JP2682490B2 - Line failure monitoring method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line fault monitoring method and device in a flag synchronization system.

[0002]

2. Description of the Related Art In the conventional line failure monitoring of the flag synchronization method, a method using an HDLC procedure is used to send a P-attached frame at a timing when there is no communication and to check whether or not there is a response to the frame (for example, JP-A-61-2
No. 81652), and a method of checking by paying attention to electrical characteristics in the physical layer.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
As a method of transmitting a P-attached frame at a timing when there is no communication in a method using a procedure and checking whether there is a response to the frame, the old CCITT Recommendation X. 25 of 2.
4.3 Other usage of P bit in P / F bit usage procedure of LAPB is in the category of comment that it is a subject for further study, and there is a problem that it cannot be used. Moreover, there is a problem in electrical characteristics in the physical layer. The method of checking by paying attention has a problem that there is a risk of shifting to forced disconnection of the line by detecting a failure due to line disturbance that can be relieved by an increase in the amount of hardware or protocol retransmission.

In view of the above-mentioned drawbacks of the conventional example, an object of the present invention is to detect a line failure without transmitting / receiving a frame with p, and to distinguish between a temporary failure and a permanent failure due to line disturbance. Another object of the present invention is to provide a line fault monitoring method and device capable of preventing an increase in the amount of hardware.

[0005]

SUMMARY OF THE INVENTION The method of the present invention counts the length of the non-flag between the start flag and the end flag in the frame being received, and the value being counted is a preset maximum frame length. If it exceeds, report the line failure. Furthermore, if the value being counted exceeds the preset maximum frame length, counting is stopped and the timer is started.If the preset termination flag is received before the timeout occurs, the timer is stopped and before the termination flag is received. The line failure is reported only when a timeout occurs.

The apparatus of the present invention comprises a start flag detecting means for detecting a start flag in a frame to be received, a termination flag detecting means for detecting a termination flag in a frame, and the detected start flag and termination flag. Frame length counting means for counting the length of the interval, maximum frame length setting storage means for storing the maximum received frame length, and frame length comparison means for comparing the counted frame length with the stored maximum frame length And a line fault reporting means for reporting a line fault based on the comparison result of the comparison means. Further, timer means that is activated based on the comparison result of the comparison means, and timeout value setting storage means that sets and stores a timeout value for temporally discriminating between a permanent line failure and a burst line disturbance. , And a line fault reporting unit for reporting a line fault only when a time-out occurs in the timer unit before receiving the termination flag.

In addition, the old CCITT Recommendation X. The frame length monitoring function based on the maximum number of bits N1 in the information frame of the 25 link layer is stored in the maximum frame length setting storage means, the frame length counting means, the frame length comparison means, etc., and the long idle monitoring function based on the timer T3 is stored in the timeout value. It is possible to prevent an increase in the amount of hardware by using the means and the timer means.

[0008]

The line fault monitoring of the present invention is performed by the HDLC procedure (X.
(Corresponding to 25 link layers) In order that a line fault can be detected without transmitting / receiving a frame with p, the frame length to be judged as a line fault is stored by the maximum frame length setting storage means, and the start flag detection means and the termination flag detection means And the frame length counting means counts the frame length between the start flag and the end flag, compares the counted frame length with the stored maximum received frame length by the frame length comparison means, and stores the count value. Only when it is judged that it is larger than the maximum reception frame length, the line fault reporting means can report the occurrence of the line fault.

Further, when the maximum received frame length in the state where no line fault or line disturbance occurs is stored in the maximum frame length setting storage means, bursty line disturbance that lasts for a long time can be distinguished from the line fault. By adding the timer means and the timeout value setting storage means, the frame length counting means, the comparing means, etc., activate the timer after it is once judged that the line is abnormal, and the termination flag is set before the timeout occurs due to the preset timer value. When detected, the timer is stopped, and the line failure can be reported only when a time-out occurs before the termination flag is detected.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of the first embodiment of the present invention, and FIG. 2 is a flow chart showing the operation of the first embodiment of the present invention. In FIG. 1, reference numeral 1 is a maximum frame length setting storage means for storing a maximum reception frame length which is regarded as a line failure non-occurrence state, 2 is a start flag detection means for detecting a start flag in a received frame, and 3 is an end in the frame. It is a termination flag detecting means for detecting a flag. 4 is between the detected start flag and end flag under the condition of ignoring the frame type indicated by the address and control field and ignoring the occurrence of an error such as a frame check sequence (FCS). A frame length counting means for counting the length of the non-flag portion. Reference numeral 5 is a frame length comparing means for comparing the counted frame length with the maximum frame length stored in the storage means 1, and 6 is a line failure reporting means for reporting a line failure based on the comparison result.

The operation of the first embodiment will be described with reference to FIG. In step 10, the start flag detecting means 2 detects the start flag in the frame, and if it is detected, the process proceeds to step 11. If it cannot be detected, the detection is continued. In step 11, the frame length count value of the frame length counting means 4 is cleared, and in step 12, the frame length counting means 4 counts the frame length. In step 13, the frame length comparison means 5 compares the frame length counted by the counting means 4 with the maximum frame length stored in the maximum frame length setting storage means 1. When it is determined in step 14 that the count value is larger than the stored maximum reception frame length, the process proceeds to step 16, in which the line fault reporting means 6 reports the occurrence of a line fault. When it is determined in step 14 that the count value is smaller than the stored maximum reception frame length, the process proceeds to step 15, and the counting of the frame length is continued until the termination flag detecting means 3 detects the termination flag, and the termination flag detecting means. Upon detection of the termination flag by 3, the process returns to step 10 in preparation for reception of the subsequent frame.

A second embodiment of the present invention will be described.

FIG. 3 is a block diagram showing the configuration of the second embodiment of the present invention, and FIG. 4 is a flow chart showing the operation.

In the second embodiment, in addition to the structure of the first embodiment, the timeout value setting storage means 7 and the timer means 8 are added.
It is characterized by the addition of. Reference numeral 7 is a timeout value setting storage means for setting and storing a timeout value for temporally discriminating between a permanent line failure and a burst line disturbance, and 8 is a timer means, and a frame length comparison means 5 The output is output to the line fault reporting means 6 after a timeout. Other configurations are similar to those of the first embodiment.

The operation of the second embodiment will be described with reference to FIG. The operation from step 10 to step 15 is the same as the operation of the first embodiment, and therefore its explanation is omitted.

In the second embodiment, when it is determined in step 14 that the count value of the frame length counting means 4 is larger than the maximum reception frame length stored in the maximum frame length setting storage means 1, the process proceeds to step 17. In step 17, the timer means 8 is started. In the time-out value setting storage means 7, a time-out value for distinguishing a long-lasting burst-like line disturbance from a line failure is set and stored in advance. Therefore, in step 18, the stored time-out value and timer means are stored. 8 compares with the time value being measured. If the time-out exceeds the time-out value stored in the time-out value setting storage means 7 by the timer means 8 before the termination flag detection means 3 detects the time-out flag, the process proceeds to step 16 and the line fault reporting means 6 causes the line Report a problem. If the termination flag detecting means 3 detects the termination flag before the time-out occurs (step 19), the timer means 8 is stopped (step 20). That is, the timer means 8 and the timeout value setting storage means 7 are added, and after the frame length counting means 4 and the frame length comparison means 5 etc. determine once that there is a line abnormality, the timer means 8 is activated and the timer value is set according to the preset timer value. If the termination flag detecting means 4 detects the termination flag before the occurrence of a timeout, the timer means 8 is stopped, and the timer means 8 exceeds the timeout value stored in the timeout value setting storage means 7 before the termination flag is detected. Report line failure only if it occurs.

In the second embodiment, the old CCITT is used.
Recommendation X. The frame length monitoring function based on the maximum number of bits N1 in the information frame of 25 link layers is set to the maximum frame length setting storage means 1, the frame length counting means 4, the frame length comparison means 5, etc., and the long idle monitoring function by the timer T3 is timed out. By using the value setting storage means 7 and the timer means 8, it becomes possible to prevent an increase in the amount of hardware.

Each means of the first and second embodiments of the present invention may be specifically configured by being integrated in a communication control LSI.

[0019]

As described above, the present invention provides HDLC.
The line failure can be detected without transmitting / receiving the p-added frame of the procedure (corresponding to X.25 link layer), and the temporary failure and the permanent failure due to the line disturbance can be distinguished, and
It is also possible to prevent an increase in hardware.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of a first embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the embodiment shown in FIG.

FIG. 3 is a block diagram showing the configuration of a second embodiment of the present invention.

FIG. 4 is a flowchart showing the operation of the embodiment shown in FIG.

[Explanation of symbols]

 1 maximum frame length setting storage means 2 start flag detection means 3 end flag detection means 4 frame length counting means 5 frame length comparison means 6 line fault reporting means 7 timeout value setting storage means 8 timer means

Claims (3)

(57) [Claims] 1. A non-flag length between a start flag and an end flag in a received frame is counted, and when the value being counted exceeds a preset maximum frame length, counting is stopped and a timer is started. A line fault monitoring method characterized in that a timer is stopped when a termination flag is received before a preset timeout occurs, and a line fault is reported only when a timeout occurs before the termination flag is received. 2. A start flag detection means for detecting a start flag in a frame, a termination flag detection means for detecting a termination flag in a frame, and a length between the detected start flag and termination flag. Frame length counting means, maximum frame length setting storage means for storing a maximum received frame length, frame length comparison means for comparing the counted frame length with the stored maximum frame length,
Timer means that is activated based on the comparison result of the comparison means; timeout value setting storage means that sets and stores a timeout value for temporally discriminating between a permanent line failure and a burst line disturbance; A line fault monitoring device comprising line fault reporting means for reporting a line fault only when a time-out occurs in the timer means before receiving a flag. 3. The maximum frame length is the maximum number N of bits in an information frame of X25 link layer protocol.
3. The line fault monitoring device according to claim 2, wherein the timeout value is set to a value obtained by adding 4 octets to 1 and the same value as the timer T3 of the X25 link layer protocol.