JP2004048398A - Lan interface device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an LAN interface device capable of preventing a deterioration in transmission efficiency due to repetition of data collision. <P>SOLUTION: A transmitting part 11 transmits transmission data from terminal equipment 100 through a priority signal superimposing part 15 to a transmission path X. A collision detecting part 13 detects the collision of the transmission data on a transmission path. A collision count part 14 counts the number of times of the collision of the transmission data transmitted by its own node device 1. A priority signal superimposing part 15 superimposes a priority signal on re-transmission data when the count reaches the predetermined number of times of collision. When detecting a priority signal from other node devices 200, 300, and 400, a priority signal detecting part 16 inhibits the transmission of the transmission data of the transmitting part. A priority signal removing part 17 removes the priority signal from the reception data on which the priority signal is superimposed. A receiving part 12 outputs the reception data to the destination of its own node device from which the priority signal is removed to the terminal equipment. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a LAN interface device, and more particularly to a LAN interface device suitable for transmission control at the time of data collision in a LAN employing a CSMA / CD (Carrier Sense Multiple Access / Collision Detection) system.
[0002]
[Prior art]
In a LAN system in which a plurality of nodes are connected by a bus, CSMA / CD is known as one method for data transmission. In the CSMA / CD system, when a plurality of nodes transmit data at the same time, the data collide on a transmission path. In this case, usually, the colliding nodes stop sending data and try to send data again after a random time has elapsed. As a result, if data collision occurs again, data transmission is repeated several times (prior art 1).
[0003]
However, in the prior art 1, since the timing of data transmitted from each node is random, a node that can transmit and receive data at one time without collision or a data transmission and reception is established by repeating collision many times. There is a problem that unfairness occurs because there is a node that cannot.
[0004]
An example of a technique for solving this kind of problem is described in Japanese Patent Application Laid-Open No. 7-307759 as "inter-network connection apparatus" (prior art 2). This device optimizes the transmission timing after sensing that there is a communication packet transmitted by another communication node and the transmission delay time when taking the retransmission timing after detecting data collision using a simple membership function. It is set to a value. As the factors for determining the transmission delay time, the standby time from the previous transmission of the data packet to the present and the number of collisions per unit time are employed.
[0005]
[Problems to be solved by the invention]
However, in the above-described related art 2, since the transmission delay time is determined by fuzzy inference using the membership function of the knowledge base, the above-described problem of the related art 1 is alleviated, but data collision occurs. Repetition of retransmission in this case is still the same, so it does not solve the fundamental problem.
[0006]
Therefore, an object of the present invention is to provide a LAN interface device that can limit the number of continuous collisions and prevent a decrease in transmission efficiency due to repetition of data collision.
[0007]
[Means for Solving the Problems]
The LAN interface device according to the present invention is a LAN interface device for controlling communication between terminal devices via the same LAN transmission line by the CSMA / CD method. When transmission data from the terminal device collides on the LAN transmission line, The number of continuous collisions is counted, and when the counted number reaches a predetermined number, a priority signal is transmitted to prevent data transmission from another terminal device.
[0008]
More specifically, the LAN interface devices (node devices 1 to 4 in FIG. 1) of the present invention perform communication between terminal devices (100, 200, 300, and 400 in FIG. 1) via the same LAN transmission line. The transmission unit (11 in FIG. 1) for transmitting the transmission data from the terminal device to the transmission line in the LAN interface device corresponding to the terminal device controlled according to the one-to-one method, and the transmission data colliding on the transmission line. A collision detecting unit (13 in FIG. 1) for detecting a collision, a collision counting unit (14 in FIG. 1) for counting the number of consecutive collisions of transmission data transmitted from the own LAN interface device, The priority signal superimposing unit (15 in FIG. 1) that superimposes the priority signal on the retransmission data when the priority signal is reached, and the transmission unit that detects the priority signal from another LAN interface device. A priority signal detecting unit (16 in FIG. 1) for inhibiting transmission of transmission data; a priority signal removing unit (17 in FIG. 1) for removing a priority signal from received data on which the priority signal is superimposed; And a receiving unit (12 in FIG. 1) for outputting the received data addressed to the own LAN interface device to the terminal device.
[0009]
As described above, in the present invention, the number of continuous collisions is counted when transmission data between the node devices collides on the transmission path, and when the number of collisions reaches a predetermined number, the data is preferentially transmitted on the transmission path. Since the transmission is re-transmitted and the transmission of transmission data to the transmission path is prohibited when a priority signal is detected in another node device, a data output is performed after each of the conflicting node devices waits for a random time. This eliminates the multiple repetitions of data collisions that occur in the method described above, thereby preventing a reduction in transmission efficiency due to repeated data collisions.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings.
[0011]
[Configuration of the embodiment]
FIG. 1 is a block diagram showing one embodiment of the LAN interface device of the present invention. Referring to FIG. 1, the LAN interface device is embodied as a node device interposed between a LAN transmission line and a terminal device. In FIG. 1, four node devices 1, 2, 3, and 4 having the same configuration connect terminal devices 100, 200, 300, and 400 corresponding to one-to-one to a transmission line X.
[0012]
The node devices 1 to 4 in this embodiment are positioned not as branch points on the network but as relay points. Therefore, the node devices 1 to 4 can be built in the terminal devices 100 to 400. However, such external node devices 1 to 4 are the same as existing terminal devices that do not have the functions of the node devices 1 to 4. It is significant when the devices 100 to 400 are connected to the transmission line X.
[0013]
In FIG. 1, the node device 1 includes a transmitting unit 11, a receiving unit 12, a collision detecting unit 13, a collision counting unit 14, a priority signal superimposing unit 15, a priority signal detecting unit 16, and a priority signal removing unit 17.
[0014]
When there is data to be transmitted in the terminal device 100 or when there is retransmission data, the transmission unit 11 transmits the transmission data 100a from the terminal device 100 in response to the transmission permission signal 11c. The signal is sent to the priority signal superimposing unit 15 as 11a. However, as the transmission permission signal 11c, the reception notification signal 12b from the reception unit 12, the transmission inhibition signal 16a from the priority signal detection unit 16, or the collision detection signal 13a for transmission data from the other node devices 2 to 4 is input. Is input, the transmission of the transmission permission signal 11c to the terminal device 100 is blocked.
[0015]
The transmission data 11a is transmitted from the priority signal superimposing unit 15 to the transmission line X as transmission data 15a. When the transmission data 15a collides with other transmission data on the transmission line X, the collision detection unit 13 The collision detection signal 13a is input to the transmission unit 11. In response to the input of the collision detection signal 13a, the transmission unit 11 outputs the transmission permission signal 11c to the terminal device 100 for the retransmission data as described above.
[0016]
When the continuous collision of the transmission data transmitted from the own node device 1 reaches a predetermined number, a priority notification signal 14 a is input from the collision counting unit 14 to the transmission unit 11. In this case, the timing at which the transmission unit 11 outputs the transmission permission signal 11c to the terminal device 100 is slightly delayed. This is because preparation for superimposing a priority signal on transmission data is required in the priority signal superimposing unit 15 as described later.
[0017]
When detecting a collision of data generated on the transmission path X, the collision detection unit 13 outputs a collision detection signal 13a to the transmission unit 11 and the collision counting unit 14. The collision is not limited to the transmission data 15a transmitted by the node device 1, but also includes the transmission data from the other node devices 2 to 4.
[0018]
The collision count unit 14 counts the number of continuous collision detections of the transmission data 15a by inputting both the transmission notification signal 11b and the collision detection signal 13a. This is because the input of the transmission notification signal 11b and the collision detection signal 13a recognizes that the collision detection signal 13a was for the transmission data 15a from the node device 1. If only the transmission notification signal 11b is input, it means that no collision has occurred at the time of data transmission, so the number of times of collision detection is reset to zero.
[0019]
When the number of continuous collisions reaches a predetermined number in the collision counting unit 14, the transmission data of the node device 1 is transmitted over the transmission path X in order to transmit the transmission data from the node devices 2 to 4 in preference to the transmission data. The priority notification signal 14a is output to the unit 11 and the priority signal superimposing unit 15.
[0020]
When there is no input of the priority notification signal 14a, the priority signal superimposing unit 15 uses the transmission data 11a as it is as the transmission data 15a, and when there is an input of the priority notification signal 14a, superimposes the priority signal on the transmission data 11a. This is referred to as transmission data 15a. The priority signal can be, for example, a constant DC bias voltage.
[0021]
The priority signal detection unit 16 detects the priority signal when any of the node devices 2 to 4 transmits the transmission data on which the priority signal is superimposed on the transmission path X when the node device 1 is not in priority, The transmission unit 11 outputs a transmission prohibition signal 16a.
[0022]
When any one of the node devices 1 to 4 transmits transmission data on which a priority signal is superimposed on the transmission line X, the priority signal removal unit 17 removes the priority signal from the transmission data and receives the data as reception data 17a. Output to the unit 12. When the priority signal is not superimposed, the data on the transmission path X is output to the receiving unit 12 as received data 17a as it is.
[0023]
When receiving data 17a is input, receiving unit 12 determines whether the received data 17a is addressed to node device 1. As a result, when the reception data 17a is addressed to the node device 1, the reception data 17a is output to the terminal device 100 as the reception data 12a, and the reception notification signal 11b is output to the transmission unit 11. If the received data 17a is not addressed to the node device 1, the received data 17a is discarded.
[0024]
[Operation of the embodiment]
Next, the operation of the present embodiment configured as described above will be described.
[0025]
The node devices 1 to 4 connected to the transmission path X of the LAN can mutually transmit and receive data from the terminal devices 100 to 400, respectively. Here, it is assumed that the node device 1 transmits and receives transmission data 100a from the terminal device 100 to the transmission line X as transmission data 15a.
[0026]
[Sending operation]
First, the transmission operation will be described with reference to the flowchart shown in FIG. 2 and the time chart shown in FIG.
[0027]
The transmitting unit 11 checks whether there is a transmission request from the terminal device 100 (Step A1 in FIG. 2). As a result, if there is a transmission request (YES in step A1), it is further confirmed that there is no input of the reception notification signal 12b or the transmission prohibition signal 16a (NO in step A4), and the transmission permission signal 11c is transmitted to the terminal. Output to the device 100 (step A7). This is because the data transmission from the node device 1 must be prevented when the node device 1 is receiving or when the other node devices 2 to 4 have a transmission priority.
[0028]
Even if there is no transmission request in step A1 (NO in step A1), if the collision detection signal 13a is input (YES in step A2) and it is for transmission data from the node device 1 (step (YES in A3), after confirming that there is no input of the reception notification signal 12b or the transmission prohibition signal 16a (NO in step A4), outputs the transmission permission signal 11c to the terminal device 100 for retransmission of transmission data. (Step A7).
[0029]
In any case, when the transmission permission signal 11c is output, if the priority notification signal 14a is input (YES in step A5), the transmission permission signal 11c is delayed (step A6).
[0030]
On the other hand, if there is an input of collision detection signal 13a (YES in step A2) and it is for transmission data from node devices 2 to 4 (NO in step A3), transmission permission signal 11c is output. Therefore, data transmission from the node device 1 is blocked. This is because data collision has already occurred on the transmission line X.
[0031]
Now, it is assumed that the terminal device 100 is going to transmit data 1 to data 5, which are five transmission data. When transmission data 100a (data 1) is input to the node device 1 from the terminal device 100 that has received the transmission permission signal 11c, the transmission unit 11 outputs the transmission data 11a to the priority signal superimposition unit 15 and collides with the transmission notification signal 11b. Output to the counting section 14 (step A8). At this time, if the priority notification signal 14a is not input to the priority signal superimposing section 15 (NO in step A9), the priority signal superimposing section 15 sends the transmission data 11a as it is to the transmission path X as the transmission data 15a (step A10). ).
[0032]
Since transmission data is asynchronously transmitted from the node devices 1 to 4 to the transmission line X, if a plurality of node devices transmit data at the same time, data collision on the transmission line X may occur. Get up. If a data collision occurs on the transmission path X (YES in step A11), the collision detection unit 13 detects that a data collision has occurred and outputs a collision detection signal 13a to the collision counting unit 14 and the transmission unit 11 ( Step A12). The effect of the input of the collision detection signal 13a to the transmission unit 11 by the data transmission of the node devices 2 to 4 is that the data transmission is temporarily stopped as described above (NO in step A3).
[0033]
Since the transmission notification signal 11b has already been input to the collision counter 14 (step A8), when the collision detection signal 13a is input, the number of times of collision detection is counted (step A13). This is because the input of the transmission notification signal 11b has confirmed that the collision detection signal 13a is for the transmission data 15a from the node device 1. In the absence of the transmission notification signal 11b, the collision detection signal 13a was detected. Even if the signal 13a is input, the number of times of collision detection is not counted.
[0034]
On the other hand, if the collision detection signal 13a is not input while the transmission notification signal 11b is being input (step A8), the collision counting unit 14 determines that no collision has occurred during data transmission. The number of detections of the counting section 14 is reset to 0 (step A16). This means that the priority notification signal 14a is output only when the number of times of collision detection is counted continuously for a predetermined number of times. As a result of the transmission unit 11 receiving the collision detection signal 13a retransmitting the data, This is because priority handling is not performed when transmission is possible and collision does not continue.
[0035]
When the number of continuous collisions reaches a predetermined number in the collision counting unit 14 (YES in step A14), the transmission of the collision counting unit 14 is performed in order to preferentially transmit the transmission data of the node device 1 onto the transmission path X. The priority notification signal 14a is output to the unit 11 and the priority signal superimposing unit 15 (step A15). Special processing when the priority notification signal 14a exists is step A6 and step A17.
[0036]
Step A6 is executed when the transmission unit 11 receives the priority notification signal 14a (YES in step A5). When outputting the transmission permission signal 11c to the terminal device 100, as described above, the transmission unit 11 delays the timing by a small amount, so that the priority signal superimposition unit 15 performs the process of superimposing the priority signal on the transmission data. give.
[0037]
Step A17 is executed when the priority signal superposition section 15 receives the priority notification signal 14a (YES in step A9). The priority signal superimposing unit 15 superimposes, as a priority signal, a fixed DC bias voltage indicating transmission data 11a from the transmission unit 11 as priority data. Then, the transmission data 15a is transmitted to the transmission path X (step A10).
[0038]
FIG. 3 shows an example of a time chart when the node device 1 sends out transmission data 100a from the terminal device 100 to the transmission line X as transmission data 15a. In this example, the terminal device 100 is going to transmit data 1 to data 5 to the transmission line X as five transmission data 100a, and the number of continuous collisions set in the collision counting unit 14 is five.
[0039]
In FIG. 3, in response to the transmission request signal 11c output from the transmission unit 11 to the terminal device 100 at the timing T1, data 1 is transmitted from the terminal device 100 to the transmission path X via the node device 1 as transmission data 15a. However, the collision detection signal 13a has been generated. Therefore, the node device 1 repeatedly outputs the transmission request signal 11c to the terminal device 100 and sends the data 1 retransmitted from the terminal device 100 to the transmission path X (at timings T2 to T5). Each time, the collision detection signal 13a is generated, and finally the priority notification signal 14a is output (timing T5).
[0040]
In this case, the transmission unit 11 outputs the transmission permission signal 11c slightly delayed to the terminal device 100a as described above (timing T6). The transmission data 15a is obtained by superimposing a constant DC bias voltage on the data 1. This DC bias voltage functions as a priority signal.
[0041]
The transmission data 15a on which the priority signal is superimposed is handled with higher priority than the transmission data from the node devices 2 to 4. In FIG. 3, the collision detection signal 13a is not generated after the timing T6. Accordingly, it is shown that data 2 to data 5 that were originally planned can be transmitted at timings T7 to T10.
[0042]
[Reception operation]
Next, the reception operation will be described with reference to the flowchart shown in FIG. 4 and the time chart shown in FIG.
[0043]
When the priority signal is not superimposed on the data on the transmission path X (NO in step B1 in FIG. 4), the priority signal removing unit 17 outputs the data as it is to the receiving unit 12 as the reception data 17a (step B2). . When the reception data 17a is data addressed to the node device 1 (YES in step B3), the reception unit 12 outputs the reception notification signal 12b to the transmission unit 11 while outputting the reception data 12a to the terminal device 100 (YES in step B3). Step B4). The transmitting unit 11 receiving the reception notification signal 12b refrain from transmitting. If the received data 17a is not data addressed to the node device 1 (NO in step B3), the receiving unit 12 discards the received data 17a (step B5).
[0044]
On the other hand, when the priority signal is superimposed on the data on the transmission path X (YES in step B1), the priority signal removing unit 17 removes the priority signal that is a constant DC bias voltage (step B6), and thereafter, The received signal 17a is output to the receiving unit 12 (Step B2). When the node device 1 has no priority (NO in step B7), the priority signal detection unit 16 detects the priority signal and outputs the transmission inhibition signal 16a to the transmission unit 11 (step B8). Thereby, the transmission unit 11 suspends transmission. Note that the fact that the node device 1 is not prioritized is determined by the priority signal detection unit 16 detecting a priority signal in the transmission data 15a from the node devices 2 to 4.
[0045]
FIG. 5 shows a case where five transmission data (data a to data e) destined for another node on which the priority signal is superimposed and five transmission data (data f to data j) destined for the own node on which the priority signal is superimposed. 3 shows a time chart when the node device 1 receives a message. Since the priority signal is superimposed on any of data a to data e and data f to data j and the node device 1 is not prioritized, the transmission prohibition signal 16a is output for any data group. It is output from the priority signal detector 16.
[0046]
Further, data a to data e and data f to data j obtained by removing the priority signal from the transmission data 17 a are output from the priority signal removing unit 17. However, since the data a to data e are not destined for the node device 1, they are discarded by the receiving unit 12, and only the data f to data j destined for the node device 1 are output to the terminal device 100 a as the reception data 12.
[0047]
The data transmission method and the data reception method described above can also be performed by causing a computer constituting a node device to execute a program. The program controls the computer to perform the same processing as the processing shown in FIGS.
[0048]
【The invention's effect】
The present invention counts the number of continuous collisions when transmission data between node devices collides on a transmission path, and when a predetermined number of collisions is reached, preferentially retransmits data on the transmission path, When another node device detects a priority signal, transmission of transmission data to the transmission path is prohibited. Therefore, according to the present invention, after each of the colliding node devices waits for a random time, the data collision that occurs in a conventional method such as outputting data is not repeated many times, and the data collision is repeated. , It is possible to prevent the transmission efficiency from being degraded.
[Brief description of the drawings]
1 is a block diagram showing an embodiment of a LAN interface device according to the present invention; FIG. 2 is a flowchart showing a transmission operation of the embodiment shown in FIG. 1; FIG. 3 is a flowchart showing a transmission operation of the embodiment shown in FIG. FIG. 4 is a flowchart showing a receiving operation of the embodiment shown in FIG. 1; FIG. 5 is a time chart showing an example of a receiving operation of the embodiment shown in FIG. 1;
1-4 Node device 11 Transmitting unit 12 Receiving unit 13 Collision detecting unit 14 Collision counting unit 15 Priority signal superimposing unit 16 Priority signal detecting unit 17 Priority signal removing unit 100 Terminal device 200 Terminal device 300 Terminal device 400 Terminal device X Transmission path

Claims (6)

In a LAN interface device for controlling communication between terminal devices via the same LAN transmission line by the CSMA / CD method, when transmission data from the terminal device collides on the LAN transmission line, the number of continuous collisions is counted. When the count reaches a predetermined number, a LAN interface device transmits a priority signal to prevent data transmission from another terminal device. In a LAN interface device corresponding to the terminal device for controlling communication between terminal devices via the same LAN transmission line by the CSMA / CD method,
A transmission unit for transmitting transmission data from the terminal device to the transmission path,
A collision detection unit that detects that transmission data has collided on the transmission path,
A collision counting unit for counting the number of consecutive collisions of transmission data transmitted from the own LAN interface device;
A priority signal superimposing unit that superimposes a priority signal on retransmission data when the count reaches a predetermined number of collisions,
A priority signal detection unit for prohibiting transmission of transmission data of the transmission unit when detecting the priority signal from another LAN interface device;
A priority signal removing unit that removes a priority signal from the received data on which the priority signal is superimposed,
A receiving unit for outputting, to the terminal device, reception data addressed to the own LAN interface device from which the priority signal has been removed. 3. The LAN interface device according to claim 1, wherein the priority signal is a constant DC bias voltage. 4. The LAN interface device according to claim 1, wherein the LAN interface device is a node device interposed between the terminal device and the LAN transmission line. A LAN interface method for controlling communication between terminal devices via the same LAN transmission line by a CSMA / CD method,
Transmitting the transmission data from the terminal device to the LAN transmission path;
A procedure for detecting that transmission data has collided on the transmission path,
A step of counting the number of continuous collisions of transmission data transmitted from the own LAN interface device;
When the count reaches a predetermined number of collisions, a procedure for superimposing a priority signal on retransmission data,
Prohibiting transmission of the transmission data upon detecting the priority signal from another LAN interface device;
Removing the priority signal from the received data on which the priority signal is superimposed,
Outputting to the terminal device the received data addressed to the own LAN interface device from which the priority signal has been removed. A program executed by a computer constituting a LAN interface device for controlling communication between terminal devices via the same LAN transmission line by a CSMA / CD method,
A function of transmitting transmission data from the terminal device to the LAN transmission path;
A function of detecting that transmission data has collided on the transmission path,
A function of counting the number of continuous collisions of transmission data transmitted from the own LAN interface device;
A function of superimposing a priority signal on retransmission data when the count reaches a predetermined number of collisions,
A function of prohibiting transmission of the transmission data upon detecting the priority signal from another LAN interface device;
A function of removing the priority signal from the reception data on which the priority signal is superimposed,
A program for causing the computer to perform a function of outputting to the terminal device reception data addressed to the own LAN interface device from which the priority signal has been removed.

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