number “67” indicating the DHCP server. I do. The conversion unit 324 outputs a response packet after conversion of header information (hereinafter referred to as a converted response packet) to the communication unit 322.

  The communication unit A33 and the communication unit B34 perform packet transmission / reception. The communication unit A33 is set with a global IP address. The communication unit A33 can communicate with the client 1 via the Internet 2 using a global IP address. The communication unit A33 receives the request packet from the client 1 and outputs it to the load distribution unit 31. The communication unit A33 receives the converted response packet from the relay conversion unit 32 and transmits it to the client 1. The communication unit B34 is set with a private IP address. The communication unit B34 can communicate with the DHCP servers 41 to 43 of the DHCP server group 4 using a private IP address. The communication unit B 34 receives the transfer request packet from the load distribution unit 31 and transmits it to the transfer destination DHCP server among the DHCP servers 31 to 34 of the DHCP server group 4. Further, the communication unit B34 receives the response packet from the transfer destination DHCP server and outputs the response packet to the relay conversion unit 32.

  The above is description of the structure of the load distribution system in this embodiment.

[Description of operation method]
Next, the operation method of the load distribution system in this embodiment will be described with reference to FIGS. First, an operation method when the load distribution apparatus 3 according to the present embodiment receives a request packet from the client 1 will be described with reference to FIGS. 2, 3, 5, and 6. FIG. 5 is a diagram showing a flow of packets transmitted and received and header information in the load balancing system of the present embodiment. FIG. 6 is an operation flow of the load distribution apparatus that has received a request packet from the client 1 in this embodiment.

(Step S10)
The client 1 transmits a request packet. The request packet is a packet for making an IP address assignment request from the DHCP client to the DHCP server. In this embodiment, the client 1 is set to “terminal IP” as a global IP address for the Internet. The client 1 sets “terminal IP” as the source IP address of the request packet and “68” indicating the DHCP client as the source port number. In the present embodiment, the load balancer 3 sets “VIP” as the global IP address for the Internet. The client 1 sets “VIP” as the destination IP address of the request packet, and sets “67” indicating the DHCP server as the destination port. The header information 100 in FIG. 5 indicates the header information of the request packet set in this way. The client 1 transmits a request packet to the load balancer 3 via the Internet 2. The Internet 3 transfers the request packet transmitted from the client 1 to the load balancer 3.

(Step S20)
The load distribution unit 31 arbitrarily selects a transfer destination DHCP server from the DHCP server group 4. The communication unit A33 of the load balancer 3 receives the request packet transmitted from the client via the Internet 2. The communication unit A33 outputs the request packet to the load distribution unit 31. When receiving the request packet, the load distribution unit 31 arbitrarily selects a transfer destination DHCP server from among the DHCP servers 41 to 43 of the DHCP server group 4. In the following description, it is assumed that the load distribution unit 31 has selected the DHCP server 41 as the transfer destination DHCP server. Note that an operation method by which the load distribution unit 31 selects the transfer destination DHCP server is based on a well-known technique, and a description thereof will be omitted.

(Step S30)
The load distribution unit 31 records header information of the transfer request frame. When selecting the transfer destination DHCP server, the load distribution unit 31 performs NAT conversion using the IP address of the transfer destination DHCP server. The DHCP servers 41 to 43 set “DHCP # 1 to # 3”, respectively, as private IP addresses for the local network. The load distribution unit 31 converts the destination IP address of the request packet from “VIP” to “DHCP # 1”. Further, the load distribution unit 31 converts the destination port number of the request packet from “67” to “Port A” arbitrarily selected. The load distribution unit 31 converts the header information of the request packet in this way, and generates a transfer request packet. The header information 101 in FIG. 5 indicates the header information of the transfer request packet set in this way. If the load distribution unit 31 selects the DHCP server 42 as the transfer destination server, the transfer request packet sets the destination port number “PortB” with the destination IP address “DHCP # 2”. If the load balancer 31 selects the DHCP server 43 as the transfer destination server, the transfer request packet sets the destination IP address “DHCP # 3” and the destination port number “PortC”. Here, “Port A to C” may be arbitrarily selected by the load distribution unit 31, or the port numbers corresponding to the DHCP servers 41 to 43 may be determined in advance. The load distribution unit 31 records the header information of the transfer request packet in the address table A311. In this description, the load distribution unit 31 selects the DHCP server 41 as the transfer destination DHCP server, and the header information recorded in the address table A311 is as shown in FIG. The load distribution unit 31 transmits the transfer request packet to the DHCP server 41 via the communication unit B34.

(Step S40)
The transfer destination DHCP server executes a predetermined process. The DHCP server 41 that is the transfer destination DHCP server receives the transfer request packet from the load balancer 3. The DHCP server 41 executes a predetermined IP address assignment process based on the transfer request packet. Note that the IP address assignment processing by the DHCP server is based on a well-known technique, and thus description thereof is omitted.

  The above is the description of the operation method of the load distribution system in the present embodiment.

  Next, using FIG. 2, FIG. 3, FIG. 4, and FIG. 7, the operation method of the address table synchronization processing by the load balancer 3 in this embodiment will be described. FIG. 7 is an operation flow of address table synchronization processing by the load balancer 3 according to this embodiment.

(Step S100)
The synchronization unit 322 synchronizes the address table A311 and the address table B324. The synchronization unit 322 of the relay conversion device 32 of the load distribution device 3 periodically performs synchronization processing between the address table A 311 and the address table B 324 to make the data in the address table A 311 and the address table B 324 coincide. The synchronization unit 322 replaces the destination IP address and the destination port number with the transmission source IP address and the transmission source port number when performing synchronization processing between the address table A311 and the address table B324. FIG. 3 shows the address table A311 in which the request packet from the client 1 is recorded as described above. The address table A311 in FIG. 3 records “terminal IP” as the source address, “68” as the source port number, “DHCP # 1” as the destination IP address, and “PortA” as the destination port number. is doing. FIG. 4 described above is the address table B324 after the synchronization unit 322 performs the synchronization process. The address table B324 of FIG. 4 records “DHCP # 1” as the source address, “Port A” as the source port number, “terminal IP” as the destination IP address, and “68” as the destination port number. is doing. As described above, the synchronization unit 322 performs recording by switching the destination and source records of the address table A311 and the address table B324.

  The above is the description of the operation method of the address table synchronization processing by the load balancer 3 in the present embodiment.

  Next, an operation method when the load distribution apparatus 3 according to the present embodiment receives a response packet from the transfer destination DHCP server will be described with reference to FIGS. 2, 4, 5, and 8. FIG. 8 is an operation flow when the load distribution apparatus 3 according to the present embodiment receives a response packet from the transfer destination DHCP server.

(Step S200)
The transfer destination DHCP server transmits a response packet. The DHCP server 41 serving as the transfer destination DHCP server transmits a response packet toward the client 1 when the predetermined processing is completed. The DHCP server 41 sets “DHCP # 1” as the source IP address of the response packet, “Port A” as the source port number, “terminal IP” as the destination IP address, and “68” as the destination port number. Set and send. The DHCP server 41 receives the packet converted by the load balancer 31, and when transmitting a response packet, the IP address set in the own node (DHCP server 41) and the designated port number are respectively Set as the sender. The data included in the response packet includes an IP address assigned to the client 1 and the like, which are conventional techniques and will not be described. The header information 102 in FIG. 5 indicates the header information of the transfer request packet set in this way. If the transfer destination server is the DHCP server 42, the response packet sets the transmission source IP address “DHCP # 2” and the transmission source port number “Port B”. If the transfer destination server is the DHCP server 43, the response packet sets the source IP address “DHCP # 3” and the source port number “PortC”.

(Step S210)
The packet inspection unit 321 performs a match determination on the header information of the response packet. The communication unit B34 of the load distribution apparatus 3 receives the response packet from the DHCP server 41 that is the transfer destination DHCP server. The communication unit B34 outputs the response packet to the packet inspection unit 321. The packet inspection unit 321 performs a match determination using the header information of the response packet and the data recorded in the address table B324. Specifically, the packet inspection unit 321 determines whether data matching the transmission source IP address and the transmission source port number included in the header information of the response packet is recorded in the address table B324.

(Step S220)
If it is determined in the match determination by the packet inspection unit 321 that they match, the process proceeds to step S240. On the other hand, if it is determined that they do not match, the process proceeds to step S230. In this embodiment, the header information of the response packet received from the transfer destination DHCP server has “DHCP # 1” set as the source IP address and “Port A” set as the source port number. The packet inspection unit 321 can detect the data recorded as the transmission source IP address “DHCP # 1” and the transmission source port number “PortA” with reference to the address table B324. Therefore, the packet inspection unit 321 determines that they match.

(Step S230)
The synchronization unit 322 synchronizes the address table A311 and the address table B324. When it is determined in the match determination by the packet inspection unit 321 that they do not match, the synchronization unit 322 synchronizes the address table A 311 and the address table B 324. This is because there may still be data that is not reflected in the address table B324. In this case, when the synchronization between the address table A311 and the address table B324 is completed, the process returns to step S210. Even if the synchronization unit 322 performs the synchronization process again in this way, there may be a case where the match determination does not match. In that case, for example, an operation of transmitting to the destination IP address via the communication unit A33 without performing a conversion process on the packet described later may be performed, or an operation of discarding the packet may be performed. This is because the load balancer 3 may receive a packet other than the response packet from the local network side.

(Step S240)
The conversion unit 323 converts the header information of the response packet. The conversion unit 323 converts the header information of the response packet when it is determined that they match in the match determination by the packet inspection unit 321. Specifically, the conversion unit 323 sets the source IP address and the source port number included in the header information of the response packet, the global IP address “VIP” set in the load balancer 3, and the port indicating the DHCP server. The number is converted to “67”. In the present embodiment, “DHCP # 1” is set as the transmission source IP address of the response packet, and “Port A” is set as the transmission source port number. The conversion unit 323 converts the transmission source IP address from “DHCP # 1” to “VIP” and the transmission source port number from “Port A” to “67”. In this way, when the header information of the received response packet matches the header information of the transfer request packet, the conversion unit 323 converts the header information of the response packet to generate a converted response packet.

(Step S250)
The conversion unit 323 transmits the response packet after conversion. The conversion unit 323 transmits the generated response packet after conversion to the client 1 via the communication unit A33. The header information 103 in FIG. 5 indicates header information of the response packet after conversion transmitted from the load balancer 3. As can be understood by comparing with the header information 100 of the request packet, the destination IP address and destination port number of the request packet match the source IP address and source port number of the response packet after conversion. Therefore, when the client 1 receives the conversion number response packet, the client 1 can detect that the packet is a response from the DHCP server to the request transmitted as a DHCP client.

  The above is the description of the operation method when the load distribution apparatus 3 according to the present embodiment receives a response packet from the transfer destination DHCP server.

Up to this point, the present embodiment has been described. According to the load distribution system of the present invention, when receiving a request packet from the client 1, the load distribution unit 31 of the load distribution apparatus 3 assigns a transfer destination DHCP server from among a plurality of DHCP servers, and header information of the request packet. To generate a transfer request packet. When transmitting the transfer request packet, the load distribution unit 31 records the header information of the transfer request packet in the address table A311. The relay conversion unit 32 of the load distribution device 3 performs synchronization processing between the address table A 311 and the address table B 324 in advance to match the recorded data. When the relay conversion unit 32 receives the response packet from the transfer destination DHCP server, the relay conversion unit 32 determines whether the header information of the response packet matches the data recorded in the address table B324. When the relay conversion unit 32 determines that they match in the match determination, the relay conversion unit 32 converts the header information of the response packet, generates a converted response packet, and transmits the response packet to the client. Therefore, the source IP address and source port number of the converted response packet transmitted from the load balancer 31 to the client 1 match the destination IP address and destination port number of the request packet transmitted from the client 1. Can be made.

  Although the present embodiment has been described as a load distribution system for a plurality of DHCP servers, the present invention can also be applied as a load distribution system for a DNS or other servers, for example. In this case, the transmission source port number after conversion by the relay conversion unit 32 may be a port number corresponding to the type of the server system. Alternatively, the relay conversion unit 32 may convert the source port number of the response packet into the destination port number of the request packet.

  Moreover, although the load distribution unit 31 and the relay conversion unit 32 have been described as configurations included in the load distribution device 3, they may be installed as independent devices. In this embodiment, the destination IP address and destination port number of the transfer request packet and the source IP address and source port number of the response packet are targeted for matching. The source IP address and source port number of the request packet and the destination IP address and destination port number of the response packet may be included in the match determination target.

  The present invention has been described above with reference to the embodiment. However, the present invention is not limited to the above embodiment, and the configuration and details of the present invention will be understood by those skilled in the art within the scope of the present invention. Various changes can be made.

1 Client 2 Internet 3 Load Balancing Device 4 DHCP Server Group 31 Load Balancing Unit 32 Relay Conversion Unit 33 Communication Unit A
34 Communication Department B
41 DHCP server 42 DHCP server 43 DHCP server 100 Header information 101 Header information 102 Header information 103 Header information 311 Address table A
321 Packet inspection unit 322 Synchronization unit 323 Conversion unit 324 Address table B

Claims (15)

Multiple servers,
Selecting a transfer destination server from the plurality of servers, generating a transfer request packet in which header information of a request packet received from a client is rewritten to header information indicating the transfer destination server, and The load balancer to transmit to the transfer destination server;
A relay conversion unit that transfers a response packet from the transfer destination server to the client terminal;
With
The load distribution unit stores the header information of the transfer request packet in a first address table;
The relay conversion unit
A synchronization unit that obtains header information of the transfer request packet from the first address table and records it in a second address table;
When the response packet is received, a packet inspection unit that determines whether header information of the response packet matches header information recorded in the second address table;
If they match, a conversion unit that rewrites the header information of the response packet to predetermined header information to generate a converted response packet, and transmits the converted response packet to the client;
A load balancing system comprising: The load distribution system according to claim 1,
The header information includes a destination IP (Internet Protocol) address, a destination port number, a source IP address, and a source port number.
The packet inspection unit determines whether the source IP address information and the source port number in the header information of the response packet match the destination IP address of the transfer request packet and the destination port number. system. The load distribution system according to claim 2,
The synchronization unit records the destination IP address and the destination port number recorded in the first address table in the second address table as a source IP address and a source port number, and stores them in the first address table. Record the recorded source IP address and source port number as the destination IP address and destination port number in the second address table,
The packet inspection unit determines whether the source IP address information and the source port number in the header information of the response packet match the source IP address recorded in the second address table and the source port number. A load balancing system that determines whether The load distribution system according to claim 2 or claim 3,
The load distribution unit sets an arbitrary port number as a destination port number of the transfer request packet. The load distribution system according to claim 2 or claim 3,
Each of the plurality of servers is assigned a unique designated port number;
The load distribution unit sets the designated port number of the transfer destination server as a destination port number of the transfer request packet. The load distribution system according to any one of claims 1 to 5,
The plurality of servers are DHCP (Dynamic Host Configuration Protocol) servers.
Load balancing system. The load distribution system according to claim 6,
The conversion unit sets a port number indicating a DHCP server as a transmission source port number of the converted response packet.   A load distribution apparatus comprising a load distribution unit and a relay conversion unit used in the load distribution system according to any one of claims 1 to 7. Multiple servers,
Selecting a transfer destination server from the plurality of servers, generating a transfer request packet in which header information of a request packet received from a client is rewritten to header information indicating the transfer destination server, and The load balancer to transmit to the transfer destination server;
A relay conversion unit that transfers a response packet from the transfer destination server to the client terminal;
In a load balancing system comprising:
Storing header information of the transfer request packet in a first address table;
Obtaining header information of the transfer request packet from the first address table and recording it in a second address table;
Receiving the response packet, determining whether the header information of the response packet matches the header information recorded in the second address table;
If they match, the header information of the response packet is rewritten into predetermined header information to generate a converted response packet, and the converted response packet is sent to the client;
A load balancing method comprising: The load distribution method according to claim 9, wherein
The header information includes a destination IP address, a destination port number, a source IP address, and a source port number,
The step of determining whether or not the header information matches,
A load balancing method comprising: determining whether a source IP address information and a source port number in header information of the response packet match a destination IP address and a destination port number of the transfer request packet. The load distribution method according to claim 10, wherein
Recording in the second address table comprises:
The destination IP address and destination port number recorded in the first address table are recorded in the second address table as a source IP address and source port number, and the source recorded in the first address table Recording the IP address and the source port number in the second address table as the destination IP address and the destination port number,
The step of determining whether or not the header information matches,
Determining whether the source IP address information and the source port number in the header information of the response packet match the source IP address recorded in the second address table and the source port number; Including load balancing method. The load distribution method according to claim 10 or 11,
A load distribution method further comprising: setting an arbitrary port number as a destination port number of the transfer request packet. The load distribution method according to claim 10 or 11,
Each of the plurality of servers is assigned a unique designated port number;
The load distribution method further comprising: setting the designated port number of the transfer destination server to the destination port number of the transfer request packet. A load distribution method according to any one of claims 9 to 13, wherein
The plurality of servers are DHCP servers;
Load balancing method. The load distribution method according to claim 14,
Sending to the client comprises:
A load distribution method comprising: setting a port number indicating a DHCP server as a transmission source port number of the response packet after conversion.

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