JP2012175294A - Communication system, switching hub and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To identify a switching hub to which a communication terminal accommodated in a network under control of a router is to be connected, without imposing excessive load on the network.SOLUTION: An adjacent repeating device table about a router and about each switching hub under control of the router is stored beforehand. The router refers to a MAC address table to identify a communication port corresponding to a terminal to be searched for, and refers to an adjacent repeating device table of the local device to identify a switching hub corresponding to the communication port. Next, the router inquires the switching hub about a communication port corresponding to the terminal as a candidate to be connected to, and refers to the stored content of the adjacent repeating device table of the switching hub to determine whether the destination for the communication port to be connected is some other switching hub. Then, if the destination is some other switching hub, the router makes the inquiry again at the other switching hub about a new candidate to be connected to.

Description

  The present invention relates to a technique for supporting operation management of a LAN (Local Area Network).

  In recent years, corporations have established LANs (hereinafter referred to as local LANs) at each base such as a branch office, and connected these local LANs to an IP (Internet Protocol) network such as the Internet via a router. Building is generally done. Such a local LAN is often configured by cascading a plurality of switching hubs, and a communication terminal used by each user (for example, a company employee) is connected to any one of those switching hubs. Here, the router is a relay device that performs transfer control of packets (data transmission / reception unit in the third layer) according to the communication protocol of the third layer (network layer) in the OSI (Open Systems Interconnection) reference model. The switching hub is a relay device that performs transfer control of a frame (data transmission / reception unit in the second layer) according to the communication protocol of the second layer (data link layer) in the OSI reference model, and is also called an L2 switch.

  When operating and maintaining an in-company information system (or each local LAN that is a communication system of its constituent elements), it is possible to grasp which switching hub each communication terminal is connected to. It is convenient if you can. For this reason, various technologies have been proposed that make it possible to grasp which switching hub each communication terminal is connected to (hereinafter, communication terminal search). For example, Patent Document 1 discloses a technique for transferring a MAC (Media Access Control) address table between switching hubs included in a LAN and searching for a communication terminal by referring to the stored contents of the MAC address table. Has been. Here, the MAC address is a hardware identifier that uniquely identifies each communication device in the second layer of the OSI reference model. The MAC address table is a table provided in a relay device such as a switching hub or router, and stores the port identifier of the communication port that received the frame in association with the transmission source MAC address of the frame received by the relay device. Is to do.

JP 2010-171502 A

  In general, a larger LAN includes a larger number of communication terminals and switching hubs, and the connection relationship between the switching hubs is often complicated. For this reason, the importance of searching for a communication terminal increases as the LAN becomes larger. However, the technique disclosed in Patent Document 1 has a problem that application becomes more difficult as the LAN becomes larger. This is because as the size of a LAN increases and the number of switching hubs included in the LAN increases, the load due to the transfer of the MAC address table between the switching hubs increases, and the original data communication performed via the LAN (for example, This is because there is a high possibility of adversely affecting data communication between communication terminals accommodated in the LAN.

  The present invention has been made in view of the above problems, and grasps to which switching hub a communication terminal accommodated in the network is connected without applying an excessive load to the network under the router. The purpose is to provide a technology that makes this possible.

  In order to solve the above problems, the present invention provides a communication system including a router and a plurality of switching hubs included in a network under the router, wherein (A) at least one of the plurality of switching hubs and the router are: A first identifier that stores a port identifier of a communication port that has received the frame in association with a hardware identifier that uniquely identifies a communication terminal that has transmitted a frame addressed to the own device in the second layer of the OSI reference model A second table that stores a hardware identifier of a relay device that is a transfer source of a frame received via the communication port in association with a port identifier of the communication port, and (B) the router The stored contents of the second table are notified by a notification from the switching hub having the first and second tables. First means for obtaining and storing; and a hardware identifier of the communication terminal as data indicating the communication terminal to be searched or another identifier uniquely converted to the hardware identifier, and the other in the OSI reference model The second means for specifying the communication port corresponding to the communication terminal in the own apparatus from the stored contents of the first table of the own apparatus, by the input of the identifier of the hierarchy of It is determined whether or not a switching hub is connected to the specified communication port with reference to the stored contents of the second table for the own device, and it is determined that the connection destination of the communication port is not a switching hub. In this case, a third means for informing that the communication terminal to be searched is connected to its own device and the communication specified by the second means If the third means determines that the connection destination of the communication port is a switching hub, a fourth means for selecting the switching hub as a connection destination candidate for the search target communication terminal, and the search A fifth means for inquiring a communication hub corresponding to the communication terminal to be searched in the switching hub with respect to the switching hub selected as a connection destination candidate of the target communication terminal; and an inquiry destination by the fifth means Whether the connection destination of the communication port returned from the switching hub is another switching hub or not is referred to the stored contents of the second table obtained by the first means from the switching hub of the inquiry destination. If the connection destination of the communication port is not another switching hub, the communication terminal to be searched is the inquiry destination When the connection destination of the communication port is another switching hub, the other switching hub is selected again as a new candidate, and the fifth communication hub is notified. (C) the switching hub having the first and second tables notifies the router of the contents stored in the second table of its own device. And an eighth means for specifying and returning the communication port corresponding to the communication terminal involved in the inquiry from the stored contents of the first table of its own device in response to the inquiry from the router. A communication system characterized by the above.

  According to the present invention, the router determines whether or not the search target terminal is connected to each of the switching hubs on the communication path from the router to the search target communication terminal. Identified. In the present invention, the MAC address table is not transferred between the router and the switching hub, and an excessive load is not applied to the network under the router.

  In a more preferred aspect, the hardware identifier is a MAC address, while the other layer identifier is an IP address, and the router assigns an IP address to a communication terminal accommodated in a subordinate network. And a DHCP (Dynamic Host Configuration Protocol) server means for performing mutual conversion between the IP address and the MAC address of the communication terminal. The second means sets the IP address of the communication terminal to be searched. It is converted into a MAC address by the DHCP server means, and a communication port corresponding to the communication terminal is specified from the MAC address and the stored contents of the first table of the own device. In another preferred embodiment, the hardware identifier is a MAC address, while the other layer identifier is a host name, and the router sends an IP address to a communication terminal accommodated in a subordinate network. DHCP server means for performing mutual conversion between the IP address and the MAC address of the communication terminal, and DNS (Domain Name System) server means for performing mutual conversion between the host name and the IP address of the communication terminal And the second means converts the host name of the communication terminal to be searched into an IP address by the DNS server means, and further converts the IP address into a MAC address by the DHCP server means. And corresponding to the communication terminal from the MAC address and the stored contents of the first table of the own device. And identifies the communication port.

  According to these aspects, it becomes possible to search for a communication terminal by specifying an IP address or a host name. In general, an IP address is easier for a person to understand than a MAC address, and a host name is easier for a person to understand than an IP address. According to the above aspect, since the communication terminal to be searched can be specified by the IP address or host name that is easier to understand than the MAC address, the convenience is improved.

  In order to solve the above problems, the present invention provides (A) a communication interface unit having a plurality of communication ports and (B) a communication terminal that transmits a frame addressed to the router. A first table storing a port identifier of a communication port that has received the frame in association with a hardware identifier uniquely identified in the second layer; and (C) an association with each port identifier of the plurality of communication ports. And (D) a switching hub included in a network under the router, the second table storing a hardware identifier of a relay device that is a transfer source of a frame received via the communication port. The second table by notification from the switching hub having the first table and the second table And (E) a hardware identifier of the communication terminal or other identifier that is uniquely converted to the hardware identifier as data indicating a communication terminal to be searched, In response to the input of an identifier of another layer in the OSI reference model, the first process for specifying the communication port corresponding to the communication terminal from the stored contents of the first table, and the first process It is determined whether the connection destination of the specified communication port is a switching hub included in the subordinate network based on the stored contents of the second table for the router, and is not a switching hub In the case where the search is performed, the communication terminal to be searched is specified by the second process for informing that the communication terminal is connected to the own apparatus and the first process. A third process for selecting the switching hub as a candidate for a connection destination of the search target communication terminal when the second process determines that the connection destination of the communication port is a switching hub; A fourth process for querying the switching hub selected in the process 3 for a communication port corresponding to the communication terminal to be searched; and a communication port returned from the switching hub that is the inquiry destination of the fourth process Is determined by referring to the stored contents of the second table for the switching hub stored in the storage means, and the connection destination of the communication port is determined. If it is not another switching hub, the communication terminal to be searched notifies that it is connected to the switching hub of the inquiry destination, If the connection destination of the communication port is another switching hub, a terminal search unit that executes a fifth process of reselecting the other switching hub as a new candidate and repeating the fourth process A router characterized by comprising:

  This is because the communication system described above can be configured by combining such a router and a switching hub having the first and second tables and having the seventh and eighth means. As another aspect of the present invention, an aspect of providing a program characterized by causing a computer to execute the first to fifth processes is also conceivable. As a specific mode of providing such a program, a mode in which the program is written and distributed on a computer-readable recording medium such as a CD-ROM (Compact Disk-Read Only Memory), or an electric communication line such as the Internet is used. A mode of distribution by downloading is conceivable.

  In order to solve the above problems, the present invention provides (A) a communication interface unit having a plurality of communication ports, and (B) a communication terminal that transmits a frame addressed to the switching hub. A first table storing a port identifier of a communication port that has received the frame in association with a hardware identifier uniquely identified in the second layer; and (C) corresponding to each port identifier of the plurality of communication ports. And a second table for storing the hardware identifier of the relay device that is a transfer source of the frame received via the communication port, and (D) the contents of the second table stored in the network including the switching hub and the like. And (E) an inquiry frame transmitted from the router, which is a search frame. From the stored contents of the first table, the corresponding communication port is received when an inquiry frame containing the hardware identifier of the target communication terminal is included and the reception port of the frame transmitted from the communication terminal is inquired. There is provided a switching hub characterized by comprising communication port notification means for specifying and returning the specified result to the router. This is because the above-described communication system can be constructed by combining such a switching hub with the router. Of course, an aspect of providing a program that causes a computer to function as a storage unit that stores the first and second tables, an adjacent relay device notification unit, and a communication port notification unit is also conceivable.

It is a figure which shows the structural example of LAN1A of 1st Embodiment of this invention. It is a figure which shows the structural example of the switching hub 50 contained in the LAN1A. FIG. 10 is a diagram for explaining frame transfer control processing, adjacent relay device notification frame transmission processing, and communication port notification frame transmission processing executed by the switching engine unit 520 of the switching hub 50. It is a figure which shows the data structure of the flame | frame transmitted / received in the same LAN1A. It is a figure which shows the structural example of the router 60 which connects the same LAN1A to an IP network. It is a flowchart which shows the flow of the terminal search process which the routing engine part 620 of the router 60 performs. It is a figure which shows an example of the connection relation of each communication port of the communication terminal 40, the switching hub 50, and the router 60 in the same LAN1A. FIG. 5 is a diagram for explaining operations of a switching hub 50 and a router 60. FIG. 5 is a diagram for explaining operations of a switching hub 50 and a router 60. It is a figure which shows an example of the storage content of the MAC address table of the switching hub 50 and the router 60. FIG. It is a figure which shows an example of the communication sequence in the search process of a communication terminal. It is a figure which shows the structural example of LAN1B of 2nd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<A: First Embodiment>
<A-1: Configuration>
FIG. 1 is a diagram illustrating a configuration example of a LAN 1A that is a communication system according to a first embodiment of this invention. The LAN 1A is a local LAN laid at a company branch, for example, and is connected to an IP network (not shown) such as the Internet by a router 60. The LAN 1A serves as a communication system in the branch, and constitutes an in-company information system in the company together with the LAN in the base laid in another branch. As shown in FIG. 1, the LAN 1A includes four switching hubs (switching hubs 50A, 50B, 50C, and 50D), two communication terminals (communication terminals 40A and 40B), and one operation terminal 30. , Including. As shown in FIG. 1, a switching hub 50A and an operation terminal 30 are connected to the router 60, and a switching hub 50B is connected to the switching hub 50A. Switching hubs 50C and 50D are connected to switching hub 50B. Communication terminal 40A is connected to switching hub 50C, and communication terminal 40B is connected to switching hub 50D.

  Each of the operation terminal 30 and the communication terminals 40A and 40B is, for example, a personal computer. The operation terminal 30 is used to cause the operation manager of the LAN 1A to perform various operations for operation management of the LAN 1A. The communication terminals 40A and 40B are accommodated in the LAN 1A by being connected to any switching hub included in the LAN 1A. Each of the communication terminals 40A and 40B accommodated in the LAN 1A is connected to another communication device (for example, another communication terminal accommodated in the LAN 1A, a communication terminal accommodated in another local LAN, or an IP network). Packet communication in accordance with the IP. Hereinafter, when it is not necessary to distinguish each of the communication terminals 40A and 40B, they are referred to as “communication terminal 40”. Although FIG. 1 illustrates the case where two communication terminals 40 are accommodated in the network under the router 60 (that is, LAN 1A), three or more communication terminals 40 may be accommodated in LAN 1A. Of course, only one communication terminal 40 may be accommodated.

  Each of the switching hubs 50A, 50B, 50C, and 50D in FIG. 1 has the same configuration. Below, when it is not necessary to distinguish each of these four switching hubs, it describes with the "switching hub 50". The switching hub 50 is a relay device that relays data communication in a second layer (data link layer) that is a protocol layer lower than IP. The router 60 is a relay device that relays data communication in the network layer, and serves as a default gateway of the LAN 1A. If the destination IP address of the packet received from the IP network is one of the communication terminals 40A or 40B, the router 60 transfers the packet to the subordinate LAN 1A, and the destination IP address is the communication terminal 40A. If it is not 40B, it is transferred to another router according to the stored contents of the routing table. Since the router 60 functions as a default gateway of the LAN 1A as described above, the LAN 1A may be hereinafter referred to as a “network under the router 60”. In addition, the router 60 in FIG. 1 has a DHCP server function and a DNS server function. With this DHCP server function, the router 60 assigns an IP address to each of the terminals when the operation terminal 30 or the communication terminal 40 is connected to the LAN 1A, and performs mutual conversion between the IP address and the MAC address of each terminal. The router 60 performs mutual conversion between the host name and the IP address assigned to the operation terminal 30 or the communication terminal 40 by the DNS server function.

  In the LAN 1A shown in FIG. 1, each relay device (that is, the router 60 and the switching hub 50) included in the LAN 1A is executed in the process of executing data communication (that is, frame transmission / reception and transfer control) according to the communication protocol of the second layer. ) To detect the adjacent relay device. Here, the adjacent relay device is another relay device that has transferred a frame to the relay device, and in the LAN 1A, is another relay device that is directly connected to the relay device. For example, in the LAN 1A, the adjacent relay device for the router 60 is the switching hub 50A, and the adjacent relay devices for the switching hub 50A are the router 60 and the switching hub 50B. The adjacent relay devices for the switching hub 50B are the switching hubs 50A, 50C and 50D, and the adjacent relay device for the switching hub 50C (or 50D) is the switching hub 50B.

  In the LAN 1A shown in FIG. 1, each of the switching hubs 50 detects the adjacent relay device of its own device and notifies the router 60 of the detection result, while the router 60 indicates the adjacent relay device of each switching hub 50. Information is stored for each switching hub 50. In the LN 1A, the operation manager operates the MAC address, IP address, or host name of a terminal (in this embodiment, the communication terminal 40A or the communication terminal 40B: hereinafter, a search target terminal) for which the connection destination is desired to be specified. When the router 60 is instructed via the terminal 30, the router 60 communicates with each switching hub 50 to identify the connection destination of the search target terminal, and informs the operation terminal 30 of the identification result. Thereby, the said operation manager can grasp | ascertain which switching hub 50 the search object terminal is connected to. As described above, in this embodiment, since the search target terminal can be specified by the IP address or the host name, the convenience is improved as compared with the mode in which the search target terminal can be specified only by the MAC address. Hereinafter, the switching hub 50 and the router 60 that clearly show the features of the present embodiment will be mainly described.

<A-1-1: Configuration of the switching hub 50>
FIG. 2 is a block diagram showing the configuration of the switching hub 50. As shown in FIG. 2, the switching hub 50 includes a communication interface (hereinafter referred to as I / F) unit 510, a switching engine unit 520, and a storage unit 530.

  Communication I / F unit 510 has a plurality of communication ports. Each of the plurality of communication ports is connected to another communication device (in this embodiment, either the router 60, another switching hub 50, or the communication terminal 40) via a communication cable such as 100BASE-T. Is done. Each of the plurality of communication ports is assigned a unique port identifier (for example, a port number) for each communication port, and each communication port can be uniquely identified using the port identifier. The communication I / F unit 510 provides a frame received via each communication port to the switching engine unit 520, and transmits a frame provided from the switching engine unit 520 from a communication port instructed by the switching engine unit 520.

  The storage unit 530 includes, for example, a volatile memory such as a RAM (Random Access Memory) and a nonvolatile memory such as an EPROM (Erasable Programmable Read Only Memory) (none of which is shown in FIG. 2). In this nonvolatile memory, firmware (program) for causing the switching engine unit 520 to execute processing that clearly shows the characteristics of the switching hub of the present invention is stored in advance. On the other hand, the volatile memory is used by the switching engine unit 520 as a work area when executing the firmware. The volatile memory serves as a buffer for temporarily storing frames received by the communication I / F unit 510, and the volatile memory further includes a MAC address table in FIG. 2 and the adjacent relay apparatus table of FIG. 2 are stored.

  The MAC address table in FIG. 2 is not particularly different from that of a conventional switching hub. This MAC address table stores the port identifier of the communication port that received the frame in association with the transmission source MAC address of the frame received by the communication I / F unit 510. The writing of the MAC address and the port identifier to the MAC address table is performed along with the frame transfer control. For example, in the transfer process of a frame (a frame in which an ARP (Address Resolution Protocol) packet is written in the payload portion) transmitted from the communication terminal 40 for resolving the MAC address of the router 60, the transmission source MAC address (that is, the frame) , The MAC address of the communication terminal 40) and the port identifier of the receiving port of the frame are associated and written into the MAC address table. On the other hand, in the transfer process of the response frame to the frame, a process of writing the transmission source MAC address of the frame (that is, the MAC address of the router 60) and the port identifier of the reception port of the frame in association with each other is performed. Is called. The stored contents of the MAC address table are used when frame transfer control based on the destination MAC address is performed.

  In the adjacent relay device table, a connection destination identifier is stored in association with each port identifier of a plurality of communication ports included in the communication I / F unit 510. Here, the connection destination identifier indicates whether or not the connection destination of the communication port associated with the connection destination identifier is an adjacent relay device, and when the connection destination is an adjacent relay device, This is information that uniquely indicates an adjacent relay device. As described above, the adjacent relay device is another relay device (in this embodiment, the router 60 or another switching hub 50) that has transferred a frame to the switching hub 50. In this embodiment, the port identifier of the communication port connected to the adjacent relay device is associated with the MAC address of the adjacent relay device as a connection destination identifier, and other communication devices other than the adjacent relay device (in this embodiment) The communication port to which the communication terminal 40) is connected or the communication port not connected to another communication device is associated with NULL (0x00) as the connection destination identifier.

  This adjacent relay device table is generated in a state where each connection destination identifier is set to NULL when a power source (not shown) of the switching hub 50 is turned on. Then, along with relaying a predetermined specific frame, the stored contents of the table are updated (that is, the connection destination identifier corresponding to the port identifier of the communication port to which the adjacent relay device is connected is set to the adjacent Rewriting to the MAC address of the relay device). Although details will be described later, in this embodiment, as the specific frame, the adjacent relay device notification frame transmitted by each switching hub 50 to notify the router 60 of the stored contents of the adjacent relay device table, and the adjacent relay Two types of request frames that the router 60 multicasts to the subordinate LAN 1A in order to request transmission of the device notification frame are determined in advance.

  The switching engine unit 520 is, for example, a CPU (Central Processing Unit). The switching engine unit 520 functions as a control center of the switching hub 50 by executing the firmware stored in the storage unit 530. The switching engine unit 520 operating according to this firmware executes the processing shown in the flowchart of FIG. 3 every time a frame is received via any one of the communication ports. As shown in FIG. 3, there are three processes executed by the switching engine unit 520 according to the firmware: a frame transfer control process, an adjacent relay apparatus notification frame transmission process, and a communication port notification frame transmission process. Prior to detailed description of the processing contents of these three processes, a data structure of a frame transmitted / received in the LAN 1A will be described.

  FIG. 4A is a diagram showing a data structure of a general frame transmitted / received in the LAN 1A. As shown in FIG. 4A, the frame has a header portion and a payload portion. The header part stores a transmission destination MAC address, a transmission source MAC address, and a type identifier. For example, in the case of the request frame described above, the multicast address is set as the destination MAC address, and the MAC address of the router 60 is set as the source MAC address. This is because the request frame is multicast from the router 60 toward the subordinate LAN 1A. In the case of the adjacent relay device notification frame, the MAC address of the router 60 is set as the transmission destination MAC address, and the MAC address of the switching hub 50 of the transmission source is set as the transmission source MAC address. This is because the adjacent relay device notification frame is unicast from the switching hub 50 to the router 60 as described above.

  The type identifier is an identifier indicating the type of data (packet) stored in the payload portion. Among the frames transmitted and received between the switching hub 50 and the router 60 in the present embodiment, the features of the present embodiment are remarkably shown in addition to the request frame and the adjacent relay device notification frame, Communication port notification frame. Here, the inquiry frame is a frame that the router 60 unicasts to inquire the switching hub 50 of the port identifier of the communication port corresponding to the communication terminal designated as the search target. The communication port notification frame is the inquiry port. This is a frame returned (unicast) by the switching hub 50 to the router 60 as a response to the frame. A value (0xe812) for distinguishing these four types of frames from other frames is set in the header portions of the four types of frames that clearly show the features of the present embodiment. In the following, among the above four types of frames, the request frame and the adjacent relay device notification frame may be collectively referred to as “adjacent relay device information collection frame”.

  FIG. 4B is a diagram illustrating the data structure of the payload portion of the request frame. As shown in FIG. 4B, the destination MAC address, the source MAC address, the frame type identifier, and the transfer source identifier are written in the payload portion of the request frame. The destination MAC address and the source MAC address written in the payload portion of the request frame are the same as those written in the header portion of the request frame. The frame type identifier is an identifier indicating which of the above-described four types of frames. A different value is set in the frame type identifier for each of the four types of frames. A value indicating a request frame is set in the frame type identifier of the payload portion of the request frame. The transmission source identifier is set with the MAC address of the transmission source when the request frame is transmitted, and rewritten to the MAC address of the switching hub 50 that performed the transfer every time the switching hub 50 transfers the frame. It is done.

  FIG. 4C is a diagram illustrating the data structure of the payload portion of the adjacent relay device notification frame. As shown in FIG. 4C, in addition to the transmission destination MAC address, the transmission source MAC address, the frame type identifier, and the transfer source identifier, the adjacent relay device information is written in the payload portion of the adjacent relay device notification frame. . In the frame type identifier of the payload portion of the adjacent relay device notification frame, a value that clearly indicates that the frame is the adjacent relay device notification frame is set. Also, the adjacent relay device information in the payload portion includes the content stored in the adjacent relay device table of the switching hub 50 that is the transmission source of the adjacent relay device notification frame at the time of transmission of the adjacent relay device notification frame (that is, the switching hub). The port identifiers for all 50 communication ports and a list of connection destination identifiers corresponding to the port identifiers) are written. The transmission destination MAC address, transmission source MAC address, and transfer source identifier written in the payload portion of the adjacent relay device notification frame are the same as those in the request frame.

FIG. 4D shows the data structure of the payload portion of the inquiry frame. As shown in FIG. 4D, a destination MAC address, a source MAC address, a frame type identifier, and a search target identifier are written in the payload portion of the inquiry frame. A value that clearly indicates that the frame is an inquiry frame is set in the frame type identifier of the payload portion of the inquiry frame. The search target identifier is an identifier for uniquely identifying a communication terminal designated as a search target (in this embodiment, the MAC address of the communication terminal). FIG. 4E shows the data structure of the payload portion of the communication port notification frame. As shown in FIG. 4E, the destination MAC address, the source MAC address, the frame type identifier, and the connection destination port identifier are written in the payload portion of the communication port notification frame. A value that clearly indicates that the frame is a communication port notification frame is set in the frame type identifier of the payload portion of the communication port notification frame. As described above, the communication port notification frame is a frame returned by the switching hub 50 that has received the inquiry frame as a response to the inquiry frame, and is a port associated with the search target identifier in the MAC address table of the switching hub. An identifier is written as the connection destination port identifier. The destination MAC address and the source MAC address written in the payload portion of these inquiry frame and communication port notification frame were also written in the respective header portions as in the request frame (or the adjacent relay device notification frame). Is the same.
The above is the data structure of the frame transmitted / received in the LAN 1A.

  Next, processing contents of the frame transfer control process, the adjacent relay device notification frame transmission process, and the communication port notification frame transmission process will be described with reference to FIG. As shown in FIG. 3, when the switching engine unit 520 receives a frame via any one of the communication ports of the communication I / F unit 510, the switching frame unit 520 sends the inquiry frame transmitted from the router 60 to the own device. Is determined with reference to the transmission destination MAC address of the header portion of the received frame and the frame type identifier of the payload portion (step SA100). That is, when the transmission destination MAC address is the MAC address of the own device and the frame type identifier is a value indicating that it is an inquiry frame, the determination result in step SA100 is “Yes”. When the determination result in step SA100 is “Yes”, switching engine unit 520 executes the communication port notification frame transmission process (step SA110), and conversely, the determination result in step SA100 is “No”. In some cases, a frame transfer control process is executed as shown in FIG. Prior to step SA100, it is determined whether or not the received frame is any of the above-described four types of frames (that is, whether or not the type identifier of the header portion of the received frame is 0xe812). When the result is “No” (that is, when the type identifier of the received frame is not 0xe812), the processing of SA170 is executed, and conversely, when the determination result of the determination is “Yes” (that is, Of course, the determination of step SA100 may be performed when the type identifier of the received frame is 0xe812.

  As shown in FIG. 3, the frame transfer control process includes transfer control (step SA170) based on the destination MAC address. Here, the transfer control based on the transmission destination MAC address of the received frame is a unicast address in which the transmission destination MAC address is not a unicast address or the transmission destination MAC address is not stored in the MAC address table. In this case, the received frame is flooded, while when the destination MAC address is a unicast address stored in the MAC address table, it is stored in the MAC address table in association with the MAC address. The received frame is transmitted only from the communication port indicated by the port identifier. Here, a MAC address that is not a unicast address includes a multicast address or a broadcast address. Also, flooding means sending the received frame from all communication ports other than the communication port that received the received frame. The transfer control based on the destination MAC address is not particularly different from that in the conventional switching hub. In other words, in the conventional switching hub, only the transfer control based on the destination MAC address (the process of step SA170) is executed as the frame transfer control process.

  The frame transfer control process of the present embodiment includes the processes of steps SA120 to SA140 in addition to the process of step SA170. As shown in FIG. 3, in the frame transfer control process of this embodiment, the switching engine unit 520 first determines whether the received frame is an adjacent relay device information collection frame (that is, a request frame or an adjacent relay device notification frame). It is determined by referring to the frame type identifier of the payload portion of the received frame (step SA120). Specifically, when the frame type identifier of the received frame is a value indicating a request frame or a value indicating an adjacent relay device notification frame, the switching engine unit 520 is an adjacent relay device information collection frame. Judge that there is. When the determination result in step SA120 is “No”, the switching engine unit 520 executes the process in step SA170 described above to end the frame transfer control process, and conversely, the determination result in step SA120. Is “Yes”, the processing after step SA130 is executed.

  In step SA130 executed when the determination result in step SA120 is “Yes”, the switching engine unit 520 associates the adjacent relay device information collection frame with the port identifier of the communication port that has received the adjacent relay device information collection frame in the adjacent relay device table. The stored connection destination identifier is rewritten with the transfer source identifier written in the payload portion of the frame. Next, the switching engine unit 520 rewrites the transfer source identifier of the received adjacent relay device information collection frame with the MAC address of the own device (step SA140). Next, as shown in FIG. 3, the switching engine unit 520 determines whether or not the received frame is a request frame with reference to the frame type identifier of the payload portion of the received frame (step SA150), and the determination result Is Yes, the adjacent relay device notification frame transmission process (step SA160) is further executed. In the adjacent relay device notification frame transmission process, the switching engine unit 520 generates the above-described adjacent relay device notification frame and transmits (unicasts) it to the router 60.

On the other hand, in the communication port notification frame transmission process executed when the determination result in step SA100 is “Yes” (that is, when the received frame is an inquiry frame addressed to the own apparatus), the switching engine unit 520 displays the inquiry frame. The MAC address table of the own device is searched using the search target identifier written in the payload part of the search key as a search key, and the port identifier stored in the MAC address table is specified in association with the MAC address indicated by the search target identifier . Then, the switching engine unit 520 generates a communication port notification frame in which the port identifier is written as a connection destination port identifier in the payload portion, and returns (unicast) the inquiry frame to the transmission source of the inquiry frame. As described above, the port identifier and the MAC address are written to the MAC address table in accordance with the frame transfer control. When the communication terminal 40 is connected to the LAN 1A, the communication terminal 40 always multicasts (or broadcasts) an ARP frame for specifying the MAC address of the router 60 as a default gateway. For this reason, the MAC address of the communication terminal 40 is always registered in the MAC address table of each switching hub 50. Therefore, as long as the communication terminal 40 is designated as a search target, in this communication port notification frame transmission process, the communication port corresponding to the search target identifier is always specified.
The above is the configuration of the switching hub 50.

<A-1-2: Configuration of the router 60>
FIG. 5 is a block diagram showing a configuration of the router 60. As illustrated in FIG. 5, the router 60 includes a communication I / F unit 610, a routing engine unit 620, and a storage unit 630. The communication I / F unit 610 has a plurality of ports like the communication I / F unit 510 of the switching hub 50, and a unique port identifier is assigned to each port. An IP network (not shown in FIG. 1), the switching hub 50A, and the operation terminal 30 are connected to three of the plurality of ports. Similar to communication I / F unit 510, communication I / F unit 610 provides a frame received via each communication port to routing engine unit 620, while a frame provided from routing engine unit 620 is provided by routing engine unit 620. Send out from the specified communication port.

  Similarly to the storage unit 530 of the switching hub 50, the storage unit 630 includes a volatile memory such as a RAM and a nonvolatile memory such as an EPROM (not shown). Firmware is stored in the nonvolatile memory. In the present embodiment, by operating the routing engine unit 620 according to this firmware, the function of the router 60 that significantly shows the features of the present embodiment is realized. On the other hand, the volatile memory is used by the routing engine unit 620 as a work area when executing the firmware, and serves as a buffer for temporarily storing received frames (or packets). . The volatile memory stores the routing table shown in FIG. 5, the MAC address table for the router 60, and the adjacent relay device table.

  The routing engine unit 620 is a CPU (Central Processing Unit) like the switching engine unit 520 of the switching hub 50. The routing engine unit 620 executes firmware stored in the storage unit 630 and functions as a control center of the router 60. The routing engine unit 620 executes DHCP server processing, DNS server processing, packet transfer control processing, multicast processing, adjacent relay device information storage processing, and terminal search processing according to the firmware.

  Of the six processes executed by the routing engine unit 620 according to the firmware stored in the storage unit 630, three of the DHCP server process, the DNS server process, and the packet transfer control process differ from the conventional ones. There is no. That is, the DHCP server process is a process for realizing the DHCP server function, and the DNS server process is a process for realizing the DNS server function. The packet transfer control process is a process for transferring the packet based on the transmission destination IP address of the packet received via the communication I / F unit 610 and the stored contents of the routing table.

  The multicast process is a process of multicasting the request frame toward the network under the router 60 (that is, the LAN 1A). Although details will be described later, in this embodiment, this multicast processing is periodically executed every time a predetermined time T (for example, 3 seconds) elapses after the power of the router 60 (not shown) is turned on.

  The adjacent relay device information storage process is executed every time an adjacent relay device notification frame is received. In this adjacent relay device information storage process, the routing engine unit 620 uses the connection destination identifier stored in the adjacent relay device table of its own device in association with the port identifier of the communication port that received the adjacent relay device notification frame. Overwrite with the transfer source identifier of the relay device notification frame, and use the adjacent relay device information written in the payload portion of the adjacent relay device notification frame as the adjacent relay device table of the transmission source of the frame, the transmission source MAC address of the frame Are written in the storage unit 630 in association with each other (if already written, they are overwritten with new adjacent relay device information). The adjacent relay device table of each switching hub 50 stored in the storage unit 630 in this way is used in terminal search processing described later.

FIG. 6 is a flowchart showing the flow of the terminal search process.
This terminal search process is a process that is executed when a search target terminal is designated by an operation on the operation terminal 30, and is searched for in any of the relay devices (that is, the router 60 and the switching hub 50) included in the LAN 1A. This is processing for identifying whether the target terminal is connected. As shown in FIG. 6, the routing engine unit 620 first stores the contents stored in the adjacent relay device table of the own device and the adjacent relay device table of each switching hub 50 written in the storage unit 630 by the adjacent relay device information storage process. It is determined whether or not there is a contradiction in the connection relationship between the relay devices represented by the contents (step SB100). Here, there is a contradiction in the connection relationship of each relay device. For example, although the MAC address of the switching hub 50A is stored in the adjacent relay device table of the switching hub 50B, the adjacent relay device table of the switching hub 50A includes A state in which the MAC address of the switching hub 50B is not stored.

  If the determination result in step SB100 is “Yes” (that is, if there is a contradiction), the routing engine unit 620 notifies the operation terminal 30 of a message indicating that it is preparing to enable terminal search. (Step SB170) and the execution of the terminal search process is terminated. On the other hand, when the determination result in step SB100 is “No”, the routing engine unit 620 executes the processing after step SB110 in FIG. As described above, the reason why the processing after step SB110 is not executed when there is a contradiction in the connection relation of each relay device is to avoid erroneous determination of the connection destination of the search target terminal due to the contradiction. . This point will be described in detail in the operation example of this embodiment.

  In step SB110 executed subsequently when the determination result in step SB100 is “No”, the routing engine unit 620 determines whether or not there is a communication port corresponding to the search target terminal, and the MAC address table of its own device. The determination is made based on the stored contents. As described above, as a method of specifying the search target terminal, there are a mode of specifying by the MAC address of the terminal, a mode of specifying by the IP address, and a mode of specifying by the host name. When the search target terminal is designated by the MAC address, the communication port corresponding to the search target terminal depends on whether or not there is a communication port whose port identifier is stored in the MAC address table in association with the MAC address. What is necessary is just to determine the presence or absence. When a search target terminal is specified by an IP address, the IP address is converted into a MAC address by the DHCP server function described above, and a port identifier is stored in the MAC address table in association with the MAC address. It may be determined whether or not there is a communication port. Similarly, when the search target terminal is designated by a host name, the host name is converted into an IP address by the DNS server function, and further, the MAC address table is converted by the DHCP server function into the MAC address. The presence / absence of the corresponding communication port may be determined by referring to the stored contents.

  If the determination result in step SB110 is “No”, the routing engine unit 620 informs the operation terminal 30 that the search target terminal is not accommodated in the subordinate network (step SB180), and this terminal The search process is terminated. On the other hand, if the determination result in step SB110 is “Yes”, the routing engine unit 620 selects the port identifier of the communication port as a candidate port identifier, and selects its own device as a connection destination candidate of the search target terminal. (Hereinafter referred to as a candidate relay device) is selected (step SB120). Then, the routing engine unit 620 searches the adjacent relay device table of the candidate relay device using the candidate port identifier as a search key (step SB130), and determines whether the search target terminal is connected to the candidate relay device. (Step SB140). More specifically, the routing engine unit 620 associates with the same port identifier as the candidate port identifier, and if the connection destination identifier stored in the adjacent relay device table of the candidate relay device is NULL, the search target terminal It is determined that the candidate relay device is connected.

When the determination result in step SB140 is “Yes” (that is, when it is determined that the search target terminal is connected to the candidate relay device), the routing engine unit 620 connects the search target terminal to the candidate relay device. The operation terminal 30 is notified (step SB190) that this is done, and the terminal search process is terminated. On the other hand, when the determination result in step SB140 is “No”, the routing engine unit 620 reselects the relay device indicated by the connection destination identifier as a new candidate relay device, and the new candidate relay device. An inquiry frame is transmitted to the apparatus (step SB150). Then, the routing engine unit 620 updates the candidate port identifier with the connection destination port identifier written in the payload portion of the communication port notification frame returned from the new candidate relay device (step SB160), and after step SB130. Repeat the process.
The above is the configuration of the router 60.

<A-2: Operation>
Hereinafter, the operation of this embodiment will be described by taking as an example the case where the router 60 and each switching hub 50 have eight communication ports and are connected to each other as shown in FIG. In FIG. 7, the communication port is indicated by a black circle, and the port number of the communication port is indicated by a number with #. As shown in FIG. 7, the switching hub 50A is connected to the communication port with the port number = 1 of the router 60, and the router 60 is connected to the communication port with the port number = 8 of the switching hub 50A as viewed from the switching hub 50A. Has been.

  As shown in FIG. 7, a switching hub 50B is connected to the communication port of port number = 7 of the switching hub 50A. From the viewpoint of the switching hub 50B, the switching hub 50A is a communication port of port number = 5 of the switching hub 50B. It is connected to the. The switching hub 50C is connected to the communication port of port number = 4 of the switching hub 50B, and the switching hub 50D is connected to the communication port of the same port number = 6. From the viewpoint of the switching hub 50C, the switching hub 50B is connected to the communication port of port number = 3, and from the viewpoint of the switching hub 50D, the switching hub 50B is connected to the communication port of port number = 2. The communication terminal 40A is connected to the communication port of port number = 7 of the switching hub 50C, and the communication terminal 40B is connected to the communication port of port number = 8 of the switching hub 50D. At the start of the operation described below, the connection destination identifiers in the adjacent relay device tables of the router 60 and each switching hub 50 are NULL cleared.

<A-2-1: Neighboring Relay Device Information Collection Operation>
As described above, in the LAN 1A of this embodiment, the connection destination of the search target terminal is specified based on the contents stored in the MAC address table and the adjacent relay device table of the router 60 and each switching hub 50. Therefore, prior to specifying the connection destination of the search target terminal, the MAC address of each adjacent relay device is stored in the adjacent relay device table, and the stored contents of the adjacent relay device table of each switching hub 50 are notified to the router 60. It is necessary to keep it. In the present embodiment, by causing the router 60 and each switching hub 50 to perform the operation described below, the MAC address of the adjacent relay device is stored in each adjacent relay device table, and each switching hub 50 to the router 60 is stored. Notification of the stored contents of the adjacent relay device table is realized.

  The routing engine unit 620 of the router 60 multicasts the request frame at a time T0 when a predetermined time T has elapsed after the power (not shown) of the router 60 is turned on. The request frame multicasted from the router 60 in this manner is first received by the switching hub 50A. The switching engine unit 520 of the switching hub 50A receives the request frame via the communication port of port number = 8, and executes the processes of steps SA130, SA140, SA160, and SA170 in FIG. The reason is as follows. In this operation example, the frame received by the switching hub 50A from the router 60 is a request frame, and a value indicating that the frame is a request frame is set in the frame type identifier of the payload portion. Therefore, the determination result of step SA100 in FIG. 3 is “No”, the determination result of step SA120 is “Yes”, and the determination result of step SA150 is also “Yes”. Therefore, the processes of steps SA130, SA140, SA160 and SA170 in FIG. 3 are executed.

  Since the process of step SA130 is executed, the connection destination identifier stored in the adjacent relay device table of the switching hub 50A in association with port number = 8 is the transfer source identifier (that is, the router) assigned to the received frame. 60 MAC addresses). Further, the transfer source identifier of the received frame is rewritten to the MAC address of the switching hub 50A by the process of step SA140. In step SA160, the adjacent relay device notification frame in which the stored contents of the updated adjacent relay device table by the processing in step SA130 is written as adjacent relay device information is unicast from the switching hub 50A to the router 60. In step SA170, the request frame in which the transfer source identifier has been rewritten by the processing in step SA140 is flooded. This is because the destination MAC address of the request frame is a multicast address as described above. The request frame flooded in this way is received by the switching hub 50B.

  Similarly, when the switching engine unit 520 of the switching hub 50B receives the request frame transferred from the switching hub 50A, the processing of steps SA130, SA140, SA160, and SA170 in FIG. 3 is executed. More specifically, in the switching engine unit 520 of the switching hub 50B, the connection destination identifier corresponding to port number = 5 in the adjacent relay device table of the own device is assigned to the request frame transferred from the switching hub 50A. The adjacent relay device notification frame, which is rewritten by the transfer source identifier (that is, the MAC address of the switching hub 50A) and in which the stored contents of the renewed adjacent relay device table is written as the adjacent relay device information, is unicast to the router 60. In addition, the switching engine unit 520 of the switching hub 50B performs flooding of a request frame in which the transfer source identifier is rewritten to the MAC address of the switching hub 50B. The request frames flooded in this way are received by the switching hubs 50C and 50D, respectively.

  Similarly, when the switching engine unit 520 of the switching hub 50C (or 50D) receives the request frame transferred from the switching hub 50B, the processing of steps SA130, SA140, SA160, and SA170 in FIG. 3 is executed. More specifically, when the switching hub 50C receives the request frame transferred by the switching hub 50B, the switching hub 50C transfers the connection destination identifier corresponding to the port number = 3 in the adjacent relay device table of the own device from the switching hub 50B. The adjacent relay device notification frame that is rewritten by the transfer source identifier (that is, the MAC address of the switching hub 50B) assigned to the requested frame and the rewritten contents of the adjacent relay device table is written as the adjacent relay device information. Unicast to 60.

  Similarly, the switching hub 50D also rewrites the connection destination identifier corresponding to port number = 2 in the adjacent relay device table with the MAC address of the switching hub 50B, and stores the rewritten contents of the adjacent relay device table in the adjacent relay device information. The adjacent relay device notification frame written as is unicast to the router 60. The switching hubs 50C and 50D also perform a process of flooding a request frame in which the transfer source identifier is rewritten to the MAC address of the own device. However, since the switching hub is not connected to the downstream side of the switching hubs 50C and 50D, these request frames are not transferred thereafter.

  As described above, the contents stored in the adjacent relay device table of each of the switching hubs 50A, 50B, 50C, and 50D are in the state shown in FIG. An adjacent relay device notification frame in which the stored contents of each adjacent relay device table is written as adjacent relay device information is unicast from each switching hub 50 to the router 60. In FIG. 8, the stored contents of the adjacent relay device table of each switching hub 50 are indicated by balloons (the same applies to FIG. 9).

  Next, the update of the adjacent relay device table performed in accordance with the transfer control of the adjacent relay device notification frame will be described. When the switching engine unit 520 of the switching hub 50B receives the adjacent relay device notification frame unicast from the switching hub 50C to the router 60 via the communication port with the port number = 4, the steps SA130, SA140 in FIG. The process of SA170 is executed. In this operation example, the frame received by the switching hub 50B from the switching hub 50C is an adjacent relay device notification frame, and a value indicating that the frame is an adjacent relay device notification frame is set in the frame type identifier of the payload portion. ing. Therefore, in the process executed by the switching engine unit 520 when the frame is received (the process shown in the flowchart of FIG. 3), the determination result in step SA100 is “No”, while the determination result in step SA120 is “ Yes, and the determination result in step SA150 is “No”. Therefore, the processes of steps SA130, SA140, and SA170 in FIG. 3 are executed.

  Since the process of step SA130 is executed, the connection destination identifier stored in the adjacent relay device table of the switching hub 50B in association with port number = 4 is the transfer source identifier (ie, switching) assigned to the received frame. The MAC address of the hub 50C is rewritten, and the transfer source identifier of the received frame is rewritten to the MAC address of the switching hub 50B by the process of step SA140. In step SA170, the adjacent relay device notification frame in which the transfer source identifier has been rewritten by the processing in step SA140 is transmitted via the communication port of port number = 5. Similarly, when the adjacent relay device notification frame unicast from the switching hub 50D to the router 60 is received, the switching engine unit 520 of the switching hub 50B executes the processes of steps SA130, SA140, and SA170 in FIG. . As a result, the connection destination identifier corresponding to port number = 6 in the adjacent relay device table of the switching hub 50B is rewritten by the transfer source identifier (that is, the MAC address of the switching hub 50D) assigned to the received frame, and the received frame Is transmitted through the communication port with port number = 5 after rewriting the transfer source identifier.

  When the switching engine unit 520 of the switching hub 50A receives the adjacent relay device notification frame transmitted from the switching hub 50B (or the adjacent relay device notification frame transferred by the switching hub 50B), the switching engine unit 520 similarly performs step SA130 of FIG. , SA140, and SA170 are executed. The switching hub 50A transfers the connection destination identifier corresponding to port number = 7 in the adjacent relay device table to the transfer source identifier given to the adjacent relay device notification frame received from the switching hub 50B (that is, the MAC address of the switching hub 50B). ), The transfer source identifier of the adjacent relay device notification frame is rewritten to the MAC address of the own device and transferred to the router 60. When the router 60 receives the adjacent relay device notification frame transferred from the switching hub 50A via the communication port having the port number = 1, the router 60 sets the connection destination identifier corresponding to the port number in the adjacent relay device table of the own device. Rewrite with the transfer source identifier assigned to.

  As described above, in the process of performing the transfer control of the adjacent relay device notification frame transmitted from the other switching hub 50 to the router 60, the contents stored in the adjacent relay device table of each of the switching hubs 50A and 50B are shown in FIG. The state shown is updated to the state shown in FIG.

  The point to be noted here is that in the above-described operation, the adjacent relay device information written in the adjacent relay device notification frame received by the router 60 from each switching hub 50 is stored in the adjacent relay device table shown in FIG. This corresponds to not the stored contents but the stored contents of the adjacent relay device table shown in FIG. Only the connection relationship between the router 60 and the switching hub 50A is represented in a consistent manner between the stored contents of the adjacent relay apparatus table of the router 60 shown in FIG. 9 and the stored contents of the adjacent relay apparatus table of each switching hub 50 shown in FIG. And other connection relationships are inconsistent. For example, although the MAC address of the switching hub 50B is not stored in the adjacent relay device table of the switching hub 50A, the MAC address of the switching hub 50A is stored in the adjacent relay device table of the switching hub 50B. And so on. For this reason, even if the search target communication terminal is instructed to the router 60 at the time when the adjacent relay device table of each switching hub 50 in the state shown in FIG. 8 is stored in the storage unit 630, the determination result of step SB100 described above Becomes “Yes” and only a notification that preparation is in progress is made.

  When a predetermined time T further elapses from time T0, the routing engine unit 620 multicasts the request frame, and each switching hub 50 executes the same processing as described above. In each adjacent relay device notification frame returned by each switching hub 50 as a response to the request frame transmitted from the router 60 at time T0 + T, the adjacent relay device information corresponding to the stored contents of the adjacent relay device table shown in FIG. Has been written. Therefore, when the adjacent relay device notification frame for the request frame multicasted at time T0 + T (that is, the second multicast if the multicast at time T0 is the first) is received, it is stored in the storage unit 630 of the router 60. The adjacent relay device table (the adjacent relay device table of the router 60 and the adjacent relay device table of each switching hub 50) represents the connection relationship between the router 60 and each switching hub 50 without contradiction. In this state, when a search target terminal is instructed, the determination result in step SB100 is “No”, and the routing engine unit 620 executes the processing after step SB110.

<A-2-2: Communication terminal search operation>
Next, taking as an example a case where the search of the communication terminal 40A is performed under the situation where the stored contents of the adjacent relay device table of the router 60 and each switching hub 50 are in the state shown in FIG. An operation performed by the hub 50 will be described. At the start of the operation described below, the contents stored in the MAC address tables of the router 60 and the switching hub 50 are controlled by the transfer control of the ARP packet transmitted from the communication terminal 40A for MAC address resolution of the router 60. Is as shown in FIG.

  As shown in FIG. 10, the port number = 1 is stored in the MAC address table of the router 60 in association with the MAC address of the communication terminal 40A. In the MAC address table of the switching hub 50A, port number = 7 is stored in association with the MAC address of the communication terminal 40A. In the MAC address table of the switching hub 50B, port number = 4 is stored in association with the MAC address of the communication terminal 40A. In the MAC address table of the switching hub 50C, port number = 7 is stored in association with the MAC address of the communication terminal 40A. In the MAC address table of the switching hub 50D, port number = 2 is stored in association with the MAC address of the communication terminal 40A.

  When the search target terminal (that is, the communication terminal 40A) is designated via the operation terminal 30, the routing engine unit 620 automatically stores the contents stored in the adjacent relay device table of each switching hub 50 stored in the storage unit 630. It is determined whether or not there is a contradiction in the connection relationship represented by the stored contents of the adjacent relay device table of the device (step SB100). As described above, if the stored contents of the adjacent relay device tables of the router 60 and each switching hub 50 are in the state shown in FIG. 9, there is no contradiction in the connection relationship represented by these adjacent relay device tables. Therefore, the determination result in step SB100 is “No”, and the processing after step SB110 is executed. As shown in FIG. 10, the port number = 1 is stored in the MAC address table of the router 60 in association with the MAC address of the communication terminal 40A. For this reason, the determination result in step SB110 is “Yes”, and the routing engine unit 620 executes the processing after step SB120. In step SB120, the routing engine unit 620 selects port number = 1 as a candidate port identifier, and further selects its own device as a candidate relay device. In step SB130, the routing engine unit 620 searches the adjacent relay device table of the candidate relay device (that is, the adjacent relay device table of the router 60), and acquires the connection destination identifier corresponding to the candidate port identifier.

  As is clear from FIG. 9, at the start of the search for the communication terminal 40A, the MAC address of the switching hub 50A is stored in the adjacent relay device table of the router 60 in association with the candidate port identifier (port number = 1). Has been. Therefore, the determination result in step SB140 is “No”, and the routing engine unit 620 reselects the switching hub 50A as a candidate relay device and transmits an inquiry frame (step SB150). That is, in this operation example, as shown in FIG. 11, the inquiry frame Q010 is transmitted from the router 60 to the switching hub 50A. In the payload portion of this inquiry frame Q010, the MAC address of the communication terminal 40A is written as a search target identifier.

  When switching engine unit 520 of switching hub 50A receives inquiry frame Q010, it executes communication port notification frame transmission processing (FIG. 3: step SA110). In the MAC address table of the switching hub 50A, port number = 7 is stored in association with the MAC address of the communication terminal 40A (see FIG. 10). Therefore, the switching engine unit 520 of the switching hub 50A returns a communication port notification frame R010 in which port number = 7 is written as a connection destination port identifier to the router 60, as shown in FIG.

  When receiving the communication port notification frame R010, the routing engine unit 620 selects the connection destination port identifier (that is, port number = 7) written in the payload portion of the communication port notification frame as a new candidate port identifier ( FIG. 6: Step SB160), the processing after Step SB130 is executed again. Since the candidate relay device at this point is the switching hub 50A, in the process of step SB130 executed for the second time in this operation example, the routing engine unit 620 determines the adjacent relay device table of the candidate relay device (that is, the switching hub 50A). The adjacent relay device table) is searched, and the connection destination identifier corresponding to the candidate port identifier (that is, port number = 7) is acquired.

  As is clear from FIG. 9, the adjacent relay device table of the switching hub 50A stores the MAC address of the switching hub 50B in association with the candidate port identifier (port number = 7). Therefore, the determination result of step SB140 executed for the second time in this operation example is also “No”, and the routing engine unit 620 reselects the switching hub 50B as a candidate relay device and transmits an inquiry frame Q020 (FIG. 11). If the adjacent relay device table of the switching hub 50A is not the one shown in FIG. 9 but the one shown in FIG. 8 is stored in the storage unit 630 of the router 60, the adjacent relay device table of the switching hub 50A in FIG. The connection destination identifier associated with the candidate port identifier (port number = 7) is NULL, the determination result in step SB140 is “Yes”, and the search target terminal is connected to the switching hub 50A. An announcement is made. However, it is clear that this notification content is incorrect with reference to FIG. The determination in step SB100 is performed in order to avoid such an erroneous determination. In this embodiment, the routing engine unit 620 performs the determination of step SB100 in order to avoid the occurrence of the erroneous determination as described above. However, the multicast interval of the request frame is sufficiently short, If the search for the communication terminal is rarely performed prior to the multicast being performed twice, or if it is sufficient if a correct result is obtained after repeating the search for the communication terminal several times, step The determination of SB100 and the notification process (step SB170) when the determination result is Yes may be omitted.

  Similar to the inquiry frame Q010, the MAC address of the communication terminal 40A is written in the payload portion of the inquiry frame Q020 as a search target identifier. In the switching hub 50B, the same processing as that of the switching hub 50A described above is executed. More specifically, port number = 4 is stored in the MAC address table of switching hub 50B in association with the MAC address of communication terminal 40A (see FIG. 10). Therefore, as shown in FIG. 11, a communication port notification frame R020 in which port number = 4 is written as a connection destination port identifier in the payload portion is transmitted from the switching hub 50B to the router 60. When the routing engine unit 620 receives the communication port notification frame R020 returned from the switching hub 50B, the connection destination written in the payload portion of the communication port notification frame R020 is the same as when the communication port notification frame R010 is received. A port identifier (that is, port number = 4) is selected as a new candidate port identifier (FIG. 6: Step SB160), and the processes after Step SB130 are executed again. In the process of step SB130 executed for the third time in this operation example, the routing engine unit 620 searches the adjacent relay device table of the candidate relay device (that is, the adjacent relay device table of the switching hub 50B) and searches for the candidate port identifier ( That is, a connection destination identifier corresponding to port number = 4) is acquired.

  As is clear from FIG. 9, the adjacent relay device table of the switching hub 50B stores the MAC address of the switching hub 50C in association with the candidate port identifier (port number = 4). Therefore, the determination result of step SB140 executed for the third time in this operation example is also “No”, and the routing engine unit 620 reselects the switching hub 50C as a candidate relay device and transmits an inquiry frame Q030 (FIG. 11). Similar to the inquiry frames Q010 and Q020, the MAC address of the communication terminal 40A is written in the payload portion of the inquiry frame Q030 as a search target identifier.

  Also in the switching hub 50C, the same processing as that of the switching hubs 50A and 50B described above is executed. More specifically, the port number = 7 is stored in the MAC address table of the switching hub 50C in association with the MAC address of the communication terminal 40A (see FIG. 10). For this reason, as shown in FIG. 11, a communication port notification frame R030 in which port number = 7 is written in the payload portion as a connection destination port identifier is transmitted from the switching hub 50C to the router 60. When the routing engine unit 620 receives the communication port notification frame R030 returned from the switching hub 50C, it is written in the payload portion of the communication port notification frame R030 in the same manner as when the communication port notification frames R010 and R020 are received. The connection destination port identifier (that is, port number = 7) is selected as a new candidate port identifier (FIG. 6: Step SB160), and the processing after Step SB130 is executed again. In the process of step SB130 executed for the fourth time in this operation example, the routing engine unit 620 searches the adjacent relay device table of the candidate relay device (that is, the adjacent relay device table of the switching hub 50C) and searches for the candidate port identifier ( That is, the connection destination identifier corresponding to port number = 7) is acquired.

  As is apparent from FIG. 9, the connection destination identifier associated with the candidate port identifier (port number = 7) in the adjacent relay device table of the switching hub 50C is NULL. Therefore, the determination result of step SB140 executed for the fourth time in this operation example is “Yes”, and the routing engine unit 620 indicates that the search target terminal (that is, the communication terminal 40A) is connected to the switching hub 50C. (FIG. 6: Step SB190). By this notification, the operation manager of the LAN 1A grasps that the search target terminal (communication terminal 40A) is connected to the switching hub 50C.

  As described above, according to the present embodiment, the communication terminal accommodated in the network (ie, LAN 1A) under the router 60 without passing the MAC address table between the router 60 and each switching hub 50. Search can be performed. Thus, in this embodiment, since the MAC address table is not transferred between the router 60 and each switching hub 50, an excessive load is not applied to the network under the router 60.

<B: Second Embodiment>
FIG. 12 is a block diagram illustrating a configuration example of the LAN 1B according to the second embodiment of this invention.
12 and 1, LAN 1B differs from LAN 1A in that it has a switching hub 500 in place of switching hub 50B and that communication terminal 40C is connected to switching hub 500. The switching hub 500 is a conventional switching hub, and is different from the switching hub 50 in that only the frame transfer control based on the transmission destination MAC address of the received frame (that is, the process of step SA170 in FIG. 3) is executed. The communication terminal 40C is a general personal computer like the communication terminal 40A and the communication terminal 40B.

  In the LAN 1B, the request frame transferred from the switching hub 50A to the switching hub 500 is transferred to the switching hubs 50C and 50D without rewriting the transfer source identifier. Therefore, the MAC address of the switching hub 50A is written in the adjacent relay device table of each of the switching hubs 50C and 50D in association with the port identifier of the communication port to which the switching hub 500 is connected.

  Similarly, the adjacent relay device notification frame returned from each of the switching hubs 50C and 50D to the router 60 is transferred to the switching hub 50A by the switching hub 500 without rewriting the transfer source identifier. The switching control unit 520 of the switching hub 50A receives the adjacent relay device notification frame transmitted from each of the switching hubs 50C and 50D via the communication port to which the switching hub 500 is connected, and these adjacent relay device notification frames. The content stored in the adjacent relay device table is updated every time. That is, the content of the update performed in response to the previously received one of the adjacent relay device notification frames transmitted from each of the switching hubs 50C and 50D depends on the content of the update performed in response to the one received later. Overwritten.

  For this reason, for example, when the former reaches the switching hub 50A first among the adjacent relay device notification frames returned by each of the switching hubs 50C and 50D in response to the request frame multicasted first from the router 60, In the adjacent relay device information included in the adjacent relay device notification frame returned by the switching hub 50A according to the second request frame multicast, the switching hub 50D is included in the port identifier of the communication port to which the switching hub 500 is connected. Are associated with each other. On the other hand, in the adjacent relay device information received by the router 60 from the switching hub 50C, the MAC address of the switching hub 50A is associated with the port identifier of the communication port to which the switching hub 500 is connected. That is, a contradiction arises in the connection relationship between the switching hub 50A and the switching hub 50C.

  On the other hand, when the latter of the adjacent relay device notification frames returned by each of the switching hubs 50C and 50D in response to the request frame multicasted first from the router 60 reaches the switching hub 50A first. In the adjacent relay device information included in the adjacent relay device notification frame returned by the switching hub 50A in response to the second request frame multicast, the port identifier of the communication port to which the switching hub 500 is connected is the switching hub. Only 50C MAC addresses are associated. On the other hand, in the adjacent relay device information received by the router 60 from the switching hub 50D, the MAC address of the switching hub 50A is associated with the port identifier of the communication port to which the switching hub 500 is connected. That is, a contradiction arises in the connection relationship between the switching hub 50A and the switching hub 50D. Thus, no matter which of the adjacent relay device notification frames returned by each of the switching hubs 50C and 50D arrives at the router 60 first, the connection relationship between the switching hub 50A and the switching hub 50C (or 50D) is inconsistent. Occurs. For this reason, the determination result in step SB100 in FIG. 6 is always Yes, and the communication terminal cannot be searched.

  However, if the determination in step SB100 in FIG. 6 is not performed, it is possible to specify the connection destination of either the communication terminal 40A or the communication terminal 40B. For example, when the adjacent relay device notification frame transmitted from the switching hub 50C reaches the switching hub 50A earlier than the frame transmitted from the switching hub 50D, it is possible to search for the communication terminal 40B. However, the connection destination of the communication terminal 40A cannot be specified accurately. The reason is as follows.

  The MAC address table of the switching hub 50A stores the port identifier of the communication port to which the switching hub 500 is connected in association with the MAC address of the communication terminal 40A. This is because the ARP frame transmitted from the communication terminal 40A reaches the switching hub 50A through flooding by the switching hub 500. Therefore, when the router 60 transmits an inquiry frame in which the MAC address of the communication terminal 40A is written as a search target identifier to the switching hub 50A, the switching hub 50A sets the port identifier of the communication port to which the switching hub 500 is connected to the connection destination. The communication port notification frame written as the port identifier is returned to the router 60. On the other hand, as described above, the MAC address of the switching hub 50D is stored in the adjacent relay device table of the switching hub 50A in association with the port identifier. Therefore, the router 60 transmits an inquiry frame in which the MAC address of the communication terminal 40A is written as a search target identifier to the switching hub 50D.

  The MAC address table of the switching hub 50D stores the port identifier of the communication port to which the switching hub 500 is connected in association with the MAC address of the communication terminal 40A. This is because the ARP frame transmitted from the communication terminal 40A reaches the switching hub 50D through flooding by the switching hub 500 as described above. For this reason, the switching hub 50D returns a communication port notification frame in which the port identifier of the port identifier of the communication port to which the switching hub 500 is connected as a connection destination port identifier is returned to the router 60. Although the MAC address of the switching hub 50A is stored in the adjacent relay device table of the switching hub 50D in association with the port identifier, an inquiry frame has already been transmitted to the switching hub 50A, and again the switching hub 50A. Even if you send an inquiry frame to, it just goes around. As described above, when the same inquiry frame is transmitted again to the switching hub 50 that has already transmitted the inquiry frame, the search for the communication terminal is terminated at this point, and the communication terminal to be searched It may be determined that the switching hub 50 is connected. However, it goes without saying that the connection destination of the search target communication terminal is not accurately specified. When the adjacent relay device notification frame transmitted from the switching hub 50C reaches the switching hub 50A earlier than the frame transmitted from the switching hub 50D, the connection destination of the communication terminal 40A is accurately specified. That's why you can't. For the same reason, when the adjacent relay device notification frame transmitted from the switching hub 50D reaches the switching hub 50A earlier than the frame transmitted from the switching hub 50C, the connection destination of the communication terminal 40B is accurately set. It cannot be specified. Similarly, the communication terminal 40C connected to the switching hub 500 cannot be searched.

  As described above, when a conventional switching hub is included in the network under the router 60, a communication terminal connected to the conventional switching hub cannot be searched, but the network is connected to the switching hub 50. It does not mean that the search for a communication terminal that is present cannot be performed at all. In addition, when the above-described cruising occurs, it can be inferred that there may be one or more conventional switching hubs at the occurrence location based on the occurrence.

  Needless to say, if all of the switching hubs included in the network under the router 60 are conventional, the search for the communication terminals accommodated in the network cannot be performed at all. If at least one switching hub 50 according to the present invention is included, a search for a communication terminal connected to the switching hub 50 can be performed. Also in this embodiment, since the MAC address table is not transferred between the router 60 and each switching hub 50, an excessive load is not applied to the network under the router 60.

<C: Deformation>
Although the first and second embodiments of the present invention have been described above, the following modifications may of course be added to these embodiments.
(1) In each of the embodiments described above, the router 60 periodically executes request frame multicasting at predetermined time intervals, while the switching hub 50 sends the adjacent relay device notification frame to the router 60 when the request frame is received. To reply to. However, in addition to the periodic multicast (or instead of the periodic multicast), the request frame may be multicast to the router 60 when a predetermined type of packet is received.

  For example, the request frame is transmitted to the router 60 when the ARP packet is received for resolving the MAC address of the own device. The fact that a new ARP packet has been received means that a new communication terminal has been connected to the network under the router 60. When a new communication terminal is additionally connected in this way, a new switching hub 50 is connected to the existing switching hub 50, and the new communication terminal is connected to the new switching hub 50. There is also. If the router 60 is made to transmit a request frame when a new ARP packet is received, even if a new switching hub 50 is added as a new communication terminal is connected, It becomes possible to search for the new communication terminal. When the router 60 also serves as a DHCP server as in the above embodiments, a request frame is triggered when a packet requesting IP address assignment is received from a subordinate communication terminal. You may make it multicast.

(2) In each of the above-described embodiments, the adjacent relay device notification frame is transmitted to the switching hub 50 when the request frame is received. However, the adjacent relay device notification frame may be transmitted to the switching hub 50 periodically at predetermined time intervals. As described above, in the aspect in which the adjacent relay device notification frame is periodically transmitted to the switching hub 50, it is not necessary to multicast the request frame from the router 60, and among the frames to be multicast from the router 60 to the subordinate LAN. A transfer source identifier may be assigned to a predetermined part and multicasted. This is because each switching hub 50 stores the MAC address of the adjacent relay device on the upstream side (side closer to the router 60) in the adjacent relay device table.

(3) In each of the above-described embodiments, the router 60 selects a new candidate relay device, but the switching hub 50 can also perform the selection. Specifically, when the inquiry frame is received, the switching engine unit 520 performs the following processing. That is, the switching engine unit 520 searches the MAC address table of its own device using the search target identifier written in the payload portion of the inquiry frame as a search key, and stores the MAC address table in association with the search target identifier. Get the port identifier. Next, the switching engine unit 520 searches its own MAC address table using the port identifier as a search key, and acquires a connection destination identifier corresponding to the port identifier. Then, the switching engine unit 520 unicasts to the router 60 the communication port notification frame in which the connection destination identifier is written in the payload portion. If the connection destination identifier written in the payload portion of the communication port notification frame is NULL in the router 60, the search target terminal is connected to the switching hub 50 that is the transmission source of the communication port notification frame. If the connection destination identifier is a value other than NULL, an inquiry frame is transmitted using the switching hub 50 indicated by the connection destination identifier as a new candidate relay device. The process is executed. In such an aspect, it is not essential to store the adjacent relay device table of each switching hub 50 in the router 60. However, in order to make the routing engine unit 620 determine whether the contents stored in the adjacent relay device table of each switching hub 50 are inconsistent with each other (that is, determine whether the communication terminal can be searched). Of course, the adjacent relay device table of each switching hub 50 may be stored in the router 60. However, in such an aspect, since the processing load in the switching hub 50 is higher than that in each of the above embodiments by the amount of searching for the adjacent relay device table, the switching hub 50 having a sufficiently high processing capability is used. Needless to say, there is a need.

(4) In each of the above-described embodiments, every time the request frame is received, the adjacent relay device notification frame in which the adjacent relay device information is written in the payload portion is returned to each switching hub 50. However, if there is no change in the stored contents of the adjacent relay apparatus table between the reception of the N (natural number) request frame and the reception of the (N + 1) th request frame, the request frame received for the (N + 1) th request frame When responding, an adjacent relay device notification frame in which data indicating that there is no change in the adjacent relay device information instead of the adjacent relay device information is written in the payload portion may be returned. When the adjacent relay device notification frame in which the data indicating that there is no change in the adjacent relay device information is received in the payload portion is received, the routing engine unit 620 needs to update the adjacent relay device information by overwriting. It goes without saying that there is nothing.

(5) In each embodiment described above, the router 60 has a DHCP server function and a DNS server function. However, if a DHCP server and DNS server separate from the router 60 are provided in the network under the router 60 and the router 60 can access these servers, the router 60 can function as a DHCP server. It is not necessary to have a DNS server function. That is, the DHCP server function and the DNS server function are not essential for the router of the present invention. In each of the above-described embodiments, the IP address is dynamically allocated to each communication terminal 40 by the DHCP server function of the router 60. However, it is of course possible to assign an IP address to each communication terminal 40 in a fixed manner. . Even when an IP address is fixedly assigned to each communication terminal 40 and a search target terminal is designated by the fixedly assigned IP address, the communication is started from the IP address by using ARP. This is because the MAC address of the terminal can be obtained. In each embodiment described above, the MAC address is used as a hardware identifier for uniquely identifying each communication device in the second layer. However, a new hardware identifier different from the MAC address is defined, and the identifier May be used.

(6) In each of the above-described embodiments, the frame transfer control processing, the adjacent relay device notification frame transmission processing, and the communication port notification frame transmission processing that clearly show the characteristics of the switching hub of the present invention are realized by software. However, each of the frame transfer control means for executing the frame transfer control process, the adjacent relay apparatus notification means for executing the adjacent relay apparatus notification frame transmission process, and the communication port notification means for executing the communication port notification frame transmission process is used as an electronic circuit or the like. Of course, the switching hub 50 may be configured by incorporating these units in place of the switching engine unit 520. Similarly for the router 60, the multicast processing, the adjacent relay device storage processing, and the terminal search processing may be realized by hardware such as an electronic circuit.

(7) In each of the above-described embodiments, the frame is adjacent based on the frame type identifier written in the payload portion of the frame (or based on the type identifier of the header portion and the frame type identifier of the payload portion). Although it is determined whether or not the information is for collecting relay device information, the determination may be performed depending on whether or not a transfer source identifier is assigned. For example, when collecting adjacent relay device information using frames transmitted / received according to the existing communication protocol in the second layer, based on the frame type identifier (or the header part type identifier and the payload part frame) This is because the above determination cannot be made (based on the type identifier). In a mode in which a frame transmitted / received according to an existing communication protocol is used, the transfer source identifier (or the transfer source identifier and the adjacent relay device information) may be written in an empty area of the header portion of the frame.

  1A, 1B ... LAN, 30 ... operation terminal, 40A, 40B, 40C ... communication terminal, 50A, 50B, 50C, 50D, 500 ... switching hub, 60 ... router, 510, 610 ... communication I / F unit, 520 ... switching Engine unit, 530, 630 ... storage unit, 620 ... routing engine unit.

Claims (8)

In a communication system including a router and a plurality of switching hubs included in a network under the router,
(A) At least one of the plurality of switching hubs and the router are
A first identifier that stores a port identifier of a communication port that has received the frame in association with a hardware identifier that uniquely identifies a communication terminal that has transmitted a frame addressed to the own device in the second layer of the OSI reference model Table,
A second table that stores a hardware identifier of a relay device that is a transfer source of a frame received via the communication port in association with a port identifier of the communication port;
(B) The router
First means for acquiring and storing the stored contents of the second table by notification from the switching hub having the first and second tables;
The fact that the identifier of another layer in the OSI reference model, which is a hardware identifier of the communication terminal or other identifier uniquely converted into the hardware identifier, is input as data indicating the communication terminal to be searched As a trigger, a second means for specifying a communication port corresponding to the communication terminal in the own device from the stored contents of the first table of the own device;
It is determined whether or not a switching hub is connected to the communication port specified by the second means with reference to the contents stored in the second table for the own device, and the connection destination of the communication port is the switching hub A third means for informing that the communication terminal to be searched is connected to its own device,
When the third means determines that the connection destination of the communication port specified by the second means is a switching hub, the switching hub is selected as a connection destination candidate of the communication terminal to be searched. A fourth means to:
A fifth means for querying a switching hub selected as a connection destination candidate of the search target communication terminal for a communication port corresponding to the search target communication terminal in the switching hub;
Whether the connection destination of the communication port returned from the inquiry-destination switching hub by the fifth means is another switching hub or not is obtained from the inquiry-destination switching hub by the first means. When the determination is made with reference to the stored contents of the table, and the connection destination of the communication port is not another switching hub, a notification that the communication terminal to be searched is connected to the switching hub of the inquiry destination On the other hand, if the connection destination of the communication port is another switching hub, a sixth means for re-selecting the other switching hub as a new candidate and repeating the processing by the fifth means, Have
(C) a switching hub having the first and second tables,
A seventh means for notifying the router of the contents stored in the second table of its own device;
An eighth means for specifying and returning a communication port corresponding to the communication terminal involved in the inquiry from the stored contents of the first table of the own device in response to an inquiry from the router; system. The hardware identifier is a MAC (Media Access Control) address, while the other layer identifier is an IP address,
The router assigns an IP (Internet Protocol) address to a communication terminal accommodated in a subordinate network and performs mutual conversion between the IP address and the MAC address of the communication terminal. ) Have server means,
The second means converts the IP address of the communication terminal to be searched into a MAC address by the DHCP server means, and performs communication corresponding to the communication terminal from the MAC address and the contents stored in the first table of the own apparatus. The communication system according to claim 1, wherein a port is specified. The hardware identifier is a MAC address, while the other layer identifier is a host name;
The router assigns an IP address to a communication terminal accommodated in a subordinate network, and performs DHCP server means for mutual conversion between the IP address and the MAC address of the communication terminal, and a host of the communication terminal DNS (Domain Name System) server means for performing mutual conversion between names and IP addresses,
The second means converts the host name of the communication terminal to be searched into an IP address by the DNS server means, and further converts the IP address into a MAC address by the DHCP server means. The communication port corresponding to the communication terminal is specified from the stored contents of the first table. The communication system according to claim 1. In a communication system including a router and a plurality of switching hubs included in a network under the router,
(A) At least one of the plurality of switching hubs and the router are
A first identifier that stores a port identifier of a communication port that has received the frame in association with a hardware identifier that uniquely identifies a communication terminal that has transmitted a frame addressed to the own device in the second layer of the OSI reference model Table,
A second table that stores a hardware identifier of a relay device that is a transfer source of a frame received via the communication port in association with a port identifier of the communication port;
(B) The router
The fact that the identifier of another layer in the OSI reference model, which is a hardware identifier of the communication terminal or other identifier uniquely converted into the hardware identifier, is input as data indicating the communication terminal to be searched As a trigger, a first means for specifying a communication port corresponding to the communication terminal in the own device from the stored contents of the first table of the own device;
It is determined whether or not a switching hub is connected to the communication port specified by the first means with reference to the contents stored in the second table for the own device, and the connection destination of the communication port is the switching hub A second means for informing that the communication terminal to be searched is connected to the own device;
When the second means determines that the connection destination of the communication port specified by the first means is a switching hub, the switching hub is selected as a connection destination candidate of the communication terminal to be searched. A third means to:
A fourth means for inquiring whether the search target communication terminal is connected to the switching hub selected as a connection destination candidate of the search target communication terminal;
If there is a response from the switching hub that is the inquiry destination of the fourth means that the search target communication terminal is connected, the connection destination of the search target communication terminal is the switching hub. While performing notification, if there is a reply that another switching hub should be a new inquiry destination, the other switching hub is selected again as a connection destination candidate of the search target communication terminal, and the And fifth means for repeating the processing by the fourth means,
(C) a switching hub having the first and second tables,
In response to an inquiry from the router, a sixth means for specifying a communication port corresponding to the communication terminal involved in the inquiry from the stored contents of the first table of the own device;
When it is determined whether another switching hub is connected to the communication port specified by the sixth means based on the stored contents of the second table of its own device, and the other switching hub is connected If it is determined, the router responds to the router that the other switching hub should be a new inquiry destination, and if it is determined that the other switching hub is not connected, the communication to be searched And a seventh means for replying to the router that the terminal is connected to its own device. (A) a communication interface unit having a plurality of communication ports;
(B) Stores the port identifier of the communication port that received the frame in association with the hardware identifier that uniquely identifies the communication terminal that has transmitted the frame to the router in the second layer of the OSI reference model. A first table;
(C) a second table that stores a hardware identifier of a relay device that is a transfer source of a frame received via the communication port in association with each port identifier of the plurality of communication ports;
(D) A switching hub included in the network under the router, and the contents stored in the second table by notification from the switching hub having the first table and the second table for the switching hub Storage means for acquiring and storing
(E) As data indicating a communication terminal to be searched, a hardware identifier of the communication terminal or another identifier uniquely converted to the hardware identifier, and an identifier of another layer in the OSI reference model is input. In response to this, a first process for specifying a communication port corresponding to the communication terminal from the stored contents of the first table;
Determining whether the connection destination of the communication port identified in the first process is a switching hub included in the subordinate network based on the stored contents of the second table for the router; If it is determined that it is not a switching hub, a second process for notifying that the communication terminal to be searched is connected to its own device;
If the second process determines that the connection destination of the communication port identified in the first process is a switching hub, the switching hub is used as a candidate for the connection destination of the communication terminal to be searched. A third process to select;
A fourth process of inquiring a communication port corresponding to the communication terminal to be searched with respect to the switching hub selected in the third process;
Whether the connection destination of the communication port returned from the switching hub that is the inquiry destination of the fourth process is another switching hub, the second table for the switching hub stored in the storage means If the connection destination of the communication port is not another switching hub, the search target communication terminal notifies that it is connected to the inquiry switching hub. On the other hand, when the connection destination of the communication port is another switching hub, a terminal that executes the fifth process of reselecting the other switching hub as a new candidate and repeating the fourth process Search means;
A router characterized by comprising: (A) a communication interface unit having a plurality of communication ports;
(B) Stores the port identifier of the communication port that received the frame in association with the hardware identifier that uniquely identifies the communication terminal that has transmitted the frame to the switching hub in the second layer of the OSI reference model. A first table to
(C) a second table that stores a hardware identifier of a relay device that is a transfer source of a frame received via the communication port in association with each port identifier of the plurality of communication ports;
(D) Adjacent relay device notification means for notifying the contents stored in the second table to a router connecting the network including the switching hub and another network;
(E) An inquiry frame transmitted from the router is received, and includes an inquiry frame that includes the hardware identifier of the communication terminal to be searched and inquires the reception port of the frame transmitted from the communication terminal. And a communication port notifying means for specifying the corresponding communication port from the stored contents of the first table and returning the specified result to the router. On the computer,
A first table that stores a port identifier of a communication port that has received the frame in association with a hardware identifier that uniquely identifies the communication terminal that has transmitted the frame to the computer in the second layer of the OSI reference model And a second table for storing the hardware identifier of the relay device that is the transfer source of the frame received via the communication port in association with the port identifier of each communication port, and A switching hub included in a network connected to another network via the network, the storage contents of the second table being obtained from the switching hub having the first table and the second table for the switching hub First processing to be stored,
The fact that the identifier of another layer in the OSI reference model, which is a hardware identifier of the communication terminal or other identifier uniquely converted into the hardware identifier, is input as data indicating the communication terminal to be searched As a trigger, a second process for specifying a communication port corresponding to the communication terminal from the stored contents of the first table for the computer;
Determining whether the connection destination of the communication port identified in the second process is a switching hub included in the subordinate network based on the stored contents of the second table for the computer; If it is determined that it is not a switching hub, a third process for notifying that the communication terminal to be searched is connected to its own device;
If it is determined in the third process that the connection destination of the communication port specified in the second process is a switching hub, the switching hub is a candidate for the connection destination of the communication terminal to be searched. A fourth process to select as
A fifth process of querying the switching hub selected in the fourth process for a communication port corresponding to the search target communication terminal;
Whether the connection destination of the communication port returned from the inquiry destination switching hub in the fifth process is another switching hub or not is referred to the contents stored in the second table for the inquiry destination switching hub. If the connection destination of the communication port is not another switching hub, the communication terminal to be searched notifies that it is connected to the switching hub of the inquiry destination, while the communication port A connection destination is another switching hub, a sixth process of reselecting the other switching hub as a new candidate and repeating the fifth process;
A program characterized by having executed. Computer
A first table that stores a port identifier of a communication port that has received the frame in association with a hardware identifier that uniquely identifies the communication terminal that has transmitted the frame to the computer in the second layer of the OSI reference model Storage means for storing a second table for storing a hardware identifier of a relay device that is a transfer source of a frame received via the communication port in association with a port identifier of each communication port;
Neighboring relay device notifying means for notifying the storage contents of the second table to a router connecting the network including the computer and another network;
Corresponding to the inquiry frame transmitted from the router, received the inquiry frame that includes the hardware identifier of the communication terminal to be searched and inquires the reception port of the frame transmitted from the communication terminal. And a communication port notifying means for specifying a communication port to be specified from the stored contents of the first table and returning the specified result to the router.

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