JPH01228231A - Data transfer control system - Google Patents

Abstract

PURPOSE:To improve the activity efficiency of a line by omitting the wasteful transfer of data by storing a data frame during one propagation delay time until the data frame whose re-transmission is requested after detecting a transmission error is re-transmitted. CONSTITUTION:The data is transmitted from a station 1a to a station 1b via the line 2. When the error detection controller 6b of the station 1b detects the transmission error of a reception data frame, the station 1b requests the re-transmission of the data frame to the station 1a. And simultaneously, the data frame during one propagation delay time until the above stated data frame whose re-transmission is requsted after detecting the transmission error is re- transmitted is stored in a memory buffer 7b. And in case of succeeding in the reception of the above stated frame whose re-transmission is requested, no request of the re-transmission is issued even when the transmission error is detected in the frame re-transmitted after that within the above stated one propagation delay time, and a corresponding data frame is taken out by the buffer 7b.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a simultaneous monitoring data transfer control system in a data link layer level communication system between two stations.

[Conventional technology]

FIG. 5 is a block diagram showing a conventional data transfer control method in the simultaneous monitoring method.
At any given time, one is a transmitting station that transmits digitally encoded data divided into fixed-length data frames in order according to the frame numbers attached to the data frames, and the other is a receiving station that receives the data frames. 2 is a data/evening communication line that connects stations la and lb and transmits the data frame from, for example, station 1a, which acts as a transmitting station, to station 1b, which acts as a receiving station; 3, which also serves as station la; , ib, and serves as a receiving station, for example, station 1b, and for example, station 1, as a transmitting station.
This is a delivery confirmation line that transmits a retransmission request frame requesting retransmission of a data frame. Also, 4a, 4
b is located in the station 1a+1b, and has a transmission function that encodes the data to be transmitted, divides it into fixed-length data frames, and transmits them in the order of frame numbers, and receives data frames from the other station in order. Transceivers 5a and 5b are also stations 1a and ib.
a grossing buffer 5a located within the transmitter/receiver 4a and 4b for storing data frames being transmitted by the transceivers 4a and 4b;
5b is also located within the stations 1a and 1b, and is connected to the transmitter/receiver 4.
ar 4 bs and grossing puffer 5a,
5b, and the transmitter/receiver 4a, 4b.
This is an error detection/control device that detects whether a data frame received by the receiver has been sent, generates a retransmission request frame requesting retransmission of the data frame, and sends the retransmission request frame to the delivery confirmation line 3 from the transceivers 4a and 4b. .

Next, the operation will be explained. Here, FIG. 4 shows the above-mentioned interval l.
a, a flowchart showing the operation as a receiving station of lb;
FIG. 6 is a flowchart showing the operation of the stations 1a and 1b as transmitting stations, and FIG. 7 is a time chart showing the status of frame transmission and reception between the transmitting side, for example, station 1a, and the receiving side, for example, station 1b. It is a chart.

The error detection/control device 6a of the transmitting station 1a initially sets frame number 1 to i=1 in step ST1 of FIG. A data frame Dl with frame number l=1 is sent to the data communication line 2 from the transmitter/receiver 18 4a at time Tnt. Next, in step ST3, a retransmission request frame REJ requesting retransmission of the data frame at the frame number.
It is determined whether or not k has arrived, and if it has not arrived, the process goes to step ST4 and the frame number! Increment the frame number! -2 and process at step ST
Return to 2. Similarly, as shown in FIG. 7, data frame D2 with frame number 1=2 is at time TO2, data frame D8 with frame number i=3 is at time Toa,
..., data frames are sent from the transceiver 4a to the data communication line 2 in the order of frame number 1.

In step ST6 of FIG. 6, the error detection/control device 6b of the receiving station 1b detects the data frame D1 with frame number j=l transmitted on the data communication line 2 at time 101 as shown in FIG. is received by the transmitter/receiver 4b, and in step ST7, the presence or absence of a transmitting device for the data frame D1 is identified using the transmission error detection code therein. If there is no transmission error, the frame number J is incremented in step S'l and the process returns to step ST5. As shown in FIG. 7, if there is a transmission error υ in the data frame D2 with frame number J-2 received at time t02 in step ST5, the process proceeds from step ST7 to step ST.
frame number J = 2 where this transmission error occurred.
A retransmission request frame REJ2 requesting retransmission of the data frame D2 is generated and sent from the transceiver 4b to the delivery confirmation line 3 at time t1.
At T10, all of the frame data from the data frame D2 received at time t02 up to the data frame D7 received at time t07, in which the data frame D2 requested for retransmission is retransmitted, is rejected.

As shown in FIG. 7, when this retransmission request frame REJ2 is received by the transceiver 4a at time T1, the error detection/control device t6a starts the data frame I' with frame number 1=7 in step ST2 of FIG. J7'fz Immediately after sending at time TO7, the arrival of the retransmission request frame BJk is determined in step ST3, and the retransmission request frame RE requests all retransmissions of the data frame D2 with frame number =2.
The arrival of J2 is detected. Therefore, the process is passed from step ST3 to step ST5, and the frame number l
becomes 1=2, and the process returns to step ST2. Therefore, in step ST2, the data frame D2 with frame number i=2 is read out by the grossing bath sofa 5a, and as shown in FIG.
It is sent from a side. Thereafter, as in the case described above, as shown in FIG. 7, data frame D8 is placed at time TO9, data frame D4 is placed at time Tin, and so on, frame number 凰=
Seven frames of data of 3 or less are sequentially transmitted from the transceiver 4a to the data communication line 2.

The receiving station 1b receives this data frame D as shown in FIG.
2 is received at time jn8, the receiving process is repeated as in the case described above until a transmission error is detected in step ST7 of FIG. When it is detected in step ST7 that there is a transmission error in the data frame D4 received at time 110, a retransmission request frame requesting retransmission of the data frame D4 with frame number -4 is sent as shown in FIG. EJ4 is generated and sent to the transmitting station 1a at time t2, and the received data frames D4 to D9 are discarded at step 10 from time 110 to time t15. After that, after time ttS, this retransmission request frame
Based on J4, the data frame D4 and subsequent data frames transmitted by the transmitting station 1a are received in order.

Such a conventional data transfer control method based on the simultaneous monitoring method was introduced, for example, at the Global Communication Conference '87 (GlobalComm) held in January 1987.
conference '87
)'s presentation paper - Performance Analysis Off'Kohatsuku NARQ with Limited Receiving Bassofa'' (Performance Ana
lysis of Go-Back-NARQwith
Limited receiving Buffer
) etc.

[Problem to be solved by the invention]

Conventional data transfer control systems are configured as described above, so when a transmission error is detected in a certain data frame, there is a one-propagation delay from when the transmission error is detected until the data frame is retransmitted. All data frames received during that period are discarded, and retransmitted data frames are received in order. For example, as in data frame D4 in Fig. 7, even though there is no transmission error at first, Therefore, if there is a transmission error during retransmission, it becomes necessary to send retransmission request frames R and EJ4 requesting retransmission of the data frame D4, and time is wasted in data transfer, resulting in poor data communication. There was a problem in that the utilization rate of line 2 decreased.

This invention was made to solve the above-mentioned problems, and even if a transmission error occurs during retransmission for a data frame that has been received without any transmission error, the transmission of the retransmission request frame is completely unnecessary and is wasted. The purpose is to obtain a data transfer control method that reduces time and increases the utilization rate of data communication lines.

[Means to solve the problem]

The data transfer control method according to the present invention accumulates data frames corresponding to l propagation delay time from when a transmission error υ is detected until the data frame requested for retransmission is sent, and Retransmission of Frame If a transmission error occurs due to retransmission of a data frame that is retransmitted within the propagation delay time after the frame has been successfully received, a memory buffer is provided in which the corresponding data frame is accumulated and picked up. It is something.

[For production]

In the data transfer control method according to the present invention, when a transmission error is detected in a received data frame, the data frame is requested to be retransmitted, and after this transmission error is detected, the data frame for which retransmission was requested is retransmitted. The data frames within the l propagation delay time up to the l propagation delay time are accumulated in a memory buffer, and if the data frame that requested retransmission is successfully received, the data frames within the l propagation delay time that are retransmitted thereafter are Even if a transmission error due to retransmission is detected, the corresponding data frame is retrieved from the memory buffer without generating a full retransmission request, thereby eliminating unnecessary data transfer and increasing the utilization rate of the data communication line. Realize data transfer control method.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, la and ib are stations that act as transmitting stations or receiving stations, 2 is a data communication line, 3 is a delivery confirmation line, and 4
a and 4b are transceivers that realize a transmitting function and a receiving function;
5a and 5b are processing buffers, and 5a and 5b are error detection and control devices, which are the same or equivalent parts to those of the conventional device denoted by the same reference numerals in FIG. 5, and detailed explanation thereof will be omitted. Moreover, 7a and 7b are the above-mentioned space 1a.

1b is a memory buffer that stores data frames for l propagation delay time from when a transmission error is detected in a received data frame until the data frame for which retransmission is requested is retransmitted.

Next, the operation will be explained. Here, Figure 2 Prisoner and (B
) is a flowchart showing the operation of the transmitting station between ia and ib, and FIG. 3 is a time chart showing the status of frame transmission and reception between the transmitting side, for example, station 1a, and the receiving side, for example, station 1b. It is. The operations of the stations ia and 1b as receiving stations are performed according to the flowchart of FIG. 4, as in the conventional case. That is, the frame number i is initialized to i=l (step 8T1), and the data frame DI of the frame number i=1 is all the times T o
Step ST2)
, it is determined whether the data frame retransmission request frame R, EJ k has arrived at the frame number (step 5T3). If it has not arrived, increment the frame number window in step 5T4), frame number l=
2, the process returns to step ST2, and the data frame with the frame number i is sent to the data communication line 2 in the same manner.

The error detection/control device 6b of the station 1b on the receiving side detects the time t0 at step 5T11 of the second hole opening as shown in FIG.
The number of frames transmitted on data communication line 2 in 1 is %
The data frame D1 with jj=1 is received by the transceiver 4b, and in step 5T12 it is determined whether there is a transmission error 9 in the data frame D1. As a result of the identification, if there is no transmission error, the process proceeds to step 5T13, and the memory buffer I
If data frame Dl exists in b, release it,
Further, in step 5T14, the frame number j is incremented and the process returns to step 5T11.

In this case, since nothing is stored in the memory buffer 7b, only the frame number j is incremented. As shown in FIG.
If there is a transmission error in the data frame D2 with frame number "=2" received at time t02, the process proceeds to step 5T.
12, the process moves to step 5T15, where it is determined whether this data frame D2 is stored in the memory buffer 7b. In this case, since nothing is stored in the memory buffer 7b, a retransmission request frame RE J 2 requesting retransmission of the data frame D2 in which the transmission error occurred is generated in step 5Ti5, and at time t1, the retransmission request frame RE J 2 is sent to the delivery confirmation line 3. sent to. Next, the process moves to a routine RT1 for storing data frames, and the data frames from which data frames D2 are retransmitted are stored in the memory buffer 7b.

FIG. 2(B) is a flowchart showing the details of this routine RT1. First, in step 5T21, the frame number m is initialized to m=j+1.

Here, j is the frame number of the data frame in which the transmission error occurred, and in this case is J-2. Next, in step 5T22, the data frame D8 with frame number m-''+1-3 is received, and in step 5T23, it is determined whether there is a transmission error.

If there is no transmission error, it is determined in step ST24 whether the data frame D8 has already been stored in the memory buffer 7b, and if it has not been stored, it is stored in the memory buffer 7b in step ST25, and processing is performed. is passed to step 5T26, the frame number m is incremented, and the process returns to step 5T22. Also, if there is a transmission error like data frame D5, or if the data frame is already stored in the memory buffer 7b, the frame number m is incremented without storing the data frame in the memory buffer 7b. The process returns to step 5T22.

As shown in FIG. 3, the data frame D2 retransmitted in response to the retransmission request frame REJ2 sent at time t1 is received at time to8 in step 5T11 of FIG. 2, and a transmission error υ is detected in step 8T12. will be held. Since this data frame D2 is not stored in the memory buffer 7b, the frame number j is directly incremented in step 5T14, and the process returns to step 5T11, where data frame D8 is received. Since this data frame D8 is stored in the memory buffer Tb, after the transmission error is detected in step 5T12, the data frame D8 in the memory buffer Ib is released in step 5Ti3. Further, when it is detected in step 5T12 that there is a transmission error in the data frame D4 received in step s'r11, it is determined in step 5Ti5 whether or not the data frame D4 is stored in the memory buffer 7b. It will be judged. Since the data frame D4 has been stored in the memory buffer Tb through the process shown in FIG. The retransmission request frame REJ4 of the data frame D4 is not sent. After that, in step 5Ti3, the memory buffer Tb
The data frame D4 in the data frame D4 is released. Here, if a transmission error occurs in the data frame D5 that was not stored in the memory buffer 7b due to a transmission error during storage, a retransmission request frame REJ5 requesting its retransmission is sent out, and the same process as described above is performed. It is processed.

In the above embodiment, a retransmission request frame is sent as a retransmission request when a transmission error is detected, but conversely, a delivery confirmation signal is sent back when the frame is correctly received.
It is also possible to request retransmission of a data frame in which a transmission error occurs by stopping the transmission of the delivery confirmation signal when a transmission error is detected.

Furthermore, if the size of the buffer is small, a stable system can be constructed by limiting the number of frames that can be continuously transmitted from the transmitting station.

〔Effect of the invention〕

As described above, according to the present invention, data frames corresponding to one propagation delay time from when a transmission error is detected until the data frame for which retransmission is requested are sent are stored in the memory buffer, and retransmission is requested. After successfully receiving a data frame, if a transmission error occurs due to the retransmission of a data claim within the propagation delay time, the system is configured to pick up the corresponding accumulated data frame. This has the effect of eliminating the need for data transfer processing and providing a data transfer control method with a high utilization rate of the data communication line.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a data transfer control system according to an embodiment of the present invention, FIG. 2 is a flowchart showing the operation of the station of the present invention as a receiving station, and FIG. 3 is a block diagram showing the operation of the station of the present invention as a receiving station. FIG. 4 is a flowchart showing the operation of the present invention and the conventional station as a transmitting station; FIG. 5 is a block diagram showing the conventional data transfer control method; FIG. 6 7 is a flowchart showing the operation of a conventional receiving station, and FIG. 7 is a time chart showing the status of frame transmission and reception performed between the conventional transmitting and receiving stations. 1a and ib are stations, 2 is a line (data communication line), 3 is a line (delivery confirmation line), 4a and 4b are transceivers that realize transmitting and receiving functions, 5a and 5b I-i grossing buffer , 6a, 6b UiA detection/control device,
7a and 7b are memory buffers. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Patent Applicant: Mitsubishi Electric Corporation Figure 2 (A) Transmitter side fl ad side ☆ L partner Iri 1 Receiving a Jun 1^ station 10
station 1b

Claims (1)

[Claims] A station connected via a line has a transmission function in which it sequentially transmits data in the form of a digital signal divided into fixed-length data frames, a reception function in which it sequentially receives the data frames from the other station, and a transmission function. A processing buffer that stores the data frame being transmitted, and an error detection control that controls the transmission function, reception function, and processing buffer, and detects transmission errors in the data frame received from the partner station by the reception function. and a data transfer control device that, when a request for retransmission is received from a partner station that has detected a transmission error in the data frame, retransmits the data frame in order from the data frame in which the transmission error was detected, which is stored in the processing buffer. In the method, the station is provided with a memory buffer for storing data frames sent during one propagation delay time from when a transmission error is detected in a certain data frame until the data frame is retransmitted; Retransmission of a data frame with a transmission error After successful reception of the frame, if a transmission error due to retransmission of the data frame accumulated in the memory buffer is received, the data frame stored in the memory buffer will be retransmitted without generating a retransmission request. A data transfer control method characterized by extracting a corresponding data frame.