JPH02285752A - Communication controller using hdlc protocol - Google Patents

Abstract

PURPOSE:To prevent a busy state by informing production of a fault to a host layer processing and untransmitted data, and stopping a data transmission request from a host layer processing when a fault of disabling data transmission in the link layer processing is detected. CONSTITUTION:If a fault disabling communication between stations A and B takes place, when a link layer processing 1a2 of a station A detects line interruption through a physical layer 1a1, the data transmission to a station B is stopped and the occurrence of a fault is informed to a host layer processing 1a3. The content of notice includes transmission data 4, 5, 6 having the presence of the transmission request from the host layer processing 1a3 but have been not sent and the host layer processing 1a3 stops the further data transmission request and stores the data 4-6 for retransmission. Thus, the resident data in the link layer processing is eliminated to prevent a busy system.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention uses HDL as a link layer protocol.
C (High 1 level Data' Link C
The present invention relates to a communication control device using the (ontrol) procedure.

[Conventional technology]

Figure 1 shows the system configuration of a general communication control device. In the figure, 1a is the communication control device A station, 1b is the communication control device B station,
is a communication line, and lal in the communication control devices 1a and lb
, 1a2, 1a3.1a4, and lbl, 1b2.1
b3 and 1b4 indicate the processing configuration in each device. Note that station A 1a operates as a primary station, and station B lb operates as a secondary station.

Next, the operation of the 0 communication control device 1a will be explained.

Communication processing of 1b is performed by OS I (Open System
s Interc.

physical layer processing 1al that controls the line, and link layer processing 1 that logically controls the exchange of data on the line.
a2 and upper layer processing 1a3 which is the processing above it
．． It consists of other control processing 1a4, and link layer processing 1a is
2 manages and controls data transmission to the other station, and physical layer processing 1al sends the data to the line. This apparatus, which also performs reception processing by similar functional division, uses the HDLC procedure standardized by 130 (International Organization for Standardization) and JIS as link layer processing.

In the HDLC procedure, data is transmitted using I frames with transmission/reception sequence numbers attached. For example, "rlo, OP" in Figure 4 is the first transmission data, and data from the other station is not yet transmitted. Reception, P (boring bit off)
This indicates that station A has the right to transmit. In the case of FIG. 4, station A receives data transmission request 1 from the upper layer.
2.3, sends an I frame to the B station and sends "I2
By turning on the boring bit with "゜0-P", the transmission right is passed to the B station, and the B station sends an RR as a data delivery confirmation.
receiving a frame. Here, "rRR3-F" indicates that up to three pieces of data have been successfully received and the transmission/reception right is returned to the A station. When communicating between two stations in this way, if station B breaks down or a failure such as a line disconnection occurs,
In a state where data transmission/reception between stations A and B is impossible, the link layer processing 1a2 of station A detects that data transmission is impossible due to a failure, and does not perform data transmission processing.
Since the upper layer processing 1a3 cannot detect such a failure, it continues the data transmission requests 4, 5, 6゜7, ..., n, so the link layer processing 1a2 accumulates unsent data and becomes busy. Become.

[Problem to be solved by the invention]

Conventional communication control equipment is configured as described above, so if a failure occurs in the other station or line, data transmission requests from the upper layer do not stop, resulting in a busy state in link layer processing. There was a problem.

This invention was made to solve the above-mentioned problems, and an object thereof is to obtain a communication control device using an HDLC procedure in which untransmitted data does not accumulate and link layer processing does not become busy. .

[Means to solve the problem]

A communication control device using an HDLC procedure according to the present invention includes:
When link layer processing detects a fault that makes data transmission impossible, it notifies upper layer processing of the occurrence of the fault and unsent data.

(Operation) The link layer processing of the communication control device using the HDLC procedure in this invention notifies the upper layer processing of the occurrence of a fault and the unsent data, so the upper layer processing can detect the occurrence of a fault. Stops data transmission requests from upper layer processing to prevent link layer processing from becoming busy.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

The configuration of a communication system according to an embodiment of the present invention is similar to that of the prior art shown in FIG. FIG. 2 shows the processing procedure according to this embodiment.

In the system configuration of FIG. 1 and the processing procedure of FIG. 2, station A 1a and station B lb are communicating via communication line 2, and station A receives a data transmission request 1 from upper layer processing 1a3. 2.3, the link layer processing 1a2 controls data transmission to the B station. Data transmission and reception between A station and B station is done using HDLC procedure using 17 frames rlO,0.
-PJ rll, O-P, rI2. OP, and is similar to the conventional technology.

If a failure occurs that makes communication impossible between A station and B station, such as a line disconnection, the link layer processing 1a2 of A station will detect the line disconnection through the physical layer LAL and stop sending data to B station. At the same time, the upper layer processing 1a3 is notified of the occurrence of the failure. This notification content includes transmission data numbers 4, 5, and 6, which were requested to be sent from the upper layer processing 1a3 but could not be sent, and as a result, the upper layer processing 1a3 does not request any further data transmission. The second processing procedure is to stop the data and hold the data (data numbers 4, 5, 6) for retransmission.
As shown in the figure.

In the above embodiment, when a failure occurs, the link layer process 1a2 sends a failure notification including the unsent data number to the upper layer process 1a3, but the upper layer process 1a
If the data numbers are not managed between the link layer processing 1a2 and the link layer processing 1a2, or if the data areas that can be handled by each layer processing are different, the processing procedure of another embodiment of the present invention shown in FIG. Following the fault notification, the unsent data 4.5.6 itself may be sent back from the link layer processing 1a2 to the upper layer processing 1a3, and the same effect as in the above embodiment is achieved.

〔Effect of the invention〕

As described above, according to the present invention, when a failure occurs, link layer processing notifies upper layer processing of the failure occurrence and unsent data, so that data transmission requests from upper layer processing can be stopped. This has the effect of eliminating data stagnation in link layer processing and preventing a busy state.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a system configuration of a communication control device according to an embodiment of the present invention and a conventional technology, FIG. 2 is a diagram showing a processing procedure in an embodiment of the present invention, and FIG. FIG. 4 is a diagram showing the processing procedure in the embodiment, and FIG. 4 is a diagram showing the processing procedure according to the prior art. In the figure, 1a is a communication control device (station A), 1b is the same device (station B), 2 is a communication line, 1a2 is link layer processing, 1a3
is upper layer processing. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) In a communication system that consists of a pair of communication control devices and a line between the devices and sends and receives data using HDLC procedures, if data cannot be sent or received due to a problem with the other device or the line, etc. A communication control device using an HDLC procedure, characterized in that link layer processing of a fault detection side device notifies its upper layer processing of the occurrence of a fault and unsent data.