JPH06103897B2 - Data transmission method in HDLC procedure processor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a data transmission method in an HDLC procedure processing device, and more particularly to a host device before the host device recognizes the link setting at the time of link resetting. The present invention relates to a data transmission method in an HDLC procedure processing device in which an erroneous transmission of data by the command is prevented by discarding a data transmission request command issued by the.

[Prior Art] The HDLC procedure corresponds to the layer 2 protocol of the OSI reference model of ISO, and LAPB and LAPD are included in this, but in the conventional HDLC procedure processor, the document "Signal control method in ISDN exchange-LAPD function" is used. Study on LSI implementation- "(Shingakukai, Exchange Research, SE85-35, pp37-42 (1985)),
A memory for transmitting and receiving information is used for the interface between the layer 2 and the upper layer. That is,
The interface between the HDLC procedure processing device and the host device has a memory shared by both the command, which is an instruction from the host device to the HDLC procedure processing device, and the status, which is a report from the HDLC procedure processing device to the host device. The method of transmitting and receiving via is adopted. Such commands and reports are specified as primitives in CCITT Recommendation I441, pp213-217, and 16 types of information are provided for link setting and releasing, and data transmission / reception.

By the way, FIG. 3 shows an example of a data transmission / reception sequence using the LAPD procedure, which is one of the HDLC procedures. In the figure, L2 indicates an HDLC procedure processing device and L3 indicates a higher-level device. The sequence will be described below with the left side being the partner system and the right side being the own system.

That is, while the frame is transmitted and received between the partner system and the own system via the communication line, the primitives defined in CCITT Recommendation I441 are transmitted and received between the HDLC procedure processing device and the host device. . Here, the HDLC procedure processor from the higher-level device is used as a command for the HDLC
When the host device sends data to the partner system by using the report from the processing device to the host device as the status, first, the host device must set a logical connection link between the host system and the partner system. Is "DL / Settings /
The "request" command is issued to the HDLC procedure processor, and based on this, the SALCME frame for requesting link setting is transmitted from the HDLC procedure processor to the partner system. HD in response to that UA frame
When received by the LC procedure processor, the self-host device displays "DL
・ "Setting / confirmation" status is reported, and the status shifts to the link setting status. In the link setting state, data can be exchanged between the own system and the partner system. The HDLC procedure processing device attaches a transmission sequence number to data from its own host device and then transmits it as an In (n: transmission sequence number) frame. That is, the host device issues a "DL / data / request" command requesting data transmission to the HDLC procedure processing device. Based on this, the HDLC procedure processing device transmits data as an I1 frame to the partner system. By receiving a certain RR frame, it is confirmed that the data has been received by the partner system.

Now, if the partner system detects a line failure (for example, an unexpected response frame is received) and the partner system sends a SABME frame to reestablish the link, the HDLC procedure processor will send that SABME frame. The data has already been transmitted as an I2 frame by the data transmission request command from the host device before receiving the, but the other system is in the process of link reconfiguration, so that I2 frame will be discarded. . After that, the HDLC procedure processing device receives the SABME frame requesting the link re-setting, and based on this, the "DL / setting / display" is sent to the host device.
While the status is reported, the response UA frame is sent to the other system, and the link reconfiguration in the own system is completed. However, if a "DL / data / request" command requesting data transmission is issued at this time, this command will be accepted by the HDLC procedure processing device after link reconfiguration, so the HDLC procedure processing device will send the command to the partner system. The data is transmitted as an I3 frame.

[Problems to be Solved by the Invention] As can be seen from the above sequence example, although the I2 frame is lost so far, the I3 frame is received by the other party, the HDLC procedure processing is performed. The problem is that the sequence control in the device is broken. The cause of this problem is that the "DL, data, request" command requesting the transmission of data transmitted as an I3 frame was issued before the link was reconfigured, but was executed after the link was reconfigured. It depends on the state changing. Such an error cannot be recovered by the HDLC procedure,
Layer 3 which is the upper level is Layer 3 as well as Layer 2.
When the order control at the level is performed, it is recovered by the retransmission by layer 3, but the transmission efficiency of the entire system is reduced. Moreover, when a simple protocol without order control is used in the upper layer, it is impossible to recover from such an error.

Eventually, until now, information was sent and received between the HDLC procedure processing device and its own host device via the memory, and waiting had occurred on the memory. While the status of the HDLC procedure processor changes, or the status of the HDLC procedure processor reporting the status change is in the memory, the host device issues a command, such as the host device issues a command. The state of the link recognized at the time when the command was executed and the state of the link at the time when the command is actually executed may be different, which causes an error that cannot be recovered by the HDLC procedure. In the example of the above sequence, the link is re-established from the partner system, but a similar error may occur in the link re-establishment from the own HDLC procedure processor.

An object of the present invention is to provide a data transmission method in an HDLC procedure processing device in which the occurrence of an error that cannot be recovered by the HDLC procedure can be prevented.

[Means for Solving Problems] The above-mentioned purpose is a request from the partner system or the own HDLC.
Procedure Achieved by discarding a data transmission request command that has been issued and has not been executed by the host device before the host device recognizes the link setting when the link is reset by a request from the processing device. To be done.

[Operation] For example, if the link is re-established from the partner system, HD
The LC procedure processor reports that the link has been reset to its own device, but if there is a command that has been issued before the host device recognizes the link reset and has not been processed, it All commands are abandoned. As a result, erroneous transmission of data due to these commands is prevented, and after the host device recognizes the link reset, it notifies the HDLC procedure processing device of the transmission restart and starts transmission again from the data for which delivery confirmation has not been taken. In this way, the order of the data will not be lost.

EXAMPLES The present invention will be described below with reference to FIGS. 1 and 2.

First, the configuration of an example of an HDLC procedure processing device and its own host device according to the present invention will be described with reference to FIG. As shown in the figure, the HDLC procedure processing device 1 is composed of a processor 11, a line interface 12, a DMA controller 13 and a memory 14, which are connected to each other via an internal bus 101. The host device 2 is composed of a processor 21 and a memory 22, both of which are connected via a host bus 102. The HDLC procedure processing device 1 is connected to its own host device 2 via a bus 102, while receiving line 103 and transmitting line 1
It is designed to be connected to the partner system via 04.
Here, the HDLC procedure processing device 1 will be further described. The line interface 12 is for transmitting and receiving a frame defined in the HDLC procedure, and the DMA controller 13 accesses the memory 22 via the upper bus 102. While the status from the HDLC procedure processing device 1 to the self upper device 2 is written to the status queue 221, the command from the self upper device 2 to the HDLC procedure processing device 1 is read from the command queue 222. Further, the reset flag 141 set in the memory 14 indicates whether or not there is a command issued before the link reset in the command queue 222, and whether or not the command is issued. That is, at the time of link resetting from the partner system, the status is set at the same time when the "link reset" status is notified to the self upper apparatus 2, and is reset by the "restart transmission" command by the self upper apparatus 2.
While the reset flag 141 is set, the "DL / data / request" command is discarded.

Now, FIG. 1 shows an example of the data transmission / reception sequence according to the present invention when data is transmitted in the same manner as in FIG.

That is, to explain the operation of the own system after the failure of the partner system, the processor 21
While writing the “DL, data, request” command to 2, the processor 11 uses the DMA controller 13
22 is being looked in at regular intervals, but if the "DL / data / request" command related to the I2 frame is read from the command queue 222 in such a state, I2
After assembling the frame, the transmission line 10 via the line interface 12
4 will send an I2 frame. However, at this time, the partner system has already detected a line failure and the SABME frame is being transmitted based on this, so the I2 frame will be received by the partner system after the SABME frame has been transmitted, and the I2 frame Such data will be discarded. On the other hand, in the HDLC procedure processing device 1, the SABME frame passes through the receiving line 103 and the line corresponding unit 12
If it is received at, processor 11 will be notified to that effect,
Based on this, the processor 11 assembles the "DL / setting / display" status and then writes the status in the status queue 221 using the DMA controller 13. At the same time, the reset flag 141 is set, the UA frame is assembled, and the line interface 12
It is adapted to be transmitted on the transmission line 104 via the.
After that, the HDLC procedure processing device 1 writes the "DL / data / data" written in the command queue 222 before the link reset report.
The "request" command is processed, but since the reset flag 141 has already been set at this point, all written commands will be discarded. Eventually,
From the status queue 221, the processor 21 displays “DL / Setting /
When the "Display" status is read, the "Resume transmission" command and the "DL / data / request" command for retransmitting unconfirmed data related to I2 and I3 frames are in the command queue.
It is written in 222, and the HDLC procedure processor 1 "resumes transmission".
After resetting the reset flag 141 at the time of reading the command, the subsequent "DL / data / request" command is accepted and the transmission line 104 as I2 and I3 frames is received.
It is supposed to be sent over. These frames are to be received by the partner system in this order.

In this example, the confirmation that the link has been re-established is notified by the "restart transmission" command, but a new command that resets the re-establishment flag and requests the next data transmission is newly added and It may be issued.
Also, in the processing of commands and statuses, if there is no waiting in the host device, it is confirmed that the link reconfiguration has been notified at the time when the host device reads the "DL / setting / display" status. A method is also possible.

[Effects of the Invention] As described above, according to the present invention, at the time of link re-establishment, the data transmission request command issued by the upper-level device is discarded before the higher-level device recognizes the link re-setting, and the data by the command is discarded. Since incorrect transmission of is prevented,
There is an effect that an error due to erroneous data transmission, which cannot be recovered by the HDLC procedure, can be avoided.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a data transmission / reception sequence according to the present invention, FIG. 2 is a diagram showing a configuration of an HDLC procedure processing device according to the present invention and an example of a host device, and FIG. It is a figure which shows the data transmission / reception sequence which concerns on. 1 ... HDLC procedure processor, 2 ... (own) host device, 11 ...
… Processor, 12 …… Line interface, 13 …… DMA controller, 14 …… Memory, 141 …… Reset flag, 21 …… Processor, 22 …… Memory, 221 …… Status queue, 2
22 …… Command queue, 103 …… Receive line, 104 …… Send line.

Claims (1)

[Claims] 1. A physical line is connected to a partner system, and a link, which is a logical connection to the partner system, is set on the physical line by a request from the own host device or the partner system. Is a data transmission method in an HDLC procedure processing device for transmitting data to a partner system by the data transmission command and confirming the data from a frame from the partner system, which is a link from the partner system, which is reported to its own host device. Reset or self
The data transmission command issued by the host device before the link reconfiguration from the HDLC procedure processor is actually recognized by the host device, and the data transmission command that is not issued at the time of link reconfiguration is the own HDLC procedure. A data transmission method in an HDLC procedure processing device, which is characterized by being discarded in the processing device.