JPS62186636A - Error recovery control system for final information frame - Google Patents

Abstract

PURPOSE:To recover the error of a series of sent final information frame at high speed by sending a short frame including a transmission finish sequence number after the transmission of a series of information frame. CONSTITUTION:A transmission sequence number frame 20 having a short frame length is provided. Then a sensor equipment 10 generates the frame 20 after the sending of a series of information frames 17-19 and sends the result. When a reception side 11 receives the frame 20, a sequence number analysis section 24 is started. The analysis section 24 detects an error in the sending sequence number as the result of analysis, then the section 24 starts a retransmission request section 25 to request the retransmission of the information frame clearly missed. Thus, a series of missing final information is started again earlier and the error is recovered at high speed.

Description

[Detailed Description of the Invention] [Summary] HDLC (High Level Data Li
In a system that performs data communication using nk Control) procedures, etc.

Early initiation of retransmission of the last lost sequence of information frames by sending a short frame containing the transmitted sequence number after a sequence of information frame transmissions to ensure that the other station has a chance to send back a retransmission request This makes it possible to speed up error recovery.

[Industrial application field]

The present invention relates to a data communication system related to HDLC procedures and the like, and particularly to a final information frame error recovery control system that enables high-speed recovery from errors in a series of transmitted final information frames.

[Conventional technology]

FIG. 3 shows an example of transmission control using the conventional HDLC procedure.

In FIG. 3, I(N(S), N(R)) represents an information frame, and RR, RR, P, RR, and F represent a monitoring frame. N(S) in the information frame I (N(S), N(R)) is a transmission order number stored in a control field within the frame, and indicates the order of a series of information frames to be transmitted. Further, N(R) indicates the number next to the confirmed reception order number.

As shown in FIGS. 3 and 3, when transmitting data, the transmitting device transmits data using information frames in which the transmission order number N(S) is incremented by one. The monitoring frame of RR (3) shown in Figure 3 (■) notifies the transmitting device that information frames up to N(S) = 2 have been correctly received and that the expected transmission order number for the 9th is 3. This is a frame that

Here, the transmitting side device is as shown in FIG.

Final information frame I of a series of information frames (3°3)
, but this frame is lost due to an error in the communication path. This error is.

It will not be detected until the predetermined timeout monitoring period has elapsed. If there is no response within the timeout monitoring period, the sending device sends an RR command monitoring frame displaying ball via) P (FIG. 3).

Since the third information frame has not yet arrived in response to this monitoring frame, the receiving device receives the frame that should be received as the second frame in response to the RR response with the final bit F set, as shown in Figure 3 (■). It is notified that the sequence number is 3. As a result, the transmitting device sends the information frame I (3°3) again (FIG. 3).

[Problem that the invention seeks to solve]

According to the above-mentioned conventional system, there is a problem that if the last transmitted information frame and several consecutive information frames preceding it are lost on the communication channel, it takes time to recover them. In other words, after waiting for a timeout, Fig. 3 ■
Since the P/F cycles shown in , (2) are required, there is a problem that early recovery is not possible.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a method for quickly recovering from errors in a series of final information frames sent out.

[Means for solving problems]

FIG. 1 shows a block diagram of the principle of the present invention.

In FIG. 1, 10 is a transmitting side device, 11 is a receiving side device, 12 is an information frame transfer unit that transmits an information frame,
13 is a transmission sequence number notification frame generation unit that is activated after the transfer of the final information frame and generates a transmission sequence number notification frame; 14 is a sequence number setting/transmission unit that transmits a transmission sequence number notification frame; 15 is from the receiving side device 11; 16 is an information frame retransmission unit that retransmits information frames, 17 to 19 are information frames, and 20 is a transmission order number notification frame.

21 is a monitoring frame, 22 is an information frame, 23 is a frame receiving unit that receives the frame, 24 is a sequence number analysis unit that is activated when the received frame is a transmission sequence number notification frame 20, and 25 is a sequence number analysis unit that is activated when the last frame is lost. represents a retransmission request unit that issues a retransmission request to the transmitting device 10 when a request is received.

In the case of the present invention, a transmission sequence number notification frame 20 with a short frame length is newly provided. Generally, a frame is provided with a flag sequence F followed by an address field A and a control field C. The transmission sequence number notification frame 20 according to the present invention may include 2 eg within or after the control field C.

A transmission order number N (S) is set. This transmission order number notification frame 20 indicates that [the transmitting side has already sent out the information frames up to the one before the transmission order number N(S) set in this frame. ” means.

After transmitting the series of information frames 17 to 19, the transmitting device IO uses the 2 transmission order number notification frame generation unit 13 to
A transmission sequence number notification frame 20 is generated, and the transmission sequence number N(S) is set and transmitted by the sequence number setting/transmission unit 14.

When the receiving device 11 receives this transmission sequence number notification frame 20 through the frame receiving unit 23, it activates the sequence number analyzing unit 24. The sequence number analysis unit 24 analyzes the received sequence number and the transmission sequence number N(S) in the frame 20.
The retransmission requesting unit 25 is activated if they do not match. The retransmission requesting unit 25 requests retransmission of the information frame 1 (in this example, the transmission order number is 3) whose loss is revealed by the monitoring frame 21 .

In the sending device 10, when the retransmission request detection section 15 detects this monitoring frame 21, the information frame retransmission section 16
and retransmits the information frame 22 having the same content as the information frame E9.

[Effect]

For example, as shown in FIG.
Even if the information frame 19 at the end of ~19 is lost due to an error on one communication path, the transmitting device 10
Since the transmission sequence number notification frame 20 is immediately transmitted after the transmission of the last information frame 19, the receiving side can detect the loss of the final information frame 19. Therefore, the receiving device 11 requests to selectively transmit the third information frame using the selective reject SRE, T monitoring frame 21, and performs error recovery by retransmission.
This can be done quickly without waiting for a timeout. Note that it is also possible to use a REff frame instead of the Sn2go for the retransmission request.

The transmission order number notification frame 20 according to the present invention is as follows.

It is sufficient to have frame type information and transmission sequence number information, and general information fields are not required.
Frame length is short. Therefore, the communication cost associated with this new frame 20 is small.

It also has the characteristic that errors are less likely to occur compared to long frames.

〔Example〕

FIG. 2 is a block diagram for explaining one embodiment of the present invention.

In FIG. 2, 30 is a host processing device that processes data, 31 is a communication control device (CCP), 32 is a control unit that controls frame transmission and reception, 33 is a timer for time monitoring, and 34 is a control unit that controls the data to be transmitted. 35 is an I frame creation unit that creates an information (I) frame; 36 is a new frame creation unit that creates a transmission order number notification frame according to the present invention; 37 is a buffer for saving transmitted data; 38 represents a frame transmission unit that transmits the frame to the other party.

Further, 39 is a frame receiving unit that receives frames from the partner station, 40 is a U frame analysis unit that analyzes unnumbered (U) frames, 41 is an I frame analysis unit that analyzes information frames, and 42 is the received information. 43 is a new frame analysis unit that analyzes the transmission order number notification frame according to the present invention;
44 is a retransmission request generation unit that issues a retransmission request when loss of the final information frame is detected; 45 is an S frame generation unit that generates a monitoring (S) frame; and 46 is a U frame generation unit that generates a non-numbered frame. , 47 represents a P/F bit control unit that controls the poll bit/final bit, and 48 represents an S frame analysis unit that analyzes the received monitoring frame.

The transmitting device 10 and receiving device 11 shown in FIG.
Both are realized by the internal configuration of the communication control device 31 as shown in FIG. The creation, transmission, reception, and analysis of the U frame that initializes the link state, and the $ frame that performs retransmission control and flow control of information are the same as control using conventional HD LC procedures, so a detailed explanation will be given below. Omitted.

When a data transmission request is received from the host processing device 30 after the link with the other party device is established, the data is stored in the pre-transmission data buffer 34. (2) The frame creation unit 35 sets the data stored in the pre-transmission data buffer 34 in the information field within the frame, and also sets the transmission order number etc. in the control field to create an information frame.

Frame transmitter requests transmission on the 3rd.

When the pre-transmission data buffer 34 becomes empty after transmitting a series of information frames, or in response to a special instruction from the host processing device 30, the new frame creation unit 36 is activated. The new frame creation unit 36 creates a transmission sequence number notification frame, sets a transmission sequence number obtained by adding 1 to the sequence number of the transmission unit in the frame, and requests the frame transmission unit 38 to transmit the frame. do.

In the communication control device 31 on the receiving side, when the frame receiving unit 39 receives the transmission order number notification frame,
The new frame analysis section 43 is activated.

The new frame analysis unit 43 compares the transmission sequence number set in the transmission sequence number notification frame with the received sequence number stored in the frame suspension buffer 42, so that the final information frame is correctly received. determine whether or not.

If there is a discrepancy in this transmission order number, the retransmission request generation unit 4
4 is activated, and the retransmission request generation unit 44 is activated.

The S frame creation unit 45 is requested to create a monitoring frame requesting retransmission. The created monitoring frame is sent from the frame transmitting section 38 to the transmitting side device.

In the communication control device 31 on the transmitting side, when the frame receiving unit 39 receives the retransmission request monitoring frame, the S
The frame analysis section 48 is activated.

When the S frame analysis section 48 detects that it is a retransmission request, it starts the frame creation section 35 (2).

(2) The frame creation unit 35 creates the information frame for which retransmission is requested again using the data stored in the delivery confirmation waiting buffer 37, and the frame transmission unit 38 transmits the information frame.

The transmission order number notification frame according to the present invention is similar to the conventional HD
The configuration of the control field in the LC procedure may be modified to create a new frame separate from the information frame, monitoring frame, and non-numbered frame, or as a special information frame that does not have an information field, it may be used as a general information frame. It may be possible to distinguish between In this case, it is desirable to be able to select as an option whether or not to use the error recovery function using the transmission sequence number notification frame.

〔Effect of the invention〕

As explained above, according to the present invention, after transmitting a series of information frames, it is possible to transmit a short frame including a transmission sequence number to reliably give the other station an opportunity to return a retransmission request. It is possible to start retransmission of a series of final information frames at an early stage, and error recovery can be speeded up. Since this transmission order number notification frame is short in length, it is easier to reach the other station than two normal information frames.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the principle of the present invention, Fig. 2 is a block diagram for explaining an embodiment of the present invention, and Fig. 3 is a block diagram of the conventional H
An example of transmission control using the DLC procedure is shown. In the figure, IO is a transmitting side device, and 11 is a receiving side device. 12 is an information frame transfer unit, 13 is a transmission sequence number notification frame generation unit, 14 is a sequence number setting/transmission unit, 15 is a retransmission request detection unit, 16 is an information frame retransmission unit, 17 to 19
is an information frame, 20 is a transmission order number notification frame, 2
1 represents a monitoring frame, 22 an information frame, 23 a frame reception section, 24 a sequence number analysis section, and 25 a retransmission request section.

Claims (1)

[Claims] In a system that performs data communication by transferring a series of information frames between a sending device (10) and a receiving device (11), the sending device (10) means (13) for generating a short transmission sequence number notification frame (20) having a field for setting a transmission sequence number therein and having no substantial information field; means (14) for setting and transmitting a sequence number related to the transmitted sequence number in the notification frame (20); 20), and means (23) for determining whether the received frame is a transmission order number notification frame (20).
an analysis means (24) that performs an error check based on the transmission order number in the frame and the transmission order number of the received information frame, and when an error is detected by the analysis means (24); , means (25) for generating a frame requesting retransmission and transmitting it to the transmitting side device (10).