JPH03128553A - Data transmission system - Google Patents

Abstract

PURPOSE:To improve efficiency for transmitting data in packet communication by changing the number of data frames to be sent out from a transmission side corresponding to the generating condition of data error. CONSTITUTION:When the error is generated in a frame I1, a reception side abandons this frame I1 and request retransmission after the frame I1 by an REJ signal. When the REJ signal is received, the transmission side counts a first count value A by (+1) and stores this count value A in a memory area 4a of a memory 4. Next, when a second count value is more than a prescribed value, it is checked whether the count value A is counted more than a prescribed number (m) of times or not and when the count value A is more than the prescribed number (m) of times, a window size is set to be half.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a data transmission system, and particularly to a data transmission system that improves communication efficiency in bucket communication.

(Prior Art) In recent years, various OA devices such as personal computers and facsimile machines have been widely used as office processing becomes more automated. The data processed by these OA devices is exchanged via a data line network established between cities or companies, and the data exchange (which is said to be on the rise). (Various data transmission methods have been developed and put into practical use to efficiently perform t.

Conventionally, as this type of data transmission method, there is a bucket exchange method using a digital data exchange network, for example. In this bucket exchange method, transmission ff! +I is a series of transmissions ↑rI
f[: is divided into data frames of a predetermined length that can be divided into packets, and stored, and when sending each packet, a destination 1n is assigned to each packet.
The packet is sent to the packet with the order number 1111'l with an order number added without indicating the order of the information and its (j4 order).The receiving side checks whether or not there is an error in each received packet. is detected, and if there is no error, the transmission (ε continuation is notified), and if an error occurs, the sequence number of the packet in which the error occurred is notified by an REJ signal (reject signal) and a retransmission request is made.

In the packet switching method, flow control is performed to ensure smooth packet transfer within the network; for example, there is a window control method. In the window control method, the number of packets that the sender can send consecutively (window size) is set in advance, and the sender cannot send the next number of packets until it receives a response from the receiver (ε permission). This is a control method that says that it is not possible.

Here, the sequence according to the window control method described above is shown in FIG. 6 and will be explained. Note that the sequence in FIG. 6 shows a case where an error occurs in a packet, and the window size is assumed to be 4.

If the sending side sends Io, I + Iz, lz frames and a data error (Fe2: error due to frame check sequence) occurs in the second ■1, the receiving side discards 11 and receives the next ■2. and check the sequence number. As a result, since the sequence number is incorrect, the receiving side notifies the incorrect frame number 11 using the REJ signal and requests retransmission.

The transmitting side detects the incorrect frame 1. based on this REJ signal. From h, :l, I 4 (7) Ilrt ni send (itr.Next) Then, if there is an error in frame I2, the receiving side sends RE again.
J signal is sent, and the sending side sends an incorrect frame ■2 to Il.
, ■4, and ■.

(Problem to be Solved by the Invention) However, in the packet switching method of such a conventional data transmission method, since a frame in which an error occurs is retransmitted with a constant predetermined window size,1.
Frames other than the erroneous frame are sent twice, significantly deteriorating communication efficiency.

(Purpose of the Invention) Therefore, the present invention has been proposed to change the number of take-out frames sent by the transmitting side depending on the line quality condition, that is, the occurrence of data errors, so that the data The purpose of the present invention is to provide a data transmission method that improves data transmission efficiency in packet communications by making the transmission efficiency appropriate.

(Structure of the Invention) In order to achieve the above-mentioned object, the present invention provides that the sending side divides the sending (ε information) into a plurality of data blocks of a predetermined length, and sends information on a sequence number indicating the order and a destination for each data block. etc. are added to create a data frame, and a predetermined number of data frames are transmitted in the order of the sequence number according to the response from the receiving side. The receiving side detects whether or not there is an error in the received data frame, and if there is no error, the data frame is sent. The sending side is notified to continue frame transmission, and if there is an error, the sending side is notified of the sequence number of the erroneous data frame and requested to retransmit, and the sending side sends the predetermined number of data frames after the notified sequence number. In the data transmission method for retransmission, the transmitting side counts the number of retransmission requests notified from the receiving side and sets it as a first count value, and also counts the number of sent data frames and sets it as a second count value, The present invention is characterized in that the number of data frames to be transmitted is changed in increments of the predetermined number based on the first count counted until the second count reaches a predetermined value.

Hereinafter, the present invention will be specifically explained based on examples.

1 to 5 are diagrams showing an embodiment of the present invention.

FIG. 1 is a block diagram of a communication device 1 applied to the data transmission system of the present invention.
(system control section) 2, CCU (ill signal control section) 3, memory 4, I10 interface 5, etc., and each section is connected to a system bus 6.

The 5CU2 executes packet communication by controlling each part in accordance with the packet communication program stored in the memory 4, and at the same time, the CCU3 analyzes the data frame received from the data circuit LmL and displays the window according to the analysis result. Performs size change processing.

As shown in FIG.
The transmitting/receiving unit 11 performs processing for transmitting data frames to the data line and receiving from the data line '43 L (3
Performs data frame reception processing. Frame creation/
The decomposition unit 12 divides a series of information to be transmitted into data blocks of a predetermined length to create data frames, and decomposes the received data frame and reconstructs it into the original series of information. The bus interface 13 has a function of transmitting and receiving data to and from the system bus 6.

The memory 4 has an area for storing programs related to packet communication and memory areas 4a to 4c as shown in FIG. The memory area 4b stores the second count value B, which is the number of frames of the transmitted data by 31, and the memory area 4C stores the first count value and the second count value. The comparison result C is stored.

The I10 interface 5 transfers data input from a data input device such as a scanner device or a keyboard connected outside the figure to each section via the system bus 6 under the control of the 5CtJ2.

Next, the effect will be explained.

The present invention is characterized in that, in packet communication, the transmitting side counts the number of retransmission requests from the receiving side, and changes the number of data blocks to be sent (window size) based on this counted value. The packet communication process will be described below according to the flowchart shown in FIG. 4 and the sequence shown in FIG. In the data transmission system of this embodiment, it is assumed that the communication device 1 shown in FIG. 1 is installed on both the transmitting side and the receiving side.

FIG. 4 shows a flowchart on the transmitting side. When transmitting, the transmitting side first clears the memory areas 4a to 4C (step P1), and clears the data frame of a predetermined window size (20 to I7 = window size). -8) (step P2). Next, the number of sent data frames is counted and a second count (l!!B(
B=-B+window size) is stored in the memory area 4b of the memory 4 (step P, "), and it is checked whether the REJ signal has been received (step P4). In this embodiment, the sequence diagram shown in FIG. If an error occurs in frame 1 as shown, the receiving side will receive this frame 11.
Discard the frame by REJ signal! .

Request further retransmission. When the transmitting side receives the REJ signal, it counts the first count value A by (+l) and calculates (A=A+
1) (Step P,) This count value A is stored in the memory area 4a of the memory 4. Next, in step P, it is checked whether or not the second count value B has exceeded a predetermined value (window size xn). (Step P,). When the number of counted injections is greater than the predetermined number m (A>m), it is determined that the quality of the data line is poor because the number of retransmission requests is large, and the window size is reduced to half of the previous one. ("8" - "4"> (step ps). Also, when the count implantation is smaller than the predetermined number of times m (Arm), it is determined that the quality of the data line is good because the number of retransmission requests is small. The window size set at the beginning is maintained. Note that the first count implantation and the second count value B
The comparison result is stored in the memory area 4C of the memory 4. On the other hand, even when the second count value B is not greater than or equal to the predetermined value, the initially set window size is maintained (step P6
). Next, the receiving side retransmits frames 1° to h or frames It to ! after changing the window size. Step P, check whether there is a response to 4)
, if there is no response, the process moves to response waiting processing (step P+o).
), when a response is received, the above steps are performed until the transmission is completed.
Nobu P! In this embodiment, the process of ~P1° is repeated and executed, as shown in the sequence of FIG.
After retransmitting ~I4, no error is detected and the third side sends a receive (RR double signal receive ready signal) to notify that it is ready to receive, and the transmitting side sends this RR (;
The next frame I6.1 and I7, ! . is being sent.

As in the above packet communication process, if the quality of the data times L% L is poor, by setting the window size to half and transmitting, the number of data frames to be retransmitted will be reduced and the waste of communication will be greatly reduced. . Therefore, the data transmission efficiency in packet communication can be appropriately adjusted according to the line quality, and the data transmission efficiency for 1llll packets can be improved.

(Effects) According to the present invention, the number of data frames sent by the transmitting side is changed depending on the line quality condition, that is, the occurrence of data errors, so the data transmission efficiency can be improved depending on the line condition. It is possible to improve the data transmission efficiency in packet communication.

[Brief explanation of the drawing]

1 to 5 are diagrams showing an embodiment of the data transmission method of the present invention, FIG. 1 is a block diagram of a communication device applied to the data transmission method, and FIG. 2 is a diagram similar to that of FIG. FIG. 3 is a block diagram of the communication control unit; FIG. 3 is a diagram showing the memory area of the memory shown in FIG. 1; FIG.
The figure is a control sequence diagram in the packet communication. FIG. 6 is a control I sequence diagram in conventional packet communication. 1...A communication device, 2...SCU. 3...CCU. 4...Memory, 5...I10 interface, 6...
・System bus, 11... Transmission/reception section, 12... Frame creation/disassembly section, 13...
...Bus interface, A...First count value, B...-Second count value, L-...Data line. agent

Claims (1)

[Claims] The transmitting side divides the transmission information into multiple data blocks of a predetermined length, adds a sequence number indicating the order and destination transmission information, etc. to each data block to create a data frame, and then divides the transmission information into a plurality of data blocks of a predetermined length, and adds a sequence number indicating the order and transmission information of the destination, etc., to form a data frame. A predetermined number of data frames are transmitted, the receiving side detects whether or not there is an error in the received data frame, and if there is no error, the transmitting side is notified to continue transmitting the data frame, and if there is an error, the error is detected. In a data transmission method in which a transmitting side is notified of a sequence number of a certain data frame and a retransmission request is made, and the transmitting side retransmits the predetermined number of data frames after the notified sequence number, the transmitting side is notified by the receiving side. The number of retransmission requests is counted as a first counted value, the number of transmitted data frames is counted as a second counted value, and the second counted value is counted until the second counted value reaches a predetermined value. A data transmission method characterized in that the number of data frames to be transmitted is changed in units of the predetermined number based on a count value of 1.