JPH02100538A - Data communication method for local area network - Google Patents

Abstract

PURPOSE:To simplify packet structure and to facilitate an acknowledge(ACK) processing by returning a sequence number itself or an acknowledge number which is selected in accordance with the sequence number from a reception side whenever packet data is communicated. CONSTITUTION:When packet data is accurately received, the acknowledge number is returned without fail. A transmission-side recognizes transmission by the reception of the acknowledge number and shifts a system to the transmission of packet data of a subsequent sequence number. Fundamentally, the acknowledge number can be only the sequence number itself, and a bit quantity and a returning time required for acknowledge are considerably shortened by the simple selection of the acknowledge signal, whereby the efficiency of a whole device is improved. When the sequence number is duplicated with the prior sequence number, only the return of acknowledge(ACK) is performed, and the system returns to a main processing by the return. Thus, a processing at the time of duplicate reception can considerably speedily be completed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a data communication method in a local area network, and in particular to an improvement in an authorized communication method in a simplified local area network.

[Prior Art] Local area networks that perform data communication in a limited area, such as an office or a specific closed area, have been put into practical use, and are effective communication systems for use within a wide range of specific areas. The company is steadily solidifying its footing.

In particular, multiple computers, facsimiles, office computers, and other OA equipment are connected to the in-building line, and high-speed, large-capacity data transmission is performed using optical fibers, etc., and distributed processing is performed at each workstation through mutual communication within the building. However, it has the advantage that all data within the area can be shared.

In such local area networks, each data is often communicated using a non-procedural communication method. Although such non-procedural communication has the advantage of being able to transmit the desired communication data at high speed, it also , there was a problem of low communication reliability.

That is, there is a problem in that communication data may be lost or contain data errors due to interference or noise in the communication channel itself or communication hardware.

Conventional non-procedural communication systems cannot deal with such data degradation, and in local area network non-procedural communication systems, transmitted data is temporarily stored in a receive buffer on the receiving side; The receiving buffer has a limited capacity, and there is a problem in that the capacity of the receiving buffer becomes insufficient when the communication data exceeds the capacity or when the processing speed on the receiving side is slower than the sending speed.

With respect to the latter receiving buffer capacity, it is beneficial to divide the transmission data into packet data of a predetermined data length or less and transmit the data.

However, when dividing such packet data, during transfer, it is necessary to reliably convey the relevance of each packet data to the receiving side and reconfigure the data without error.
Even in such a case, the conventional non-procedural communication system has the problem that packet data is likely to be omitted midway or the order of packet data may be incorrect. - Conventionally, for data communication in large-scale networks, a method has been established in which the transmitting side and the receiving side communicate while sequentially performing shake hands, and various standard communication protocols have been put into practical use.

According to such a shake-hand communication method, a header indicating the content is attached to each transmitted data, and when such header-attached data is received, the receiving side reliably acknowledges (the ACIO signal is sent by the transmitting side). The data communication proceeds while confirming that each data is transmitted correctly.

Therefore, if such a standard communication protocol is followed, highly reliable communication can be performed without causing the data deterioration described above.

[Problems to be Solved by the Invention] However, in the communication procedure in such a standard protocol, the header and authorization signal must themselves contain a large amount of standardized information, and the header requires a considerable amount of bit area. The problem was that I had to give.

Therefore, it is not necessarily advantageous to use a header with such detailed authorization information in a communication system where the amount of communication data itself is relatively small, such as a local area network. A simpler communication method was desired for local area networks.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a communication method equipped with a simplified communication data authorization protocol that is optimal for local area networks consisting of small-scale systems.

[Means for Solving the Problem] In order to achieve the above object, the present invention divides transmission data into packet data of a predetermined data length or less and transmits the divided data within a local area network. The capacity of the buffer 82 can be efficiently set according to the maximum length of packet data to be transmitted.

In addition, a series of related transmission data divided into packet data in this way is assigned a sequence number for each packet, usually a sequence number represented by a string of numbers starting from a predetermined stat number, This allows each packet data to be identified on the receiving side.

According to the present invention, for each data transmission, the receiving side performs acknowledgment (ACK) by returning an authorization signal, and the authorization signal at this time is the authorization number corresponding to the sequence number, and in the normal case This is done on the sequence number itself.

On the transmitting side, if there is no authorization for a predetermined period of time, the same data is retransmitted, while on the other hand, when authorization is correctly returned, the transmitting side transmits the next packet data according to the sequence number.

Furthermore, if data is lost or a data error occurs when an authorization is returned, the same data will be retransmitted by the operation in the case of no authorization described above, but in the present invention, such retransmitted data can be processed correctly on the receiving side. If so, double sending will occur, so in order not to reduce the communication speed, only the authorization signal is sent back, and the processing of the duplicately received data is omitted.

Furthermore, according to the present invention, the aforementioned sequence number is repeated with the start number removed during one or more repetitions, thereby indicating the completion of a series of related data communications and the subsequent new series of related data. Communication can be reliably classified.

[Operation] Therefore, according to the present invention, communication data is divided into packet data within a standardized data length, and an acknowledgment (ACK) is returned from the receiving side every time packet data is communicated, thereby ensuring reliable reception. Communication of data associated with a series of sequence numbers continues while confirming that the signal has been transmitted to the other side.

Since the authorization of the present invention is performed simply by returning the sequence number itself or the authorization number selected in accordance with the sequence number, there is no need for a header that requires a large bit area as in the conventional standard communication protocol. This has the advantage that the packet structure is simplified and the acknowledgment (ACK) process is also extremely easy.

Further, according to the present invention, the time from data communication is measured, and when this timeout occurs, the data is retransmitted because it is assumed that the communication is defective. The side receives the same data repeatedly, and in such a case, only the authorization is returned again, but the data processing is omitted to shorten the processing time.

Further, the above-mentioned sequence number setting is selected as a predetermined start number, such as a number string increasing from "0", and when this is repeated for one cycle or more, the start number is removed, and the start number is set to "0", for example. When , the second cycle is repeated from the next "1", thereby reliably preventing confusion between separate data groups.

"Example" Preferred embodiments of the present invention will be described below based on the drawings.

FIG. 1 schematically shows a communication section of a workstation to which a communication method according to the present invention is applied.

In the figure, a network 100 is set up as a relatively narrow local area network within a facility, and predetermined workstations are arbitrarily connected to this network 100.

Each workstation includes a network controller 10 and is connected to the network 100 by this controller 10.

The network control unit 10 connects the 2
It is connected to point RAM14, and this two point RAM
Inside M14, both the reception buffer memory and the transmission buffer memory are allocated to different areas.

The network control unit 10 is controlled by the CPU 16, and as described later, when the network control unit 10 receives data from the network 10, it supplies an interrupt signal to the CPU 16 and operates.
Further, the CPU 16 sends an attention signal to instruct data transmission when the network control unit 10 is not performing a receiving operation.

A control program for the CPU 16 is stored in the ROM 18, and both are connected via a system bus 20. A RAM 22 is further connected to this system bus 20, and the transmitted data is first written to the RAM 22 and then sent from there to the two-port RAM 14 through the system bus 20, and the received data is once written to the two-port RAM 14 as described later. after being stored in R via the system bus 20.
It is transmitted to AM22.

A timer 24 is connected to the CP01B, and counts the timeout time required for timeout retransmission control, which will be described later.

The hardware to which the present invention is applied has the communication function unit as described above, and the transmission and reception procedures according to the present invention will be explained in detail below using FIGS. 2 and 3.

FIG. 2 shows a transmission flowchart, in which the CPU
16 writes the transmission data once written in the RAM 22 to a determined transmission buffer area on the two-point RAM 14 via the system bus 20 (step 101).

Next, the CPU 16 writes a transmission command according to the control program in the ROM 18 into the command area of the two-point RAM 12, and further sends an attention signal to the network control unit 10 (102).

As is well known, by supplying the attention signal, the network control unit 10 connects the transmission data stored in the two-point RAM 14 from the local bus 12 to the network 100 according to the transmission command, and sends it to a desired receiving workstation. Transmit.

When the attention signal is output from the CPU 16 and the transmission is completed, the CPU 16 starts the timer 24 and starts counting a predetermined time (step 103).

When a reception signal designating this workstation as a receiving terminal is input from the network 100 during transmission by the network control section 10, the network control section 10 immediately gives an interrupt signal to the CPU 16 (step 104).

When this reception interrupt signal is supplied, the CPU 16 executes a reception mode in which the reception data is stored in the reception area of the 2-point RAM 14 (step 105), and this reception flowchart is detailed in the following FIG. 3. explain.

On the other hand, if there is no reception interrupt in step 104, a timeout determination is performed in step 106, and during this time, an acknowledgment (ACK) from the receiving side is awaited.

In the flowchart of FIG. 2, reception of acknowledgment (ACK) is the same as normal reception data, and in step 104 it is determined that there is a reception interrupt, and in step 105, the acknowledgment (ACK) reception mode in the reception mode is executed. and returns to main processing.

On the other hand, if the authorization is not returned even after the predetermined timeout period has elapsed after transmitting the data, the timer 24 is temporarily canceled in steps 106 and 107, and then the process returns to step 101 and the same process is performed. The data, ie, the transmission data stored in the 2-point RAMI 4, is retransmitted and this process is repeated.

Although not shown in detail in the figure, if acknowledgment (ACK) is still not obtained even after retransmission is repeated a predetermined number of times, it is determined that there is a permanent hardware failure or the like, and transmission is stopped.

As described above, according to this transmission mode, the predetermined time from transmission is always measured, and it is always determined whether or not the reception confirmation of each packet data has been performed within this timeout period, and the authorization ( 80K), the data will be retransmitted.

FIG. 4 shows an example of the transmission data mentioned above.
A series of related transmission data is divided into packet data of a predetermined data length or less, and a header is added to each packet data.

The header in an embodiment includes a data length, a sequence number, and a data/ACK bit, where the data length indicates the effective length of the packet data, and the sequence number is a series of numbers indicating the order of the packet data relative to a series of related transmitted data. For example, sequence numbers as shown in FIG. 6 are set, starting from the start number "0" and continuing to rlooj as rlJ, "2", and "3".

Further, the data/A CK bit is a bit for determining whether this transmission data is data or just an authorization, and in the embodiment, it is set to "0" in the case of data, and is set to "0" in the case of ACK. "1" is used.

As described above, when transmission data as shown in FIG. 4 is sent, the receiving side can read the header, especially the sequence number, and reconstruct the divided packet data into the original data.

FIG. 3 shows a reception flowchart in the communication method of the present invention, and as described above, this reception flowchart includes data reception and authorization reception, and further includes authorization return upon data reception.

Timeout retransmission control is not required when receiving data,
At step 201, the timer 24 is canceled.

Next, the network control unit 10 stores the received signal supplied from the network 100 in the reception area of the 2-bot RAM 14 via the local bus 12 (step 202
).

Then, the CPU 16 determines whether this signal is data or not (
ACK) based on the header data/ACK bit (step 203).

If the transmitted signal is data, then the sequence number of the header is read (step 204), and if it is processed immediately before and differs from the sequence number of the received data, it is authorized (A) as newly sent transmitted data. CK) and processes the received data in the 2-port 1-RAM 14 (step 205), returning to main processing.

In the communication method in a simplified local area network according to the present invention, normally a series of related transmission data is received in the order of sequence numbers, but when the network is extremely congested, packet data transmission The sequence numbers of the received data may not always be in the correct order because the packets may take different routes. Even in such cases, reading the sequence numbers on the receiving side is extremely effective for later reassembling the packet data. Also, even when receiving out-of-order data as described above, the same sequence number will not come in the correct reception state, so in the sequence number judgment in step 204, if a different sequence number is received, this is judged as normal data. It is possible to do so.

FIG. 5 shows an example of an acknowledgment (ACK) signal, which in the present invention mainly includes an acknowledgment number corresponding to a sequence number.

The authorization signal in the embodiment uses the same data as the header of the transmitted data, but the data/ACK bit at this time is of course the authorization 111 (AC
It has been switched to "1" indicating K).

Therefore, the authorization signal consists of the data length and sequence number of the transmission data, and the data "1" as shown in Figure 5.
Contains K bits.

In the present invention, this authorization number does not necessarily have to be the same as the transmitted sequence number, but it is preferable to select a closely related number, such as a sequence number of "+1".

As described above, according to the present invention, an authorization signal is always returned when packet data is correctly received, and the transmitting side confirms the transmission by receiving this authorization signal, and then transmits the packet data of the next sequence number. transmission, ensuring extremely reliable communication.

Further, the authorization signal of the present invention is as shown in FIG.
It has an extremely simple configuration, in particular, basically only the sequence number itself is required, and by selecting such a simple authorization signal, the bit capacity required for authorization and the return time are extremely short, increasing the efficiency of the entire device. Can be done.

On the other hand, if the sequence number overlaps with the previous sequence number in step 204, only an acknowledgment (ACK) is returned in step 206, and the process returns to the main process.

In other words, for a sequence number that is the same as a sequence number that has already been received, there may be some reason, such as a case where the return of an acknowledgment (ACK) signal did not reach the sending side due to a faulty communication line, and in this case, the sending side sends the same data again through the timeout retransmission process described above. Therefore, such retransmission of data is data that has already been received and processed on the receiving side, and is simply a failure to return an authorization signal. The process is simplified by simply giving

Therefore, according to the method of the present invention, it is possible to complete processing at the time of duplicate reception extremely quickly.

The reception of data is understood from the above-1, and the processing when this received signal is an acknowledgment rl (ACK) will be described below.

If the received signal is an acknowledgment (ACK) in step 203, it is determined in step 207 whether it matches or does not match the sequence number of the transmitted data. Normally, the same sequence number as the transmission sequence number is returned as the acknowledgment (ACK), as explained in FIG.

On the other hand, in step 207, if the authorization sequence number is different from the transmission sequence number, it is determined that there has been a transmission failure for some reason, and data retransmission processing is performed in step 208.

It is preferable to perform this retransmission process a predetermined number of times and, if normality does not return, to stop the transmission itself.

The reception mode of data or acknowledgment (ACK) can be understood as described above.Next, the setting of sequence numbers in the present invention will be explained based on FIG. 6.

As mentioned above, in the embodiment, the sequence number is shown as a sequence of numbers that increase sequentially from the start number "0", and in FIG. 6, rl 00J is the maximum value. Therefore, according to this example, a series of related communication data can be divided into 101 packet data.

However, if the transmitted data is larger than this, “1
The sequence number used for one cycle up to ``00'' must be used again, and in the present invention, this number
When repeating for more than one period, the start number is removed and repeated, that is, as shown by the arrow in FIG. 6, the start number for two or more periods is set to "]".

Therefore, by using such repetition, it becomes possible to process transmission data of any length even in a simple communication system such as the present invention.

Of course, in step 204 of FIG. 3 mentioned above, it is determined whether the sequence number of the received signal is the same as before, but in the present invention, the sequence numbers match every 100 times due to this repetition, and it is not normal. By using a reliable communication channel, even in the most congested conditions, 100
There is no difference in the sequence number from time to time, and it is possible to reliably identify the previous and subsequent sequence numbers due to such repetition and the length and shortness of the route.

The selection of repeat sequence numbers as described above produces the following effects. That is, if the repetition is applied to all sequence numbers and returns from rl 00J to, for example, the stat number "0", there is a possibility that it will not be possible to distinguish between processing different communication data.

In other words, assuming that the first transmission data has a length of one cycle or more and that the final data is assigned a sequence number of "0", the next new transmission data will always start from the start number "0". start that sequence number,
As a result, the receiving side receives two identical sequence numbers, ie, "0" in duplicate.

According to the present invention, such duplicate reception is handled by 2 in the sequence number determination step 204 of FIG.
Since data processing is omitted by only transmitting an acknowledgment (ACK) as ffi data, the result is that the start packet data of this new transmission data cannot be received, and the sequence number shown in FIG. Repetition can definitely prevent such situations.

[Effects of the Invention] As explained above, according to the present invention, a simplified communication protocol is provided to a local area network,
While shaking hands during data transmission, it is possible to ensure simple and highly reliable communication with extremely shortened bit length and processing time required.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a transmitting/receiving section of a workstation to which the communication method according to the present invention is applied. FIG. 2 is a flowchart showing the transmitting mode of the present invention. FIG. 3 is a receiving mode of the present invention. FIG. 4 is an explanatory diagram showing an example of transmission data of the present invention; FIG. 5 is an explanatory diagram showing an example of an authorization signal of the present invention; FIG. 6 is an example of sequence number setting of the present invention. FIG. PU network

Claims (1)

[Claims] In a local area network data communication method in which a series of related transmission data is divided into packet data of a predetermined data length or less and transmitted, each packet data is assigned a series of sequence numbers, Reception authorization is performed by returning an authorization number that corresponds to the sequence number, and if no authorization is returned for a predetermined period of time, the same data is retransmitted, and if the same data is received twice on the receiving side, the subsequent data is not processed. A data communication method for a local area network, characterized in that only an authorization return process is performed, and the sequence number is repeated by removing a start number when repeating one cycle or more.