JPH11355275A - Line fault detection method and device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To detect a line failure without providing a complicated protocol for a device on a transmission side and a device on a reception side. SOLUTION: In a transmission side device, after data input from a line interface is separated into a payload portion and an alarm data portion, an error detection code is added to the alarm data portion, and the alarm data portion to which the error detection code is added. And the payload portion are assembled into fixed-length data of the same transmission unit and transmitted to the transmission destination, and the fixed-length data received from the transmission side is separated into a payload portion and an alarm data portion by the receiving device, and the separated alarm is output. The presence or absence of an error in the data portion is detected by an error detection code added to the alarm data portion. If there is an error in the alarm data portion, it is determined that a line failure has occurred, and the alarm data of the line disconnection is sent to the receiving end line. Send to interface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of converting data input from a line interface into data having a fixed bit length (AT).
The present invention relates to a method and an apparatus for detecting a line failure in a communication system that assembles into an M cell or a packet and transmits it to a destination, and an alarm information transfer method.

[0002]

2. Description of the Related Art Conventionally, there is a communication system in which data such as video, audio, and text are assembled into cells or packets of a fixed length and transmitted from a transmitting device to a receiving device. Here, the transmitting device and the receiving device are
For example, an ATM switch.

In such a communication system, if a failure occurs in a line or a communication path from a transmission end to a reception end and a predetermined transmission quality cannot be guaranteed, the line is rejected. Alternatively, it is necessary to take measures to disconnect the line so that the communication path is not used.

Conventionally, as a method of detecting a failure in a line or a communication path, for example, as disclosed in Japanese Patent Application Laid-Open No. 5-63761, time information until the next transmission data is added to the beginning of transmission data. If the time information can be confirmed normally on the receiving side, a normal acknowledgment signal is returned to the transmitting side.If the time information cannot be confirmed normally, a retransmission request is sent to the transmitting side, or Some abnormal states are output to the outside.

On the other hand, in an ATM network system, when alarm information indicating a line failure, such as line disconnection or loss of synchronization, detected at a receiving end is transferred to an opposing destination device, maintenance management is included in the flow of ATM cells. OAM cell (Operation And Maintenance; OAM cell, hereinafter) is inserted into the OAM cell, and alarm information is inserted into the OAM cell and transmitted to the opposite ATM exchange.
The TM switch extracts the alarm information obtained by disassembling the OAM cell and transmits it to the line side of the receiving end.

On the other hand, as shown in FIG.
There is a system in which nodes constituting a network are connected in a ring. That is, a plurality of nodes 261 to 264
Are connected by an outer ring transmission path 265 and an inner ring transmission path 266, and each node has a terminal (A) 267 such as a camera or a personal computer for inputting / outputting image data, text data, audio, video data, and the like. Terminal (B)
268 is connected to the terminal (A) 267 to transmit image data, text data, and the like to the terminal (B) 268 via the ATM network. Here, each of the nodes 261 to 264 is 64 Kbps, 1.5
It is provided with an existing STM line interface unit such as Mbps and 2 Mbps and an ATM switch.

[0007] A connected by such a ring-shaped transmission line
In the TM network, usually, the terminal (A) 267
When data is transmitted from the terminal to the terminal (B) 268, one of the ring transmission lines (the outer ring transmission line 264 in the example of FIG. 26) is used as shown by the broken line in the figure. here,
As indicated by the mark “x” in FIG. 25, when a failure occurs in the node 264 that is a relay node in the transmission path from the terminal (A) 267 to the terminal (B) 268 or in the relay transmission path,
As shown by the broken line, loop-back is performed at the relay node 264, a transmission path to the terminal (B) is secured via the ring transmission path 266 inside the standby system, and the transmission path from the terminal (A) 267 to the terminal (B) 268. Is transmitted.

However, as shown by the “x” mark in FIG.
When a failure occurs in the node 261 to which the terminal (B) 268 is connected, as shown by a broken line in FIG.
64 and the node 262 perform a loopback, and the data output from the terminal (A) 267 is changed to the terminal (A) as shown in the figure.
It returns to 267. Therefore, the terminal (B) 26
8 cannot be detected, and no fault alarm is output to the terminal (A) 267.

On the other hand, as a method of using a loopback switch for relieving a transmission path failure in a ring network system, a BLSR (Bidrectional L
ineSwitched Ring). In this BLSR, node chain information indicating how nodes are connected in the ring system, and ADD / D
A squelch table for setting squelch information indicating at which node the ROP signal is assigned is provided, and line switching is performed using the squelch table.

FIG. 30 shows the structure of the squelch table. The squelch table includes node chain information, cross connect type information, squelch information, and WO.
RKLINE information.

The node chain information indicates how the nodes are connected in the ring system, the cross-connect type information indicates the channel, that is, the type of line, a one-way type line is 1WAY, and a two-way type. Line is 2W
AY, Primary NODE of Interconnection
Is 2WAYBR, interconnection (ON PRO
T) Primary NODE of line is 2WAYBRP
P, Se of the interconnection (ON PROT) line
The secondary NODE is 2WAYBRPS.

[0012] The squelch information is obtained for each line by the AD of the line.
D NODE and DROP NODE, each 2
Node can be set. In particular, when setting a one-way line (1 way), the setting is made in consideration of the ADD / DROP NODE and the line direction. WORKLine information indicates that a signal that has been ADD / DROPed on a channel-by-channel basis
This is information indicating whether the RK line is used. Also,
Protection channel (ST) as TO channel
BY) is also added to the element.

The squelch table shown in FIG. 30 uses the transmission line channel 1 to connect the interconnection line shown in FIG. 28A, channel 2 to the interconnection (ON PROT) line shown in FIG. FIG. 29C shows an example in which the broadcast line of FIG. 29C is set. It should be noted that a general line shown in FIG. 27A can be set using this squelch table.

Although this squelch table is shown for each node, a setting state using the squelch table of the node 4 shown in FIG. 31D will be described. WEST on interconnection line (channel 1), interconnection (ON PROT) line (channel 2)
The squelch information of the TO channels 1 and 2 on the
Note 3 (NODE3), which is the Primary NODE, is set in NODE (1), and ADD NODE (2)
Is a secondary node, node 2 (N
ODE2) is set, and the end node 1 (NODE1) is set in DROP NODE1. Further EAST
The squelch information of the TO channels 1 and 2 on the
Node 1 (NODE1), DROP to NODE (1)
Node 3 (NODE3) and DLOP at NODE (1)
Node 2 (NODE2) is set in NODE (2).

The broadcast line is set in the squelch table as a combination of one way line. This broadcast line does not cause a misconnection even if a node failure occurs at the end nodes Node 3 and Node 4. Therefore, the longest end node Node 2 is set in the DROP NODE of the squelch information. Therefore, the squelch table stores the node 1 (NOD) in ADDNODE (1) of the squelch information of the TO channel 3 on the EAST side.
E1), the longest terminal node 2 (NODE2) is set in DROP NODE (1).

As described above, FIG. 28 shows examples of various lines. Among them, the difference between (a) interconnection line and (b) interconnection (ON PROT) line is that node 3 and node 2 WORK the line between
When using the channel or the STBY channel, the latter allows the WORK channel side to be used for other applications by using the STBY channel, especially when the node 2 does not require protection, This is an improvement in line utilization efficiency. The service selector SS31 of the node 3 selects the signal from the trip line and the signal from the line on a line-by-line basis. A node that branches the line in the SS31 is called a primary node, and a branch destination node is called a secondary node. I do.

When there is a transmission line failure, each line performs a loopback switch, but no misconnection occurs in this line example. In the case of a node failure, no misconnection occurs for one node failure.
If one of the nodes fails, a misconnection occurs.

A method for dealing with a misconnection in this case will be described with reference to FIG.

In FIG. 29, node failures occur in the nodes 3 and 2 at the same time, and the node 3 and the nodes 4 and 1 adjacent to the node 2 start transmission line rescue processing. The node 4 and the node 1 recognize that the node 3 and the node 2 have a node failure at the same time by the same method of detecting a failed node as before. Node 4 is WORK of squelch table
With reference to the squelch information of the channel, a search is made as to whether there is a path communicating with the nodes 3 and 2 in which the node has failed. The STBY channel is used for transmission line rescue and does not need to be searched.

As a result, the TO channel is west (work) -1 in the squelch table. WEST (WOR
K) -2, EAST (WORK) -1, EAST (WO
RK) -2 and EAST (WORK) -3. A
DD NONE (1), ADDNODE (2) or D
If the ROP NODE (1) and the DROP NODE (2) are set at the same time, the path is used for interconnection, so the ADD NODE
(1), ADD NODE (2) or DROPNOD
When E (1) and DROP NODE (2) simultaneously recognize that a node failure has occurred, the channel is recognized as a channel in which a misconnection may occur.

Therefore, in this example, WEST (WOR
K) -1, WEST (WORK) -2, EAST (WO
Since RK) -1 and EAST (WORK) -2 satisfy the above conditions, it is decided to insert PATH AIS into the channel.

EAST (WORK) 13 is DROP N
Although node 2 is set in ODE (1), PATH AIS is not set as the insertion target channel because of the one-way path. Regarding the method of actually inserting the PATH AIS, when a failure node is found in “ADD NODE”, the PATH AIS is
If S201 is inserted and a failed node is found in “DROP NODE”, PA
Insert the TH AIS 202.

Therefore, in this example, in FIG. 31 (2), WEST (WORK) -1, WEST (WORK) -2
Then, PATH AISs 301 and 302 are inserted into WEST (STBY) -1 and WEST (STBY) -12. After the process of preventing misconnection is completed, a loopback switch is performed to rescue the transmission path.

[0024]

However, according to the method disclosed in Japanese Patent Laid-Open Publication No. Hei 5-63761, whether the time information is normally received between the transmitting side and the receiving side or not. A protocol is needed to constantly check if there was any. For this reason, there is a problem that protocols provided on the transmission side and the reception side become complicated.

On the other hand, in a method of conducting a continuity test, a performance test, and an alarm notification with an opposite ATM exchange using an OAM cell, the cell disassembly and assembly unit of one ATM exchange and the cell disassembly of the other ATM exchange are used. Only the line failure between the assembly unit can be detected, and the range between the communication path before cellification and the communication path after decellularization is expanded to detect normal or abnormal line. There is a problem that you can not.

The OAM of the alarm information received from the line
The cell is multiplexed with the user data (payload data) cell stream and transferred. However, even when there is no change in the alarm content, the cell is always multiplexed with the user data and transferred, which causes a problem of lowering the user data transmission efficiency. is there.

Also, in the ATM network system using the ring transmission path, when a failure occurs in the opposite node, the transmission path is looped back before the opposite node in which the failure has occurred. The problem that the output data is looped back at the loopback point and returned to its own node, and the failure is not detected even if the opposing device is disconnected, and (2) as described with reference to FIGS. P.AIS for misconnection at loopback
However, there is a problem that the method of outputting the data cannot respond to a logical connection such as an ATM cell or a packet.

It is a first object of the present invention to provide a line fault detecting method and apparatus capable of detecting a line fault without providing a complicated protocol for the transmitting and receiving apparatuses.

Further, the present invention provides a line fault detecting method capable of detecting a normal or abnormal line by extending the range between a communication line portion before celling and a communication line portion after decellularization. The second object is to provide

It is a third object of the present invention to provide an alarm information transfer method capable of transferring alarm information while minimizing a decrease in transmission efficiency of user data.

Further, according to the present invention, even if a failure occurs in the opposite device in the ring network configuration, the failure of the opposite device is detected by the own node at the ATM connection / packet connection level, and the failure information is output to the terminal. It is a fourth object of the present invention to provide a method for detecting a line failure that can be performed.

[0032]

To achieve the above object, according to the present invention, there is provided a line communication system for assembling data input from a line interface into data having a fixed bit length and transmitting the data to a destination. In the failure detection method, after the data input from the line interface is separated into a payload part and an alarm data part in the transmission side device, an error detection code is added to the alarm data part, and the error detection code is added. The alarm data portion and the payload portion are assembled into fixed-length data of the same transmission unit and transmitted to the transmission destination, and the fixed-length data received from the transmission side in the receiving device is separated into a payload portion and an alarm data portion. The presence or absence of an error in the separated alarm data portion is detected by an error detection code added to the alarm data portion, and the alarm data If there is no error, the received payload part and alarm data part are assembled into fixed length data of the same transmission unit and sent to the receiving end line interface, and if there is an error in the alarm data part, a line failure has occurred. And sending out the line disconnection alarm data to the receiving end line interface.

According to a second aspect of the present invention, in the first aspect of the present invention, when the error in the alarm data portion continues over a predetermined value or more, the line disconnection alarm data is transmitted, and when the error is less than the set value. Is characterized by transmitting the last alarm data having no error to the line interface at the receiving end.

According to a third aspect of the present invention, in the first or second aspect of the present invention, an underflow of the receiving buffer for sequentially storing fixed-length data received from the transmitting side is detected, and the underflow is detected for a predetermined time or more. Is detected, the alarm data of the line disconnection is sent to the line interface of the receiving end.

Further, the invention of claim 4 is characterized in that, in the invention of claims 1 to 3, the payload portion and the alarm data portion transmitted from the transmitting side device are transmitted by different connections.

Further, the invention of claim 5 is characterized in that, in the invention of claims 1 to 4, the alarm data portion is transmitted to the receiving end line interface only when the content of the alarm changes.

According to a sixth aspect of the present invention, in the first to fifth aspects of the present invention, the calculation formula of the error detection code added to the alarm data portion is made different depending on the up / down direction of the bidirectional path of the payload portion. It is characterized by the following.

A seventh aspect of the present invention is a line fault detection method in a communication system for assembling data input from a line interface into data having a fixed bit length and transmitting the data to a destination. An error detection code of a different calculation formula is added to the data input from the line interface according to the up / down direction of the bidirectional path, and the data with the error detection code is assembled into fixed-length data and transmitted to the destination. After transmitting, wait for data reception from the transmission destination device on the downlink path, and if data is received on the downlink path, check whether the calculation formula of the error detection code of the received data corresponds to the downlink direction. And if it corresponds to the downlink direction, the presence or absence of an error in the received data is detected by the error detection code added to the received data, If the transmitted data loops back and returns to the transmitting device on the downstream path, it is determined that a failure has occurred in the destination device due to a mismatch in the calculation formula of the error detection code, and the In the device, the presence or absence of an error in the fixed-length data received from the transmission side is detected by an error detection code of an upward calculation formula added to the fixed-length data, and if an error is found, a line failure has occurred. And sending out the line disconnection alarm data to the receiving end line interface.

An eighth aspect of the present invention is a line fault detection method in a communication system for assembling data input from a line interface into data having a fixed bit length and transmitting the data to a destination. The data input from the line interface is separated into a payload part and an alarm data part, and an error detection code of a different calculation formula is added to the alarm data part according to the up / down direction of the bidirectional path. After assembling the alert data portion and the payload portion added with the fixed length data and transmitting the data to the transmission destination, waits for data reception from the transmission destination device on the downlink path, and receives data on the downlink path. If it is determined whether the calculation formula of the error detection code of the received data corresponds to the downlink direction, The presence or absence of an error in the alarm data portion is detected by the error detection code added to the alarm data portion in the received data, and the data transmitted by the transmitting device loops back and returns to the transmitting device on the downlink path. In this case, it is determined that a failure has occurred in the destination device due to a mismatch in the expression for calculating the error detection code, and the destination device determines whether there is an error in the payload portion of the fixed-length data received from the transmitting side. It is detected by the error detection code of the upward calculation formula added to the payload part, if there is an error, it is determined that a line failure has occurred, and alarm data of line disconnection is sent to the receiving end line interface. And

Further, according to the present invention, an underflow of a receiving buffer for sequentially storing fixed-length data received from the transmitting side is detected, and if an underflow is detected for a predetermined time or more, the line is disconnected. It is characterized in that the alarm data is transmitted to the receiving end line interface.

The invention according to claim 10 is the invention according to claims 8 to 9
According to the invention, the payload portion and the alarm data portion transmitted from the transmission side device are transmitted by different connections.

An eleventh aspect of the present invention is a transmission apparatus in a communication system for assembling data input from a line interface into data having a fixed bit length and transmitting the data to a transmission destination. Means for separating the data input from the line interface into a payload part and an alarm data part, means for adding an error detection code to the separated alarm data part, and an alarm data part to which an error detection code is added. Means for assembling the payload portion into fixed-length data of the same transmission unit and transmitting the fixed-length data to the destination.The transmission device on the reception side converts the fixed-length data received from the transmission device on the transmission side into a payload portion and an alarm data portion. Means for separating, and the presence or absence of an error in the separated alarm data portion is detected by an error detection code added to the alarm data portion, If there is no error in the data part, the received payload part and the alarm data part are assembled into fixed length data of the same transmission unit and transmitted to the receiving end line interface, and if there is an error in the alarm data part, a line failure has occurred. Means for judging that the line has been disconnected and sending alarm data of the line disconnection to the line interface of the receiving end.

According to a twelfth aspect of the present invention, there is provided a line fault detecting method in a communication system for assembling data input from a line interface into data having a fixed bit length and transmitting the data to a destination. A test data generating unit and a test data comparing unit are provided in the line termination unit, and when a failure occurs during the start of operation of the communication system or during operation, test data is generated from the test data generating unit, and the test data is transmitted through the set line. The test data is transmitted toward the line termination unit of the opposing line interface unit, and the test data returned via the opposing line termination unit is compared with the transmitted test data by the test data comparison unit. In this case, the presence or absence of an abnormality in the line reaching the line termination unit of the opposing line interface unit is detected.

According to a thirteenth aspect of the present invention, in the twelfth aspect, the line interface unit is provided in an ATM exchange for inputting and outputting non-ATM data such as video and audio. .

A fourteenth aspect of the present invention is a method for transferring alarm information in a communication system for assembling data input from a line interface into data of a fixed bit length and transmitting the data to a destination, wherein the method detects the alarm information at a receiving end. When transmitting the alarm information indicating the line failure to the opposing device, the alarm information is assembled into data having a fixed bit length only when the contents of the alarm change, and transmitted to the opposing destination.

[0046]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a line fault detecting method according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a configuration diagram showing an embodiment of a communication system to which the present invention is applied. As the simplest configuration example, ATM exchanges 1 and 2 are connected between exchanges such as an ATM cross connector (VPH). The configuration connected by the connection devices 3 and 4 is shown.

Each of the ATM exchanges 1 and 2 has a plurality of DSUs.
(Digital Service Units) 5-1 to 5-n and 6-1 to 6-n are connected to these DSUs 5-1 to 5-n and 6-1 to 6-n. 7 and 9 and a telephone 8 are connected as terminal devices, and exchange data such as text data, video and audio.

FIG. 2 is a block diagram showing one embodiment of the detailed configuration of the transmission section of the line interface section provided in the ATM exchanges 1 and 2.
1, a payload / alarm data separating unit 102, an error detection code adding unit 103, a cell / packet assembling unit 104, and a cell / packet transmitting unit 105.
01 is input with data from a terminal device such as the computer 7 via the DSU.

FIG. 3 is a block diagram showing one embodiment of the detailed configuration of the receiving section of the line interface section provided in the ATM exchange.
Packet decomposing unit 107, payload data / alarm data separating unit 109, error detecting unit 110, line disconnection alarm output unit 1
11, a payload data / alarm data synthesizing unit 112, and a line data transmitting unit 113.

In such a configuration, the ATM exchange 1
Is assumed to be a transmitting device and the ATM switch 2 is a receiving device, the line interface unit of the transmitting ATM switch 1 receives, for example, data input from the DSU 5-1 by the line data receiving unit 101, and The data is input to the data / alarm data separation unit 102. Payload data /
The alarm data separation unit 102 separates the input data into a payload part and an alarm data part.

Here, the alarm data is information indicating a line failure such as line disconnection or loss of synchronization, and is information detected at the line receiving end.

Payload data / alarm data separation unit 10
In 2, the separated payload data is input to the cell / packet assembling unit 104, and the alarm data is input to the error detection code adding unit 103. Error detection code adding section 103 adds an error detection code to the input alarm data portion,
The data is input to the packet assembling unit 104. The cell / packet assembling section 104 assembles the alarm data portion to which the error detection code is added and the payload portion separated by the payload data / alarm data separating portion 102 into one cell / packet and transmits the cell / packet transmitting portion 105. The data is transmitted to the ATM switch 2. In this case, the cellization is based on ITU-T
I. 363.1.

Regarding the method of transmitting the alarm data,
As shown in FIG. 4, transmission may be performed through one connection, or as illustrated in FIGS. 5 and 6, transmission may be performed through another connection. In addition, FIG.
In FIG. 6, SN is a sequence number, SH is a SAR header byte, SP is a structure pointer byte, TS
1 to TS93 are 8-bit data constituting the payload. The alarm data 120 is composed of 8-bit or 16-bit data.

On the other hand, the ATM switch 2 on the receiving side
The ATM cell line failure detection unit 106 from the transmitting side
The packet is received by the packet decomposer 107. Line fault detection unit 10
6 detects a line failure at the entrance of the network, for example, line disconnection, loss of frame synchronization, etc.
Report to 11.

On the other hand, the cell / packet decomposing unit 107 decomposes the received cell and inputs the cell to the payload data / alarm data separating unit 109. Payload data / alarm data separating section 109 separates the received cell into a payload section and an alarm data section, and inputs the separated alarm data section to error detecting section 110. Error detection unit 110
Detects the presence or absence of an error in the alarm data portion by using an error detection code added to the alarm data portion, and inputs the detection result to the line disconnection alarm output section 111.

On the other hand, underflow detection section 108 detects an underflow in the reception buffer for receiving cells / packets, and, if an underflow is detected for a predetermined time or more, reports this underflow alarm output section. 111
Report to

The line disconnection alarm output unit 111 is
If there is no error in the alarm data portion as a result of the check in step 10, the received payload portion and the alarm data portion are assembled in a cell of fixed length data of the same transmission unit in the payload data / alarm data synthesizing section 112 and the line data The data is sent from the sending unit 113 to the receiving end line interface.

However, if there is an error in the alarm data portion, it is determined that a line failure has occurred, and the line data transmission section 113 transmits the line disconnection alarm data to the receiving end line interface.

Further, even when the underflow detection unit 108 detects an underflow for more than a preset time, the line disconnection alarm output unit 111 transmits the line disconnection alarm data from the line data transmission unit 113 to the receiving end line interface. To be sent. Further, even when the line failure detection unit 106 detects a line failure at the entrance of the network, for example, a line disconnection, a loss of frame synchronization, or the like, the line data transmitting unit 113 sends the line disconnection alarm data to the receiving end line interface.

As described above, the error detection code is added to the alarm data and transmitted to the reception side, and the reception side checks the presence or absence of the error of the alarm data by the error detection code. By transmitting the alarm data to the receiving end line interface, there is no need to provide a protocol for checking the state of the line between the transmitting side device and the receiving side device. Can be easily detected.

If there is an error in the alarm data,
The alarm data for line disconnection is output immediately, but the alarm data for line disconnection is output if errors continue for a preset value or more, and if less than the set value, the last alarm data without errors is output. Only the data may be output.

FIG. 7 is a block diagram showing a configuration of an ATM exchange according to a second embodiment of the present invention. An ATM switch 701 of this embodiment includes a 6.3M existing line interface unit 702 accommodating an existing line 706 of 6.3 Mbps, an ATM network interface unit 703 accommodating an ATM network 707, and an ATM switch for routing ATM cells. Unit 704 and control unit 70 for controlling the whole
5 is provided.

6.3M Existing Line Interface Unit 702
The data such as video and text input to the
The 3M existing line interface unit 702 terminates the line transmission frame, converts it into a 53-byte ATM cell, and sends it to the ATM switch unit 704. The ATM switch unit 704 transfers the ATM cell to a predetermined ATM network interface unit 703 based on the cell header of the input ATM cell.

The ATM cell input to the ATM network interface unit 703 is sent to the opposite AT via the ATM network 707.
The data is transferred to the M exchange and is routed to the 6.3M existing line on the opposite side.

FIG. 8 shows the detailed configuration of the 6.3M existing line interface unit 702. The illustrated 6.3M existing line interface unit 702 includes a line interface unit 7021, a frame termination unit 7022, a cell disassembly / assembly unit 7023, and an ATM switch interface unit 7024.
It has.

The data input from the 6.3M existing line 706 is subjected to optical / electrical conversion and transmission code conversion in the line interface unit 7021, and the frame of the data flow assigned to the 6.3M format in the next frame termination unit 7022. Frame synchronization and data extraction from the transmission frame are performed by the synchronization bit. The extracted data is converted by a cell disassembly / assembly unit 7023 into a 53-byte ATM cell to which a 5-byte cell header of VPI (virtual path number) and VCI (virtual channel number) is added. The ATM cell is input to the ATM switch unit 704 via the ATM switch interface unit 7024.

FIG. 9 is a block diagram showing a detailed configuration of the frame termination unit 7022.
022, a frame synchronization processing unit 70221, a data extraction unit 70222, a data switching unit 70223, a transmission frame mapping unit 70224, a test data generation unit 7022
5. A test data comparison unit 70226, which generates test data from a test data generation unit 70225 before starting operation of the ATM communication system or when a failure occurs during operation, and a line interface unit which is opposed via a set line. The test data transmitted through the opposite line termination unit, the test data returned via the opposite line termination unit, and the transmitted test data are compared by a test data comparison unit 70226. It is configured to detect the presence or absence of an abnormality in the line reaching the line termination unit.

Here, the test data generator 70225
It is configured to repeatedly generate fixed-length random data. The test data generated by the test data generation unit 70225 is input to the data switching unit 70223 from the data extraction unit 7022 before the start of operation of the ATM communication system or when a failure occurs during the operation of the ATM communication system.
By switching to the 25 side, the data switching unit 7
The data is input to the cell disassembly / assembly unit 7023 via the unit 0223. Then, the cell disassembly / assembly unit 7023 uses the ATM.
The data is converted into cells and transmitted to the line termination section of the line interface section of the opposite ATM switch.

The line termination unit of the line interface unit in the opposite ATM exchange sends the received test data back to the transmission source line termination unit 7022 via the reverse route.

On the other hand, test data comparing section 70226, which has received the test data returned via data switching section 70223, compares the test data transmitted by test data generating section 70225 with the returned test data. If the two do not match, it is determined that there is a line abnormality in the path leading to the line terminal of the line interface unit of the opposite ATM switch, and the control unit 705 of the ATM switch 701 is notified. However, if they match, the control unit 705 is notified that the line is normal.

Note that the data switching unit 70223 normally operates in response to a switching command from the control unit 705, and the data extraction unit 70222 and the transmission frame mapping unit 7022
4 is connected.

As described above, before the start of operation of the communication system or when a failure occurs during the operation, the test data generation unit 7022
5 generates test data, transmits the data via the set line to the line termination unit of the opposing line interface unit, and transmits the test data returned via the opposing line terminal unit and the transmitted test. By comparing the data with the test data comparing unit 70226, and detecting the presence or absence of an abnormality in the line reaching the line termination unit of the opposing line interface unit due to the difference, the end-to-end operation that cannot be realized by the OAM cell is performed. The normality of the communication path can be confirmed without connecting a tester or the like.

That is, as shown in FIG. 10, the range of confirming the line using the OAM cell is up to the cell disassembly / assembly unit, but by configuring as described above, it can be extended to the range up to the end of the frame. However, it is possible to confirm whether the line including the decellularized portion is normal or abnormal.

FIG. 11 is a block diagram showing the detailed structure of the cell disassembly / assembly unit 7023.
The assembling unit 7023 includes a multiplexing unit 70231, an AAL1 transmitting unit 70232, an AAL1 receiving unit 70234, and a separating unit 702.
35, and is configured to transmit and receive data at a fixed bit rate (CBR).

Conventionally, when multiplexing signals of a fixed bit rate of a plurality of lines, the band of the input line is, for example, 1.
In the case of 536 Kbps (24 TS), when only 384 Kbps (6 TS) of them is used, for example, 1.5
Multiplexing is performed for 36 Kbps. Therefore, there is a problem that the transmission efficiency (throughput) is low, the traffic of the entire system is increased, and it is difficult to increase the number of other lines.

In the case of a low speed (for example, 64 Kbp
s) Since it takes about 6 ms to make a cell, transmission delay becomes a problem in a line such as a telephone that requires immediacy, and it has been desired to make the cell faster.

The cell disassembly / assembly unit 7023 in FIG.
A function for solving such a problem is newly provided. That is, when the band to be used is smaller than the line band to be input, only the band to be used is multiplexed, so that the traffic of the system is reduced and the number of lines can be easily increased. Furthermore, by combining the bands used on a plurality of lines into cells as one block, the band used on one line is converted into cells faster than the cells. The details will be described below.

In FIG. 11, a multiplexing section 70231 receives data from the receiving lines Li1 to Lin, multiplexes the data, and outputs the multiplexed data. The next AAL1 transmitting section 70232 converts the multiplexed data into ITU-T I. According to the standard defined in 432, the cell is formed and output to the ATM switch interface unit 7024.

On the other hand, the ATM switch interface unit 7
ATM cells received from the AAL1 receiving unit 70
ITU-T I.234. In accordance with the criterion defined in 432, the cell is decellularized and separated by the demultiplexer 702355.
~ Lon and output.

FIG. 12 is a diagram showing the detailed structure of the cell disassembly / assembly unit 7023 on the assembling side.
The CBR data input from Lin is input to the multiplexing unit 7023
In the area assigned to each line of the buffer memory 70237 in the block No. 1, the data is written in the line number order by the write control unit 70238. Here, the band setting unit 70240
Are provided, and the start value and the end value of the time slot (TS) of the band used for each line are set in advance. FIG.
In the example of No. 2, the data of “line number 1” is TS = 1 to 6
It is set to use up to.

The read control unit 70239 reads out and multiplexes the CBR data from the reception lines Li1 to Lin stored in the buffer memory 70237 according to the set time slot value of each line. As a result, the CBR data A of “line number 1” is multiplexed into TS = 1 to 6 in one frame, and the AAL1 transmission unit 702
32, where ITU-TI. The cell is formed according to the standard specified in 432.

FIG. 13 shows that the receiving lines Li1 to Lin are 64
FIG. 7 is a diagram illustrating a state of multiplexing in the case of a Kbps band.
In the example shown here, the band setting in the band setting unit 70240 is set such that the first value of the TS is 1 and the last value of the
1, the leading value of TS for the next receiving line Li1 + 1 is 2,
Assuming that the final value is 2, data from the receiving line is stored in the buffer memory 70237 every 2TS, and further, AA
Connection setting unit 7024 in L1 transmission unit 70232
1 indicates a case where the start value of cell formation is 1 and the end value is 2 and cell formation is performed with 2 TSs as one block for each line. By doing so, it is possible to convert the cells into cells in half the time required to store the data for each TS.

FIG. 14 is a diagram showing a detailed configuration of the disassembly side of the cell disassembly / assembly unit 7023.

The cell received from the ATM exchange is AAL
1 receiving unit 70232 in ITU-T I. 432 is decelerated in accordance with the standard specified in 432. The decelerated data is written to the buffer memory 70245 in the separation unit 70235 by the write control unit 70246. In the band setting section 70248, the leading and last values of the TS of the band used for each line and the transmission band of the line are set in advance. Therefore, the read control unit 70247 reads the data stored in the buffer memory 70245 according to the time slot value of each line set in the band setting unit 70248, and separates the data.

For example, for the line number = 1, the used band is 384 Kbps (6TS) and the transmission band is 1.53
In the case of 6 Mbps (24 TS), since the used band is smaller than the transmission band, after reading the data of 6 TS, 18 TS minutes are obtained from the difference between the transmission band of the line number = 1 set in the band setting unit 70248 and the used band. To the data adding unit 7
0249 as fixed data, line number = 1
Is input to the selector 70250 corresponding to, and the fixed data for 18 TS is added to the data of 6 TS and output from the line with the line number = 1.

As a result, the band of the decelerated data can be controlled for each line.

The transmission efficiency (throughput) can be increased, and the traffic on the accommodated line is reduced, so that the line can be easily added. Further, by dividing data of two or more lines into one block and forming cells, it is possible to solve the problem of transmission delay in a line such as a telephone that requires immediacy.

Next, an embodiment will be described in which alarm information is transferred while minimizing deterioration of the transmission efficiency of user data.

FIG. 15 is a block diagram showing another embodiment of the line interface unit of the ATM exchange. The line interface unit of this embodiment is provided in the 6.3M existing line interface unit of FIG.

The line interface shown in FIG.
It comprises a 6.3M line frame terminating unit 171, an alarm detection / insertion unit 172, a cellization / decellulation unit 173, and an alarm information cell insertion / detection unit 174.

Data from the 6.3M existing line is transmitted to the 6.3M line frame termination unit 17 in the same manner as in the embodiment of FIG.
At 1, the line transmission frame is terminated, and the alarm detection / insertion unit 172 detects alarm information from specific bits of the frame, and separates the data into user data (payload) and alarm information data.

Only the user data is transferred to the cell / de-cell unit 173 at the next stage, and the VPI and VC set in advance are set.
I is added, and the packet is sent to the alarm information cell insertion / detection unit 174 as a 53-byte ATM cell. The alarm information cell insertion / detection section 174 adds an ATM header of a designated payload type value based on the alarm information from the alarm detection / insertion section 172, and outputs the alarm data with the added ATM header to the user data cell stream. At the position of the invalid cell, AT
The data is transferred to the M switch unit (corresponding to 704 in FIG. 7).

FIG. 16 is a diagram in which the input / output relationship between the alarm detection / insertion unit 172 and the alarm information cell insertion / detection unit 174 is extracted. Alarms A, B, The case where C is transferred is shown as an example.

Alarm from Line Side B and C are for alarm detection /
When the content of each alarm is monitored by the insertion unit 172, as shown in the time chart of FIG. 20A, an alarm change point pulse indicating that the content of the alarm has changed is detected / inserted. Output from the unit 172. In addition,
In FIG. 20, the changes in the alarms A, B, and C are indicated by pulses, but this does not indicate that the alarm itself is a pulse.

The change point pulse and the sound reports A, B, and C are transferred to the alarm information cell insertion / detection section 174, and as shown in the time chart of FIG. Alarm at time A. B. The state of C becomes a payload portion of the cell, and a predetermined payload type value and a preset VPI and VCI values are added to become an ATM cell.

This ATM cell is converted into a cell / decell unit 17.
3 is inserted at the position of the invalid cell according to the user data cell flow and the valid / invalid cell display signal, and transmitted to the ATM switch unit.

In this case, the number of alarm information cells transmitted at the alarm change point can be arbitrarily set in consideration of cell loss on the network from the viewpoint of system reliability.

FIG. 17 shows the input / output relationship of the line frame terminator 171, the alarm detector / inserter 172, and the celling / decelerating unit 173. FIG. 18 shows the data / alarm separation inside the alarm detector / inserter 172. 17 shows a detailed configuration of a unit 1721 and a data / alarm multiplexing unit 1722.

As shown in FIG. 18, on the output side of the data / alarm separation section 1721, there is provided an alarm change point extraction section 1723 for extracting a change point of the separated alarm data and outputting it as a change point pulse. . On the input side of the data / alarm multiplexing unit 1722, there is provided an alarm state updating unit 1724 for acquiring and updating the alarm data received from the opposite device when the change point pulse changes.

FIG. 19 shows the alarm information cell insertion / detection section 17.
4 is a block diagram showing a detailed configuration of an alarm cell generation unit 1741, a cell multiplexing unit 1742, and an alarm cell separation unit 174.
6. The alarm cell disassembly unit 1745 is provided, and the alarm state when the alarm change point pulse is “1” becomes the payload portion of the cell, and is set in advance to the predetermined payload type value generated by the ATM header generation unit 1743 VPI, VCI
The value is added by the ATM header multiplexing unit 1744, and is input to the cell multiplexing unit 174 as an ATM cell.

This ATM cell is converted into a cell / decell conversion unit 17.
In response to the user data cell flow and the valid / invalid cell display signal from No. 3, it is inserted at the head position of the invalid cell and transmitted to the ATM switch section.

On the other hand, cells input from the ATM switch unit are filtered by the VPI / VCI filter 1747 of the alarm cell separation unit 1746, and are separated into user cells and alarm cells. The separated alarm cells are separated in header by an ATM header separating unit 1748 of the alarm cell decomposing unit 1745 according to the alarm cell head display signal, and output as alarm data.

FIG. 21 shows the difference between the prior art and the present invention in the form of transfer of the alarm information cell. Conventionally, the alarm information is transferred to the celling / de-celling unit 173, and a designated ATM header is added so that the value of the alarm information is converted into a cell as it is. Therefore, as shown in FIG. Regardless of this, the cell is always transferred. However, in the actual continuous use mode, the alarm information hardly changes and changes only when an abnormality occurs or when maintenance and operation are necessary, so that the same value is transferred as a cell.

In the present invention, as shown in FIG. 21, a cell is generated only when the content of the alarm information changes.
The state is changed.

As a result, it is possible to transfer the alarm information while minimizing a decrease in the transmission efficiency of the user data.
It should be noted that such a transfer form of the alarm information can be similarly applied to the embodiments shown in FIG. 1 and FIG.

Next, when an ATM cell is transmitted / received on the ring transmission line, even if a failure occurs in the opposite device, the failure of the opposite device is detected by the own node at the ATM connection / packet connection level, and the failure information is transmitted to the terminal. FIG. 22 shows an embodiment of a line failure detection method capable of outputting
This will be described with reference to (a) and (b).

FIG. 22A is a block diagram showing a configuration of a transmission unit of a line interface unit of an ATM exchange, and FIG. 22B is a block diagram showing a configuration of a reception unit. FIG.
In (a), 240 is an input terminal to which line data is input. The line data receiving unit 241 receives line data from the input terminal 240 and outputs frame data to the payload data / alarm data separating unit 242 as in the embodiment of FIG.

Payload data / alarm data separation unit 24
2 separates the alarm data and the payload data from the received frame data. The error detection selection control circuit 243 selects a different formula for calculating the error detection code to be added to the alarm data depending on the up / down direction of the path.

That is, in the uplink communication path from the terminal (A) 267 to the terminal (B) 268 in the ring transmission path as shown in FIG. 23, the error detection code calculated by the equation for calculating the error code type (A) is used. Select On the other hand, terminal (B)
In the downstream communication path from the terminal 268 to the terminal (A) 267, the ATM exchange in the node 261 selects the error detection code calculated by the error code type (B) calculation formula.

As described above, by making the error detection code different between the upstream direction and the downstream direction of the bidirectional path, a failure occurs in the opposite node, and the cell transmitted from the own node is looped back and returned to the own node. Since the calculation formula of the error detection code is different, it is possible to detect that a failure has occurred in the node on the opposite side.

The error detection code adding sections 244a and 244b add an error detection code to the alarm data extracted and separated by the payload data / alarm data separation section 242, and output the result to the selection section 245. Here, the calculation formula of the error detection code differs between the error detection code adding units 244a and 244b.

In the selection section 245, the error code selection control section 2
The error detection code selected at 43 is selected and output to the cell / packet assembly unit 246. The cell / packet assembling unit 246 assembles the payload data and the alarm data to which the error detection code is added into cells / packets by the following method. In this case, the cellization is based on ITU TI
• According to AAL1 of 363.1.

The payload data and the alarm data are transmitted by one connection as shown in FIG. 4, and the transmission cell data and the alarm data are transmitted by another connection as shown in FIGS. 5 and 6. 247 forwards the assembled cell / packet to the receiver of the opposing node.

Next, the receiving section shown in FIG. 22B will be described.

First, the line failure detection unit 258 monitors a line failure at the entrance of the network transferred from the transmission unit via the network. When a network failure (line disconnection, loss of frame synchronization, etc.) occurs, a notification is sent to the line disconnection alarm output unit 256, and the terminal outputs an alarm.

The cell / packet deassembly section 249 deassembles the received cell / packet. In this case, the deceleration is performed according to the AAL of ITU-TI 363.1.
Follow 1

The underflow detection unit 250 monitors the presence or absence of an underflow in the buffer memory storing the received cells / packets, and notifies the line disconnection alarm output unit 256 if the underflow has continued for a predetermined time or more. I do.

The deassembled data is separated into a payload section and a warning section in a payload / warning data separation section 251, respectively, and the separated warning data is sent to error detection sections (1) 252a and (2) 252b. The presence / absence of an error is calculated based on the error detection code added by the error detection code adding section 244a or 244b on the transmission side.

Error detectors (1) 252a, (2) 252
b, the error detecting code adding section 244a or 2
The error is calculated by the error detection code calculation formula corresponding to the error detection code added at 44b. Error detection control unit 2
53 is an error detection circuit 252a or 25 depending on the set up / down direction of the bidirectional path, similarly to the transmission unit.
The selection unit 254 is instructed to select the result of 2b. The selection section 254 outputs the selection result to the payload data / alarm data synthesis section 255 and the line disconnection output control section 256.

Payload data / alarm data synthesizing section 25
5 outputs the combined data to the line disconnection alarm output unit 257. The line disconnection alarm output unit 257 performs an operation of outputting the line disconnection alarm output and the alarm data from the transmission side as they are.

In the line disconnection alarm output operation, when any one of the following three notifications is notified, or when there is no underflow error of the underflow detection unit 250 and a line disconnection alarm is sent from the transmission side. A) Notification of line failure from line failure detection unit 258 B) Notification of underflow from underflow detection unit 250 C) Notification of error from error detection units (1) 252a and (2) 252b.

On the other hand, the payload data / alarm data synthesizing unit 255 synthesizes the payload data and the alarm data separated by the demultiplexing unit 251 and outputs them to the line side from the line data output unit (not shown) as line data.

As described above, (1) AAL1 underflow, (2) addition of an error detection code to alarm data,
(3) By monitoring the detection of the line disconnection at the entrance of the network on the receiving side, it becomes possible to detect the line disconnection on the receiving side when an abnormality occurs in the middle vertical node line from the transmitting side to the receiving side. .

In particular, since the error detection code is made different depending on the up / down direction of the bidirectional path, in the network for transmitting the ATM cells on the ring transmission path, the opposite node becomes an obstacle and loopback is performed. Therefore, even when the data output by the own node is turned back, the error of the opposite node can be reliably detected, and in addition, the corresponding detection can be performed for each connection, and the failure of the opposite device can be output to the corresponding terminal. it can.

The method of differentiating the calculation formula of the error detection code between the upstream direction and the downstream direction can be applied to the embodiments shown in FIGS.

[0127]

As described above, according to the present invention, it is possible to detect a line fault without providing a complicated protocol for the transmitting and receiving devices.

Further, the normal or abnormal state of the line can be detected by extending the range between the communication path before the cell and the communication after the decell.

Further, it is possible to transfer the alarm information while minimizing the decrease in the transmission efficiency of the user data.

Further, even if a failure occurs in the opposite device in the ring network configuration, the failure of the opposite device can be detected by the own node at the ATM connection / packet connection level, and the failure information can be output to the terminal.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of an ATM communication system to which the present invention is applied.

FIG. 2 is a block diagram showing one embodiment of a detailed configuration of a transmission unit of a line interface unit provided in the ATM exchange shown in FIG. 1;

FIG. 3 is a block diagram showing one embodiment of a detailed configuration of a receiving unit of a line interface unit provided in the ATM exchange in FIG. 1;

FIG. 4 is a mapping diagram when alarm data is transmitted through one connection.

FIG. 5 is a mapping diagram of payload data when alarm data and payload data are transmitted through different connections.

FIG. 6 is a mapping diagram of alarm data when alarm data and payload data are transmitted through different connections.

FIG. 7 is a configuration diagram of an ATM exchange according to a second embodiment of the present invention.

FIG. 8 is a detailed configuration diagram of a 6.3M existing line interface unit in FIG. 7;

FIG. 9 is a detailed configuration diagram of a frame termination unit in FIG. 8;

FIG. 10 is an explanatory diagram showing a confirmable range of a communication path when the configuration in FIG. 9 is used.

FIG. 11 is a detailed configuration diagram of a cell disassembly / assembly unit.

FIG. 12 is a diagram showing a detailed configuration of an assembly side of a cell disassembly / assembly unit.

FIG. 13 is a diagram showing a state of multiplexing when receiving lines Li1 to Lin have a bandwidth of 64 Kbps.

FIG. 14 is a diagram showing a detailed configuration of a disassembly side of a cell disassembly / assembly unit.

FIG. 15 is a block diagram showing another embodiment of the line interface unit of the ATM exchange.

FIG. 16 is a diagram illustrating an input / output relationship between an alarm detection / insertion unit and an alarm information cell insertion / detection unit.

FIG. 17 is a diagram showing an input / output relationship of a line frame termination unit, an alarm detection / insertion unit, and a cellization / decellulation unit.

FIG. 18 is a detailed configuration diagram of a data / alarm separation unit and a data / alarm multiplexing unit inside the alarm detection / insertion unit.

FIG. 19 is a block diagram showing a detailed configuration of an alarm information cell insertion / detection unit.

FIG. 20 is a diagram showing a relationship between a point of change in alarm content and alarm data.

FIG. 21 is a diagram showing a difference between a transfer form of the alarm information cell according to the related art and the present invention.

FIG. 22 is a block diagram showing a configuration of a transmission unit and a reception unit of the line interface unit of the ATM exchange.

FIG. 23 is a diagram showing an example of a ring-shaped transmission line for transmitting an error detection code by making the uplink and downlink of a bidirectional path different from each other.

FIG. 24 is a diagram showing an example of a system in which nodes constituting an ATM network are connected in a ring shape.

FIG. 25 is a diagram showing that loopback is performed when a failure occurs in a relay node in a transmission path from a terminal (A) to a terminal (B).

FIG. 26 is a diagram showing that data output from the terminal (A) returns to the terminal (A) when a failure occurs in a node to which the terminal (B) is connected.

FIG. 27 is a block diagram showing a normal state and a switching state at the time of a transmission line failure in the related art.

FIG. 28 is a block diagram showing a configuration of various branch line examples.

FIG. 29 is a block diagram showing a configuration of a squelch table at the time of a node failure.

FIG. 30 is a block diagram showing a conventional configuration of a squelch table.

FIG. 31 is a block diagram showing a further conventional configuration of a squelch table.

[Explanation of symbols]

 1, 2 ATM switch 102 Payload data / alarm data separation unit 103 Error detection code adding unit 106 Line failure detection unit 107 Underflow detection unit 110 Error detection unit 111 Line disconnection alarm output unit 120 Alarm data 243 Error detection code selection control unit 1723 Alarm change point extraction unit 1724 Alarm status update unit 7022 Frame end unit 70225 Test data generation unit 70226 Test data comparison unit 70237 Buffer memory 70240 Band setting unit 70241 Connection setting unit

Claims (14)

[Claims] A method for detecting a line failure in a communication system for assembling data input from a line interface into data having a fixed bit length and transmitting the data to a destination, comprising: Is separated into a payload part and an alarm data part, an error detection code is added to the alarm data part, and the alarm data part with the error detection code added and the payload part are assembled into fixed length data of the same transmission unit. The fixed-length data received from the transmitting side is separated into a payload portion and an alarm data portion by the receiving device, and the presence or absence of an error of the separated alarm data portion is added to the alarm data portion. If there is no error in the alarm data part detected by the error detection code, the received payload part and the alarm data Is assembled into fixed length data of the same transmission unit and sent to the receiving end line interface. If there is an error in the alarm data part, it is determined that a line failure has occurred, and the line disconnection alarm data is sent to the receiving end line interface. A line failure detection method. 2. When the error in the alarm data portion continues over a predetermined value or more, the alarm data of the line disconnection is sent out. If the error is less than the set value, the last alarm data without error is sent to the receiving end line interface. 2. The method according to claim 1, wherein the signal is transmitted to the network. 3. An underflow of a receiving buffer for sequentially storing fixed-length data received from a transmitting side is detected, and if underflow is detected for a predetermined time or more, alarm data of line disconnection is transmitted to a receiving end line interface. 3. The method according to claim 1, wherein the signal is transmitted to the network. 4. The line fault detecting method according to claim 1, wherein the payload portion and the alarm data portion transmitted from the transmitting side device are transmitted by different connections. 5. The line fault detecting method according to claim 1, wherein the alarm data portion is transmitted to the receiving line interface only when the content of the alarm changes. 6. The method according to claim 1, wherein a formula for calculating an error detection code to be added to the alarm data portion is made different depending on the up / down direction of the bidirectional path of the payload portion.
6. The method for detecting a line fault according to claim 5. 7. A method for detecting a line failure in a communication system for assembling data input from a line interface into data having a fixed bit length and transmitting the data to a destination, wherein a transmission side device receives the data input from the line interface. An error detection code of a different calculation formula is added to the data in accordance with the up / down direction of the bidirectional path, and the data with the error detection code is assembled into fixed-length data and transmitted to the transmission destination. Waits for data reception on the downlink path from the device, and if data is received on the downlink path, determines whether the calculation formula of the error detection code of the received data corresponds to the downlink direction, If the data is transmitted by the transmitting device, the presence or absence of an error in the received data is detected by the error detection code added to the received data. If the transmission destination device returns to the transmission side device on the downlink path after the backup, the destination device is determined to have failed due to a mismatch in the error detection code calculation formula. The presence or absence of an error in the fixed-length data received from the base station is detected by the error detection code of the upward calculation formula added to the fixed-length data. If there is an error, it is determined that a line failure has occurred, and Transmitting the alarm data to the receiving end line interface. 8. A line fault detecting method in a communication system for assembling data input from a line interface into data having a fixed bit length and transmitting the data to a destination, wherein the data input from the line interface in a transmission side device is provided. Into a payload part and an alarm data part,
An error detection code of a different calculation formula is added to the alarm data portion according to the up / down direction of the bidirectional path, and the alarm data portion to which the error detection code is added and the payload portion are assembled into fixed length data. After transmitting to the transmission destination, wait for data reception from the transmission destination device on the downlink path, and if data is received on the downlink path, the calculation formula of the error detection code of the received data corresponds to the downlink direction. It is determined whether or not there is an error in the alarm data portion by the error detection code added to the alarm data portion in the received data, and if the data transmitted by the transmitting side device is When looping back and returning to the transmitting device on the downstream path, it is determined that a failure has occurred in the destination device due to a mismatch in the calculation formula of the error detection code, and In the device, the presence or absence of an error in the payload portion of the fixed-length data received from the transmitting side is detected by the error detection code of the upward calculation formula added to the payload portion, and if there is an error, a line failure has occurred. A line failure detection method comprising: determining that the line has been disconnected; and sending line disconnection alarm data to a line interface at the receiving end. 9. An underflow in a reception buffer for sequentially storing fixed-length data received from a transmission side is detected, and if underflow is detected for a predetermined time or more, alarm data of line disconnection is transmitted to a reception end line interface. 9. The method for detecting a line fault according to claim 8, wherein 10. The line fault detecting method according to claim 8, wherein the payload portion and the alarm data portion transmitted from the transmitting side device are transmitted by different connections. 11. A transmission device in a communication system for assembling data input from a line interface into data having a fixed bit length and transmitting the data to a destination, wherein the transmission device on the transmission side receives the input from the line interface. Means for separating data into a payload part and an alarm data part; means for adding an error detection code to the separated alarm data part; and an alarm data part to which an error detection code is added and the payload part in the same transmission unit. Means for assembling into fixed-length data and transmitting the same to a destination, wherein the receiving-side transmitting device separates the fixed-length data received from the transmitting-side transmitting device into a payload portion and an alarm data portion; The presence or absence of an error in the alarm data portion is detected by the error detection code added to the alarm data portion, and no error is detected in the alarm data portion. If so, the received payload portion and the alarm data portion are assembled into fixed length data of the same transmission unit and transmitted to the receiving end line interface, and if there is an error in the alarm data portion, it is determined that a line failure has occurred, Means for transmitting alarm data of line disconnection to the line interface of the receiving end. 12. A line fault detecting method in a communication system for assembling data input from a line interface into data having a fixed bit length and transmitting the data to a destination, wherein test data is generated at a line terminal of a line interface. Unit and a test data comparison unit, and generates a test data from the test data generation unit before the start of operation of the communication system or when a failure occurs during the operation, and a line interface unit that is opposed via a set line. The test data transmitted to the line termination unit, and the test data returned via the opposing line termination unit and the transmitted test data are compared by the test data comparison unit. A method for detecting a line failure, characterized by detecting the presence or absence of an abnormality in a line reaching a line termination unit. 13. The image processing apparatus according to claim 1, wherein the line interface unit includes:
13. The method according to claim 12, wherein the method is provided in an ATM exchange for inputting and outputting non-ATM data such as voice. 14. An alarm information transfer method in a communication system for assembling data input from a line interface into data having a fixed bit length and transmitting the data to a destination, the alarm information indicating a line failure detected at a receiving end. A method of transmitting alarm information, comprising: assembling data of a fixed bit length only when the content of an alarm changes, and transmitting the data to an opposite destination when transmitting the alarm to an opposite device.