JP2011166466A - Network system, method of identifying loop generating switch , network management device, and switch device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily identify a switch device generating a loop in a network. <P>SOLUTION: A network management device 110 transmits a loop detecting frame 300a to a terminal device 210a. The switch devices 120A to C register their MAC addresses in the received loop detecting frame 300a, and the loop detecting frame 300a is transferred to the terminal device 210a. In this case, however, when the MAC addresses are already registered in the received loop detecting frame 300a in the switch devices 120A to C (when the loop detecting frame 300a is looped), the loop detecting frame 300a is transferred to the network management device 110. The network management device 110 specifies that a loop has occurred in the switch device 120C on the basis of the MAC addresses of the switch devices 120A to C registered in the returned loop detecting frame 300a. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a network system, a loop generation switch identification method, a network management apparatus, and a switch apparatus that detect a loop in a network and identify a location where the loop occurs.

If there is a switch device connected in a loop at layer 2 (data link layer) of the network, broadcast data continues to be repeatedly broadcast by the switch device. This is called broadcast storm.
When a broadcast storm occurs, the communication bandwidth is consumed, and in the worst case, other communication cannot be performed.

In order to prevent such a situation from occurring, there is a network system to which IEEE 802.1D is applied.
A network system to which IEEE 802.1D is applied has a mechanism for logically constructing a route so that a loop does not occur.

However, when IEEE 802.1D is applied, there are many restrictions such as a long spanning time of Spanning Tree Protocol (STP) and a limited number of switch devices.
For this reason, a network system is often constructed without applying IEEE 802.1D, and this network system does not have a mechanism for avoiding loops and maintaining network communication.

A network failure due to a loop such as a broadcast storm significantly impedes the convenience of network users.
In order to restore the network at an early stage, it is necessary to quickly identify the switch device that is causing the loop.

IEEE 802.1d (ISO / IEC Final DIS 15802-3 (IEEE P802.1D / D17), May 25, 1998)

A network system to which IEEE 802.1D is applied has a mechanism for logically constructing a route so that a loop does not occur.
However, when IEEE 802.1D is applied, there are many restrictions such as STP reconfiguration time and the number of switch devices.
On the other hand, when IEEE 802.1D is not applied, there is no mechanism for avoiding a loop. When a loop occurs, it takes a lot of time to search for and restore the cause, which significantly impedes the convenience for network users.

  An object of the present invention is to make it possible to easily identify, for example, a switch device that generates a loop in a network.

The network system of the present invention
A network management device for transmitting data including an address registration area for registering an address for identifying a switch device to a specific terminal device via the switch device as a loop detection frame;
The loop detection frame is received, it is determined whether or not its own address is registered in the address registration area of the received loop detection frame, and if its own address is not registered, its own address is registered in the address registration area of the loop detection frame. A switch device that registers an address and transfers the loop detection frame registered with its own address to the terminal device, and transfers the loop detection frame to the network management device when its own address is registered. Have
The network management device receives the loop detection frame transferred to itself, and identifies the loop occurrence switch based on the address registered in the address registration area of the received loop detection frame.

  According to the present invention, for example, a switch device (loop generation switch) that generates a loop in a network can be easily identified.

1 is a configuration diagram of a network system 100 according to Embodiment 1. FIG. FIG. 3 is a diagram illustrating an example of hardware resources of the network system 100 and the communication system 200 in the first embodiment. 2 is a functional configuration diagram of a network management device 110 and a switch device 120 according to Embodiment 1. FIG. FIG. 4 shows a data structure of a loop detection frame 300 in the first embodiment. 6 is a flowchart showing processing of the network management device 110 in the loop generation switch specifying method according to the first embodiment. 5 is a flowchart showing processing of the switch device 120 in the loop generation switch specifying method according to the first embodiment. FIG. 3 is a configuration diagram of a network system 100 according to a second embodiment. 10 is a flowchart showing processing of the network management apparatus 110 in the loop occurrence switch specifying method according to the second embodiment. FIG. 5 is a configuration diagram of a network system 100 in a third embodiment. FIG. 9 is a functional configuration diagram of a network management device 110 and a switch device 120 in a third embodiment. FIG. 11 shows a data structure of a loop detection notification frame 400 in the third embodiment. 10 is a flowchart showing processing of the switch device 120 in the loop generation switch specifying method according to the third embodiment.

Embodiment 1 FIG.
The management device transmits specific data, the switch device sets its own address to the specific data and transfers the specific data, and the management device generates a loop based on the address set in the specific data returned. A mode for specifying the switching device is described.

FIG. 1 is a configuration diagram of a network system 100 according to the first embodiment.
The configuration of the network system 100 and the outline of the loop generation switch specifying method in the first embodiment will be described below with reference to FIG.

  The network system 100 includes a network management device 110 and a plurality of switch devices 120A to 120E (switches with a loop detection function).

  The network management device 110 is a device that identifies a switch that generates a network loop.

The network loop means that communication data is repeatedly transferred between the same switches in the network.
Hereinafter, the network loop is simply referred to as “loop”.

A switch is a device that relays (transfers) communication data, and a switching hub (layer 2 switch) in the data link layer and a router (layer 3 switch) in the network layer are examples of switches.
Hereinafter, a switch that generates a loop is referred to as a “loop generation switch”.

  The switch devices 120A to 120E are switches having a function (loop detection function) for processing (for example, updating) a loop detection frame 300 described later.

The network management device 110 and the switch devices 120A to 120E are connected to each other by a communication cable.
In FIG. 1, the network management device 110 is connected to the switch device 120A, the switch device 120A is connected to the switch device 120B and the switch device 120D, the switch device 120B is connected to the switch device 120C, and the switch device 120D is connected to the switch device 120E. Connected.

  The network system 100 is connected to other network systems via a network. Hereinafter, this other network system is referred to as “communication system 200”.

The communication system 200 includes terminal devices 210a and 210b and connecting devices 220a and 220b (switches having no loop detection function).
The terminal devices 210a and 210b are devices (for example, personal computers) having a communication function.
The connecting devices 220a and 220b are conventional switches and do not have a loop detection function.

  In FIG. 1, the connecting device 220a is connected to the switch device 120C and the terminal device 210a, and the connecting device 220b is connected to the switch device 120E and the terminal device 210b.

Each switch (switch devices 120A to 120E, connecting devices 220a and 220b) includes a plurality of terminals (ports) (not shown) to which communication cables are connected.
Each switch stores information (hereinafter referred to as a switching table) in which a MAC address is associated with a port number, and outputs data to be transferred to a port corresponding to a destination MAC address.

  The network management apparatus 110 transmits loop detection frames 300a and 300b, which will be described later, to the terminal apparatuses 210a and 210b in order to specify the loop generation switch.

In the network configuration of FIG. 1, originally, the loop detection frame 300a addressed to the terminal device 210a is transmitted to the terminal device 210a via the switch device 120A, the switch device 120B, the switch device 120C, and the connecting device 220a.
The loop detection frame 300b addressed to the terminal device 210b is transmitted to the terminal device 210b via the switch device 120A, the switch device 120D, the switch device 120E, and the connecting device 220b.

Here, it is assumed that an incorrect port number is set in the switching table of the switch device 120C in association with the MAC address “MACa” of the terminal device 210a.
That is, in the switching table of the switch device 120C, not the port number of the port connected to the connection device 220a but the port number of the port connected to the switch device 120B is set in association with the MAC address “MACa” of the terminal device 210a. ing.

For this reason, the switch device 120C returns the communication data (including the loop detection frame 300a) addressed to the terminal device 210a transferred from the switch device 120B to the switch device 120B.
Since the communication data (excluding the loop detection frame 300a) returned to the switch device 120B is addressed to the terminal device 210a, it is transferred again from the switch device 120B to the switch device 120C. Communication data continues to be transferred between the switch device 120B and the switch device 120C. That is, a loop occurs between the switch device 120B and the switch device 120C.
At this time, the switch device 120C is a loop generation switch.

  However, since the switch device 120B has a function of processing the loop detection frame 300a (loop detection function), the loop detection frame 300a returned from the switch device 120C is not re-transferred to the switch device 120C, and the switch device 120B passes through the switch device 120A. To the network management apparatus 110.

The switching devices 120A to 120C set their own MAC address in the loop detection frame 300a when receiving (or transferring) the loop detection frame 300a, and transfer the loop detection frame 300a in which their own MAC address is set.
The network management device 110 identifies the loop generation switch based on the MAC address of the switch device 120 set in the loop detection frame 300a returned from the loop generation switch (switch device 120C).

  When no loop has occurred, the loop detection frame 300a reaches the terminal device 210a and is discarded by the terminal device 210a.

FIG. 2 is a diagram illustrating an example of hardware resources of the network system 100 and the communication system 200 according to the first embodiment.
In FIG. 2, the network management device 110, the switch device 120, the terminal device 210, and the connecting device 220 include a CPU 911 (Central Processing Unit) (also referred to as a microprocessor or a microcomputer).
The CPU 911 is connected to the ROM 913, the RAM 914, and the communication board 915 via the bus 912. The CPU 911 of the network management device 110 and the terminal device 210 is also connected to a display device 901, a keyboard 902, a mouse 903, a drive device 904, a magnetic disk device 920, and the like. The drive device 904 is a device that reads and writes a storage medium such as an FD (Flexible Disk Drive), a CD (Compact Disc), and a DVD (Digital Versatile Disc).
The CPU 911 controls these hardware devices to be connected.

  The communication board 915 is wired or wirelessly connected to a communication network such as a LAN (Local Area Network), the Internet, or a telephone line.

An OS 921 (operating system), a window system 922, a program group 923, and a file group 924 are stored in the magnetic disk device 920 of the network management device 110 and the terminal device 210.
An OS 921, a program group 923, and a file group 924 are stored in the ROM 913 or the RAM 914 of the switch device 120 and the connecting device 220.

  The program group 923 includes programs that execute the functions described as “units” in the embodiment. The program is read and executed by the CPU 911. That is, the program causes the computer to function as “to part”, and causes the computer to execute the procedures and methods of “to part”.

  The file group 924 includes various data (input, output, determination result, calculation result, processing result, etc.) used in “˜part” described in the embodiment.

  In the embodiment, arrows included in the configuration diagrams and flowcharts mainly indicate input and output of data and signals.

  In the embodiment, what is described as “to part” may be “to circuit”, “to apparatus”, and “to device”, and “to step”, “to procedure”, and “to processing”. May be. That is, what is described as “to part” may be implemented by any of firmware, software, hardware, or a combination thereof.

  The network management device 110, the switch device 120, the terminal device 210, and the connection device 220 operate using hardware as described above.

FIG. 3 is a functional configuration diagram of the network management device 110 and the switch device 120 according to the first embodiment.
The functional configurations of the network management device 110 and the switch device 120A in the first embodiment will be described below with reference to FIG. The functional configuration of the other switch devices 120B to 120E is the same as the functional configuration of the switch device 120A.

  The network management device 110 includes a loop detection frame generation unit 111 (an example of a management device frame transmission unit), a management device communication unit 112 (an example of a management device frame reception unit), a loop generation switch specification unit 113 (a loop generation switch specification unit). An example) and a management device storage unit 119.

  The loop detection frame generation unit 111 generates data including an address registration area for registering an address for identifying the switch devices 120A to 120E as a loop detection frame.

The management device communication unit 112 transmits the loop detection frame 300 generated by the loop detection frame generation unit 111 to the terminal devices 210a and 210b via the switch devices 120A to 120E.
The management device communication unit 112 receives the loop detection frame 300 transferred to itself by any switch device 120.

The loop generation switch specifying unit 113 specifies a loop generation switch based on the address registered in the address registration area of the loop detection frame 300 received by the management device communication unit 112.
For example, the loop generation switch specifying unit 113 specifies the address registered in the middle of the plurality of addresses registered in the address registration area of the loop detection frame 300 as the address of the loop generation switch.

The management device storage unit 119 stores data used by the network management device 110.
The loop detection frame 300, the network configuration information, and the MAC address of the network management device 110 are examples of data stored in the management device storage unit 119. The network configuration information is information indicating a network configuration between the network system 100 and the communication system 200, such as connection relationships between the switch devices 120A to 120E and MAC addresses of the switch devices 120A to 120E and the terminal device 210. The network configuration information is defined in advance and stored in the management device storage unit 119.

  The switch device 120A includes a switch device communication unit 121 (an example of a switch device frame reception unit), a loop detection frame processing unit 122 (an example of a switch device frame transmission unit), and a switch device storage unit 129.

  The switch device communication unit 121 receives the loop detection frame 300 transmitted from the network management device 110 or the loop detection frame 300 transferred from another switch device 120.

The loop detection frame processing unit 122 determines whether its own address is registered in the address registration area of the loop detection frame 300 received by the switch device communication unit 121.
When the own address is not registered, the loop detection frame processing unit 122 registers the own address in the address registration area of the loop detection frame 300, and the loop detection frame in which the own address is registered is transmitted to the switch device communication unit 121. To the terminal device 210.
When the own address is registered in the loop detection frame 300, the loop detection frame processing unit 122 transfers the loop detection frame 300 to the network management device 110 via the switch device communication unit 121.

For example, when the own address is not registered, the loop detection frame processing unit 122 adds the own address to the address registration area of the loop detection frame 300, and adds the own loop address to the terminal device. Forward to 210.
Further, when the own address is registered, the loop detection frame processing unit 122 adds the own address to the address registration area of the loop detection frame 300, and adds the own address to the loop detection frame 300. Transfer to 110.

The switch device storage unit 129 stores data used by the switch device 120.
The loop detection frame 300, the switching table, and its own MAC address are examples of data stored in the switch device storage unit 129. The switching table is defined in advance by a network administrator, or is defined by a switch learning function using an address resolution protocol (ARP).

FIG. 4 is a diagram showing a data structure of the loop detection frame 300 in the first embodiment.
The loop detection frame 300 in the first embodiment will be described below with reference to FIG.

  The loop detection frame 300 includes a destination MAC address 310, a transmission source MAC address 320, TYPE 330, user data 340, and error detection information 350.

In the area of the destination MAC address 310, the MAC address of the terminal device 210a (or the terminal device 210b) that is the transmission destination of the loop detection frame 300 is set.
In the area of the source MAC address 320, the MAC address of the network management apparatus 110 that generates the loop detection frame 300 is set.
A predetermined identifier indicating a loop detection frame is set in the TYPE 330 area.
The area of user data 340 includes a frame reception count registration area 341 and a frame reception MAC address registration area 342.
In the area of the error detection information 350, a checksum of the loop detection frame 300 is set.

In the frame reception frequency registration area 341, the number of times received by the switch devices 120A to 120E is registered (set).
In the frame reception MAC address registration area 342, the MAC address of the switch device 120 that has received the loop detection frame 300 is registered (set).

FIG. 5 is a flowchart illustrating processing of the network management apparatus 110 in the loop generation switch specifying method according to the first embodiment.
The processing of the network management apparatus 110 in the loop generation switch specifying method in the first embodiment will be described below with reference to FIG.

In S110, the loop detection frame generation unit 111 generates a loop detection frame 300 (see FIG. 4) addressed to the terminal device 210.
For example, the network management device 110 generates the loop detection frame 300a addressed to the terminal device 210a.
At this time, the destination MAC address 310 of the loop detection frame 300a is the MAC address of the terminal device 210a, and the transmission source MAC address 320 is the MAC address of the network management device 110. TYPE 330 is a predetermined identifier indicating that it is the loop detection frame 300. The frame reception count registration area 341 has an initial value “0”, and nothing is registered in the frame reception MAC address registration area 342.
After S110, the process proceeds to S120.

In S120, the management apparatus communication unit 112 transmits the loop detection frame 300 generated in S110.
For example, in the case of FIG. 1, the loop detection frame 300a reaches the switch device 120A connected to the network management device 110 via a communication cable.
After S120, the process proceeds to S130.

In S130, the management apparatus communication unit 112 determines whether or not the loop detection frame 300 is received within a predetermined waiting time after the transmission of the loop detection frame 300 in S120.
If the loop detection frame 300 is received (YES), the process proceeds to S140.
If the loop detection frame 300 has not been received (NO), the processing of the network management device 110 ends. In this case, the loop detection frame 300 reaches the destination terminal device 210 without looping, and it is considered that there is no loop generation switch in the route to the destination terminal device 210.

  In S140, the loop occurrence switch specifying unit 113 refers to the frame reception MAC address registration area 342 of the loop detection frame 300 received in S130. Then, the loop generation switch specifying unit 113 specifies a loop generation switch based on the MAC address registered in the referenced frame reception MAC address registration area 342.

For example, in the case of FIG. 1, “5” is registered in the frame reception count registration area 341 of the loop detection frame 300a, and “MACA”, “MACB”, and “MACB” are sequentially registered in the frame reception MAC address registration area 342 of the loop detection frame 300a. “MACC”, “MACB”, and “MACA” are registered. Let MACA-C be the MAC addresses of the switch devices 120A-C.
The loop generation switch specifying unit 113 registers the MAC address registered in the middle of the MAC addresses registered in the frame reception MAC address registration area 342 in the order of registration “3 (= 5/2) (rounded up after the decimal point)” Is calculated based on the value registered in the frame reception frequency registration area 341.
The loop generation switch specifying unit 113 sets the MAC address “MACC” registered in the calculated order “3” as the MAC address of the loop generation switch.
That is, the switch device 120C identified by the MAC address “MACC” is a loop generation switch.

  By providing the frame reception frequency registration area 341 in the loop detection frame 300a, it is easy to identify the loop occurrence switch.

  After S140, the process proceeds to S141.

In S141, the loop generation switch specifying unit 113 displays information (for example, switch name, MAC address) indicating the loop generation switch specified in S140 on the display device.
However, information indicating the loop generation switch may be output to an output device (for example, a printer) other than the display device.
After S141, the processing of the network management device 110 ends.

FIG. 6 is a flowchart showing processing of the switch device 120 in the loop generation switch specifying method according to the first embodiment.
The processing of the switch device 120 in the loop generation switch specifying method in the first embodiment will be described below with reference to FIG.

In S210, when the loop detection frame 300 arrives, the switching device communication unit 121 receives the reached loop detection frame 300.
For example, in the case of FIG. 1, the loop detection frame 300a transmitted from the network management device 110 arrives at the switch device 120A, and the loop detection frame 300a transferred from the switch device 120B arrives.
Whether the received data is the loop detection frame 300a or general communication data is distinguished according to the data format (for example, TYPE 330 of the loop detection frame 300a). When the general communication data is received, the switch device communication unit 121 transfers the communication data based on the switching table as in the conventional switch (outputs to the port corresponding to the destination MAC address).
After S210, the process proceeds to S220.

In S220, the loop detection frame processing unit 122 refers to the frame reception MAC address registration area 342 of the loop detection frame 300 received in S210, and its own MAC address is registered in the referenced frame reception MAC address registration area 342. It is determined whether or not.
When the own MAC address is registered (YES), the loop detection frame 300 received in S210 is looped by the loop generation switch. The process proceeds to S240.
When the own MAC address is not registered (NO), the loop detection frame 300 received in S210 is not looped by the loop generation switch. The process proceeds to S230.

In S230, the loop detection frame processing unit 122 adds (increments) “1” to the frame reception count registration area 341 of the loop detection frame 300 received in S210.
For example, in the case of FIG. 1, “1 (= 0 + 1)” is set in the frame reception count registration area 341 of the loop detection frame 300a transmitted by the network management apparatus 110 and received by the switch apparatus 120A. Further, “2 (= 1 + 1)” is set in the frame reception count registration area 341 of the loop detection frame 300a transferred by the switch device 120A and received by the switch device 120B.
After S230, the process proceeds to S231.

In S231, the loop detection frame processing unit 122 adds its own MAC address to the frame reception MAC address registration area 342 of the loop detection frame 300 processed in S230.
For example, in the case of FIG. 1, the MAC address “MACA” of the switch device 120A is set in the frame reception MAC address registration area 342 of the loop detection frame 300a transmitted by the network management device 110 and received by the switch device 120A. When the loop detection frame 300a is transferred by the switch device 120A and received by the switch device 120B, the MAC address “MACB” of the switch device 120B is added to the frame reception MAC address registration area 342. At this time, the MAC addresses are registered in the frame reception MAC address registration area 342 in the order of “MACA” and “MACB”.
After S231, the process proceeds to S232.

In S232, the switch device communication unit 121 transfers the loop detection frame 300 processed in S231 in the same manner as the conventional switch.
For example, in the case of FIG. 1, the switch device communication unit 121 of the switch device 120A that has received the loop detection frame 300a from the network management device 110 corresponds to the MAC address “MACa” of the destination (terminal device 210a) of the loop detection frame 300a. Identify the port based on the switching table. Then, the switch device communication unit 121 of the switch device 120A outputs the loop detection frame 300a to the specified port, and the loop detection frame 300a reaches the switch device 120B.
After S232, the processing of the switch device 120 ends.

In S240, the loop detection frame processing unit 122 determines whether or not its own MAC address is the head MAC address. The head MAC address is the first MAC address registered in the frame reception MAC address registration area 342.
When the own MAC address is the head MAC address (YES), the process proceeds to S242.
When the own MAC address is not the head MAC address (NO), the process proceeds to S241.

  In S241, the loop detection frame processing unit 122 refers to the frame reception MAC address registration area 342 of the loop detection frame 300 received in S210, and transfers the MAC address registered immediately before its own MAC address to the transfer destination. It is specified as a MAC address.

For example, in the case of FIG. 1, the loop detection frame 300a is transferred to the switch device 120C (loop generation switch) via the switch device 120A and the switch device 120B. The loop detection frame 300a is looped by the switch device 120C and transferred to the switch device 120B. At this time, the MAC addresses “MACA”, “MACB”, and “MACC” of the switch devices 120A to 120C are registered in order in the frame reception MAC address registration area 342 of the loop detection frame 300a.
The loop detection frame processing unit 122 of the switch device 120B specifies “MACA” registered immediately before its own MAC address “MACB” as the transfer destination MAC address.

  After S241, the process proceeds to S243.

  In S242, the loop detection frame processing unit 122 identifies the transmission source MAC address 320 of the loop detection frame 300 received in S210 as the transfer destination MAC address.

For example, in the case of FIG. 1, the loop detection frame 300a is transferred to the switch device 120C (loop generation switch) via the switch device 120A and the switch device 120B. The loop detection frame 300a is looped by the switch device 120C and transferred to the switch device 120B. Then, the loop detection frame 300a is transferred from the switch device 120B to the switch device 120A. At this time, “MACA”, “MACB”, “MACC”, and “MACB” are sequentially registered in the frame reception MAC address registration area 342 of the loop detection frame 300a.
Since the loop detection frame processing unit 122 of the switch device 120B has its own MAC address “MACA” registered at the head, the MAC address of the network management device 110 set as the transmission source MAC address 320 in the loop detection frame 300a “MAC0” is specified as the transfer destination MAC address.

  After S242, the process proceeds to S243.

In S243, the loop detection frame processing unit 122 adds “1” to the frame reception count registration area 341 of the loop detection frame 300 received in S210.
After S243, the process proceeds to S244.

In S244, the loop detection frame processing unit 122 adds its own MAC address to the frame reception MAC address registration area 342 of the loop detection frame 300 processed in S243.
After S244, the process proceeds to S245.

In S245, the switching device communication unit 121 transfers the loop detection frame 300 processed in S244 according to the transfer destination MAC address specified in S241 or S242.
For example, in the case of FIG. 1, the transfer destination MAC address of the switch device 120B is the MAC address “MACA” of the switch device 120A. The switch device communication unit 121 of the switch device 120B specifies the port corresponding to the transfer destination MAC address “MACA” based on the switching table, and outputs the loop detection frame 300a to the specified port. The loop detection frame 300a reaches the switch device 120A.
The transfer in S245 is intended to finally transfer the looped detection frame 300 to the network management apparatus 110 that is the transmission source.
After S245, the processing of the switch device 120 ends.

  Finally, the flow of the loop detection frame 300 will be described with reference to FIG. The description is given with the processing codes of the network management device 110 and the switch device 120 described with reference to FIGS.

  The network management device 110 generates a loop detection frame 300a addressed to the terminal device 210a (S110), and transmits the generated loop detection frame 300a (S120).

The switch device 120A receives the loop detection frame 300a (S210), and determines whether or not its own MAC address “MACA” is registered in the frame reception MAC address registration area 342 of the loop detection frame 300a (S220). At this time, none of the MAC addresses of the switch devices 120A to 120E are registered in the frame reception MAC address registration area 342 of the loop detection frame 300a.
The switching device 120A adds “1” to the frame reception count registration area 341 of the loop detection frame 300a (S230), and registers its own MAC address “MACA” in the frame reception MAC address registration area 342 (S231).
The switch device 120A transfers the loop detection frame 300a (S232). At this time, the loop detection frame 300a is output to the port connected to the switch device 120B and reaches the switch device 120B.

  The frame reception count registration area 341 of the loop detection frame 300a is “1”, and the MAC address registered in the frame reception MAC address registration area 342 is “MACA”.

The switch device 120B receives the loop detection frame 300a (S210), and determines whether or not its own MAC address “MACB” is registered in the frame reception MAC address registration area 342 of the loop detection frame 300a (S220). At this time, “MACB” is not registered in the frame reception MAC address registration area 342 of the loop detection frame 300a.
The switch device 120B adds “1” to the frame reception count registration area 341 of the loop detection frame 300a (S230), and adds its own MAC address “MACB” to the frame reception MAC address registration area 342 (S231).
The switch device 120B transfers the loop detection frame 300a (S232). At this time, the loop detection frame 300a is output to the port connected to the switch device 120C and reaches the switch device 120C.

  The frame reception count registration area 341 of the loop detection frame 300a is “2”, and the MAC addresses registered in the frame reception MAC address registration area 342 are “MACA” and “MACB” in order.

The switch device 120C receives the loop detection frame 300a (S210), and determines whether or not its own MAC address “MACC” is registered in the frame reception MAC address registration area 342 of the loop detection frame 300a (S220). At this time, “MACC” is not registered in the frame reception MAC address registration area 342 of the loop detection frame 300a.
The switching device 120C adds “1” to the frame reception count registration area 341 of the loop detection frame 300a (S230), and adds its own MAC address “MACC” to the frame reception MAC address registration area 342 (S231).
The switch device 120C transfers the loop detection frame 300a (S232).

  Here, since the setting of the switching table of the switch device 120C is incorrect, the loop detection frame 300a is output to the port connected to the switch device 120B, not the port connected to the connecting device 220a.

  The frame reception count registration area 341 of the loop detection frame 300a is “3”, and the MAC addresses registered in the frame reception MAC address registration area 342 are “MACA”, “MACB”, and “MACC” in order.

The switch device 120B receives the loop detection frame 300a (S210), and determines whether or not its own MAC address “MACB” is registered in the frame reception MAC address registration area 342 of the loop detection frame 300a (S220). At this time, “MACB” is registered in the frame reception MAC address registration area 342 of the loop detection frame 300a.
The switching device 120B determines whether or not its own MAC address “MACB” is registered at the head (S240). “MACB” is registered second.
The switch device 120B sets the MAC address “MACA” registered immediately before its own MAC address “MACB” as the transfer destination MAC address (S241).
The switching device 120B adds “1” to the frame reception count registration area 341 of the loop detection frame 300a (S243), and adds its own MAC address “MACB” to the frame reception MAC address registration area 342 (S244).
The switch device 120B transfers the loop detection frame 300a according to the transfer destination MAC address “MACA” (S245). At this time, the loop detection frame 300a is output to the port connected to the switch device 120A and reaches the switch device 120A.

  The frame reception count registration area 341 of the loop detection frame 300a is “4”, and the MAC addresses registered in the frame reception MAC address registration area 342 are “MACA”, “MACB”, “MACC”, and “MACB” in order.

The switch device 120A receives the loop detection frame 300a (S210), and determines whether or not its own MAC address “MACA” is registered in the frame reception MAC address registration area 342 of the loop detection frame 300a (S220). At this time, “MACA” is registered in the frame reception MAC address registration area 342 of the loop detection frame 300a.
The switching device 120A determines whether or not its own MAC address “MACA” is registered at the head (S240). “MACA” is registered at the top.
The switch device 120A sets the MAC address “MAC0” of the network management device 110 set as the transmission source MAC address 320 in the loop detection frame 300a as the transfer destination MAC address (S242).
The switch device 120A adds “1” to the frame reception count registration area 341 of the loop detection frame 300a (S243), and adds its own MAC address “MACA” to the frame reception MAC address registration area 342 (S244).
The switching device 120A transfers the loop detection frame 300a according to the transfer destination MAC address “MAC0” (S245). At this time, the loop detection frame 300 a is output to a port connected to the network management apparatus 110 and reaches the network management apparatus 110.

  The frame reception count registration area 341 of the loop detection frame 300a is “5”, and the MAC addresses registered in the frame reception MAC address registration area 342 are “MACA”, “MACB”, “MACC”, “MACB”, and “MACA” in order. It is.

  The network management device 110 receives the loop detection frame 300a (S130), and uses the switch device 120C identified by “MACC” registered in the middle of the frame reception MAC address registration area 342 of the loop detection frame 300a as a loop generation switch. Specify (S140).

As described above, the network system 100 can specify the loop occurrence switch based on the MAC address of the switch device 120 registered in the loop detection frame 300.
However, the network system 100 may specify the loop generation switch as follows.

For example, the switch device 120 does not register its own MAC address in the frame reception MAC address registration area 342 of the loop detection frame 300 looped in S244. Then, the network management apparatus 110 specifies the MAC address registered at the end of the frame reception MAC address registration area 342 of the loop detection frame 300 looped in S140 as the MAC address of the loop generation switch.
In FIG. 1, the switch device 120B and the switch device 120A that have received the loop detection frame 300a looped by the switch device 120C do not add their own MAC addresses. Therefore, the MAC addresses registered in the frame reception MAC address registration area 342 of the loop detection frame 300a that returns to the network management apparatus 110 are “MACA”, “MACB”, and “MACC”. The network management device 110 identifies the network management device 110C identified by “MACC” registered last as a loop generation switch.
In this case, the frame reception frequency registration area 341 of the loop detection frame 300 may be omitted.

  For example, the switch device 120 may transfer the loop detection frame 300 according to the transmission source MAC address 320 (the MAC address of the network management device 110) in S245.

For example, the initial value of the frame reception count registration area 341 of the loop detection frame 300 may be other than “0”.
In this case, the network management apparatus 110 uses the registration value M in the frame reception count registration area 341 to calculate the MAC address registration order Integrator (A) of the loop generation switch from the following equation (1). “N” is an initial value of the frame reception count registration area 341.

Integrer (A) = ((M + 1) −N) / 2 Formula (1)
However, Integer (A) is a value obtained by discarding the decimal part.

In FIG. 1, if the initial value N of the frame reception count registration area 341 is “1”, the registration value M of the frame reception count registration area 341 of the loop detection frame 300 a that returns to the network management apparatus 110 is “6”. The MAC addresses registered in the frame reception MAC address registration area 342 are “MACA”, “MACB”, “MACC”, “MACB”, and “MACA”.
That is, the loop generation switch is the switch device 120C identified by the MAC address “MACC” registered in the “3 (= ((6 + 1) −1) / 2)” th.

For example, the initial value of the frame reception count registration area 341 of the loop detection frame 300 is set to other than “0”, and the switching device 120 subtracts “1” from the frame reception count registration area 341 of the loop detection frame 300 in S230 and S243. It doesn't matter.
In this case, the network management apparatus 110 calculates the MAC address registration order Integer (A) of the loop generation switch from the following equation (2) using the registration value M in the frame reception count registration area 341. “N” is an initial value of the frame reception count registration area 341.

Integrer (A) = (N− (M−1)) / 2 Equation (2)
However, Integer (A) is a value obtained by discarding the decimal part.

In FIG. 1, when the initial value N of the frame reception count registration area 341 is “10”, the registration value M of the frame reception count registration area 341 of the loop detection frame 300 a that returns to the network management apparatus 110 is “5”. The MAC addresses registered in the frame reception MAC address registration area 342 are “MACA”, “MACB”, “MACC”, “MACB”, and “MACA”.
That is, the loop generation switch is the switch device 120C identified by the MAC address “MACC” registered in the “3 (= (10− (5-1)) / 2)” th.

In the first embodiment, for example, the following network device (network system 100) has been described.
The network device includes a network management device and a switch device.
The network management device transmits a loop detection frame between any network constituent devices, identifies a switch device in which a loop has occurred from the loop detection frame received via the switch device, and displays the switch device.
When receiving the loop detection frame, the switch device registers information in the frame reception frequency registration area and the frame reception MAC address registration area in the loop detection frame, and transmits the loop detection frame.

Embodiment 2. FIG.
A case will be described in which a conventional switch (connecting device 220) having no loop detection function is a loop generation switch.

FIG. 7 is a configuration diagram of the network system 100 according to the second embodiment.
It is the same as Embodiment 1 (see FIG. 1) except that the connecting device 220a, not the switch device 120C, is a loop generation switch.

  The concatenating device 220a does not have a loop detection function for incrementing (or decrementing) the frame reception count registration area 341 of the loop detection frame 300 or registering its own MAC address in the frame reception MAC address registration area 342.

  The configurations of the network management device 110 and the switch devices 120A to 120E are the same as those in the first embodiment (see FIG. 3).

However, when the same address is continuously registered in the address registration area of the loop detection frame 300, the loop generation switch specifying unit 113 of the network management device 110 does not have the loop detection function switch (the connection device 220) of the communication system 200. Is determined as a loop generation switch.
When the same address is not continuously registered in the address registration area of the loop detection frame 300, the loop generation switch specifying unit 113 is the middle of the plurality of addresses registered in the address registration area of the loop detection frame 300. Is specified as the address of the loop occurrence switch.

  The processing of the switch device 120 is the same as that of the first embodiment (see FIG. 6).

FIG. 8 is a flowchart showing processing of the network management apparatus 110 in the loop generation switch specifying method according to the second embodiment.
Of the processes shown in FIG. 8, S110 to S130 are the same as those in the first embodiment (see FIG. 5).

In the second embodiment, S150 to S153 are executed instead of S140 to S141 described in the first embodiment.
Hereinafter, S150 to S153 will be described.

  In S150, the loop occurrence switch specifying unit 113 determines whether or not the same MAC address is continuously registered in the frame reception MAC address registration area 342 of the loop detection frame 300 received in S130.

For example, the loop occurrence switch specifying unit 113 determines whether the middle MAC address registered in the frame reception MAC address registration area 342 is the same as the MAC address registered immediately before or behind it. Determine.
In FIG. 7, “MACA”, “MACB”, “MACC”, “MACC”, “MACB”, and “MACA” are registered in the frame reception MAC address registration area 342 of the loop detection frame 300a. The two MAC addresses registered in the middle are both the same “MACC”.
However, the loop generation switch specifying unit 113 may determine whether the MAC addresses are not limited to the middle but are continuous.

When the same MAC address is continuously registered (YES), a switch (terminal device 210) having no function of registering its own MAC address in the loop detection frame 300 is a loop generation switch. The process proceeds to S151.
When the same MAC address is not continuously registered (NO), the switch device 120 is a loop generation switch as in the first embodiment. The process proceeds to S152.

In S151, the loop generation switch specifying unit 113 outputs to the display device (or other output device) that the connecting device 220 is a loop generation switch.
The loop generation switch specifying unit 113 sets the connection device 220 (connection device 220a in FIG. 7) connected to the switch device 120 (switch device 120C in FIG. 7) identified by the continuously registered MAC addresses as the loop generation switch. May be specified. It is assumed that the connection relationship between the switch device 120 and the connection device 220 is defined in the network configuration information.
After S151, the processing of the network management apparatus 110 ends.

In S152, the loop generation switch specifying unit 113 specifies a loop generation switch based on the MAC address registered in the frame reception MAC address registration area 342, as in the first embodiment (S142 in FIG. 5).
After S152, the process proceeds to S153.

In S153, the loop generation switch specifying unit 113 outputs information indicating the loop generation switch specified in S152 to the display device (or other output device).
After S153, the processing of the network management device 110 ends.

  As described above, based on the MAC address of the switch device 120 registered in the loop detection frame 300, the network system 100 identifies which switch device 120 or the connection device 220 is the loop generation switch. be able to.

As in the first embodiment, the switch device 120 may transfer the loop detection frame 300 that is looped according to the MAC address of the network management device 110.
An initial value may be set in the frame reception frequency registration area 341 of the loop detection frame 300.
Further, the frame reception frequency registration area 341 of the loop detection frame 300 may be decremented by the switch device 120.

  In the second embodiment, for example, the following network device (network system 100) has been described.

  The network management device determines whether the same MAC address is continuously registered in the frame reception MAC address registration area of the loop detection frame received via the switch device and the connection device connected to the network device, Identify the connecting device that is causing the loop.

Embodiment 3 FIG.
A mode in which the switch device 120 identifies the loop generation switch will be described.

FIG. 9 is a configuration diagram of the network system 100 according to the third embodiment.
Except that the data transmitted to the network management apparatus 110 is not the loop detection frame 300 but the loop detection notification frame 400, it is the same as in the first embodiment (see FIG. 1) or the second embodiment (see FIG. 7). .
Although FIG. 9 shows the connecting device 220a as a loop generation switch, the loop generation switch may be the switch device 120.

FIG. 10 is a functional configuration diagram of the network management device 110 and the switch device 120 according to the third embodiment.
The network management apparatus 110 does not include the loop generation switch specifying unit 113 (see FIG. 3) described in the first embodiment.
The switch device 120 includes a loop detection notification frame generation unit 123 in addition to the configuration of the first embodiment (see FIG. 3).

When the own address is registered in the loop detection frame 300, the loop detection notification frame generation unit 123 specifies the loop occurrence switch based on the address registered in the address registration area of the loop detection frame 300.
For example, when the own address is registered at the end of the address registration area of the loop detection frame 300, the loop detection notification frame generation unit 123 identifies the connecting device 220 as a loop occurrence switch.

  The loop detection notification frame generation unit 123 generates data indicating the identified loop generation switch as the loop detection notification frame 400.

  The switch device communication unit 121 transmits the loop detection notification frame 400 generated by the loop detection notification frame generation unit 123 to the network management device 110.

FIG. 11 shows the data structure of loop detection notification frame 400 in the third embodiment.
The loop detection notification frame 400 in the third embodiment will be described below with reference to FIG.

  The loop detection notification frame 400 includes a destination MAC address 410, a transmission source MAC address 420, TYPE 430, user data 440, and error detection information 450.

In the area of the destination MAC address 410, the MAC address of the network management apparatus 110 that is the transmission destination of the loop detection notification frame 400 is set.
In the area of the source MAC address 420, the MAC address of the switch device 120 that generates the loop detection notification frame 400 is set.
A predetermined identifier indicating a loop detection notification frame is set in the TYPE 430 area.
In the area of user data 440, a MAC address indicating a loop generation switch is set as a notification MAC address 441.
In the area of the error detection information 450, a checksum of this loop detection notification frame 400 is set.

FIG. 12 is a flowchart illustrating processing of the switch device 120 in the loop generation switch specifying method according to the third embodiment.
Of the processes shown in FIG. 12, S210 to S232 are the same as those in the first embodiment (see FIG. 6).

In the third embodiment, S250 to S253 are executed instead of S240 to S245 described in the first embodiment.
Hereinafter, S250 to S253 will be described.

In S250, the loop detection notification frame generation unit 123 determines whether or not its own MAC address is the last MAC address. The tail MAC address is a MAC address registered at the end of the frame reception MAC address registration area 342.
When the own MAC address is the last MAC address (YES), the loop generation switch is the connecting device 220. The process proceeds to S251.
When the own MAC address is not the last MAC address (NO), the loop generation switch is the switch device 120. The process proceeds to S252.

In S251, the loop detection notification frame generation unit 123 generates a loop detection notification frame 400 indicating that the connecting device 220 is a loop generation switch.
In the loop detection notification frame 400, the transmission source MAC address 320 (the MAC address of the network management device 110) of the loop detection frame 300 is set as the destination MAC address 410.
Further, the MAC address of the switch device 120 is set as the source MAC address 420.
In the user data 440, the destination MAC address 310 of the loop detection frame 300 is set as the notification MAC address 441.
After S251, the process proceeds to S253.

In S252, the loop detection notification frame generation unit 123 generates a loop detection notification frame 400 indicating that the switch device 120 identified by the last MAC address is a loop generation switch.
In the loop detection notification frame 400, the transmission source MAC address 320 (the MAC address of the network management device 110) of the loop detection frame 300 is set as the destination MAC address 410.
Further, the MAC address of the switch device 120 is set as the source MAC address 420.
In the user data 440, the last MAC address is set as the notification MAC address 441.
After S252, the process proceeds to S253.

In S253, the switch device communication unit 121 transmits the loop detection notification frame 400 generated in S251 or S252.
For example, when the switch device 120C generates the loop detection notification frame 400 in FIG. 9, the loop detection notification frame 400 is transferred by the switch device 120B and the switch device 120A and transmitted to the network management device 110.
After S253, the processing of the switch device 120 ends.

The management device communication unit 112 of the network management device 110 receives the loop detection notification frame 400.
Then, the management device communication unit 112 outputs information indicating the loop occurrence switch to the display device (or other output device) based on the notification MAC address 441 of the received loop detection notification frame 400.
If the notification MAC address 441 is the same as the destination MAC address 310 of the loop detection frame 300, the connecting device 220 is a loop generation switch. The management device communication unit 112 may identify the connecting device 220 (the connecting device 220a in FIG. 9) connected to the switch device 120 (the switching device 120C in FIG. 9) that is the transmission source of the loop detection notification frame 400 as a loop generation switch. Good. It is assumed that the connection relationship between the switch device 120 and the connection device 220 is defined in the network configuration information.
If the notification MAC address 441 is not the same as the destination MAC address 310 of the loop detection frame 300, the switch device 120 identified by the notification MAC address 441 is a loop generation switch.

The processing of the network management apparatus 110 is executed instead of S140 to S141 (see FIG. 5) described in the first embodiment. Other processes (S110 to S130) of the network management apparatus 110 are the same as those in the first embodiment.
Illustration of the processing of the network management apparatus 110 in the third embodiment is omitted.

As described above, the network system 100 can specify the loop occurrence switch based on the MAC address of the switch device 120 registered in the loop detection frame 300.
In addition, since the switch device 120 identifies the loop occurrence switch, the load on the network management device 110 can be reduced.

In the third embodiment, for example, the following network device (network system 100) has been described.
The switch device determines whether the MAC address registered at the end of the frame reception MAC address registration area of the received loop detection frame is the same as the MAC address of the switch device itself. If the determination results are the same, the switch device transmits a loop detection frame (error detection) (loop detection notification frame 400) to the network management device.
When the network management device receives the loop detection frame (error detection), the network management device identifies the concatenated device that generates the loop from the destination MAC address of the loop detection frame.

  100 network system, 110 network management device, 111 loop detection frame generation unit, 112 management device communication unit, 113 loop generation switch specifying unit, 119 management device storage unit, 120 switch device, 121 switch device communication unit, 122 loop detection frame processing , 123 loop detection notification frame generation unit, 129 switch device storage unit, 200 communication system, 210 terminal device, 220 concatenation device, 300 loop detection frame, 310 destination MAC address, 320 source MAC address, 330 TYPE, 340 user data , 341 frame reception count registration area, 342 frame reception MAC address registration area, 350 error detection information, 400 loop detection notification frame, 410 destination MAC address, 420 transmission Original MAC address, 430 TYPE, 440 User data, 441 Notification MAC address, 450 Error detection information, 901 Display device, 902 Keyboard, 903 Mouse, 904 Drive device, 911 CPU, 912 Bus, 913 ROM, 914 RAM, 915 Communication board 920, magnetic disk unit, 921 OS, 922 window system, 923 program group, 924 file group.

Claims (10)

In a network system that identifies a switch device that generates a loop that repeats data transfer as a loop generating switch,
A network management device for transmitting data including an address registration area for registering an address for identifying a switch device to a specific terminal device via the switch device as a loop detection frame;
The loop detection frame is received, it is determined whether or not its own address is registered in the address registration area of the received loop detection frame, and if its own address is not registered, its own address is registered in the address registration area of the loop detection frame. A switch device that registers an address and transfers the loop detection frame registered with its own address to the terminal device, and transfers the loop detection frame to the network management device when its own address is registered. Have
The network management device receives a loop detection frame forwarded to itself, and identifies a loop generation switch based on an address registered in an address registration area of the received loop detection frame . The network system includes a plurality of switch devices,
When each switch device has not registered its own address in the address registration area of the received loop detection frame, loop detection is performed by adding its own address to the address registration area of the loop detection frame and adding its own address. When the frame is forwarded to the terminal device and its own address is registered in the address registration area of the received loop detection frame, its own address is added to the address registration area of the loop detection frame. Transfer the added loop detection frame to the network management device,
2. The network management device according to claim 1, wherein an address registered in the middle among a plurality of addresses registered in an address registration area of the received loop detection frame is specified as an address of a loop generation switch. Network system. The network system has a switch with a loop detection function as the switch device,
The network system is connected to a communication system having the terminal device and a switch device that transfers received data as a switch without a loop detection function via a switch with a loop detection function,
When the same address is continuously registered in the address registration area of the received loop detection frame, the network management device determines that the switch having no loop detection function of the communication system is a loop generation switch and receives the detected loop If the same address is not continuously registered in the address registration area of the frame, the address registered in the middle of the plurality of addresses registered in the address registration area of the loop detection frame is used as the address of the loop generation switch. The network system according to claim 2, wherein the network system is specified. The network management device includes:
A loop detection frame including the address registration area and a frame reception number registration area for registering the number of times the loop detection frame is received by the switch with a loop detection function;
Based on the value registered in the frame reception count registration area of the received loop detection frame, the loop registration switch selects the address registered in the middle among the plurality of addresses registered in the address registration area of the loop detection frame. 4. The network system according to claim 2, wherein the network system is specified as an address. In a loop generation switch specifying method for specifying a switch device that generates a loop for repeating data transfer as a loop generation switch,
The network management device transmits data including an address registration area for registering an address for identifying the switch device as a loop detection frame to a specific terminal device via the switch device,
The switch device receives the loop detection frame, determines whether its own address is registered in the address registration area of the received loop detection frame, and if the own address is not registered, registers the address of the loop detection frame. Registers its own address in the area and transfers the loop detection frame registered with its own address to the terminal device. If the own address is registered, transfers the loop detection frame to the network management device. ,
The network management device receives a loop detection frame forwarded to itself, and identifies a loop generation switch based on an address registered in an address registration area of the received loop detection frame Switch identification method. In a network management device that identifies a switch device that generates a loop that repeats data transfer as a loop generation switch,
A management device frame transmission unit that transmits data including an address registration area for registering an address for identifying the switch device to a specific terminal device via the switch device as a loop detection frame;
When the self-address is not registered in the address registration area of the received loop detection frame after receiving the loop detection frame, the self-address is registered in the address registration area of the loop detection frame. When the loop detection frame is forwarded to the terminal device and the own address is registered in the address registration area of the received loop detection frame, the switch device forwards the loop detection frame to the network management device. A management device frame receiving unit for receiving a loop detection frame transferred to the management device;
A network management device, comprising: a loop generation switch specifying unit that specifies a loop generation switch based on an address registered in an address registration area of a loop detection frame received by the management device frame reception unit. A switch device frame reception unit that receives data transmitted from the network management device to a specific terminal device including an address registration area as a loop detection frame;
It is determined whether or not its own address is registered in the address registration area of the loop detection frame received by the switch device frame receiving unit, and when its own address is not registered, the address is registered in the address registration area of the loop detection frame. A switch detection frame for transferring the loop detection frame registered to the terminal device and forwarding the loop detection frame to the network management device when the self address is registered. A switch device comprising: a transmission unit. In a network system that identifies a switch device that generates a loop that repeats data transfer as a loop generating switch,
A network management device for transmitting data including an address registration area for registering an address for identifying a switch device to a specific terminal device via the switch device as a loop detection frame;
The loop detection frame is received, it is determined whether or not its own address is registered in the address registration area of the received loop detection frame, and if its own address is not registered, its own address is registered in the address registration area of the loop detection frame. When the loop detection frame in which the address is registered and the self address is registered is transferred to the terminal device, and the self address is registered, based on the address registered in the address registration area of the loop detection frame A network system comprising: a switch device that identifies a loop generation switch and transmits data indicating the identified loop generation switch as a loop detection notification frame to the network management device. The network system has a switch with a loop detection function as the switch device,
The network system is connected to a communication system having the terminal device and a switch device that transfers received data as a switch without a loop detection function via a switch with a loop detection function,
Each switch with a loop detection function adds its own address to the address registration area of the loop detection frame when its own address is not registered in the address registration area of the received loop detection frame. When the loop detection frame is forwarded to the terminal device and its own address is registered at the end of the address registration area of the received loop detection frame, data indicating the loop detection functionless switch as a loop generation switch is looped. 9. The network system according to claim 8, wherein the network system transmits the detection notification frame to the network management apparatus. In a loop generation switch specifying method for specifying a switch device that generates a loop for repeating data transfer as a loop generation switch,
The network management device transmits data including an address registration area for registering an address for identifying the switch device as a loop detection frame to a specific terminal device via the switch device,
The switch device receives the loop detection frame, determines whether its own address is registered in the address registration area of the received loop detection frame, and if the own address is not registered, registers the address of the loop detection frame. When the loop detection frame in which the self address is registered in the area and the self address is registered is transferred to the terminal device, and the self address is registered, it is registered in the address registration area of the loop detection frame. A loop generation switch identification method characterized by identifying a loop generation switch based on an address and transmitting data indicating the identified loop generation switch as a loop detection notification frame to the network management device.

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