JP3034405B2 - Local area network device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a local area network device for terminating data transfer within a required time for the data.

[0002]

2. Description of the Related Art Local area networks (hereinafter abbreviated as LANs) have been introduced as communication means in the field of plant control and industrial automation. It is important that the data be transferred to the destination within the time (hereinafter, this time is referred to as a required time) (that is, the data transfer delay is within the required time). This is called time criticality or punctuality of data transfer. Further, data requiring the time criticality is referred to as synchronous data.

In a conventional local area network device, to achieve this time criticality, LA
In each of the N nodes, a band (time) sufficient to transfer the synchronous data required to be transmitted without delay has been allocated in advance. In addition, data that does not require time criticality (hereinafter, referred to as asynchronous data) is transferred using the remaining bandwidth of the bandwidth allocated to synchronous data.

[0004] However, when the length of the synchronous data and the arrival interval are always constant, that is, when the traffic is fixed, the bandwidth allocated to the synchronous data by the above method can be used efficiently. If the traffic is dynamic, the maximum bandwidth required by the synchronous data must be allocated to each node in advance, which lowers the bandwidth usage rate and is uneconomical. Therefore, there has been proposed a method of allocating a band of synchronous data each time synchronous data arrives instead of allocating a band to each node in advance. As an example, an LA disclosed in Japanese Patent Application Laid-Open No. 3-159436 "Token passing system" is disclosed.
A method of transferring synchronous data in the N device will be described.

[0005] Here, token passing means token ring and token bus defined by International Standards Organization (hereinafter abbreviated as ISO) standard 8802 and FDDI (Fibre Di) defined by ISO standard 9314.
Structured Data Interface)
Is a method of accessing a LAN, which is used to circulate specific information called a token indicating a data transmission right between nodes.

[0006] Figure 7 is a configuration diagram of a LAN in the above publication, reference numeral 1 is LAN, 201 synchronization data bandwidth management station for allocating a data zone area (hereinafter, also referred to as the management node), 2
Reference numeral 02 denotes a calling station (hereinafter, also referred to as a transmission source node) which is a transmission source of the synchronization data, and reference numeral 203 denotes a reception station (hereinafter, also referred to as a destination node) which is a destination of the synchronization data. FIG. 8 shows a case where the transmission source node 202 to the destination node
FIG. 11 is a sequence diagram showing a procedure for transferring data to the H.03. Here, the transmitted band use request, request response, band use permission, connection request, acknowledgment, synchronization data, band return, and return response are expressed and transferred on the LAN 1 as a data format called a frame.

Next, the conventional LA shown in FIGS.
The data transfer procedure of the N device will be described. When receiving the synchronization data from the communication application that generates the data to be transmitted, the transmission source node 202 transmits a band use request to the management node and requests a band for transmitting the synchronization data. The management node first transmits a request response indicating that it has received the bandwidth use request to the transmission source node, and further transmits a bandwidth use permission if the bandwidth can be allocated. Upon receiving the bandwidth use permission, the transmission source node sends a logical communication path (hereinafter also referred to as a connection) to the destination node.
Is transmitted, and upon receiving an acknowledgment from the destination node indicating acceptance of the connection setting, transmits the synchronization data to the destination node. When the transmission of the synchronous data is completed, the transmission source node transmits a band return to the management node 201 to notify the end of the use of the allocated band. In response, the management node 201 returns a return response indicating that the bandwidth return has been received.

As an example similar to the above, Japanese Patent Application Laid-Open No.
Japanese Patent Application Laid-Open No. 2-217749 entitled "Local Area Network Device" is similar to the above-mentioned publication in that a management means for centrally managing transfer of synchronous data is provided.

[0009]

SUMMARY OF THE INVENTION LA according to the prior art
Since the N device operates as described above, there are the following problems.

That is, since the management node is provided, there is a problem that if a failure occurs in this node, a band cannot be allocated to synchronous data. The above publication discloses a procedure in which a plurality of spare management nodes are provided, and a new management node is determined from the spare nodes when a failure occurs in an operating management node. In this case, there is a disadvantage that the procedure becomes complicated and the cost increases due to the addition of the spare node function to each node.

Also, when the communication application requests synchronous data transmission from the node, it is not possible to determine whether or not the synchronous data can be transferred within the required time without inquiring of the management node. It takes time to get a response (affirmation or rejection). As a result, for example, when a communication application issues a synchronous data transmission request to a node, it cannot be described as one system call invocation, and the request and its response need to be described at different timings. There were drawbacks such as complicating the program.

In addition, since each node transmits and receives a band allocation frame and a band return frame, there is a disadvantage that complicated protocol processing for these frames is required. In particular, node power off and bandwidth return 2
Since the allocated bandwidth may not be returned due to the loss of 16, a procedure for monitoring the bandwidth usage is required in addition to the procedure shown in FIG. 8 such as inquiring the bandwidth usage of each node from the management node 201. become.

Further, the conventional time criticality is
Although the time until the synchronous data arrives at the destination node has been a problem, in fact, not only is the synchronous data received at the destination node, but the synchronous data is processed at the destination node and a response is returned. Time is a problem. For example, if the synchronization data is a request for the measurement value of the measuring device at the destination node, one node commands transmission of the measurement value to the destination node by the synchronization data, and the destination node sends the measurement value to the transmission source node. Only after transmission can the source node recognize the measured value. Even if the destination node is a control device, the command is completed only after a response to the command has been received. Therefore, time criticality including the response from the destination node is required. However, in the above-mentioned conventional example, since this is not considered, there is a problem that reliable control cannot be performed in actual plant control or the like.

[0014]

According to the present invention, there is provided a local area network apparatus for transmitting, on a local area network, synchronous data requiring a response from a destination node within a predetermined request time. transmitting means for transmitting the data transmission amount of the local area network to other nodes as transmission reservation synchronous data amount corresponding to the amount, and transmission reservation synchronization data quantity transmitted from the other node, transmission reservation of the node synchronization data quantity and the depending <br/>, determines whether it is possible to transmit over the local area network for synchronous data to be transmitted to the new in consideration of the bandwidth use secured on a local area network and determining means, in this determination means, a local area network for the transmission is determined to be impossible data And having a suppression means for suppressing transmission onto the workpiece.

Further, the local area network includes:
This is a token passing method, in which a message about the transmission reservation synchronization data amount is piggybacked on a token circulating between nodes.

[0016] and transmits equipped with a message about the transmission reservation synchronization data quantity broadcast frame.

Further, the determining means, the low free bandwidth excluding already use bandwidth reserved in each node
It is characterized in that it is determined in consideration of the number of nodes connected to the local area network and whether or not transmission is possible based on the limited band.

Further, the limited band is characterized by a ratio of available bandwidth / number of nodes.

In addition, when receiving synchronous data, there is provided response judging means for judging whether it is possible to secure a band for a response to the synchronous data. If a response is difficult, a negative response is given. The synchronous data is transmitted to the transmitting node.

[0020]

As described above, according to the present invention, each node notifies both sides of the transmission reservation synchronization data amount in its own node, and based on the notified information, whether or not a newly generated transmission request is possible. Is determined, and the transmission band is secured if possible, and transmission is suppressed if impossible. by this,
The bandwidth including the response can be secured, and the time criticality including the response can be maintained.

By synchronizing the synchronous data amount information with the tokens circulating through each node, it is possible to minimize the consumption of the bandwidth used by the LAN due to the synchronous data amount notification.

By mounting the synchronous data amount information in the broadcast frame, a commercially available LAN control LSI conforming to the standard LAN can be used.

Further, there is a possibility that the bandwidth to be secured after securing the bandwidth based on the amount of reserved synchronization data may be duplicated in each node. Therefore, by limiting the bandwidth, the probability of such an occurrence of duplication can be suppressed.

In addition, by setting the bandwidth that can be secured after securing the bandwidth based on the amount of reserved synchronization data to "free bandwidth / number of nodes", efficient limitation can be performed.

Furthermore, if the responding node cannot secure a bandwidth for a response, a negative response is sent to the transmitting side without notifying the corresponding communication application (user) that the synchronous data has been transmitted. respond. Thus, useless processing can be minimized.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. Here, in the present embodiment, similarly to the above-mentioned conventional example, basically, a token-passing LAN is targeted.

FIG. 1 is a diagram showing the overall configuration of a LAN according to an embodiment of the present invention. In FIG.
Reference numeral 2c denotes a node, and reference numerals 3a to 3c denote a reserved synchronization data amount for each of the nodes 2a to 2c to notify another node of the reserved synchronization data amount obtained from the synchronous data amount in the own node. 5 is a synchronous data queue for storing the synchronous data passed from the communication application until the data can be transmitted to the LAN, and 5 is an asynchronous data queue for storing the asynchronous data passed from the communication application until the data can be transmitted to the LAN. . Reference numeral 4a denotes a measuring unit for measuring the number of synchronous data stored in the synchronous data queue 4. The reservation synchronous data amount notifications 3a to 3c are the number of synchronous data in the synchronous data queue 4, but may be numerical values representing the time required for transmission such as the total number of octets.

Next, the notification of the reserved synchronous data amount and the data transfer in this embodiment will be described. In FIG. 2 , 2a to 2c are nodes, 3a to 3c are reserved synchronous data amount notifications, 6 is synchronous data, 7 is new synchronous data processing when new synchronous data is received after the reserved synchronous data amount notification in the node 2a, 8 Represents transmission processing of synchronous data in the node 2a.

First, each node, for example, the node 2a measures the amount of synchronous data in its own node at an appropriate timing. This measurement is performed by the measuring unit 4a, and the synchronous data queue 4 based on the number of synchronous data in the synchronous data queue 4, the total number of octets, or a combination of both.
The time required for transmitting all the data in is calculated.

Next, the obtained number is doubled and stored in the reservation synchronization data amount notification 3a.
c. This procedure is the same regardless of the node. In addition, it is preferable to store the capacity of the LAN as the number of transmission data per second and measure and notify the reserved synchronization data amount every second.

Here, the reason why the reserved synchronous data amount is set to be twice the number of synchronous data waiting for transmission is that one synchronous data is transmitted because there is always a response to this.
This is because this response is also transmitted on the LAN. In the present embodiment, transmission of one piece of synchronous data is recognized as a round trip to a destination node, and one piece of synchronous data is transmitted on the LAN.
Count with one data transmission. With this, LAN
The bandwidth for the round trip of the synchronous data can be secured.

Each node performs bandwidth securing processing 7. For example, the node 2a secures a bandwidth on the LAN for transmitting the reserved synchronous data and obtaining a response based on its own reserved synchronous data amount. Then, the node 2a executes a synchronous data transmission process 8, and sends out the synchronous data stored in the synchronous data queue 4 to the destination node on the LAN 1.

Here, a case where new synchronous data is supplied from the communication application after the above-mentioned band is secured will be described with reference to FIG. It is monitored whether new synchronization data has been passed from the communication application (201). If there is new synchronization data, it is determined whether or not a band for transmitting the synchronization data can be secured.

For this purpose, first, based on the reservation synchronization data sent from the other nodes as described above, the reservation synchronization data amounts of all the nodes on the LAN including the own node are obtained. Synchronous data total is LAN
The available bandwidth is deducted from the capacity (step 202).
Then, the available bandwidth is divided by the number of nodes (including the own node), and the available bandwidth of the own node other than the reservation is obtained (203).

Then, the new synchronous data amount sent from the communication application is compared with its own available bandwidth (204). If it is within the used bandwidth, it is added to the reception synchronization data queue 4, and in the transmission process 7, the new synchronization data is transmitted together with the synchronization data for which other bands have been secured (205). On the other hand, if the new synchronous data exceeds the available bandwidth, the synchronous data is discarded (206), and this is notified to the communication application (207).

In this way, new synchronous data is accepted only when its own available bandwidth exists. Therefore, for the synchronous data to be transmitted, the time until the response can be guaranteed.

As described above, according to the present embodiment, transmission of synchronous data is performed by securing the bandwidth for the response from the destination node, but the bandwidth for transmission of the response cannot be secured at the destination node. In some cases, this may occur. That is, although the bandwidth on the LAN is temporarily secured, the destination of synchronous data is concentrated on one node, and when the amount of transmission synchronous data at this node is small, the bandwidth for response is secured at this node. Sometimes it is impossible.

Therefore, when the destination node receives the synchronous data, the destination node first determines whether or not a band for responding to the synchronous data can be secured. Then, when a band for a response cannot be secured, the received synchronous data is discarded without being passed to the communication application, and a negative response is transmitted to the transmission source node. This makes it possible to cancel transmission when time criticality cannot be observed without performing extra processing in the communication application.

Next, FIG. 4 is a diagram showing an example of a token format of the token passing LAN. In FIG. 4, (a) shows a concatenated token format in which the amount of reserved synchronization data for each node is stored in a separate field. b) is an addition token format in which each node adds the number of reserved synchronization data in its own node to a single field,
In the figure, reference numeral 10 denotes a field of reserved synchronous data amount information in which reserved synchronous data amount information is stored in a token; 11 denotes a subfield for storing the number of reserved synchronous data of the first node in a concatenated token format; A subfield for storing the number of reservation synchronization data of the second node, a subfield 13 for storing the number of reservation synchronization data of the N-th node (N is the maximum number of nodes), and 14 in the addition token format This is a field for storing the total number of synchronous data in which each node adds the number of reserved synchronous data of its own node. Here, when using the concatenated token format, it is assumed that each node is numbered consecutively from 1 in advance.

First, transmission of reservation synchronization data amount information to another node will be described. When the token arrives at its own node, each node writes the reserved synchronization data amount information in the token as follows and transmits it to the next node. First, in the case of the concatenated token format of FIG. 3A, each node writes the number of reservation synchronous data of its own node in a subfield corresponding to its own node. For example, if the own node is the first node, the reservation synchronization data number of the own node is written in the subfield 11 and transmitted. In the case of the addition type token format shown in FIG. 3B, the reserved synchronous data number total field 14 is read, the reserved synchronous data number of the own node is added to the read numerical value, and the result is stored in the same reserved synchronous data number accumulated field 14. Write and send.

On the other hand, reception of the reservation synchronization data amount information from another node is performed as follows. First, in the case of the concatenated token format shown in FIG. 3A, when a token arrives, each node reads the number of reserved synchronization data from the subfields 11 to 13 and stores it in a storage area prepared for each node. However, the number of reserved synchronous data of the own node can be determined from the number of waits in the synchronous data queue 4, so that it is not always necessary to read out from the token. If the addition in FIG. 3B is in the other token format, each node stores the value of the reserved synchronous data total field 14 previously written in the token by the own node, and the own node writes the token when the token arrives. The difference from the previously read value is stored in the storage area as the total number of reserved synchronous data in the other nodes.

With the above operation, the token can be shared with the reservation synchronous data amount information to be notified. In the above description, the number of reserved synchronous data is used as the reserved synchronous data amount. Values can also be used.

Next, FIG. 5 shows a format example in the case of using the broadcast frame for notification of the amount of reserved synchronous data.
Shown in In the figure, reference numeral 21 denotes a source node number field of the broadcast frame, and reference numeral 22 denotes a synchronous data number field in the node represented by the source node number 21.

The transmission of the reserved synchronization data amount information to the other nodes is carried out at each node at an appropriate transmission timing in the transmission source node number field 21 in the own node number and the reserved synchronization data number field 22 in the transmission waiting state in the own node. Is created by creating a broadcast frame storing the number of reserved synchronous data in the LAN 1 and sending it out to the LAN 1.

On the other hand, when receiving the reserved synchronous data amount information from another node, when a broadcast frame carrying the reserved synchronous data amount is received from another node, the source node number field 21 is read and the reserved synchronous data This is realized by identifying whether the number is a number, and storing the number of reserved synchronous data read from the reserved synchronous data number field 22 in a storage area corresponding to the node.

As a trigger for transmitting a broadcast frame carrying the reserved synchronization data amount information, for example, in a token-passing LAN, the frame can be transmitted only when the token is held, so that the token circulates an appropriate number of times. There is a method of transmitting a broadcast frame before releasing a token every time.

Next, the hardware configuration of the LAN device according to the present invention will be described. FIG. 6 is a block diagram showing an example of a hardware configuration of a node. In the figure, reference numeral 51 denotes a communication application interface for exchanging data with a communication application, and 52 denotes data received from the communication application and transmitted to the LAN or from the LAN. Buffer memory 53 for temporarily storing data to be received and passed to the communication application.
A LAN interface for transmitting frames to the AN and receiving frames from the LAN; 54, a program memory for describing and storing the synchronous data amount notifying means and data transmission procedure described above in the form of a computer program; CPU (Central) that controls the communication application interface 51 and the LAN interface 53 according to the program in the
A processing unit 56 for transferring information between the communication application interface 51 to the program memory 54 and the CPU 55; Here, in a standardized LAN such as ISO8802, Token Bus, Token Ring, and FDDI, LAN
Since control LSIs are commercially available, commercially available LAN control LSI
I is often used.

With the above configuration, the LAN according to the present invention
The hardware of the device can be implemented without significant changes from the hardware of the LAN device according to the prior art.

[0049]

As described above, according to the present invention,
Since there is no need to provide a management node, various problems caused by providing a management node are eliminated.

Then, each node notifies both sides of the transmission reservation synchronous data amount in its own node, and determines whether or not a newly generated transmission request is possible based on the notified information. The transmission band is secured, and if impossible, transmission is suppressed. As a result, the band including the response can be secured, and the time criticality including the response can be maintained.

By sharing the synchronous data amount information with the tokens circulating through the nodes, it is possible to minimize the consumption of the bandwidth used by the LAN due to the synchronous data amount notification.

By mounting the synchronous data amount information on the broadcast frame, a commercially available LAN control LSI conforming to the standard LAN can be used.

Further, there is a possibility that the bandwidth to be secured after securing the bandwidth based on the amount of reserved synchronization data may be duplicated in each node. Therefore, by limiting the bandwidth, the probability of such an occurrence of duplication can be suppressed.

Further, by setting the bandwidth that can be secured after securing the bandwidth based on the amount of reserved synchronization data to “free bandwidth / the number of nodes”, efficient limitation can be performed.

Further, if the responding node cannot secure a bandwidth for a response, a negative response is sent to the transmitting side without notifying the corresponding communication application (user) that the synchronous data has been transmitted. respond. Thus, useless processing can be minimized.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an overall configuration of a LAN according to an embodiment.

FIG. 2 is a diagram showing a synchronous data amount notification procedure and a data transfer procedure in the embodiment.

FIG. 3 is a diagram illustrating a procedure of a process when new synchronization data is accepted.

4 is a diagram illustrating a token format example of Tokunpa Tsu single LAN.

FIG. 5 is a diagram illustrating a format example of a broadcast frame.

FIG. 6 is a diagram illustrating a hardware configuration of a node.

FIG. 7 is a diagram illustrating a configuration example of a LAN in a conventional device.

FIG. 8 is a sequence diagram showing a data transfer procedure from a source node to a destination node in a conventional device.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yuji Atsui 5-1-1, Ofuna, Kamakura City, Kanagawa Prefecture, Communication Systems Laboratory, Mitsubishi Electric Corporation (58) Fields investigated (Int. Cl. ⁷ , DB name ) H04L 12/42

Claims (6)

(57) [Claims] 1. A local area network device for transmitting synchronous data requiring a response from a destination node within a predetermined request time on a local area network, comprising: transmitting means for transmitting to the other nodes of the data transmission amount as transmission reservation synchronization data quantity, a transmission reservation synchronization data quantity transmitted from the other node,
Depending on the transmission reservation synchronization data of the own node, taking into account the bandwidth use secured on a local area network, determining whether it is possible to transmit over the local area network for synchronous data to be transmitted newly A local area network device comprising: a determination unit that performs transmission; and a determination unit that determines that transmission is impossible and suppresses transmission of data to the local area network. 2. The local area network according to claim 1, wherein the local area network is of a token passing method, and a message about a transmission reservation synchronization data amount is piggybacked on a token circulating between nodes. Network device. 3. A device according to claim 1 or 2, a local area network system and transmits equipped with a message about the transmission reservation synchronization data quantity Bed B <br/> over de cast frame . 4. The apparatus according to claim 1, wherein said determination means sets a free bandwidth excluding a used bandwidth already reserved in each node to a local area net.
A local area network device, which determines whether transmission is possible based on the limited bandwidth in consideration of the number of connected nodes . 5. The local area network device according to claim 4, wherein the limited bandwidth is available bandwidth / number of nodes. 6. The apparatus according to claim 1, wherein, when the synchronous data is received, a response determining unit that determines whether it is possible to secure a band for a response to the synchronous data is provided. A local area network device, comprising: transmitting a negative response to the node that transmitted the synchronous data when the response is difficult.