JP3948492B2 - Setting information allocation method for external network connection - Google Patents

Description

  The present invention relates to improvement of network communication availability in a client server system connectable to the Internet, which is an external network.

  FIG. 13 is a basic configuration diagram of a network system constructed by a client server system that enables access to the Internet. In FIG. 13, a gateway (GW) 4 connected to the Internet 1 via a communication line 3, a DHCP (Dynamic Host Configuration Protocol) server 5, and one or more clients 6 accessing the Internet 1 are connected to the LAN. A configuration connected to (Local Area Network) 7 is shown.

  In this configuration, the client 6 transmits an IP address assignment request to the DHCP server 5 when accessing the Internet 1. In response to the IP address assignment request, the DHCP server 5 assigns an IP address to the client 6 and sends it back together with the known gateway 4 address. The client 6 specifies the gateway 2 that requests connection to the Internet 1 based on the information sent from the DHCP server 5, and uses the IP address assigned by the DHCP server 5 to determine the gateway 4 and the communication line 3. The Internet 1 is accessed via the Internet.

  In general, the number of clients 6 connected to the LAN 7 tends to increase. However, as the number of clients 6 increases, the load on each device inevitably increases. The network administrator usually increases the load by increasing the communication capability such as making the communication line 3 a dedicated line, improving the processing performance of the server 5 and the gateway 4, or installing various proxy servers. Try to deal with it. Alternatively, the LAN 7 is segmented, and the communication line 3, the gateway 4, and the server 5 shown in FIG. 5 are separately prepared for each divided LAN.

  Here, in the case of a system configuration in which a plurality of gateways 4 and DHCP servers 5 are connected to the LAN 7, processing until the client 6 acquires the IP address and the address of the gateway 4 will be described in detail.

  A client 6 that has not yet acquired an IP address broadcasts a DHCPDISCOVER message. All of the DHCP servers 5 receive this message, and one or more DHCP servers 5 programmed to respond to the client 6 return a DHCPOFFER message to the client 6. This DHCPOFFER message includes the IP address to be assigned, the gateway 4 address, and the IP address lending period. The client 6 collects response DHCPOFFER messages from the DHCP server 5 and selects one of them. Then, a DHCPREQUEST message is transmitted to the corresponding DHCP server 5. The DHCP server 5 responds by sending DHCPACK in order to start lending an IP address in response to the sent DHCPREQUEST message. In this way, the client 6 can access the Internet 1 using the assigned IP address and the gateway 4.

  Incidentally, in DHCP, the IP server lending period (lease period) is set by the DHCP server 5, and the IP address cannot be used after the lending period. The control right for lending resides in the DHCP server 5. Therefore, the client 6 who wants to continue accessing the Internet 1 requests extension by transmitting a DHCPREQUEST message to the rented DHCP server 5. The DHCP server 5 transmits DHCPACK in the case where the continuation of use is approved according to the sent DHCPREQUEST message. In this way, the client 6 can access the Internet 1 using the assigned IP address and the gateway 4 continuously.

  If the DHCP server 5 does not approve the continued use of the IP address, a DHCPNACK is transmitted. Since the client 6 that has received DHCPPNACK cannot use the IP address in use after the lending period, the client 6 returns to the initial state, that is, the state in which the IP address has not been acquired. Therefore, as described above, the client 6 broadcasts the DHCPDISCOVER message and acquires an IP address again.

  When there is no response from the DHCP server 5 that has lent out the transmitted DHCPREQUEST message, the DHCP server 5 broadcasts the DHCPREQUEST message on the assumption that the DHCP server 5 is stopped or unreachable. As a result, the IP address and gateway address are acquired from the new DHCP server 5.

  However, conventionally, a DHCP server is selected when a client accesses the Internet. That is, since the IP address and the gateway are determined by the client, it is difficult for the DHCP server side to take measures against the gateway failure and adjust the network load.

  If the DHCP server does not approve the continuous use of the IP address when it is desired to continue accessing the Internet, the IP address can be acquired from another DHCP server, but the IP address to be used Will be changed. There has been a risk of hindering the ongoing communication with the change of the IP address.

  The present invention has been made to solve the above problems, and its purpose is to suitably assign setting information necessary for connection with an external network such as an IP address and a gateway address to a client. Another object of the present invention is to provide a setting information allocation method for connecting to an external network.

  A setting information allocation method for external network connection according to the present invention is executed by a DHCP server, and at least a gateway according to an allocation request from a client connected to an external network via any one of a plurality of gateways In the setting information allocation method that generates and returns the setting information including the location information of the gateway, the gateway location information is set so that the gateway is sequentially allocated to each client in the setting information returned in response to the allocation request from the client. It is characterized by.

  A setting information allocation method for external network connection according to another invention is executed by a DHCP server in response to an allocation request from a client connected to an external network via any one of a plurality of gateways. In the setting information allocation method for generating and returning setting information including at least gateway location information, an analysis step for analyzing the allocation request from the received client and the client based on the client-specific information included in the allocation request A confirmation step for confirming whether the setting information is already assigned to the client from the setting information correspondence table holding the setting information assigned to the client, and the setting information when the setting information is assigned to the client. Gate whose location information is included in the information A setting information generation step for including location information of other connectable gateways in the setting information when a connection with an external network cannot be made via the gateway, and a transmission step for transmitting the generated setting information to the client. It is characterized by including.

  According to the present invention, the communication line connecting the client and the external network is multiplexed, and the communication path to be connected to the external network is dynamically determined and can be connected. Alternatively, even if an abnormality occurs in the communication line, the client can access the external network through another communication path.

  In addition, since the communication path for connecting the client to the external network is not fixed, load distribution can be performed according to the load status of each server.

  In addition, since the communication address once assigned to the client can be repeatedly used, there is no possibility that a failure that may occur due to the dynamic switching of the communication address occurs.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same component as a prior art example.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a client server system that implements a setting information allocation method for external network connection according to the present invention. The client server system in the present embodiment has a configuration in which one server 10, two gateways 18 and 28, and a plurality of clients 6 are connected to a LAN 7. Except for the server 10, the same device as the conventional example may be used. Each client 6 can access the Internet 1 via one of the gateways 18 and 28. The client 6 only needs to have a function as a general-purpose DHCP client, and a function specific to this embodiment is not necessary.

  The server 10 is a server having a function equivalent to that of a conventional DHCP server, and has a processing function for dynamically assigning an IP address corresponding to DHCP. However, as will be apparent from the processing described later, the contents of the IP address assignment processing are different. The server 10 in this embodiment includes an address assignment processing unit 11, a communication path monitoring unit 13, and an address correspondence table 14. The address assignment processing unit 11 has a function equivalent to a DHCP server, and executes an address assignment process for assigning an IP address or the like to the client 6 in response to an IP address assignment request from the client 6. The communication path monitoring unit 13 is in a state of each network path formed via the gateway 18, the communication line 19 or the gateway 28, and the communication line 29 through which the client 6 accesses the Internet 1 (connection possible / impossible). To monitor.

  FIG. 2 is a diagram showing a data configuration example of the address correspondence table 14 in the present embodiment. The address correspondence table 14 holds address correspondence information in which a MAC address, an IP address, a basic GW address, and a used GW address are associated with each other. The MAC address is a client identification address uniquely assigned to each client 6. The IP address is a communication address dynamically assigned to the client 6. The basic GW address is an address of the gateways 18 and 28 newly assigned to the client 6 that has not acquired an IP address. This can be said to be an initial value in each client 6. The used GW address is an address of a gateway actually used by the client 6.

  What is characteristic in this embodiment is that the IP address used by the client 6 and the gateways 18 and 28 can be determined by the server. This characteristic address assignment processing is shown in FIG. This will be described with reference to a sequence diagram.

  First, FIG. 3 shows a communication sequence between the server 10 and the two clients 6. Assume that the MAC addresses of the clients A and B are X and Y, respectively, and that no IP address has been acquired at the present time.

  First, the client A needs to acquire an IP address in order to access the Internet 1, and for this purpose, sends an IP address assignment request (DHCPDISCOVER message) to the server 10 (S1). Although it broadcasts correctly, in this example, since there is only one server, only the server 10 receives it. The address assignment processing unit 11 of the server 10 confirms whether or not an IP address is assigned to the client A by referring to the address correspondence table 14 based on the MAC address X of the client A included in the IP address assignment request. To do. Here, since it is an explanation when the IP address is not acquired, the address assignment processing unit 11 obtains an unassigned IP address that is not registered in the address correspondence table 14 and assigns it to the client A. Further, the address assignment processing unit 11 determines one gateway used by the client A among the GW1 and GW2. Further, the address allocation processing unit 11 acquires a basic lease period (default value) as the lease period of the IP address. In this way, setting information including the acquired IP address, GW address as connection information, and lease period is generated. Then, the generated setting information (DHCPOFFER message) is transmitted to the client A (S2). FIG. 3 shows an example in which IP address P is assigned to client A, GW1 is used, and setting information with a lease period of 12 hours (basic lease period) is transmitted. The period during which the setting information assigned to the client 6 is valid (assignment period) is synonymous with the lease period of the IP address set in the setting information.

  In response to the DHCPOFFER message sent from the server 10, the client A transmits a DHCPREQUEST message to identify the server 10 according to DHCP (S3). The server 10 returns DHCPACK in order to start lending the IP address in response to the sent DHCPREQUEST message (S4). In this way, the client A can access the Internet 1 using the assigned IP address and the gateway 18. Further, after transmitting DHCPACK, the server 10 sets the address of the gateway 18 assigned by the above processing as both the basic GW address and the used GW address in the address correspondence table 14 (S5).

  Also for the client B, the address assignment processing unit 11 can cause the client B to start accessing the Internet 1 by performing exactly the same processing as the client A (S6 to S10). However, setting information having contents different from those of the client A is generated. That is, it is natural to assign a different IP address Q, but GW2 is assigned as a gateway to be used for client B, which is the target of IP address assignment following client A. This is because the address allocation processing unit 11 acts to sequentially allocate the gateways 18 and 28 to the clients 6 that issued the allocation request. Therefore, GW2 following GW1 is assigned to client B. As described above, since the clients 6 can be distributed almost equally to the gateways 18 and 28, the load applied to the gateways 18 and 28 can be made substantially equal. The lease period for client B is a basic lease period (12 hours).

  Here, it is assumed that the communication path monitoring unit 13 of the server 10 detects that a failure has occurred in the gateway 18 (S11). More precisely, the communication path monitoring unit 13 detects that connection to the Internet 1 cannot be made via the gateway 18 due to a failure of the gateway 18 itself, disconnection of the communication line 19, or the like.

  Thereafter, when a DHCPREQUEST message is sent from the client A to request extension of use of the IP address, or a DHCPDISCOVER message is sent to acquire the IP address again after the use is finished, it is omitted in FIG. (S12) The address assignment processing unit 11 generates setting information in response to the assignment request. If the gateway 18 assigned to the client A is normal in the case of the assignment request by extension use, the IP address already assigned to the client A and the address of the gateway 18 are obtained by referring to the address correspondence table 14. Setting information including the IP address, GW address, and lease period may be generated and transmitted to the client A. However, when the gateway 18 is stopped as in this example, the address assignment processing unit 11 acquires information as follows to generate setting information. First, for an IP address, an assigned IP address is acquired from the address correspondence table 14. In addition, as a gateway serving as a network route to the Internet 1, the address of the GW 2 that is operating normally is acquired. As the lease period, a time (1 hour) shorter than the basic lease period is set. Setting information including such information is generated and transmitted to the client A (S13). As a result, the client A can switch to the GW 2 that can be used by the server 10 even when a failure occurs in the assigned GW 1, and can continue to access the Internet 1. Similarly, in the case of reacquiring the IP address, access to the Internet 1 can be started without being affected by the failure of the GW 1.

  When the transmission of the setting information is completed, the address assignment processing unit 11 updates the use GW address of the client A set in the address correspondence table 14 from the address GW1 to the address GW2 (S14).

  Thereafter, after the communication path monitoring unit 13 of the server 10 detects that the gateway 18 has been restored (S15), when a DHCPREQUEST message is sent from the client A for a request to extend the use of the IP address (S16), In response to the allocation request, the address allocation processing unit 11 generates setting information as follows. That is, the address assignment processing unit 11 acquires the IP address and the basic GW address by referring to the address correspondence table 14 because the gateway 18 that is the basic GW address assigned to the client A is operating normally. . Setting information including a basic lease period as the acquired IP address, GW address, and lease period is generated. Then, the setting information is transmitted to the client A (S17). Thereafter, the address assignment processing unit 11 updates the used GW address of the client A set in the address correspondence table 14 from the GW2 to the GW1 address (S18).

  As described above, according to the present embodiment, when connection to the Internet 1 cannot be made via the gateway 18 initially assigned to the client A, it can be continuously used by allocating the GW 2 during extended use. When GW1 is restored, GW1 is returned instead of continuing to use GW2 during extended use. As described above, the server 10 assigns GW1 to the client A in consideration of load distribution at the time of initial setting. Therefore, if the GW 1 is restored during the extended use, the load distribution applied to the gateways 18 and 28 can be maintained by returning to the original GW 1. As described above, in the present embodiment, the gateways 18 and 28 initially assigned to the client 6 in consideration of load distribution are used as basic gateways that are normally used, and gateways that are used when the basic gateway cannot be used due to a failure. Is positioned as a substitute gateway during the failure occurrence period.

  Furthermore, in the present embodiment, the lease period set in the setting information together with the substitute gateway is set to be shorter than the basic lease period. Thereby, when the basic gateway is restored, the gateway to be used can be returned to the basic gateway earlier, and the time when the load is uneven can be shortened. In order to obtain this effect more, it is desirable to set a shorter lease period to be set together with the substitute gateway in the setting information. Therefore, in this embodiment, 1 hour, which is the minimum settable time, is set for the substitute gateway. Although set as the lease period, this set time is not necessarily set to 1 hour.

Embodiment 2. FIG.
FIG. 4 is a diagram showing a communication sequence between the server and two clients in the present embodiment. The same processes as those in FIG. 3 are denoted by the same reference numerals, and description thereof is omitted as appropriate.

  In the first embodiment, when the GW 1 cannot be used due to a failure or the like, the client A approaches the lease period (more precisely, when 50% of the lease period has elapsed) and transmits a DHCPREQUEST message (allocation request). (S12). Until then, an error occurs when accessing the Internet 1 and some action is required. Therefore, the present embodiment is characterized in that if the communication path monitoring unit 13 detects that a failure has occurred in the gateway 18 (S11), it notifies the client 6 to that effect at that time. .

  That is, when the failure of the gateway 18 is detected, the address allocation processing unit 11 broadcasts that fact to the client 6 (S19). Since the message for broadcasting is not prepared in DHCP, in the present embodiment, broadcasting is performed assuming a DHCPNOTICE message. In this embodiment, a DHCPNOTICE message is broadcast. However, since the client 6 using GW1 is apparent from the GW address used in the address correspondence table 14, it should be transmitted individually only to the corresponding client 6. Also good.

  Upon receiving the DHCPNOTICE message, the client A to which GW1 has been allocated transmits a DHCPREQUEST message (allocation request) regardless of the elapsed time of the lease period (S12). Thereby, the GW 2 is assigned by the procedure described in the first embodiment, and the Internet 1 can be continuously accessed in the same manner as before the use extension of the same IP address (S13).

  Thereafter, if the communication path monitoring unit 13 detects that the gateway 18 has been restored (S15), the address assignment processing unit 11 broadcasts a DHCPNOTICE message to that effect (S20). As in the case of the occurrence of a failure, the address correspondence table 14 may be referred to individually transmit only to the client 6 whose basic GW address is GW1 and whose used GW address is not GW1.

  When the client A having the basic GW address GW1 and the GW address not using GW1 receives the DHCPNOTICE message, the client A transmits a DHCPREQUEST message (allocation request) regardless of the elapsed time of the lease period (S16). Thereby, the gateway to be used can be returned to the basic GW address GW1 in the same manner as the procedure described in the first embodiment (S17).

  According to the present embodiment, by using the DHCPNOTICE message, the gateways 18 and 28 to be used can be immediately switched when the Internet 1 cannot be accessed through the gateways 18 and 28 in use. Also, when the basic gateway is restored, it can be restored immediately.

Embodiment 3 FIG.

  FIG. 5 is a block diagram showing another client-server system that implements the setting information assignment method for external network connection according to the present invention. Unlike the above embodiments, the client server system in the present embodiment has a plurality of servers 10, 20, and 30. Each server 10, 20, and 30 has an equivalent function. In the present embodiment, a case where a server system is configured by three servers 10, 20, and 30 as shown in FIG. 5 will be described as an example. Of course, it may be two or four or more. Three gateways 18, 28, and 38 are also shown for convenience, but it is not necessary to match the number of servers. The gateways 18, 28, and 38 themselves may be off-the-shelf products as in the first and second embodiments.

  One or a plurality of clients 6 connected to the same LAN 7 as this server system accesses the Internet 1 via any one of the gateways 18, 28, 38 and the communication lines 19, 29, 39. The client 6 only needs to have a function as a general-purpose DHCP client, and a function specific to this embodiment is not necessary.

  Here, the outline and configuration of the functions of the servers 10, 20, and 30 will be described. However, since the servers 10, 20, and 30 all have the same configuration, the server 10 will be described as a representative.

  The server 10 includes an address assignment processing unit 11, a server management unit 12, a communication path monitoring unit 13, an address correspondence table 14, and a coordinator list table 15. The address assignment processing unit 11 executes an address assignment process for assigning an IP address or the like to the client 6 in response to an IP address assignment request from the client 6. The server management unit 12 determines a single server (hereinafter, referred to as “coordinator server”) that executes the address assignment process. The communication path monitoring unit 13 includes a gateway 18 through which the client 6 accesses the Internet 1, a network path through the communication line 19, a network path through the gateway 28, the communication line 29, and a network through the gateway 38 and the communication line 39. Monitor the route status (connection possible / impossible). The communication path monitoring unit need not be provided in all the servers 10, 20, and 30, but may be provided in at least one server so as to notify the network path status to other servers that are not provided.

  FIG. 6 is a diagram showing a data configuration example of the address correspondence table 14 in the present embodiment. In the address correspondence table 14 according to the present embodiment, in addition to the data configuration described in the first embodiment, a server address is further held corresponding to each client 6. The server address is an address of a server that operates as a coordinator server for the corresponding client 6 and is assigned an IP address.

  FIG. 7 is a diagram showing a data configuration example of the coordinator list table 15 in the present embodiment. Although details will be described later, in this embodiment, a coordinator server is determined according to a predetermined rule described later between the server management units 12, 22, and 32 among the servers 10, 20, and 30 constituting the server system, and the coordinator server Only the address allocation processing unit installed in the system executes address allocation processing. In the coordinator list table 15, candidate server addresses that can be coordinator servers are registered. In the example shown in FIG. 7, since the addresses SA, SB, and SC of the servers 10, 20, and 30 are registered, all the servers 10, 20, and 30 can be coordinator servers. The coordinator list table 15 may be set in advance, or may be set in real time by the server management units 12, 22, and 32 of the operating server.

  The server 10 according to the present embodiment is characterized by the dynamic IP address assignment function of the DHCP server. Therefore, the server 10 is described as a DHCP server, but in addition to the function corresponding to the DHCP server. Each function of a DNS (Domain Name System) server and DAP (Directory Access Protocol) may be installed. Furthermore, it is possible to mount a gateway function in the server 10 without providing a separate gateway server.

  Next, address allocation processing to the client 6 in the present embodiment will be described using the flowchart shown in FIG. The address assignment process described in FIG. 8 is a process when the client 6 broadcasts a DHCPDISCOVER message and acquires a new IP address. The assignment process when the DHCPREQUEST message is transmitted to update the IP address lending will be described later.

  First, the client 6 broadcasts a DHCPDISCOVER message (IP address assignment request) to the servers 10, 20, 30 in order to acquire a new IP address. The servers 10, 20, and 30 that are the recipients of this request are not specified, and all the servers 10, 20, and 30 connected to the LAN 7 receive them (step 101). However, in the present embodiment, only the coordinator server actually responds to the request, and other servers do not process anything in principle even if an IP address assignment request is received (step 102). That is, it does not respond with a DHCPOFFER message. FIG. 8 shows the exception processing (steps 121 to 125), which will be described later. In the following description, it is assumed that the server 10 is currently a coordinator server. A method for determining the coordinator server will be described later.

  Since the address allocation processing unit 11 of the server 10 that has recognized that it is a coordinator server, the address correspondence information corresponding to the client 6 that is the source of the IP address allocation request is not registered in the address correspondence table 14. An IP address or the like is assigned to the client 6 (step 104). Since the process for generating the setting information by this assignment is the same as in the first and second embodiments, the description thereof is omitted. However, in this embodiment, since it is necessary to set the address of the coordinator server in the address correspondence table 14, the address assignment processing unit 11 associates the address SA of the server 10 with the client 6 together with the IP address and the like. Set. Then, setting information including the IP address, the used GW address, and the server address assigned to the client 6 is returned (step 105). Then, the address allocation processing unit 11 generates address correspondence information by associating the MAC address of the client 6 with the gateway address as the assigned IP address, server address, basic GW address, and used GW address. Register in the table 14 (step 106).

  Through the above address assignment processing, the client 6 has acquired the IP address and the like, and can access the Internet 1 via any of the gateways 18, 28 and 38 set by the server 10.

  Furthermore, the address assignment processing unit 11 notifies not only the client 6 but also the address correspondence information to the other servers 20 and 30 by broadcast transmission (step 107). The servers 20 and 30 maintain the data consistency by updating their own address correspondence tables 24 and 34 with the received address correspondence information.

  As described above, when a series of address assignment processing by the address assignment processing unit 11 is completed, the server management units 12, 22, and 32 of the servers 10, 20, and 30 perform coordinated operations and execute coordinator server rotation. As a result, the coordinator right (assignment right) is transferred (step 108). This process will be described in detail later.

  Next, IP address assignment processing when the client 6 sends a DHCPREQUEST message to request extension of use of the IP address will be described with reference to FIG.

  The DHCPREQUEST message (IP address assignment request) transmitted when the client 6 requests to extend the use is transmitted to the server to which the IP address is assigned instead of broadcast. The server address is included in the setting information received when the IP address is acquired. According to the above example, the server 10 receives the request (step 131).

  When the address allocation processing unit 11 of the server 10 receives the IP address allocation request sent from the client 6, it analyzes the content and identifies the transmission source. Then, the address correspondence information of the client 6 is acquired from the address correspondence table 14 (step 132), and the assigned IP address is reassigned to the client 6 (step 133). Further, the address assignment processing unit 11 inquires of the communication path monitoring unit 13 about the operation status of the gateway and assigns a gateway to be used (step 134). Since the processing for assigning the gateway to be used is the same as that in the first embodiment, detailed description thereof is omitted. In short, a basic GW address is assigned if the basic GW address is operating normally, and a substitute GW address is assigned if the basic GW address cannot be used. Then, setting information is generated (step 135) and returned to the client 6 (step 136). Note that the lease period set in the setting information is different between the case of the basic gateway and the case of the substitute gateway, as in the first embodiment. Then, the address assignment processing unit 11 associates the reassigned IP address and the like with the MAC address of the client 6 to generate address correspondence information, and updates the address correspondence table 14 (step 137). Then, the server 20 and 30 are notified of this update (step 138). In this process, it can be said that only the used GW address may have been changed, and others are simply overwritten with the same data.

  As described above, according to the present embodiment, the client 6 can repeatedly use the once assigned IP address, and thus a failure that may occur due to the dynamic switching of the IP address occurs. Disappear.

  Incidentally, the server that should receive the DHCPREQUEST message (IP address assignment request) sent from the client 6 may be down for some reason. In this case, the client 6 determines that the message cannot be reached because the server is down due to no response from the server, and broadcasts a DHCPREQUEST message.

  A coordinator right is acquired or the acquired server responds to this DHCPREQUEST message. Here, if the server 20 responds, the server 20 executes an IP address reassignment process on behalf of the server 10. Since the contents of this allocation process are the same as those described above (steps 132 to 138), a detailed description is omitted, but the server address set in the address correspondence table 14 is rewritten to the address SB of the server 20. This is to prepare for a DHCPREQUEST message sent for the extended use of the IP address again. However, regarding the update of the server address, the basic and substitution may be set in the same manner as the GW address.

  Here, the determination method of a coordinator server is demonstrated using FIG.

  In FIG. 8, the server management unit 12 of the server 10 that is the coordinator server refers to the coordinator list table 15, and the server (first in the last case) listed next to itself (the server 10 in this example) ( In this example, the coordinator right indicating the coordinate server is transferred to the server 20) (step 108). Specifically, messages indicating that are exchanged. The server 20 that newly becomes a coordinator server operates again as a coordinator server in accordance with the flow shown in FIG. The processing content is the same as the processing in the server 10 described above. On the other hand, the server 10 that is no longer the coordinator server performs the same processing as the servers 20 and 30 described above. That is, nothing is processed in principle for the received DHCPDISCOVER message (IP address assignment request).

  As described above, in the address assignment process in the present embodiment, when the IP address assignment process is executed by the coordinate server, the self is registered in the address correspondence table 14 as a coordinate server for the client 6. Since the coordinator right is sequentially transferred according to the coordinator list table 15 every time processing is completed, the number of clients 6 to which each server 10, 20, and 30 should correspond should be almost the same. That is, as described in the first embodiment, load distribution can be realized by executing the coordinator server rotation. Furthermore, since the sending side and the receiving side of the coordinator right cannot be transferred normally unless they operate normally, the server alive function is also achieved. Here, processing when an abnormality occurs on the sending side and the receiving side of the coordinator right will be described.

  First, in step 108, if the coordinator right is not received within a predetermined time because the receiving side is down (step 109), the server management unit 12 in the coordinator server deletes the address of the server 20 from the coordinator list table 15. At the same time (step 110), the server 30 other than the server 20 is notified by broadcast transmission (step 111). Receiving this, the server 30 maintains the data consistency by deleting the address of the server 20 from its own coordinator list table 35. Then, the server management unit 12 transfers the coordinator right indicating that it is a coordinated server to the next listed server (in this example, the server 30) (step 112). By repeating this process, the next server to be the coordinator server is found.

  In addition, the server itself that becomes the coordination server by receiving the coordination right may be down for some reason. If this state is left unattended, there is no server for processing the DHCPDISCOVER message issued by the client 6. Therefore, in this embodiment, even if it is not a coordinator server, the server that is scheduled to become the coordinator server next executes the following process.

  That is, in FIG. 8, the server that is scheduled to become the coordinator server next can be identified in advance by referring to the coordinator list table 15 (step 121). Therefore, if the corresponding server (for example, server 20) does not receive the notification in step 107 from the normal coordinator server within a predetermined time after receiving the DHCPDISCOVER message (step 122), some trouble has occurred in the coordinated server. Judge.

  When the server 20 determines that the coordinating server is inoperable as described above, the server 20 becomes a coordinating server by going to acquire the coordinator right (step 123), and deletes the failed server 10 from the coordinator list table 15. (Step 124), the fact is notified to the other servers 30 other than the server 10 by broadcast transmission (Step 125). And by becoming a coordination server, the server 20 operates again as a coordinator server according to the flow shown in FIG.

  As described above, each client 6 can access the Internet 1 using the IP address and GW address set by the server 10. When the client 6 ends access to the Internet 1, the IP address is collected according to DHCP.

  Here, the details will be described in detail with a focus on the transfer of the coordinator right using the figure. FIG. 10 is a sequence diagram showing the transfer of the coordinator right (assignment right) executed when the IP address assignment process described above is executed. In FIG. 10, two clients A and B and two servers C and D having MAC addresses X and Y are shown. It is assumed that the server C has acquired the allocation right at the start of this process. The content of the process itself is the same as that in FIG.

  When the client A broadcasts an IP address assignment request (DHCPDISCOVER message) (S21), the server C holding the assignment right generates setting information in response to this request, and the generated setting information (DHCPOFFER message) is sent to the client A. (S22). The generation of the setting information has already been described. After the DHCPREQUEST message and DHCPACK information are exchanged after receiving the setting information (S23, 24), the client A registers in the address correspondence table (S25). Then, the server D is notified of the registration (S26), and the server D that has received the notification updates the address correspondence table held and managed by itself (S27). When the assignment process as the coordinator server for transfer is completed, the client A transfers the assignment right to the server D with reference to the coordinator list table (S28). The server D operating normally acquires the assignment right transferred from the server C (S29).

  Thereafter, when the server D receives the IP address assignment request (DHCPDISCOVER message) broadcasted by the client B, the server D assigns an IP address by performing the same processing as S21 to S24 (S30 to S33). Then, it operates in the same manner as in S25 to 27 to update the address correspondence table of each server C and D (S34 to S36), and operates in the same manner as in S28 and 29 to transfer the allocation right to the next server (S37, S36). 38).

  FIG. 11 is a sequence diagram showing transfer of the assignment right when the coordinator server goes down. Since the contents of the setting information are as described above, they are omitted from this figure. In FIG. 11, when the client broadcasts an IP address assignment request (DHCPDISCOVER message) (S41), the server A holding the assignment right should transmit setting information (DHCPOFFER message) to the client in response to this request. Since server A is down due to a failure after the allocation right is acquired (S40), it cannot respond. Therefore, the server B, which can be the next coordinator server, acquires the allocation right by itself when there is no allocation notification from the server A within a predetermined time (S42), and notifies that to other servers (S43). (S44). Then, it notifies the other server that the correspondence to the client is completed (S45), and transfers the allocation right to the next server C (S46, 47). Note that this is basically the same when a new IP address is acquired, and this case has been described with reference to S121 to S125 in FIG.

  FIG. 12 is a sequence diagram when the server B that should acquire the next allocation right immediately after the allocation process by the server A holding the allocation right is down. This process corresponds to S110 to S112 in FIG. Since the processing (S51 to S58) during the IP address assignment request (DHCPDISCOVER message) from the client and the assignment of the IP address to the client has already been described, the details of the processing are omitted.

  The server A tried to transfer the allocation right to the server B to which the allocation right should be transferred according to the coordinator list table (S60), but determines that a failure has occurred in the server B due to no response from the server B, and the coordinator Delete from the list table (S61). Then, the server C that is to receive the next allocation right is specified from the coordinator list table, and an attempt is made to transfer the allocation right to the server C (S62). As a result, when the server C obtains the allocation right, the server C notifies that to other servers (S63).

  According to the present embodiment, the communication path connecting the client 6 and the Internet 1 is multiplexed, and the communication path used by each client 6 can be dynamically determined and connected. Even if an abnormality occurs in any of the gateways 18, 28, 38, the client 6 can continuously access the Internet 1 by switching the communication path.

  In this embodiment, the coordinator server rotation is executed in order to also serve as a server keep alive function. However, if attention is paid only to load distribution for the network connection process, a specific server is designated as the coordinator server. You may make it respond | correspond to an IP address allocation request | requirement. In this case, the coordinator server nominates a server that executes the actual allocation process. If that particular server goes down, the coordinator server may be switched to another server. That is, it is not always necessary to employ the coordinator server rotation as in the present embodiment.

  In this embodiment, the server is rotated and the load is simply distributed. However, the load on each of the servers 10, 20, and 30 is actually measured and compared, and the client 6 is allocated to the server with a low load. It may be.

  In this embodiment, the address correspondence tables 14, 24, and 34 and the coordinator list tables 15, 25, and 35 are arranged for each server 10, 20, and 30 to keep notification for data consistency. Also used as alive. If the keep-alive function is realized by another method, a database server or the like may be installed to make each table a shared database.

  In the above description, only the server in which the failure has occurred is deleted from the coordinator list tables 15, 25, 35. However, after the server is restored, the server management units 12, 22, 32 have their own coordinator list table. By registering addresses in 15, 25, and 35 and notifying other servers, it is possible to reinstate as a coordinator server.

  The gateways 18, 28, and 38 may also be provided with a management table similar to the coordinator list table 15 to manage availability.

1 is a block diagram illustrating a client server system that implements a setting information allocation method for external network connection according to the present invention. FIG. 6 is a diagram showing a data configuration example of an address correspondence table in the first embodiment. FIG. FIG. 3 is a diagram showing a communication sequence between a server and two clients in the first embodiment. FIG. 10 is a diagram illustrating a communication sequence between a server and two clients in the second embodiment. It is the block block diagram which showed the other client server system which implements the setting information allocation method for the external network connection which concerns on this invention. FIG. 10 is a diagram illustrating a data configuration example of an address correspondence table in the third embodiment. FIG. 10 is a diagram showing a data configuration example of a coordinator list table in the third embodiment. 14 is a flowchart showing address assignment processing (when a new acquisition is performed) to a client in the third embodiment. 10 is a flowchart showing address assignment processing (when extended use) to a client in the third embodiment. FIG. 10 is a sequence diagram showing transfer of assignment right in the third embodiment. FIG. 10 is a sequence diagram showing transfer of assignment right in the third embodiment. FIG. 10 is a sequence diagram showing transfer of assignment right in the third embodiment. It is the block block diagram which showed the conventional server system.

Explanation of symbols

  1 Internet, 6 clients, 7 LAN, 10, 20, 30 server, 11, 21, 31 Address assignment processing unit, 12, 22, 32 Server management unit, 13, 23, 33 Communication path monitoring unit, 14, 24, 34 Address correspondence table, 15, 25, 35 Coordinator list table, 18, 28, 38 Gateway, 19, 29, 39 Communication line.

Claims (2)

Setting information allocation method executed by a DHCP server and generating and returning setting information including at least gateway location information in response to an allocation request from a client connected to an external network via one of a plurality of gateways In
A setting information allocation method for external network connection, characterized in that gateway location information is set in setting information to be returned in response to an allocation request from a client so that the gateway is allocated to each client in turn. Setting information allocation method executed by a DHCP server and generating and returning setting information including at least gateway location information in response to an allocation request from a client connected to an external network via one of a plurality of gateways In
An analysis step of analyzing the allocation request from the received client;
A confirmation step for confirming whether the setting information is already assigned to the client from the setting information correspondence table that holds the setting information assigned to the client based on the client-specific information included in the assignment request;
When setting information is assigned to the client, if connection to an external network cannot be made via a gateway whose location information is included in the setting information, the location information of other connectable gateways is displayed. A setting information generation step to be included in the setting information;
A transmission step of transmitting the generated setting information to the client;
A setting information assigning method for connecting to an external network, comprising:

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