JP5651876B2 - Network relay device and network system - Google Patents

Description

  The present invention can be applied to a case where a computer apparatus (hereinafter abbreviated as “computer”) transmits and receives frames via a network, and a network relay that relays frames transmitted and received by a computer to the network. Relates to the device.

  Conventionally, in a control system that requires high reliability such as a network between stations, in order to realize the high-reliability control, the control computer is duplicated, and there is also a network that connects the control computer. Sometimes it was doubled. In general, data used in the network layer is referred to as a packet, and data used in the data link layer is referred to as a frame. However, in the following description, a packet and a frame have the same meaning and are treated as “frame” in a unified manner.

  If the networks are duplicated, even if a failure occurs in one network and data cannot be transmitted / received, the operation of the control system can be continued by switching to the other network and transmitting / receiving data. Such a duplex network system is composed of a duplex network, a network connection device connected to each duplex network and performing data input / output, and a network connection device connected to the network connection device. The network relay device relays the frame to the connected computer.

  The duplex network system performs the following operations. That is, the source computer may transmit a frame to the destination computer using a communication method called broadcast or unicast. At this time, the network relay device connected to the transmission source computer transmits two identical frames to the duplexed network connection device. Each of the duplexed network connection devices transmits the same frame to the duplex network.

  When the duplex destination network connection apparatus receives a frame from the duplex network, it transmits the frame to the destination network relay apparatus. Here, the destination network relay apparatus relays the earliest arrived frame to the destination computer, attaches the same communication number as the frame already relayed to the destination computer, and discards the later arrived frame. As described above, the network relay device performs control so that the destination computer does not receive a duplicate frame by selecting whether the frame arrived from another device is to be relayed or discarded.

  The duplex network system is employed in the construction of an industry that requires high reliability, for example, a plant control system, in addition to the above-described inter-station network. And in order to implement | achieve a duplex network system, the technique as disclosed in the following patent documents 1 has been examined.

  Patent Document 1 discloses a technique for monitoring the reception state of a control frame in two node devices connected to each other by a redundant path including a working path and a backup path.

JP 2010-283688 A

  By the way, the frame is given a communication number for each frame relayed by the transmission source network relay device, together with a code for identifying the destination computer and the destination network relay device (for example, MAC address, IP address). Yes. For this reason, even if the destination network relay device receives two identical frames from the duplicated network, it determines whether or not the frame has already been relayed based on the communication number attached to the frame. Can do. Here, when the network relay device transmits a frame by broadcast, since the destination is all computers, the code for identifying the computer and the network relay device individually (for example, the MAC address of the computer) is Not attached. On the other hand, when transmitting a frame by unicast, since the destination is a specific computer, a code for identifying the computer is added.

Here, a reception management table used by the conventional network relay device to manage the communication numbers assigned to the frames will be described.
FIG. 10 is an explanatory diagram showing a configuration example of a conventional reception management table.
This reception management table includes an arrival order field, a MAC address field, an IP address field, a user information field, and a transmission / reception number field.
In the arrival order field, the arrival order of frames is written.
In the MAC address field, a MAC address for specifying a destination computer when unicast communication is performed is written.
An IP address assigned to the network relay device is written in the IP address field.
In the user information field, it is written which communication method the unicast communication or broadcast communication transmitted. This communication method information is given as an example of user information, and includes various other information.
In the transmission communication number field, the communication number of the frame to be transmitted is written.
In the reception communication number field, the communication number of the received frame is written.

  A computer that is a transmission source may transmit a frame by mixing broadcast or unicast, but assigns a communication number to the frames to be transmitted in order regardless of the communication method. The destination network relay device manages the communication number for the frame transmitted by broadcast, and confirms the communication number according to the arrival order of the frames. For this reason, the network relay device relays the communication number assigned to the unicast to the destination computer as it is without managing the communication number.

  In the example shown in FIG. 10, when the destination network relay device receives the communication numbers of the arrived frames in the order of “1”, “2”, “4”, the frame with the communication number “3” is missing. And wait for the arrival of the frame with the communication number “3”. However, since the frame corresponding to the communication number “3” has already been relayed by unicast, when a new frame corresponding to the communication number “3” arrives from another network, it is relayed to the computer as it is. End up. At this time, the destination computer receives the frame having the communication number “3” repeatedly, and an error may occur in the processing of the destination computer.

  The present invention has been made in view of such circumstances, and an object of the present invention is to reliably identify and process the arrival order of frames arriving with various communication methods.

  The present invention relates to a network relay device that relays a frame transmitted by a computer device to another network relay device connected to the network and relays a frame received from another network relay device via the network to the computer device. A reception management table for managing the order of arrival of frames arriving from the network and managing the communication numbers indicating the order in which frames are transmitted by other network relay devices for each other network relay device; When a frame arrives in a one-to-many communication method, the communication number obtained from the frame is written to the reception management table for each other network relay device, and when a frame arrives from the network in a one-to-one communication method, it is obtained from the frame Communication number and computer Is written in the receiving control table an identification code for identifying for each other network relay apparatus, those having a frame transmission control unit that manages the finish order of frames for each communication mode, the.

  According to the present invention, the communication number of a frame is managed for each communication method with respect to a frame that arrives in a state where communication methods are mixed. For this reason, it is possible to prevent redundant reception of frames and missing reception.

1 is a network connection diagram showing a configuration example of a duplex network system in an embodiment of the present invention. It is a block diagram which shows the example of an internal structure of the network relay apparatus in one embodiment of this invention. FIG. 2 is a diagram illustrating an example of a transmission path of a frame configured between an active computer and a 1-system network and a 2-system network in a network relay device according to an embodiment of the present invention. It is a block diagram which shows the detailed structural example of the network switch and 2 branch connection apparatus which are contained in the network relay apparatus in one embodiment of this invention. It is explanatory drawing which shows the example which manages the flame | frame which flows through the duplex network system in the example of 1 embodiment of this invention. It is explanatory drawing which shows the example of the frame format which the duplex network relay apparatus in one embodiment of this invention relays. It is explanatory drawing which shows the example of the reception management table in one embodiment of this invention. It is a conceptual diagram which shows the reception state of the flame | frame in the example of 1 embodiment of this invention. It is explanatory drawing which shows the example of the process which performs the gap time of the initialization frame of a communication number, and a discard process in one embodiment of this invention. It is explanatory drawing which shows the example of the conventional reception management table.

  Hereinafter, an embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described with reference to FIGS. In the present embodiment, an example will be described in which the present invention is applied to a duplex network system 6 in which the reliability of frame transmission processing performed using a duplex network is improved. The duplex network system 6 implements a network management method performed by an internal block (to be described later) in cooperation with a computer executing a program.

FIG. 1 is a network connection diagram showing a configuration example of the duplex network system 6.
The duplex network system 6 includes a duplexed 1-system network 5a and a 2-system network 5b (hereinafter collectively referred to as “duplex network 5”). The duplex network 5 is, for example, a wide-band trunk transmission line provided by optical fibers, and can transfer frames at high speed. The duplex network system 6 includes a network relay device 2 used as an active system. The duplex network relay device 2 is connected to a 1-system computer 1a and a 2-system computer 1b (hereinafter collectively referred to as “duplex computer 1”).

  The network relay device 2 serving as a frame transmission source relays the frame transmitted by the duplex computer 1 and transmits it to another network relay device 2 connected to the network. On the other hand, the network relay device 2 that is the destination of the frame can relay the frame received from the transmission source network relay device 2 via the duplex network 5 to the duplex computer 1.

  In the duplex network 5 shown in FIG. 1, three network relay devices 2 are installed via network connection devices 3a and 3b (hereinafter collectively referred to as “duplex network connection device 3”). These three network relay devices 2 are installed, for example, for each station, and frame communication between the stations is performed via the duplex network 5. Here, the network connection device 3a installed at the first station is connected to the first-system network 5a, and the network connection device 3b is connected to the second-system network 5b. The network relay device 2 installed at the first station is connected to a 1-system computer 1a used as an active computer (computer) and a 2-system computer 1b used as a standby computer.

  The duplex computer 1 employs a so-called hot standby duplex system. That is, the 1-system computer 1a operates as an active computer that executes a predetermined application. Further, the second system computer 1b operates as a standby computer that is waiting for execution of the application.

  The hot standby duplex computer 1 performs the following operations when the normal function of the active computer is lost, or when a failure occurs in communication between the active computer and the duplex network connection device 3. Do. That is, the active computer becomes a standby computer, and the standby computer up to that time becomes the active computer, and a predetermined application is continuously executed.

  As for the other second station and n-th station, the 1-system computer 1a, 2-system computer 1b (hereinafter collectively referred to as "duplex computer 1"), network relay device 2, and duplex network connection Since the apparatus 3 is installed, overlapping description is omitted. Further, the branch line transmission path connecting the network relay apparatus 2 and the duplex network connection apparatus 3 and the branch line transmission path connecting the network relay apparatus 2 and the duplex computer 1 are also abbreviated as “branch lines”. The branch line can be increased or decreased according to the system configuration. Each device connected in the branch line is called a “network node”. For example, when a cable or the like is connected by mistake, a frame received by the duplex computer 1 or the network relay device 2 is discarded.

Next, a detailed configuration example of the network relay device 2 will be described.
FIG. 2 is a block diagram illustrating an example of the internal configuration of the network relay device 2.

  The duplex network 5 is configured as a ring network, and the 1-system network 5a and the 2-system network 5b operate simultaneously and independently of each other. Therefore, the frame sent from the duplex computer 1 (active system) installed at the first station is separated into two identical frames by the action of the network relay device 2. The separated frames are separately transmitted via the duplex network 5 to, for example, the duplex computer 1 (active system) serving as a destination installed at the nth station. However, the duplex computer 1 installed at the nth station actually receives only the frame that arrives first, and the frame that arrives later is discarded by the destination network relay device 2.

Here, the network relay device 2 includes two network switches 20 and two two-branch connection devices 10.
The network switch 20 can be configured using, for example, a general switching hub. The basic function is to extract a frame addressed to the duplex computer 1 connected to the network relay device 2 from a frame communicated in the duplex network 5 and transmit the extracted frame to the duplex computer 1. It is in.

  The network switch 20 is a transmission path that a general switching hub does not have, such as a function of returning a predetermined response frame in response to a monitoring frame transmitted from the 1-system network 5a installed at another station. It also has a function of diagnosing.

  The two-branch connection device 10 has a function of branching one transmission path into two transmission paths and merging the two transmission paths into one transmission path. That is, the two-branch connection device 10 branches the transmission path connected to the duplex computer 1 into a transmission path that reaches the 1-system network 5a and a transmission path that reaches the 2-system network 5b. Further, the transmission path from the 1-system network 5 a and the transmission path from the 2-system network 5 b are merged with the transmission path connected to the duplex computer 1.

  FIG. 3 is a diagram illustrating an example of a frame transmission path configured between the active computer and the duplex network 5 in the network relay device 2. FIG. 3A shows an operating transmission line when the 1-system computer 1a is the active system, and FIG. 3B shows an operating transmission path when the 2-system computer 1b is the active system. In FIG. 3, a thick solid line represents a transmission path in operation, and a broken line represents a standby transmission path.

  As shown in FIG. 3A, when the 1-system computer 1a is the active system, the 1-system computer 1a is connected to the 1-system computer via the two-branch connection device 10a, the network switch 20a, and the network connection device 3a. Connected to the network 5a. Furthermore, the 1-system computer 1a is connected to the 2-system network 5b via the 2-branch connection device 10a, the network switch 20b, and the network connection device 3b.

  As shown in FIG. 3B, when the second system computer 1b is the active system, the second system computer 1b is connected via the two branch connection device 10b, the network switch 20a, and the network connection device 3a through the transmission line in operation. It is connected to the system 1 network 5a. Further, the 2-system computer 1b is connected to the 2-system network 5b via the 2-branch connection device 10b, the network switch 20b, and the network connection device 3b.

  As described above, the basic functions of the network switch 20 and the two-branch connection device 10 are to switch the transmission path between the duplex computer 1 and the duplex network connection device 3.

Next, a more detailed configuration and function of the network relay device 2 will be described with reference to FIG.
FIG. 4 is a block diagram illustrating a detailed configuration example of the network switch 20 and the two-branch connection device 10 included in the network relay device 2.

  As described above, in the two-branch connection device 10, the transmission path 11 connected to the duplex computer 1 is divided into the transmission path 12 leading to the 1-system network 5a and the transmission path 13 reaching the 2-system network 5b. Branch off.

  In general, a transmission path is configured by a pair of a transmission transmission path and a reception transmission path, but frame transmission / reception processing in the two-branch connection device 10 is partially different between the transmission transmission path and the reception transmission path. Since it is, it supplements below.

  In the two-branch connection device 10, for the transmission transmission line on the side where the frame is transmitted from the duplex computer 1, the transmission line 11 is simply branched into the transmission line 12 and the transmission line 13. I just need it. Then, the same frame is sent out to the transmission line 12 on the 1-system network 5a side and the transmission line 13 on the 2 system network 5b side by the two-branch connection device 10 as to the frames output from the active computer. become. Note that a frame reaching the 1-system network 5a or the 2-system network 5b is not transmitted from the 2-system computer 1b which is a standby computer.

  On the other hand, for the transmission path on the side where the duplex computer 1 receives a frame, the transmission paths 11 to 13 are separated as a hardware configuration. This is intended to avoid a collision between a frame from the transmission path 12 and a frame from the transmission path 13. Accordingly, the two-branch connection device 10 is provided with a reception frame transmission control unit 14 that performs transmission control for adjusting the collision of frames.

  That is, the reception frame transmission control unit 14 is provided with, for example, a buffer memory 15 that temporarily stores reception frames. The received frame from the 1-system network 5 a and the received frame from the 2 system network 5 b are temporarily stored in the buffer memory 15, and then sequentially transmitted to the transmission path 11 connected to the duplex computer 1.

Next, a detailed configuration and function of the network switch 20 will be described.
The network switch 20 includes a frame transmission control unit 21, a path switching unit 22, a monitoring frame transmission control unit 23, an active connection switch control unit 24, a duplicate frame discard processing unit 25, a reception management table 26, a transmission management table 27, and a buffer memory. 28.

  The frame transmission control unit 21 has a configuration and a function corresponding to a so-called general switching hub itself, and constitutes a part of a trunk transmission line of the 1-system network 5a or the 2-system network 5b.

  That is, the frame transmission control unit 21 is provided with a plurality of communication ports (not shown). Each communication port has a connection terminal for an input transmission path and an output transmission path. The frame transmission control unit 21 appropriately determines a communication port that outputs the frame according to a destination address (MAC address or the like) included in the frame input from the input transmission path of a certain communication port. Then, the frame transmission control unit 21 sends the input frame to the output transmission path connected to the determined communication port. At this time, the frame transmission control unit 21 transmits the frame with a communication number indicating the transmission order of the frames.

  On the other hand, when a frame arrives from the duplex network 5 by a one-to-many communication method (for example, broadcast), the frame transmission control unit 21 receives and manages the communication number acquired from the frame for each network relay device 2 of the transmission source. Write to table 26. When a frame arrives from the duplex network 5 by a one-to-one communication method (for example, unicast), the communication number acquired from the frame and the identification code for identifying the computer are assigned to each network relay device 2 of the transmission source. By writing in the reception management table 26, the arrival order of frames is managed for each communication method.

  The path switching unit 22 changes the transmission path to be connected to the transmission path 21a connected to the frame transmission control unit 21 from the transmission path 22a to the first computer 1a and the transmission path 22b to the second computer 1b. And has a function to switch the connection relationship. A switch SWa is installed on the transmission path 22a, and a switch SWb is installed on the transmission path 22b, one of which is turned on and the other is turned off. In FIG. 4, the switch SWa is on and the switch SWb is off.

  The on / off control of the switches SWa and SWb is performed by an active system instruction signal supplied from the active system connection switch control unit 24. Here, the working system instruction signal is a signal that instructs either the 1-system computer 1a or the 2-system computer 1b as the working system. As for the switches SWa and SWb, the switches on the transmission lines 22a and 22b connected to the 1-system computer 1a or the 2-system computer 1b which are the active systems are turned on, and the other is turned off.

  Accordingly, the network switches 20a and 20b connect a transmission path to the first-system computer 1a or the second-system computer 1b that is the active system. Then, the transmission path to the second system computer 1b or the first system computer 1a serving as the standby system is cut, that is, blocked.

  Note that these switches SWa and SWb are not limited to those that cut the transmission line in hardware. For example, when a microprocessor is installed in the network switch 20, the switches SWa, SWb may be turned on or off.

  When the monitoring frame transmission control unit 23 receives the monitoring frame transmitted from the duplex computer 1 to the own device (network switch 20), if the own device is operating normally at that time, A response frame including information indicating normality is returned to each of the duplex computers 1 of the transmission source.

  Here, the monitoring frame transmitted from the duplex computer 1 includes information indicating its own operation state, that is, information indicating whether it is an active system or a standby system. The active connection switch control unit 24 extracts information indicating whether it is the active system or the standby system from the monitoring frame received by the monitoring frame transmission control unit 23, and sends the information to the path switching unit 22 based on the information. On the other hand, an active system instruction signal is output. The active system instruction signal is, for example, a 1-bit flag signal. When it is “0”, the 1-system computer 1a is determined as the active system, and when it is “1”, the 2-system computer 1b is determined as the standby system.

  As described above, the duplex network 5 transmits frames independently of each other. Here, the frame transmitted from the active 1-system computer 1a is delivered to the active 1-system computer 1a as the destination via both the 1-system network 5a and the 2-system network 5b. In this case, the destination active system 1 computer 1a has received the same frame twice, and it is necessary to discard one of the frames.

  Duplicate frame discard processing can be performed by the active 1-system computer 1a itself. Therefore, the duplicate frame discard processing unit 25 is provided in each of the network switches 20a and 20b included in the network relay device 2, and the duplicate frame discard processing unit 25 discards one of the duplicate frames. The duplicate frame discard processing unit 25 receives the first frame received from the frame from the frame transmission control unit 21 when the transmission source network relay device 2 transmits the same frame in the duplex network 5. The process is performed and returned to the frame transmission control unit 21. Then, the same communication number as that of the first-arrived frame is attached, and the later-arrived frame from the network is subjected to a discarding process.

  Specifically, the duplicate frame discard processing unit 25 of the network switch 20a extracts a frame addressed to the active system 1 computer 1a from the frame received by the frame transmission control unit 21. Then, the duplicated frame discard processing unit 25 of the other network switch 20b in the same network relay device 2 compares with the frame extracted in the same manner. In this comparison, a communication number attached to the frame is referred to as described later.

  For example, if the same frame as the received frame has already been taken out by the duplicate frame discard processing unit 25 of the other network switch 20b, that is, if there is a first-arrival frame, the later-arrived frame is discarded. To do. As a result, the active system 1 computer 1a does not need to receive duplicate frames.

  The above processing is similarly performed when the 1-system computer 1a is a standby system and the 2-system computer 1b is an active system. At this time, the processing blocks described as the active system and the standby system in the above process may be reversed.

  The communication numbers attached to the frames are managed using the reception management table 26 in the order in which the frames arrived at the network relay device 2. The reception management table 26 manages the arrival order of frames arriving from the duplex network 5, and also indicates a communication number indicating the order in which frames are transmitted by the transmission source network relay device 2 as the transmission source network relay device. Manage every two. The reception management table 26 is provided for each of the network switches 20 a and 20 b, and there are a plurality of reception management tables 26 for each network relay device 2 of each station connected to the duplex network 5.

  When the network switch 20a is set to the active system, the frame transmission control unit 21 appropriately synchronizes the content written in the active system reception management table 26 with the standby system reception management table 26. As a result, even when the network switch 20a is changed to the standby system and the network switch 20b is changed to the active system, the network switch 20b takes over management of the reception status of the frame by the reception management table 26 held by itself. be able to.

  Further, the communication numbers attached to the frames transmitted by the duplex computer 1 are managed using the transmission management table 27 in the order of transmission by the network relay device 2. The transmission management table 27 is provided for each of the network switches 20 a and 20 b, and there are a plurality of transmission management tables 27 for each network relay device 2 of each station connected to the duplex network 5.

  When the network switch 20a is set to the active system, the frame transmission control unit 21 appropriately synchronizes the contents written in the active system transmission management table 27 with the standby system transmission management table 27. As a result, even when the network switch 20a is changed to the standby system and the network switch 20b is changed to the active system, the network switch 20b takes over management of the reception status of the frame by the transmission management table 27 held by itself. be able to.

Next, the frame processing performed by the source and destination network relay apparatuses 2 will be described in more detail.
FIG. 5 is an explanatory diagram showing an example of managing frames flowing through the duplex network system 6. Here, in order to simplify the explanation, it is assumed that all computers that transmit and receive frames are of the 1 system, and transmit frames from the first station to the nth station. In the figure, the flow of frames is indicated by thick arrows. In FIG. 5, only the MAC address field and the communication number field are extracted from the various fields of the reception management table 26 and the transmission management table 27 for explanation.

  Each device in the duplex network system 6 is individually assigned an identification code. Examples of the identification code include a MAC address and an IP address. Thus, the source computer and the destination computer can be uniquely identified.

  First, when the transmission source 1-system computer 1a transmits a frame, the MAC address of the destination 1-system computer 1a is written in the transmission management table 27 provided in the transmission source network relay apparatus 2. The MAC address used as the identification code of the destination 1-system computer 1a has been acquired by the transmission source network relay apparatus 2 in advance using ARP (Address Resolution Protocol) as an example of an identification code acquisition protocol.

  The communication number for the MAC address of the destination 1-system computer 1a is increased by “1” and written to the transmission management table 27 every time the number of frames transmitted by the transmission source network relay device 2 increases by “1”. Go. Here, the network relay device 2 of the transmission source has already relayed four frames, and the communication number “5” to be added to the frame to be relayed next is written in the communication number field. To do.

  Therefore, when the transmission source network relay device 2 relays the frame having the communication number “5”, the value of the communication number field increases from “5” to “6”. In this way, the transmission source network relay device 2 manages the communication number of the frame relayed from the destination 1-system computer 1a.

  The network relay device 2 as the transmission source transmits the frame branched as described above to the duplex network connection device 3. For this reason, the same frame flows through the 1-system network 5a and the 2-system network 5b. Thereafter, the frames that have passed through the 1-system network 5 a and the 2-system network 5 b are received by the destination duplex network connection device 3 and transmitted to the destination network relay device 2.

  The destination network relay device 2 receives the frame that has arrived first among the duplex network connection devices 3 that are the destination, and discards the frame that has arrived next. Here, the reception management table 26 used when the destination network relay device 2 receives a frame is used to manage a frame received from the transmission-source 1-system computer 1a. In the reception management table 26, the MAC address of the destination 1-system computer 1a is written, and the communication number of the received frame is also written.

For example, if the destination 1-system computer 1a has already received 5 frames, the communication number “ 6 ” is written in the destination reception management table 26. Thereafter, when the frame having the communication number “6” is received, the communication number in the destination reception management table 26 increases from “ 6 ” to “ 7 ”. Then, the destination network relay device 2 relays the frames whose communication numbers do not overlap to the destination first-system computer 1a.

Next, a configuration example of the frame will be described.
FIG. 6 is an explanatory diagram showing an example of a frame format relayed by the network relay device 2.

  This frame format is applied to a frame transmitted / received between the network relay devices 2. The frame format includes a MAC address field, an IP address field, a user information field, and a communication number field. Note that information other than these fields may be included, but description thereof is omitted here.

  The detailed contents of each field included in the frame are the same as those of the conventional reception management table shown in FIG. 10 described above. However, in the reception management table 26 according to the present embodiment, transmission / reception is performed according to the communication method. The difference is that the communication number field is added. The number of transmission / reception communication number fields can be increased / decreased according to the number of communication methods used in the duplex network system 6 and is also referred to as “trailer”.

  When transmitting and receiving a frame using broadcast, for example, Internet Control Message Protocol (ICMP) and User Datagram Protocol (UDP) are used. Further, when transmitting and receiving frames using unicast, for example, ICMP, UDP, and TCP (Transmission Control Protocol) are used.

  When receiving a frame from the duplex computer 1 in the branch line, the network relay device 2 adds a transmission / reception communication number field and relays the frame to the duplex network 5 via the duplex network connection device 3. Processing for adding a transmission / reception communication number field to a frame in this way is called “encapsulation processing”. Conversely, the network relay device 2 reads the contents of the transmission / reception communication number field from the frame received from the duplex network 5 via the duplex network connection device 3, and then removes the transmission / reception communication number field from the frame. Thus, the frame is relayed to the duplex computer 1 in the branch line. Processing for removing the transmission / reception communication number field from the frame in this way is called “decapsulation processing”.

  Here, it is desirable to add the transmission / reception communication number field to the end of the frame. For example, when a network failure occurs during frame transmission, an operation is performed in which an analyzer is inserted in the duplex network 5 to check the contents of the frame. This analyzer generally confirms the contents extracted from the frame in the order of the MAC address field, IP address field, and user information field, and analyzes the protocol. For this reason, it is necessary to examine the location where the transmission / reception communication number field is arranged so that the analysis by the analyzer is easy. In the frame according to the present embodiment, the transmission / reception communication number field is provided after the user information field, so that the analysis by the analyzer and the execution of the journal function that are conventionally performed are not affected.

  FIG. 7 shows a configuration example of the reception management table 26. FIG. 7A shows a configuration example of the first reception management table 26a for managing frames received from the first station, and FIG. 7B shows a second example for managing frames received from the second station. The structural example of the reception management table 26b is shown.

  The network relay device 2 has a reception management table 26 for each network relay device 2 connected to the duplex network 5 and manages the communication number of the received frame for each station. Here, as an example of the reception management table 26, the first reception management table 26a provided for the first station and the second reception management table 26b provided for the second station are taken as an example. . The reception management table 26 includes an arrival order field, a MAC address field, an IP address field, a user information field, and a communication number field.

In the arrival order field, the arrival order of frames received from the network relay device 2 of the transmission source is written.
In the MAC address field, the MAC address assigned to the destination duplex computer 1 is written when unicast communication is performed.
The IP address assigned to the network relay device 2 is written in the IP address field.
In the user information field, it is written which communication method the unicast communication or broadcast communication transmitted.
In the first communication number field, the communication number of the frame that arrived by broadcast is written.
In the second communication number field, the communication number of the frame that arrived by unicast is written.

  In the first reception management table 26a provided for the first station shown in FIG. 7A, the communication numbers of the frames received by broadcast are managed in the order of “1”, “2”, “3”, and the transmission source The IP address “xxx1” of the network relay device 2 is written. The communication number received by unicast is managed as “1”, the IP address “xxx1” of the network relay device 2 of the transmission source, and the MAC address “00-11-22- of the destination 1-system computer 1a”. 33-44-55 ”is written.

  On the other hand, in the reception management table 26 provided for the second station shown in FIG. 7B, the communication numbers of the frames received by broadcast are managed in the order of “1” and “2”, and the network relay device 2 of the transmission source The IP address “xxx2” is written. The communication numbers received by unicast are managed as “1” and “2”, the IP address “xxx2” of the network relay device 2 as the transmission source, and the MAC address “00− of the destination 1-system computer 1a”. 11-22-33-44-66 "is written. In this way, the communication numbers are individually managed for each station (network relay device 2) according to the communication method. For this reason, it is possible to easily determine which network relay device 2 has transmitted a broadcast or unicast frame to the destination network relay device 2, and to manage the arrival order. As a result, it is possible to reliably prevent missing frames and duplicate reception.

Next, a determination process for confirming the frame reception state will be described.
FIG. 8 is a conceptual diagram showing a frame reception state.
The destination network relay device 2 manages the communication number assigned to the frame for each frame as described in FIG. Here, the communication number cyclically uses a value within a predetermined range. However, the value of all 0 is not attached to the frame because it is used to initialize the communication number written in the reception management table 26.

  The frame transmission control unit 21 included in the network relay device 2 performs the following calculation in order to perform first-arrival reception and second-arrival discard of two frames received from the duplex network 5. As described above, the communication number managed by the destination network relay device 2 is assigned the communication number that is expected to be attached to the frame when the frame is next received.

(1) (communication number managed by destination network relay device 2) − (communication number attached to frame) = 0
This condition corresponds to the value 27a in the figure. At this time, since the frame is normally received first, the network relay device 2 relays the frame to the duplex computer 1 of the branch line.

(2) (communication number managed by the destination network relay device 2) − (communication number attached to the frame) <predetermined value This condition corresponds to the range 27b from 0 to a predetermined value. This predetermined value is assumed to be smaller than the maximum value of the communication number. At this time, since the communication number of the first-arrived frame is larger than the communication number of the later-arrived frame, the network relay device 2 knows that the frame that should be received first comes first. Such a state is called “frame missing”. Therefore, the network relay device 2 holds the received frame in the buffer memory 28 until the condition (1) is satisfied.

(3) (communication number managed by destination network relay apparatus 2) − (communication number attached to frame) ≧ predetermined value This condition corresponds to a range 27c from a predetermined value to a maximum value. At this time, the network relay device 2 receives a frame received from either the 1-system network 5a or the 2-system network 5b and stored in the buffer memory 28 until a frame is received from another network. stand by. For this reason, the received frame is not relayed to the duplex computer 1 of the branch line.

  When the transmission source network relay device 2 transmits a frame for the first time, all 0 is added to the communication number of the frame, and the communication number managed by the destination network relay device 2 is initialized. Further, even when communication between the transmission source and the destination network relay device 2 is not performed after a predetermined period, the communication number managed by the reception management table 26 is initialized.

Next, processing for buffering a frame will be described.
As described above, when the communication number of the newly received frame is not a serial number with respect to the communication number of the frame that has already been received, the destination network relay device 2 receives the frame having the serial number of the communication number. Continue to hold the frame. Such an operation is called “buffering”.

The network relay device 2 controls the following operations by buffering.
(1) When a missing frame occurs, the subsequent frame is held together with the corresponding frame.
(2) When a frame having a communication number missing from another system is received, this frame is relayed to the duplex computer 1 in the branch line. Further, the buffered frame is also relayed.
(3) If the communication number of a frame received from another system is the same as the communication number of a frame that has already been buffered, the duplex network 5 determines that the frame has been lost. Then, the frames after the communication number of the buffered frame are relayed to the duplex computer 1 in the branch line.
(4) When a frame is not received from another system, the buffered frame is relayed to the duplex computer 1 in the branch line. At this time, the buffering wait timer is monitored. Here, the maximum delay time that can occur between the source and destination network relay devices 2 is managed as a buffering wait timer. As this buffering waiting timer, for example, a value of 7 milliseconds is used, but an arbitrary value may be set according to the characteristics of the duplex network 5.
(5) When the number of buffering exceeds the limit value, the buffered frame is relayed to the duplex computer 1 in the branch line.

Next, processing for determining whether to initialize a communication number will be described with reference to FIGS.
FIG. 9 is an explanatory diagram showing an example of the gap number of the communication number initialization frame and a process of discarding. FIG. 9A shows a problem when the same frame is received using the duplex network 5, and FIG. 9B shows a method for solving this problem.

First, a problem in receiving a frame from the duplex network 5 will be described with reference to FIG. 9A.
The destination network relay device 2 initializes the communication number by receiving the initialization frame after receiving the frames in the order of “101” and “102” from the first-system network 5a. This initialization frame is transmitted from the transmission source network relay device 2 when the transmission source network relay device 2 is activated. The frames are received from the 1-system network 5a in the order of communication numbers “1” and “2”.

  However, the network relay device 2 receives the frame having the communication number “101” from the second system network 5b while receiving the frame having the communication numbers “1” and “2” from the first system network 5a. . Further, after receiving the frame with the communication number “2” from the system 1 network 5a, the frame with the communication number “102” is received from the system 2 network 5b. Here, since the frames with the communication numbers “101” and “102” received from the 2-system network 5b are frames already received from the 1-system network 5a, if relayed to the duplex computer 1 in the branch line as it is, The duplex computer 1 receives the same frame redundantly.

  Further, the network relay device 2 receives the initialization frame from the second system network 5b after receiving the frame having the communication number "102" from the second system network 5b, and initializes the communication number. For this reason, the communication number is initialized again, and the frames having the communication numbers “1” and “2” received from the second-system network 5 b are relayed to the duplex computer 1. At this time, the duplexing computer 1 may affect the processing of the duplexing computer 1 by receiving duplicate frames with communication numbers “1” and “2”.

  For this reason, as shown in FIG. 9B, the process of receiving a frame from the duplex network 5 is changed. That is, the frame transmission control unit 21 performs a reception process for a frame having the next communication number that arrives within a predetermined time from the arrival time of a frame that has arrived from one network of the duplex network 5. On the other hand, when the frame having the communication number next to the first frame that has arrived after a predetermined time has arrived, the reception management table 26 is initialized.

  Further, the duplicate frame discard processing unit 25 performs the initialization process of the reception management table 26 by the initialization frame that arrives first from the first network 5a of the duplex network 5 after the frame transmission control unit 21 performs within a predetermined period. When an initialization frame arrives later from the second-system network 5b, a frame arrived from the second-system network 5b to which the same communication number as the frame received between the first-arrival initialization frame and the second-arrival initialization frame is attached. Dispose of.

  Specifically, first, the destination network relay device 2 receives the frame with the communication number “102” from the second network 5b immediately after receiving the frame with the communication number “101” from the first network 5a. And Here, it is assumed that the elapsed time until the next frame is received from the 1-system network 5a is, for example, 130 milliseconds or more. At this time, the destination network relay device 2 initializes the communication number based on the initialization frame received from the 1-system network 5a. Then, the frames having the communication numbers “1” and “2” received from the 1-system network 5a within 128 milliseconds after the initialization are relayed to the duplex computer 1 as normal frames.

  On the other hand, when a frame received from the second system network 5b has passed 130 milliseconds or more from the last received frame, the initialization frame received from the second system network 5b is discarded. By discarding the initialization frame that arrived in this way, it is possible to prevent the initialization frame from being initialized immediately after it has been initialized to the first initialization frame.

  Also, the frames “1” and “2” received from the second network 5b having the same communication number as the frames already received from the first network 5a are discarded. As a result, after the communication number is initialized, the frame already relayed to the duplex computer 1 is not redundantly relayed.

  According to the duplex network system 6 according to the embodiment described above, the communication number of the frame received by the destination network relay device 2 from the duplex network 5 is managed for each communication method. For this reason, the transmission source network relay device 2 manages the transmission communication number of the frame transmitted by broadcast. On the other hand, the destination network relay device 2 manages the reception communication number of the frame received by unicast and the MAC address of the duplex computer 1, and specifies the duplex computer 1 that relays the frame. For this reason, even if a frame in which unicast and broadcast are mixed arrives, the destination network relay device 2 can identify that the frame has been received correctly.

  In addition, the network relay device 2 creates a reception management table 26 for every network relay device 2 connected to the duplex network 5 via the duplex network connection device 3. For this reason, the communication number of the frame can be individually managed for the network relay device 2 that is the transmission source of the frame received from the duplex network 5.

  Further, the network relay device 2 performs the initialization process of the reception management table 26 when the frame with the communication number next to the first arrived frame after the predetermined time has arrived, so that the missing frame remains generated. Don't keep buffering. For this reason, the capacity of the buffer memory 28 can be suppressed.

  The network relay device 2 arranges the fields in the order of the MAC address, IP address, user information, and communication number assigned to the destination computer from the beginning of the frame to be transmitted. Thereby, when analyzing the communication status of the duplex network 5 using the analyzer, the analysis range of the analyzer can be made to follow the general field.

  In the duplex network system 6 according to the embodiment described above, the example applied to the duplex network 5 has been described, but it may be configured by only one network. Further, although the duplex computer 1 and the duplex network connection device 3 are also composed of the active system and the standby system, it may be configured only for the active system.

  The duplex network system 6 described above is not only used for frame communication between stations, but also when a remote server transmits a frame to a client, or when computers with different processing speeds perform processing together. Is also effective.

  Moreover, although the example applied to broadcast was demonstrated as an example of a one-to-many communication system, you may apply to a multicast and anycast. The network topology of the duplex network 5 is configured as a ring type, but various connection forms such as a mesh type, a duplexed bus network, and a duplexed star type may be employed. it can.

  Further, the encapsulation process and the decapsulation process can be applied not only to the duplex network system 6 but also to various network systems such as a VLAN (Virtual Local Area Network).

  The series of processes in the above-described embodiment can be executed by hardware, but can also be executed by software. When a series of processing is executed by software, it can be executed by a computer in which a program constituting the software is incorporated in dedicated hardware or a computer in which programs for executing various functions are installed. . For example, a program constituting desired software may be installed and executed on a general-purpose personal computer or the like.

  Further, a recording medium that records a program code of software that realizes the functions of the above-described embodiments may be supplied to the system or apparatus. It goes without saying that the same function as that of the present embodiment can also be realized by reading and executing a program code stored in a recording medium by a computer (or a control device such as a CPU) of the system or apparatus. .

  As a recording medium for supplying the program code in this case, for example, a flexible disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD-R, magnetic tape, nonvolatile memory card, ROM, etc. are used. Can do.

  Further, the functions of the above-described embodiment are realized by executing the program code read by the computer. In addition, an OS or the like running on the computer performs part or all of the actual processing based on the instruction of the program code. The case where the function of the above-described embodiment is realized by the processing is also included.

  Further, the present invention is not limited to the above-described embodiments, and various other application examples and modifications can be taken without departing from the gist of the present invention described in the claims.

  DESCRIPTION OF SYMBOLS 1 ... Duplex computer, 1a ... 1 system computer, 1b ... 2 system computer, 2 ... Network relay apparatus, 3 ... Duplex network connection apparatus, 3a, 3b ... Network connection apparatus, 5 ... Duplex network, 5a ... 1 system network, 5b ... 2 system network, 6 ... Duplex network system, 10 ... 2 branch connection device, 10a, 10b ... 2 branch connection device, 11-13 ... Transmission path, 14 ... Received frame transmission control unit, DESCRIPTION OF SYMBOLS 20 ... Network switch, 20a, 20b ... Network switch, 21 ... Frame transmission control part, 21a ... Transmission path, 22 ... Path switching part, 22a, 22b ... Transmission path, 23 ... Monitoring frame transmission control part, 24 ... Working system connection Switch control unit, 25 ... duplicate frame discard processing unit, 26 ... reception management table, 26a ... first reception management table , 26b ... second reception management table, 27 ... transmission management table, 28 ... buffer memory

Claims (8)

A network relay device that relays a frame transmitted by a computer device to another network relay device connected to a network and relays a frame received from the other network relay device via the network to the computer device. There,
A reception management table for managing the order of arrival of frames arriving from the network and managing a communication number indicating the order in which the frames are transmitted by the other network relay device for each of the other network relay devices;
When a frame arrives from the network in a one-to-many communication system, the communication number acquired from the frame is written in the reception management table for each of the other network relay devices, and the frame is transmitted from the network in a one-to-one communication system. Upon arrival, the communication number acquired from the frame and the identification code for identifying the computer device are written to the reception management table for each of the other network relay devices, and the arrival order of the frames is managed for each communication method. And a frame transmission control unit. When the network relay device of the transmission source transmits the same frame in the multiplexed network,
Of the frames delivered from the frame transmission control unit, the frame that arrives first from the network is subjected to reception processing and delivered to the frame transmission control unit. The network relay device according to claim 1, further comprising: a duplicate frame discard processing unit that performs discard processing on the frame that arrives later. The network relay device according to claim 2, wherein when the initialization frame transmitted from the other network relay device is received in response to the activation of the other network relay device, the reception management table is initialized. The frame transmission control unit performs reception processing of a frame of the next communication number that arrives within a predetermined time from the arrival time of the frame that arrives from one of the multiplexed networks, and exceeds the predetermined time The network relay device according to claim 3, wherein when a frame having a communication number next to the first received frame arrives, the reception management table is initialized. The duplicate frame discard processing unit performs initialization processing of the reception management table with an initialization frame that arrives first from one of the networks in which the frame transmission control unit is multiplexed, and then performs other processing within a predetermined period. When an initialization frame arrives later from the network, discarding the frame arriving from another network with the same communication number as the frame received between the arrival initialization frame and the arrival initialization frame The network relay device according to claim 3 that performs processing. The network relay device according to claim 1, wherein the frame transmission control unit specifies an identification code of the computer device by an identification code acquisition protocol. The network relay device according to claim 1, wherein a field for storing a MAC address, an IP address, user information, and the communication number assigned to a destination computer device from the beginning is arranged in the frame. The first network relay device serving as the frame transmission source relays the frame transmitted by the computer device to the other network relay device connected to the network, and the second network relay device serving as the destination of the frame Is a network system that relays a frame received from the first network relay device via the network to the computer device,
The first network relay device is:
A first frame transmission control unit configured to transmit the frame with a communication number indicating a transmission order of the frames;
The second network relay device is
Manages the arrival order of a frame arriving from the network, a reception management table a communication number indicating the order in which the frame is transmitted, managed for each transmission source of the network relay apparatus by the other network relay apparatus,
When a frame arrives from the network in a one-to-many communication method, the communication number acquired from the frame is written in the reception management table for each network relay device of the transmission source, and the frame is transmitted from the network in a one-to-one communication method. The communication number acquired from the frame and the identification code for identifying the computer device are written in the reception management table for each network relay device of the transmission source, and the arrival order of the frames is determined for each communication method. And a frame transmission control unit for managing the network system.

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