JPS63228838A - Communication control processing method - Google Patents

Abstract

PURPOSE:To ensure the highly efficient application of a communication circuit despite the quality variance of the communication circuit, by dividing a text to transmit it every block in a retransmission processing state and to confirm the response and retransmits a divided block of a transmission error if occurs. CONSTITUTION:When retransmission processing is performed in case no ACK is received, a text is divided by a prescribed method for production of individual transmission blocks. A circuit control part 1 transmits those divided blocks in the order of arrays in the text. If the reception of the ACK is impossible, the divided blocks are transmitted again. In such a way, the availability of a communication circuit is improved for transmission of the text in such a case where the quality of the communication circuit has variance.

Description

[Detailed Description of the Invention] [Summary] This is an improved processing method for retransmission processing when a transmission error occurs in communication control.

A line control unit that retransmits text when it cannot receive a reception confirmation signal from the receiving side, and when retransmitting, it divides the text into blocks of relatively short data length and transmits them.

This method can prevent situations in which relatively long texts must be retransmitted many times and can improve line utilization.

[Industrial application field]

The present invention relates to a method for processing retransmission when a transmission error occurs in communication control.

[Conventional technology]

FIG. 2 is a block diagram showing an example of the configuration of a communication system.

The line control unit 1 is connected to a line control unit 3 having a similar configuration via a communication line 2, and can communicate with each other.

When the line control unit 1 receives a predetermined transmission request from, for example, the application processing unit 4, it receives the text generated by the application processing unit 4, and generates a check by, for example, adding each byte of the text bit by bit. A known transmission error check means such as a byte and predetermined bytes (hereinafter referred to as STX and ETX) indicating the start and end of a transmission block are added, and the resultant block is sent to the communication line 2 as one transmission block.

When the line control unit 3 receives this block from the communication line 2, it performs a predetermined transmission error check, and if it determines that it has been received normally, passes the text of the received block to the application processing unit 5, and if it has been received normally. A predetermined response byte (hereinafter referred to as ACK), which serves as a confirmation signal indicating that the

Furthermore, if it is determined that there is an error as a result of the transmission error check, the received block is discarded and a predetermined response byte (hereinafter referred to as NAK) indicating that the reception was not successful is returned.

When the line control unit 1 transmits one block, if an ACK is returned from the other party's line control unit 3 at a predetermined time, the text transmission process is completed.

Also, if a NAK is returned, or if a response is not received even after the response waiting time described above has elapsed, it is assumed that the text did not reach the recipient normally, and the text is sent first. Retransmit the block of text to communication port wA2.

The above process is repeated until an ACK is received from the other party, but if the ACK still does not come even after repeating it a predetermined maximum number of times, the application processing unit 4 is notified to that effect and this communication is stopped. For example, the application processing unit 4 takes appropriate measures.

FIG. 3 is a flowchart of the transmission processing of the line control section 1. When a transmission request occurs, the line control unit 1 receives the text to be transmitted in processing step 10 and creates a transmission block as described above.

The block is transmitted in a processing step 11, and a response is waited for in a processing step 12. If an ACK is received, the application processing section 4 is notified to that effect and the transmission processing ends.

If ACK is not received within a predetermined time in processing step 12, the current number of retransmissions (currently 0) is checked with the maximum number of retransmissions set in advance in processing step 13, and the number of retransmissions is the maximum number. If not, the current count is increased by 1 and the process returns to processing step 11, the previously transmitted block is transmitted again, and a response is waited for in processing step 12.

In this way, retransmission is repeated until a GK response is received or it is detected in processing step 13 that the number of retransmissions has reached a predetermined maximum number of times, and after retransmission is performed up to the maximum number of times, processing step 3 is reached. If so, the application processing unit 4 is notified of the abnormality and the transmission process is stopped.

[Problem that the invention seeks to solve]

It is clear that the longer the block length of a block transmitted as described above, the greater the possibility of encountering a transmission error, and if a transmission error occurs, there is a disadvantage that a relatively long retransmission time is required. be.

On the other hand, in the case of normal transmission, it is clear that if the block is made longer, the proportion of overhead due to check bytes and other additions, ACK transmission and reception, etc. will be reduced, and the line utilization rate can be improved, so for example, If the line quality of the communication line is appropriate, texts other than extremely long texts are transmitted as one block.

However, if this is done, there is a problem that if the line quality can vary with each communication, such as in a switched line, a situation may arise in which the message cannot be transmitted even after repeated retransmissions for a long time.

[Means for solving problems]

FIG. 1 is a process flowchart showing the configuration of the present invention.

The figure shows the flow of transmission processing by the line control unit, and 20 to 27 are processing steps.

[Function] In the transmission process, the line control unit performs processing steps 20 to 2.
In step 2, as in the conventional method, a block of text to be sent is created and sent, a response from the other party is waited for, and the process ends when an ACK response is received.

In the retransmission process when an ACK is not received, first, in processing step 23, the text is divided in a predetermined manner to create individual transmission blocks.

Through processing steps 24 to 26, this divided block is
One block at a time is extracted in the order of the arrangement in the text and transmitted sequentially, a response is confirmed for each divided block in the conventional manner, and the transmission process is completed when all divided blocks are transmitted normally.

If a divided block with a transmission error occurs, the block is retransmitted in step 27, and if the retransmission is not successful, the transmission and request source is notified of the abnormality and the transmission process is canceled.

With the above processing method, the communication line can be used efficiently even when the quality of the communication line fluctuates.

〔Example〕

When the line control unit 1 receives a transmission request from the application processing unit 4, it creates a block of transmission text in a process step 20 as in the conventional manner, transmits this block in a process step 21, and responds to the other party's response in a process step 22. and if an ACK response is received, the transmission process ends.

In the retransmission process when an ACK is not received, first, in processing step 23, the text is divided in a predetermined manner to create individual transmission blocks.

In the first method of division, for example, the number of bytes of the text is counted and a preset number of divisions (for example, 2
), it is divided into y゛ equal parts.

In the second division method, a predetermined byte length is cut out from the beginning of the text to form blocks of the same length, and at the end, a text portion within this fixed byte length is made into one block.

Further, as a third method, only when the text is larger than a certain byte length, the text may be equally divided by a certain number of divisions.

In processing step 23, a transmission block is created in the conventional manner for each text divided by the above division method. However, the end of each divided block except the last divided block is not ETX but a predetermined byte (for example, ETB byte) indicating that it is an intermediate block.

By doing this, when the line control unit 3 on the receiving side receives a divided block, the text of a certain block of ETB is held in the line control unit 3, and the I!
When a TX block is received, the texts received so far are delivered to the application processing section 5 all at once.

In processing step 24, the line control unit 1 transmits the divided blocks one by one in the order of arrangement within the text, and waits for a response in processing step 25.

If an ACK is received, it is checked in processing step 26, and if there is an untransmitted divided block, the process returns to processing step 24 and transmission of the next divided block is started.If all the divided blocks are transmitted in this way, the processing ends. .

If ACK cannot be received in processing step 25, retransmission processing of this divided block is performed in processing step 27.

This retransmission process is performed, for example, by receiving an ACK or by repeating retransmission of the same divided block until a predetermined number of retransmissions, as in the conventional method.

Further, the divided block may be further divided into a plurality of blocks using the method described above, and the blocks may be retransmitted.

In this way, if the retransmission is successful, the process proceeds to step 26 and starts transmitting the next divided block as described above, or ends the process if all the divided blocks have been transmitted. .

Further, if the divided block cannot be transmitted even by retransmission, or if the retransmission is unsuccessful, the application processing unit 4 is notified of the abnormality and the transmission process is stopped.

〔Effect of the invention〕

As is clear from the above description, the present invention has a significant industrial effect of improving the efficiency of communication line usage in text transmission when the quality of the communication line fluctuates.

[Brief explanation of the drawing]

FIG. 1 is a process flowchart showing the configuration of the present invention, FIG. 2 is a block diagram of an example configuration of a communication system, and FIG. 3 is a conventional process flowchart. In the figure, 1.3 is a line control unit, 2 is a communication line, 4.5 is an application processing unit, 10 to 13, and 20 to 27 are processing steps.

Claims (3)

[Claims] (1) In a device having a line control unit that transmits a required transmission text as one block to a communication line and retransmits the text when a predetermined confirmation signal is not received from the receiving device of the text, In the case of the retransmission, the communication control processing method is characterized in that the text is divided into blocks of a predetermined data length and transmitted (23 to 27). (2) The communication control processing method according to claim 1, wherein the predetermined data length is a data length obtained by dividing the text into approximately equal parts. (3) The communication control processing method according to claim 1, wherein the predetermined data length is less than or equal to a predetermined maximum length.