JP2003348136A - Router setting method - Google Patents

Abstract

(57) [Summary] A load distribution is performed by distributing a default router in consideration of a router load without changing existing communication terminals and a DHCP server. A router recognizes a router with the lowest load by exchanging a current load state of a packet transfer function. Then, one of the routers 31 and 32 causes the communication terminals 41 to 44 to broadcast to the network 1 at the time of startup or resetting.
The HCP message is transferred to the DHCP server 5. When transferring the DHCP message to the DHCP server, the routers 31 and 32 attach additional information for identifying the router with the lowest load. As a result, the DHCP server selects the router with the lowest load as the default router, and determines the address to be assigned to the communication terminal and the address of the default router. In addition, the routers 31 and 32
The DHCP message transmitted by the HCP server is transferred to the communication terminal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a router for connecting networks, and more particularly, to a router for distributing a load among a plurality of routers and a communication terminal setting method.

[0002]

2. Description of the Related Art The Internet based on TCP / IP is configured by connecting networks by a router that relays IP packets. In the Internet, two networks may be connected by a plurality of routers for the purpose of load balancing and backup with a redundant configuration. Conventional techniques relating to load distribution using these routers and backup by a redundant configuration include the following techniques.

(1) Load distribution A communication terminal belonging to a network using TCP / IP communicates with another network via a router connecting the networks. At this time, a router used as a relay router to another network is called a default router or a default gateway.

In a network having a configuration in which a network to which a plurality of communication terminals are connected is connected to another network by a plurality of routers, a communication terminal that communicates with another network may have a router that can be a default router. There will be more than one. Therefore, load distribution can be performed by distributing the router selected as the default router for each communication terminal. For example, in a configuration in which the routers A and B can be default routers, the default router of the communication terminal 1 may be router A and the default router of the communication terminal 2 may be router B.

Conventionally, selection of a default router is performed manually or using DHCP (RFC2131, Dynamic Host Configuration).
Protocol). In these cases, a default router is assigned to each communication terminal independently of the load on the router, making it difficult to perform effective load distribution. OSPF (RF
It is possible to select a default router in a communication terminal by a dynamic routing protocol such as C2328, OSPF Version 2), but it is not practical to implement a routing protocol in all communication terminals.

(2) Backup by Redundant Configuration Many proposals have been made regarding a method of connecting two networks by a plurality of routers and establishing a redundant configuration between the routers. The result is based on IETF (The Internet). Eng
ineering Task Force), VRRP (RFC2338, Virtua
l Router Redundancy Protocol). In VRRP, one master router that actually functions as a router and has a role of transferring a packet, and one or more routers serving as a backup of the master router are virtually regarded as one router, and it is regarded as a virtual router. Call it a router. The master router notifies the backup router of the status of the device by periodically transmitting an ADVERTISE message to all backup routers belonging to the virtual router. Thus, the backup router recognizes the state of the master router and performs backup when the master router fails.

[0007] By configuring a plurality of virtual routers, each of the virtual routers adopts a configuration in which a router used as a backup router by another virtual router is used as a master router, a backup by a redundant configuration and Load distribution can be performed simultaneously. For example,
In a network in which two networks are connected by a router A and a router B, the virtual router 1
Is the master router, router B is the backup router, virtual router 2 is router A, the backup router,
Let router B be the master router. Then, in the communication terminal, the load can be distributed by distributing the router to be the default router to the virtual router 1 and the virtual router 2.

In a network configuration using a method of balancing backup and load distribution using a redundant configuration using VRRP, since each router always functions as a master router, there is no router that becomes idle, and even when a failure occurs. With the backup function, reachability between communication terminals can be guaranteed. Therefore, the reachability is ensured, but the communication quality is the best-effort, which is the preferred network construction method in the Internet that minimizes the communication cost.

[0009]

In order to effectively perform load distribution realized by distributing a default router used by a communication terminal among a plurality of communication terminals, communication is performed by reflecting the load of the router. A default router must be assigned to the terminal. Further, it is desirable that the setting of the default router in the communication terminal be an automatic setting.
Particularly, in an office environment or an Internet access service in which an end user who does not have knowledge of TCP / IP owns a communication terminal, automatic setting is essential.

[0010] DHCP is currently widely used as a standard protocol for automatically setting setting parameters such as its own address and the address of a default router in a communication terminal. However, DHCP does not have a function of assigning a default router reflecting the load on the router. DHCP
Since is already widely used, it is not desirable to change the DHCP client and the DHCP server of the communication terminal even when assigning a default router reflecting the load of the router.

Further, in a network having a configuration in which two networks to which the present invention is applied are connected by a plurality of routers, a backup by a redundant installation of routers is often used by VRRP. Therefore,
The present invention must be applicable simultaneously with VRRP even in an environment using VRRP.

[0012]

DISCLOSURE OF THE INVENTION The present invention considers the convenience of an end user who uses a communication terminal, and uses an existing DHCP.
The setting of the default router that reflects the load of the router is possible in the communication terminal without changing the default router.

The router according to the present invention has a function of exchanging the load state of the current packet transfer function among a plurality of routers.
It has a means to recognize the router with the lowest load.

A DHCP message transmitted by a communication terminal to obtain setting parameters such as its own address and an address of a default router is a broadcast to a network to which the communication terminal is connected, and is usually transmitted by a relay agent located at the router. Forwarded to DHCP server. Also, DHCP from the DHCP server
The P message is also transmitted to the communication terminal via the relay agent.

The router of the present invention selects one router from a plurality of routers connecting two networks,
By relaying the message exchange between the communication terminal and the DHCP server only by the relay agent located at the router, reception of the duplicate message at the DHCP server is prevented.

Further, when the router of the present invention transfers the DHCP message transmitted by the communication terminal to the DHCP server, the DHCP server attaches additional information for identifying the router with the lowest load in the DHCP server. This allows the DHCP server to select a default router. As additional information, RF
C3046 (DHCP Relay Agent Information Option)
Agent Circuit ID specified in the above is used.

The Agent Circuit ID is originally assigned to the router where the relay agent is located.
An identifier indicating a line that has received the HCP message,
This is information that assists the DHCP server in selecting parameters to be assigned to communication terminals. In the present invention, this Agent Circuit ID is extended and used as an identifier indicating the line of the router with the lightest load. By this method, the DHCP client of the communication terminal and the D
There is no need to add any special extensions to the HCP server, and existing software and equipment can be used in the implementation of the present invention.

In a network having a configuration in which two networks to which the present invention is applied are connected by a plurality of routers, backup by a redundant configuration by VRRP is often used, but the present invention may be used independently of VRRP. It is possible. In addition, the ADVER that the master router periodically sends to the backup router in VRRP
By exchanging the load state of the packet transfer function between a plurality of routers using the TISE message, the number of messages exchanged between the routers can also be reduced.

[0019]

Embodiments of the present invention will be described below.

FIG. 1 is a schematic diagram of a network to which an embodiment of the present invention is applied. In the present embodiment, an IP network is assumed as the network. In FIG. 1, a network 1 and a network 2 are connected by a plurality of routers 31 and 32. The router 31 is connected to the network 1 by the line 11,
It is connected to the network 2 by a line 21. The router 32 is connected to the network 1 via the line 12 and to the network 2 via the line 22. Although FIG. 1 illustrates two routers, in the present embodiment, the number of routers is not limited.

The plurality of communication terminals 41 to 44 connected to the network 1 communicate with the communication terminals belonging to the network 2 via the router 31 or the router 32. D
The HCP server 5 is connected to the network 2 capable of communicating with the router 31 and the router 32, and provides the communication terminals 41 to 44 connected to the network 1 with their own addresses used by those communication terminals and the network 1.
Has a function of allocating setting parameters such as the address of a default router that is a relay router from the network 2 to the network 2. The DHCP server 5 has an address assignment database 51. In FIG. 1, the configuration is such that the DHCP server 5 is connected to the network 2.
May be installed anywhere as long as communication with the router 31 and the router 32 is possible.

Each of the communication terminals 41 to 44 has a DHCP client function, and participates in the network 1 by acquiring setting parameters such as its own address and the address of a default router from a DHCP server at the time of startup. The communication terminals 41 to 44 transmit to the network 1 a request for assignment of setting parameters such as a terminal address and a default router address at the time of startup or resetting according to the rules of DHCP. Since this assignment request message is a broadcast addressed to all communication terminals and routers in the network 1,
The router 31 and the router 32 receive the assignment request message. The router 31 and the router 32 once receive the assignment request message, add additional information as needed, and transfer the message to the DHCP server 5. The function of relaying a DHCP message such as the allocation request message between the communication terminal and the DHCP server is called a DHCP relay agent function.

FIG. 9 is a diagram showing a specific configuration example of the network 1. Here, the network 1 includes a LAN switch 11 and a LAN switch 12, and the terminals 41 to 42 are connected to the router 31 and the router 32 by these LAN switches. The LAN switch configures a broadcast network,
With this configuration, the communication terminals 41 to 44 and the router 3
1. The router 32 belongs to the broadcast network.

In a network constituted by LAN switches, a broadcast network can be logically divided by a VLAN (Virtual LAN) function defined by IEEE802.3Q. With this function, a network in which a broadcast network is logically divided for each communication terminal may be configured. Here, the communication terminal 4
1 illustrates an example in which a VLAN 1 is logically separated from other terminals by a VLAN 13 and connected to a router 31 and a router 32.

FIG. 2 shows a message exchange sequence at the time of setting parameter assignment among the communication terminal, the router, and the DHCP server. FIG. 4 shows the format of the DHCP message. DHCP is described in detail in RFC2131 of IETF.

Hereinafter, the exchange sequence of the DHCP message related to the setting parameter assignment of the communication terminal will be described with reference to FIG. First, a communication terminal broadcasts a DHCPDISCOVER message for searching for a DHCP server to a network. The router sends its DH
Receive the CPDISCOVER message and forward it to the DHCP server. The address of the DHCP server is fixedly set in the router. The DHCP server transmits setting parameters such as an address that can be assigned to the communication terminal and a default router address to the router using a DHCPOFFER message. Router is DHCPOFFE
The R message is transmitted to the communication terminal that transmitted the DHCPDISCOVER message. If the communication terminal that has received the DHCPOFFER message uses the setting parameters such as the address and the default router address indicated by the DHCPOFFER message, the communication terminal uses the D in order to notify the DHCP server of the use.
Broadcast an HCPREQUEST message to the network. The router will send its DHCPREQ
The ST message is received and transferred to the DHCP server.
When the DHCP server receives the DHCPREQUEST messages, it grants them a DHCPACK
Sends a message to the router, and the router
The CK message is transferred to the communication terminal that transmitted the DHCPREQEST message.

The DHCP server 5 has an address assignment database 51 shown in FIG. 3, and determines an address to be assigned to a terminal, a network mask, and an address of a default router. Although not shown in this example, DH
In the CP, other setting parameters can be assigned.

The address assignment database 51 stores the DHC
Agent address field 511 containing the address of the P relay agent (address of the router where the relay agent is located), agent line ID containing the line identifier of the agent that received the DHCP message
Field 512, default router address field 5 containing the address of the default router to notify the terminal
13, an address pool field 514 containing a pool of addresses to be assigned to the terminal, a network mask length field 515 containing the network mask length, and an assigned address field 516 containing the IP address assigned to the terminal. Here, when the address of the relay agent is xxx.xx and the agent line ID is 1, the address of the default router assigned to the communication terminal is xxx.xx, and the IP address assigned to the communication terminal is , Xxx.2 to xxx.244. The network mask length is 24.
xxx.2 and xxx.3 indicate that they have already been allocated.

When the communication terminal establishes a DH
In order to transmit the CPDISCOVER message by broadcast, when there are a plurality of routers connected to the network 1 as shown in FIG. 1, these messages are received by both the router 31 and the router 32, and both of the routers are used. In the case of having a normal DHCP relay agent function, two DHCPs are sent to the DHCP server 5.
A CPDISCOVER message will be sent. That is, when a normal DHCP relay agent is used, DHCP server 5
The sender of the OVER message is identified, and for a plurality of DHCPDISCOVER messages from the same sender, only one DHCPOFFER message is transmitted, or two DHCPOFFER messages are transmitted, and either It is necessary to send only one DHCPREQUEST message for the DHCPOFFER message.

In the present embodiment, the communication terminal relays a DHCPDISCOVER message and a DHCPREQUEST message transmitted by broadcast.
Provides a function to select one CP relay agent in the network, and to add to the DHCP message additional information that allows the DHCP server to select a configuration parameter that makes the appropriate router the default gateway in the DHCP server. I do. An appropriate default gateway is, for example, the router with the lightest load among multiple routers,
The load may be defined by a packet transfer load, the number of terminals whose router is the default gateway, and the like. Thus, communication between the network 1 and the network 2 can be load-balanced by a plurality of routers. Hereinafter, the operation of the DHCP relay agent of the present embodiment will be described.

In FIG. 1, a DHCP relay agent functions in all routers connecting the networks 1 and 2. The DHCP relay agent of the present embodiment has a function of exchanging router load information between DHCP relay agents, in addition to the function of a normal DHCP relay agent. Further, it has a master state in which a DHCP message is relayed as a DHCP relay agent and a slave state in which no DHCP message is relayed. Hereinafter, the DHCP relay agent of the present embodiment is called a relay agent, a relay agent in a master state is called a master relay agent, and a relay agent in a slave state is called a slave relay agent.

FIG. 5 shows that the routers are the router 31 and the router 3
FIG. 9 is a sequence diagram illustrating the operation of the relay agent using two cases of two relay agents. In this example, the relay agent of the router 31 is in the master state, and the relay agent of the router 2 is in the slave state. Which state after initialization may be determined, for example, by initial setting. However, only one relay agent is in the master state, and all other relay agents must be in the slave state. Only the master relay agent communicates with the communication terminal
Relays DHCP messages between HCP servers.

The master relay agent has a relay agent status management table shown in FIG. The relay agent state management table includes a router ID field 521 for identifying a router, an agent line ID field 522 including a line identifier indicating an interface to be a default router for the router identified by the router ID, a load state for packet transfer. And a default router flag field 524 indicating whether or not to become a default router in response to a new registration request by DHCP. The default router flag is always set to one router. In FIG. 6, the router whose router ID is 1 is the default router for the new request at that time.

As shown in the sequence diagram of FIG. 5, the slave relay agent periodically sends an INFORM message to the master relay agent.
The default setting value of the default router may be any router, but here, the router where the master relay agent is located is set as the default router (553). FIG.
Shows an INFORM message. The INFORM message includes an address addressed to the router where the master agent is located, a message header 530 for delivering the message to the router, and a router ID indicating the router where the transmitted slave relay agent is located.
531, an agent line ID 532 indicating an interface accommodating a line used when the router becomes a default router, and a packet transfer load 533 including a load state related to packet transfer. By receiving this INFORM message, the master relay agent compares the load status between routers as shown in FIG. 5 and determines the default router (55).
4 and 555, and 556 and 557). Further, a relay agent status management table shown in FIG. 6 is created.
Details of this processing will be described below with reference to the flowchart of FIG.

FIG. 8 is a flowchart of the default router determination procedure. The master relay agent has I
When the NFORM message is received, the packet transfer load field 523 of the relay agent status management table is updated with the router ID 531 and the packet transfer load 533 included in the INFORM message. Also, the value of the agent line ID field 532 included in the INFORM message and the agent line ID field 522 of the relay agent status management table
Are different, the agent line ID field 5
The value of 22 is updated with the value of the agent line ID field 532 (541).

Subsequently, referring to the relay agent state management table, the packet transfer load value of the router with the default router flag set is subtracted by the packet transfer load value of the other routers (542). The margin value X is used to determine the result of the subtraction. The value of the margin value X is an arbitrary integer value, which prevents the default router from being excessively changed by the change of the default router due to a slight difference in load. For example, in the case where the packet transfer load value is indicated by the usage rate with respect to the packet transfer capability of the router, the margin value X can be specified as 10%. Here, if the subtraction result is smaller than the margin value X for all the routers, that is, if there is no router whose load exceeds the margin value X with respect to the current default router load, the process ends as it is. If at least one operation result is larger than the margin value X, the router with the largest value, that is, the router with the lowest load is set as the default router, and the default router flag of the router in the relay agent state management table is set. (543).

Next, a method of relaying a DHCP message by the master relay agent and assigning a terminal address, a netmask length, and a default router address by the DHCP server according to the present embodiment will be described. Incidentally, regarding the operation of the master relay agent, the normal DH
Only the part different from the operation of the CP relay agent will be described. The normal operation of the DHCP relay agent is described in detail in RFC2131 of IETF.

FIG. 2 is a diagram showing a DHCP message exchange sequence between a communication terminal, a router, and a DHCP server. Here, the function of relaying the DHCP message in the router is the master relay agent of the present embodiment. FIG. 4 is a diagram showing a format of a DHCP message. The numbers in the figure are the field sizes (the number of bytes). The message type is identified by the op value 561.

The communication terminal transmits a DHCPDISCOVER message to the network by broadcast at the time of starting or resetting. The master relay agent receives the DHCPDISCOVER message and sends a gi of the DHCPDISCOVER message.
The address of the relay agent is set in the addr field 562. The address of the relay agent is an address of the router where the relay agent is located, and is an address for identifying the relay agent by the DHCP server. The setting of the giaddr value is a process that is also performed in a normal DHCP relay agent. Subsequently, the relay agent of the present embodiment refers to the relay agent status management table, and sets the agent line ID field value 522 of the router for which the default router flag is set to the DHCP address.
An Agent Circuit ID value is set in the option field 562 of the PDISCOVER message and transferred to the DHCP server.

The Agent Circuit ID is R
This is option information of a DHCP message defined by FC3046. Originally, it is information indicating the interface that received the DHCPDISCOVER message or the like in the DHCP relay agent,
The DHCP server is used for fine selection of parameters to be allocated to communication terminals. For example, in the address assignment database shown in FIG. 3, by having an agent line ID field, it is possible to select an assignment parameter by an AgentCircuit ID in addition to an agent address 511 indicating a DHCP relay agent. In the relay agent of the present embodiment, the Agent Circuit I
By using D as the identification information of the default router, it is possible to construct a network using a standard DHCP server corresponding to the Agent Circuit ID. That is, in the present embodiment, Agent
The Circuit ID is used not only as the line identifier of the router where the master relay agent is located, but also as the line identifier of other routers.

By adding unique information to the Option field 562, it is also possible to select a communication terminal setting parameter in the DHCP server. However, in that case, it is necessary for the DHCP server to also deal with the unique information.

The DHCP server is DHCPDISCOV
Upon receiving the ER message, the relay agent line ID field 512 of the address assignment database 51
And the op of the DHCPDISCOVER message
Agent Circuit of the tion field 562
Select an entry that matches the value indicated in the t ID value. The address that can be assigned to the terminal is determined by the address pool field 514 and the assigned address field 516 of the selected entry, the netmask is determined by the netmask length field 515, and the default of the communication terminal is determined by the default router address field 513. Determine the router address.

The DHCP server sets the IP address of the determined terminal in the yaddr field 563, and sets the netmask and the IP address of the default router to opti.
DHCPOFFER set in the ons field 564
Create a message and send it to the master relay agent. The master relay agent has its DHCP
OFFER message to the terminal, and further transmits a DHCPREQUEST message transmitted from the terminal to DH
DHCP transferred to CP server and sent by DHCP server
Transfer the PACK message to the terminal.

The embodiment of the load distribution method by changing the setting parameter of the communication terminal assigned by the DHCP according to the load of the router has been described above. In the following, an embodiment will be described in which a plurality of routers serve as backups for each other so that load distribution between routers and backup between routers are simultaneously performed.

As in the network shown in FIG. 1, in a network in which two networks are connected by a plurality of routers, a protocol intended for load distribution and backup between a plurality of routers is defined by IETF. There is VRRP. However, VRRP does not prescribe a method of selecting a default router by a communication terminal, and generally requires manual setting on the communication terminal, making it difficult to perform effective load distribution. Also,
Manual setting of many communication terminals is not preferable in terms of management because of a large setting load and a possibility of improper setting.

By using this embodiment for switching the default router according to the load simultaneously with VRRP,
It becomes possible to efficiently and automatically perform load distribution in a network using RRP. In the following, VR
An embodiment of the present embodiment in an environment using an RP will be described.

First, the outline of VRRP will be described. FIG.
FIG. 1 is a diagram illustrating a network configuration using VRRP. Network 1 and network 2 are connected to router 33
And a router 34. In VRRP,
These two routers are virtually one virtual router A3
Assume 5 Here, the router 33 is a virtual router A35.
And a router that actually operates as the virtual router A35. The router 34 is a virtual router A
There are 35 backup routers that serve as backups for the failure of the master router. Similarly, the router 33 and the router 34 are virtually regarded as one virtual router B36, and the router 34 is a master router of the virtual router B36,
The router 33 is a backup router for the virtual router B36. Here, the router 34 actually operates as the virtual router B36. Therefore, in this network, load distribution is performed by the router 33 that actually transfers packets as the virtual router A 35 and the router 34 that actually transfers packets as the virtual router B 36. Further, the routers 33 and 34 are mutually backup routers.

FIG. 11 shows a VRRP message exchange sequence using the example of the network configuration of the two routers shown in FIG. In VRRP, the master router uses the ADVERTI
An SE message is periodically sent to all backup routers. As a result, the backup router monitors the status of the master router, and when a failure occurs in the master router, the backup router becomes the master router and takes over the processing of the virtual router.

In FIG. 11, the router 33 which is the master router of the virtual router A and the router 34 which is the master router of the virtual router B transmit the ADVERTISE message to the respective routers 34 and 33 which are backup routers. Then, when the failure of the router 33 occurs (571), the transmission of the ADVERTISE message from the master router of the virtual router A stops, and the master down timer of the backup router of the virtual router A operating on the router 34 times out. 34 becomes the master router of virtual router A (57
2) is shown. Furthermore, the router 33 recovers from the failure (573), resumes the operation of the virtual router A as the master router, and transmits an ADVERTISE message, whereby the router 34 becomes the backup router of the virtual router A (574). Is shown.

FIG. 12 shows an example of a message exchange sequence when VRRP and the load distribution method of the present embodiment are combined. The relay agent of this embodiment operates on the master router of each virtual router. In this example, the virtual router A is a master relay agent, and the virtual router B is a slave relay agent. Therefore, the master relay agent
The router 33 operates as the master router of the virtual router A. Also, the slave relay agent operates on the router 34 which is the master router of the virtual router B,
IN to router 33 which is the master router of virtual router A
The FORM message is transmitted periodically. INFO
The RM message is indicated by a broken line in the figure (57
5). In the figure, the ADVERTISE of VRRP is shown.
Although the message transmission interval and the INFORM message transmission interval are the same, the present embodiment and VRRP are independent and may have different transmission intervals.

The relay agent of this embodiment operates on the master router of each virtual router. Since there is only one master relay agent, it operates on the master router of one virtual router, and the slave relay agent operates on the master router of another virtual router. Therefore, in a network configuration where all routers are master routers for any virtual router and all other routers are backup routers for that virtual router, the router where the master relay agent is located is Are all slave relay agents, and a VRRP ADVERTISE message is periodically transmitted from all the routers.

By including the information transmitted in the INFORM message of the present embodiment in the ADVERTISE message, the number of messages exchanged between routers can be reduced. FIG. 13 shows a message obtained by adding information transmitted in the INFORM message used in the present embodiment shown in FIG. 7 to the ADVERISE message specified by VRRP. Numerical values in the figure are field sizes (number of bytes). Agent Line I
D534 and the packet transfer load 535 are the original AD
This is a field added to the VERTISE message, and the other fields are specified by VRRP. Note that the router ID 531 of the INFORM message shown in FIG. 7 is information for identifying a router. In this example, V is an ID for identifying a virtual router.
R ID 536 can be used.

When switching between the master router and the backup router by VRRP, information in the relay agent status management table is lost. However, in the new master router, the function of the master relay agent can be resumed by starting the master relay agent from the initialization state. However, a default router that is not optimal may be temporarily selected. In order to prevent this temporary, non-optimal selection of the default router, the INFORM message or INFORM message is also sent to the slave agent of the virtual router where the master relay agent is located.
An ADVERTISE message having information included in the message may be received and a relay agent management table may be created.

FIG. 14 is a schematic diagram of a configuration example of a router having a relay agent function according to the present embodiment. As an example, the router 31 shown in FIG. 1 is used. Router 3
Reference numeral 1 denotes an interface 311 connected to the network 1 via the line 11, and an interface 312
Is connected to the network 2 via. The packet transfer unit 313 is connected to the interface unit, and performs packet transfer between the interfaces. When the received packet is the DHCP message or the INFROM message of the present embodiment, the packet transfer unit transfers the packet to the relay agent 315. Also, the VRRP message is once transferred to the relay agent 315, the process using the agent line ID and the packet transfer load information, which are additional information of the present embodiment, is performed, and the information is deleted and transferred to the VRRP function unit 317. .

The relay agent 315 has a relay agent status management table 316, and as described above, uses the INFORM message and the ADVERTISE message to store the relay agent status management table 316.
16 is created. Then, according to the relay agent status management table 316, D
Add information to the HCP DISCOVER message,
Transfer to DHCP server. Also, other DHCP messages are transmitted to the DHCP client of the communication terminal and the
Relay on the server. These relay agent functions 3
15 and the VRRP function 317 are, for example, the CPU 31
4 is realized by the software processed.

In the above example, the relay agent always operates on a specific router or virtual router. Then, by managing the default router flag and the agent line ID in the relay agent state management table, information for selecting a setting parameter for selecting another router or a virtual router as the default router in the DHCP server is DHCP DISCOVER.
Attached to the message. In the following, an embodiment is described in which the router or virtual router where the master relay agent is located is always the default router for new subscribers at that time.

FIG. 15 is a message exchange sequence diagram between routers in the present embodiment. The network configuration exemplifies the configuration shown in FIG. here,
In an initial state, the router 31 is a master relay agent. The router 32 is a slave relay agent. The selection of which router will be the master relay agent may be determined, for example, by default. However, the master relay agent must be unique and all other relay agents must be in slave state. Then, only the master relay agent performs DHCP between the communication terminal and the DHCP server.
Relay the P message.

As shown in FIG. 15, the router 32 that has become the slave relay agent periodically sends an INFORM message to the router 31 that has become the master relay agent. The format of the INFORM message is the same as that of FIG.
82 need not be included. This is because the master relay agent is always the default router for the new settings at that time, and therefore always uses the line ID of the router in which it is located as the agent line ID.

The master relay agent sends the IN
By receiving the FORM message, the load states between the routers are compared as shown in FIG.
4) If the difference between the load on the own router and the load on the router that transmitted the INFORM message exceeds the margin value X,
The status is changed from the master to the slave, and an INDICATE message is transmitted to the router that transmitted the INFORM message (582, 585). The slave relay agent receiving the INDICATE message,
Change state to master and become master relay agent. The format of the INDICATE message includes an address addressed to the router where the master agent is located, and includes a message header for delivering the message to the router and a margin value used for comparing load information. The margin value can be set to the initial value for all relay agents, but it is possible to notify the new master relay agent by an INDICATE message in consideration of the possibility of dynamic change in the master relay agent. And

FIG. 16 shows a procedure for selecting a default router and changing a state of a relay agent in the present embodiment.
This will be described below with reference to the flowchart of FIG. Upon receiving the INFORM message, the master relay agent compares the current load of its own router with the load of the router that transmitted the INFORM message included in the INFORM message (591). When the value obtained by subtracting the load of the information notification router from the load of the own router is larger than the margin value X, the slave becomes the slave relay agent with its own state as a slave (592), and transmits an INDICATE message to the router that transmitted the INFO message. (593). If the subtraction result is smaller than the margin X, the process is terminated (594). INDICATE
The slave relay agent receiving the message
Becomes a master relay agent with its own state as the master state. In addition, in order to compare load values, INDIC
The margin value notified by the ATE message can be used.

This embodiment can also be used together with VRRP, as in the previous embodiment. As a result, load distribution in a network using VRRP can be efficiently and automatically realized. The difference from the above embodiment is that the virtual router in which the master relay agent is located in the above embodiment is fixed to one virtual router. Alternatively, it becomes a virtual router that becomes a default router in response to a setting request of a communication terminal to be reset. Also, since the router where the master relay agent is located is always the current default router,
A default router flag indicating the selection state of the default router according to the relay agent state management table,
Another difference is that there is no need to manage the load status of each router including the current default router.

[0062]

According to the present invention, the existing communication terminal and the DH
Without changing the CP server, the load can be distributed by distributing the default router in consideration of the load on the router.

[0063]

[Brief description of the drawings]

FIG. 1 is a configuration example of a network according to an embodiment.

FIG. 2 is a sequence diagram showing message exchange by DHCP.

FIG. 3 is a diagram illustrating registered contents of an address assignment database of a DHCP server.

FIG. 4 is a diagram showing a format of a DHCP message.

FIG. 5 is a sequence diagram illustrating message exchange of a relay agent in the embodiment.

FIG. 6 is a diagram illustrating registered contents of a relay agent status management table.

FIG. 7 is a diagram showing a format of an INFORM message used by a relay agent in the embodiment.

FIG. 8 is a flowchart illustrating a default router selection procedure in the relay agent according to the embodiment.

FIG. 9 is a configuration example of a network to which the embodiment is applied;

FIG. 10 is a configuration example of a network to which VRRP is applied;

FIG. 11 is a sequence diagram showing message exchange between routers by VRRP and master / backup switching.

FIG. 12 is a sequence diagram illustrating a relationship between an ADVERTISE message exchanged by VRRP and an INFORM message used by a relay agent in one embodiment.

FIG. 13 shows ADVER with extensions in one embodiment.
FIG. 4 is a diagram showing a format of a TISE message.

FIG. 14 is a diagram illustrating a configuration example of a router according to an embodiment.

FIG. 15 is a sequence diagram illustrating message exchange of a relay agent in one embodiment.

FIG. 16 is a flowchart illustrating a default router selection procedure in a relay agent according to an embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Network accommodating communication terminal, 31-34 ... Router, 41-44 ... Communication terminal, 5 ... DHCP server, 5
DESCRIPTION OF SYMBOLS 1 ... Address allocation database, 35-36 ... Virtual router, 311-212 ... Interface, 313 ... Packet transfer part, 314 ... CPU, 315 ... Relay agent, 316 ... Relay agent status management table, 3
17… VRRP function

Claims (8)

[Claims] 1. A router setting method used in a network having a configuration in which a network to which a plurality of communication terminals are connected and another network are connected by a plurality of routers, wherein the plurality of routers exchange load information with each other. By detecting the router with the lowest load from a plurality of routers, one of the communication terminals is activated or reset,
In order to obtain setting parameters such as an own address and an address of a default router, a DHCP message is broadcast to a network to which the communication terminal is connected, and a predetermined router set for each of the communication terminals
Information that identifies the detected router with the lowest load is added to the CP message and transferred to a DHCP server. The DHCP server determines that the communication terminal that has transmitted the DHCP message specifies the router with the lowest load as the default router. A setting parameter to be assigned to a communication terminal. 2. The router setting method according to claim 1, wherein the router is a master state in which relay agent means for relaying the DHCP message between the communication terminal and the DHCP server is a state for relaying a DHCP message. Alternatively, the router has one of a slave state in which it does not relay a DHCP message, one of the plurality of routers is in a master state, the other routers are in a slave state, and the router in the slave state is The relay agent function in the master state is periodically notified of the identifier of the router where the relay agent function is located, the interface identifier used when the router is set as the default router, and the load state of the router, and The router is the router By recording the identifier, interface identifier, and load state, the router with the lowest load is recognized, and the router in the master state transfers a DHCP message transmitted by a communication terminal to a DHCP server, By adding, to the DHCP message, an interface identifier when the router with the lowest load is used as the default router, the DHCP server has a setting parameter for the communication terminal that uses the router with the lowest load as the default router. A router setting method characterized by allowing the user to make a selection. 3. The router setting method according to claim 1, wherein the relay agent means for relaying the DHCP message between the communication terminal provided in the router and the DHCP server relays the DHCP message, or , One of the plurality of routers is in a master state, the other of the plurality of routers is in a slave state, and the router in the slave state is a state in which the router is not relaying a DHCP message. The identifier of the router where the relay agent function is located, and the load state of the router are periodically notified to the relay agent function in the master state. Load and relay relay in the slave state Agent compares the load information notified by the
When recognizing a router with a lower load than its own router, the router itself becomes a slave state, sends an instruction to become a master state to a router with a lower load, and receives a command to become the master state, the router in a slave state receiving the instruction to become the master state When the router in the master state transfers the DHCP message transmitted by the communication terminal to the DHCP server, the router in the master state adds an interface identifier when the router in which the relay agent function is located is used as a default router. And causing the DHCP server to select a setting parameter for the communication terminal to use a router with the lowest load as a default router. 4. The router setting method according to claim 2, wherein each of the routers is a virtual router configured by VRRP with one master router and one or more backup routers. Method. 5. The router setting method according to claim 3, wherein each of said routers is a virtual router composed of one master router and one or more backup routers by VRRP. 6. The router setting method according to claim 4, wherein the number of all routers and the number of virtual routers are the same, and all routers are master routers of one of the virtual routers, and the other routers are designated as virtual routers. In a configuration in which a router is used as a backup router, the master router of the virtual router uses the A specified by VRRP.
A DVERTISE message is periodically transmitted to another backup router of the virtual router, and the master router of the virtual router in the slave state uses the identifier of the virtual router where the relay agent function is located, and uses the virtual router as a default router. The virtual router and the virtual router, wherein the identifier of the interface in the case and the load state of the virtual router are included in the ADVERTISE message to notify the master router of the virtual router where the relay agent in the master state is located. The routers that make up the router. 7. The router setting method according to claim 5, wherein the number of all routers and the number of virtual routers are the same, and all routers are master routers of one of the virtual routers, and the other routers are the virtual routers. In a configuration in which the router is used as a backup router, the master router of the virtual router uses the A specified by VRRP.
A DVERTISE message is periodically transmitted to another backup router of the virtual router, and the master router of the virtual router in the slave state determines the identifier of the virtual router in which the relay agent function is located, and the load state of the virtual router. With the ADV
A virtual router that notifies the master router of the virtual router where the relay agent in the master state is located by including it in the ERTISE message, and a router configuring the virtual router. 8. The router setting method according to claim 6, wherein in the backup router of the virtual router in the master state, the master router of the virtual router in the slave state periodically notifies the identifier of the virtual router, Receives the identifier of the interface when the router is used as the default router, and the load status of the virtual router, and, like the master router of the virtual router in the master status, identifies the identifier of each virtual router, the interface identifier, and the load status. When the master router of the virtual router in the master state fails, if one of the backup routers of the virtual router becomes a new master router by VRRP,
An identifier of each of the virtual routers, an interface identifier,
And a router setting method using a record of a load state to start the relay agent function without initializing it.