JPH02222248A - Communication control system - Google Patents

Abstract

PURPOSE:To early avoid the increase of CPU load and deterioration in line efficiency by informing a warning message to a host layer when number of times of retransmission within a prescribed time exceeds the upper limit of number of times of retransmission. CONSTITUTION:When a transmission error is detected at the reception of an RR response from a secondary station 2 and a primary station 1 discriminates it that no timer is started, a check timer is started to count number of times of retransmission in the retransmission counter. When it is discriminated that the number of times of retransmission exceeds the preset upper limit, the primary station informs a warning message to a host layer. Thus, the processing is implemented properly for changeover of a bypass route or the like and the load of a CPU required for the retransmission processing is relieved and the deteriorated quality of the communication line is detected.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a communication control system for transmitting and receiving data.

[Conventional technology]

High-level data link control (hereinafter referred to as II DLC), which is one of the transmission control methods for data communication, accommodates the information to be transmitted in a specified frame called a frame, and transmits it uniformly regardless of the type of information. do. This is specified in the "Frame structure of high-level data link procedures" (Japanese Standards Association, JIS
, CCITT standardized HDLC procedures are often used. Figure 4 is a configuration diagram of a conventional communication system. In the figure, 1.2 is a terminal device for data communication, 3 is a communication line installed between the terminal devices 1.2, and 4 is for data transfer. 5 is a CPU, 6 is a random access memory as a transmission data buffer that stores communication data (
7 is a direct memory access controller (hereinafter referred to as a DMA controller) that controls the line control 1Ls1B and the RAM 6 and the bus 4 independently of the CPU 5, and 8 is a data link. This is the line side 1LsI for control. Next, the operation will be explained using FIG. 5. If terminal device l is the primary station and terminal device 2 is the secondary station, then 1
The next station 1 instructs the secondary station 2 to operate in the normal response mode using the SNRM and P commands (Set Norma).
401)
, the secondary station 2 is a UA if it can operate in response to this instruction. F response (Unnumbered Acknowledgment)
edge) to the primary station 1 (402), and the primary station l
When the UA receives the F response, a data link is established. After this, primary station 1 has three! Send frame (10,.. I8.., IL.). Here, the configuration of the (2) frame is as shown in FIG. ■1 of the three ■frames sent. . is not received (4
03), the secondary station 2 continues ■ frame I5. . In order to notify primary station 1 that it is ready to receive the
I, F response (ReceiveReady) is transmitted (404). At this time, the I frame Ia sent to the secondary station 2 by the primary station 11 in the transmission data buffer 6,
. Clear the contents of ■Frame 11. . (405). When the retransmission is finished and the reception of the I frame at the secondary station 2 is completed, the RRI and F response are transmitted to notify the primary station 1 that it is ready to receive the frame (406). At this time, the primary station 1 clears the contents of the received one frame in the transmission data buffer 6, and if retransmission is not completed, repeats the retransmission without clearing the transmission data buffer 6. Please note that the command or response is
or F indicates the ball (P) bit of the control unit when the frame is a command, and indicates the final (F) bit of the control unit when the frame is a response. It performs its function when ”. The P bit is used to solicit single or multiple response frames from the other station, and the F bit set to "1" is sent as a result of receiving the P bit set to "l". This indicates that the frame is a response frame. Also, in the figure, P or F indicates P bit-“1” and F bit-“1”, respectively, and for I frames that are not described, P bit-“0” and F bit-“ O” is shown.

[Question H that the invention attempts to solve]

Since the conventional communication control method is as described above,
In the case of a communication line with poor line quality, the number of retransmissions increases,
The CPU load increases due to retransmission processing, line efficiency decreases, and the transmission buffer is not cleared.
There were problems such as the buffer becoming full and sending new data having to wait for a long time. This invention was made to solve the above-mentioned problems, and aims to provide a communication control method that quickly avoids increases in CPU load and deterioration of line efficiency by monitoring the occurrence of retransmission processing. shall be.

[Means to solve the problem]

The communication control method according to the present invention sets an upper limit on the number of retransmissions within a certain period of time, counts the number of retransmissions within a certain period of time during data transmission and reception, and when the number of retransmissions exceeds the upper limit of the number of retransmissions. In this case, a warning message is sent to the upper layer.

[For use]

The communication control method according to the present invention monitors retransmission processing in the data link layer, counts the number of retransmissions, and compares it with an upper limit value, thereby making it possible to notify an upper layer of a warning message.

【Example】

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure shows the configuration of a communication system according to the present invention, but since it is the same as the system configuration according to the prior art (FIG. 4), the explanation will be omitted. Next, the operation will be explained using FIGS. 2 and 3. As in the description of the operation of the prior art, the terminal device 1 is assumed to be the primary station, and the terminal device 2 is assumed to be the secondary station. The primary station 1 should send the SNRM and P commands to the secondary station 2 (201), and in response to this transmission, the secondary station 2 should send the UA and F responses (202).
, a data link is established by the primary station 1 receiving the data. After setting, the primary station l transmits three consecutive I frames (■., ., I1.., I2..), and the second ■ frame It. is not received (203), the secondary station 2 notifies the primary station 1 with an RRi, F response that it is ready to receive the second and subsequent frames (204).
), the primary station 1 received the ■ frame! . ,. Clear the contents of the transmit data buffer 6, and ■ Frame! 1.
. (205). Secondary station 2 is R for retransmission.
Send the R□, F response to the primary station 1 (206), and repeat the above operation until there is no more data to send (207).
However, when a transmission error is detected when receiving the RR response from the secondary station 2, the primary station 1 executes the process shown in FIG. 3(a). In other words, if it is determined that the timer is not activated (step 5T1), the check timer is activated (
Step 5T2), and counts the number of times in a retransmission counter (Step 5T3). When it is determined that the number of retransmissions has exceeded the upper limit set in advance (for example, 100 times or more in 10 seconds) (step 5T4), a warning message is sent to the upper layer (step 5T5), and the retransmission counter is cleared. Step 5T6), and the starting timer is set again for a certain period of time (Step 5T7). If the number of retransmissions does not exceed the upper limit while the timer is activated (Figure 3 (b)), that is, if the timer times out, clear the counter again (step 5T8).
, sets a certain time in a check timer (step 5T9). P or F in the diagram indicates P bit - “1”
, F bit - indicates “1” and is not written! For frames, P bit - ``0'', F bit - 6
In the above embodiment, an upper limit is set for the number of retransmissions within a certain period of time, and when the upper limit is exceeded, a warning message is sent to the upper layer. The upper limit value of the number of retransmissions and the fixed time interval can be arbitrarily set depending on the communication line and device of the system in which this communication control method is to be used, the reliability of the system, the capacity of the memory, etc.

【Effect of the invention】

As described above, according to the present invention, the upper limit of the number of retransmissions within a certain period of time is set, the number of retransmissions during data transmission and reception is counted, and when this number exceeds the upper limit of the number of retransmissions, a warning message is sent to the upper layer. As a result, appropriate measures such as switching detour routes can be taken quickly, reducing the CPU load associated with retransmission processing, and making it possible to detect deterioration in the quality of communication lines. There is.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a communication system according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the operational procedure of data transmission and reception of the present invention, and FIG. 3(a). (b) is a flowchart showing the operating procedure of the present invention, FIG. 4 is a block diagram showing the configuration of a communication system of the prior art, FIG. 5 is an explanatory diagram showing the operating procedure of the prior art, and FIG. 6 is an illustration of the HDLC procedure. FIG. 3 is a frame configuration diagram. 1 is terminal equipment (primary station), 2 is terminal equipment (secondary station), 3
is a communication line, 4 is a data transfer bus, 5 is a CPU, 6 is a RAM, 7 is a DMA controller, and 8 is a line control LSI
It is. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Chapter ■ Procedural amendment (method) % formula % Name of invention Communication control method 3, person making the amendment 7. Details of the correction The subdivision numbers in Figure 3 will be corrected as shown in the attached sheet. 8゜Document stating Figure 3 after amendment of catalog of attached documents■ Written amendment (voluntary) 2. Name of the invention Communication control method 3. Relationship with the case of the person making the amendment Patent applicant address Tokyo 2-2-3 Marunouchi, Chiyoda-ku Name (601) Mitsubishi Electric Corporation Representative Moriya Shiki 4 Agent address Postal code 105 1-4 Nishi-Shinbashi, Minato-ku, Tokyo No. 6 Contents of amendment (1) ) The specification is amended as follows. . (2) Correct Figure 2 as shown in the attached sheet. (3) Correct Figure 3 as shown in the attached sheet. (4) Correct Figure 5 as shown in the attached sheet. 7. List of attached documents (1) Document stating the amended Figure 2 (2) Document stating the amended Figure 3 (3) Document stating the amended Figure 5 Figure 3 (a) ) C=D

Claims (1)

[Claims] In a communication control method in which data transmission and reception are performed by multiple layers, the layer that manages the data link sets an upper limit on the number of retransmissions within a certain period of time, and counts the number of retransmissions within a certain period of time during data transmission and reception. A communication control method characterized in that, when the number of retransmissions exceeds the upper limit of the number of retransmissions, a warning message is notified to an upper layer.