KR100195057B1 - Maintenance cell processing device of ATM network system - Google Patents

Abstract

The present invention relates to an OAM processing apparatus of an ATM-MSS, comprising: first and second receivers (10,60) for inputting a cell stream; First and second extractors (20 and 70) for extracting and analyzing OAM cells in the cell stream and separating them by function, and extracting user cells of the OAM processing target; First and second processing units (30, 80) for OAM processing the extracted user cells by the extracted OAM cells and generating OAM cells as a result; First and second inserting units 40 and 90 for inserting the generated OAM cells and OAM-processed user cells into the user cell stream bypassed from the first and second extracting units 10 and 60; The first and second transmitters 50 and 100 transmit the inserted cell stream, extract the OAM cell and the user cell of the connection requested by the user, and perform OAM processing, and transmit the generated OAM cell and the user cell. By inserting and outputting the cell flow, the OAM process can be performed more effectively.

Description

Maintenance cell processing device of ATM network system

1 is an overall configuration diagram of an AMT network system.

2 is a detailed configuration diagram of the AT network system.

3 is a format diagram showing the structure of an ATM cell.

4 is a block diagram of a maintenance cell processing apparatus of an AMT network system according to the present invention.

* Explanation of symbols for main parts of the drawings

10: first receiving unit 20: first extracting unit

30: first processing unit 31: first operation monitoring unit

32: first continuous signal detector 33: first loopback checker

34: first error bit detection unit 40: first insertion unit

50: first transmitter 60: second receiver

70: second extraction unit 80: second processing unit

81: second operation monitoring unit 82: second continuous signal detection unit

83: second loopback checker 84: second error bit detector

90: second insertion unit 100: second transmission unit

The present invention relates to a matching device of an ATM network system required for transmitting an ATM cell input from a subscriber or another node to a switching unit, and in particular, an operation received from a subscriber or a switching unit (OAM: Operation And Manintenance). The present invention relates to a maintenance cell processing apparatus of an AT network system for processing a cell.

Due to the rapid development of the information society, B-ISDN emerged as the next-generation communication network due to the rapid increase in user's communication service demand.In the B-ISDN, asynchronous so as to accommodate various narrow and wide bandwidth services regardless of band and speed The ATM method, which is a delivery mode, is used as a basic delivery means. However, since it takes a lot of investment and time to build ATM network, researches on local information communication network (MAN) that can easily develop into B-ISDN while satisfying the current user's demand are being actively conducted.

Here, 'ATM' (Asynchronous Transfer Mode) refers to a method of asynchronous high speed transmission by dividing information to be transmitted into short packet units having a fixed length called a cell. Metropolitan Area Network is a network system built in the city or city. It is composed of a multimedia system that can handle tens of thousands of people in a 50km diameter area and handle not only text but also voice and video.

Accordingly, 'ATM-MAN', which adopts ATM technology, is being developed to preserve the consistency with B-ISDN, which will be built in earnest in the future. And ATM-MSS (ATM-MAN Switching System) refers to the MAN switching system that employs the ATM method, ie ATM network system.

1 is an overall configuration diagram of an ATM network system. The ATM network system includes a Remote Switching Node (RSN) 2-1 to 2-n and a Hub Switching Node (HSN). 1) and Element Management System (EMS).

The connection between the hub switch node (HSN: 1) and the remote switch node (RSN: 2-1 to 2-n) is equivalent to the HSN (1) and RSN (2-1 to 2-n) as shown in FIG. There are a star topology method in which n) is connected point-to-point, respectively, and a ring topology method connected by dual rings having different transmission directions as shown in (b) of FIG. 1. In this case, the star topology scheme has dualized the link so that it can be recovered immediately in the event of a link failure. In the ring topology scheme, each node shares a dual link so that a node receiving a cell from a link in one direction checks the address of the cell. If the cell is delivered to itself, it is received. If the cell is delivered to another node, it is delivered to the next node.

And the remote switching node (RSN: 2-1 to 2-n) collects the traffic input from the subscriber and transmits it to the HSN (1) or transmits the traffic input from the HSN (1) to the subscriber, the same RSN ATM cell exchange function between subscribers connected to the terminal, circuit emulation, and frame relay services are provided. It also multiplexes and centralizes the traffic input from the subscriber and demultiplexes the traffic to be delivered to the subscriber.

The hub switching node (HSN: 1) is responsible for ATM cell switching and multiplexing demultiplexing, traffic centralization, and cell switching functions with other ATM or ATM-MSS exchanges between RSNs, and with the EMS (3) access and operator matching functions. And perform a subscriber connection test function.

And the element management system (EMS: 3) is responsible for the operation and maintenance of the AT network system.

Subscriber access link uses DS3 class and DS1E class and exchanges information using frame type that map ATM cell to frame type used in existing asynchronous digital network.

2 is a detailed configuration diagram of an ATM network system showing a connection relationship between a hub switch node (HSN) and a remote switch node (RSN). In the ATM network system, as shown in FIG. 2, a plurality of RSNs 2-1 to 2-n are connected to the HSN 1 through node matching modules 7-1, 7-2, and 7-3. The EMS 3 is connected to the HSN 1 through the node management module 6-2. Each RSN 2-1 includes a plurality of subscriber matching modules 4-1 and 4-2, a cell switching module 5-1, a node management module 6-1, and a node matching module 7-1. The HSN 1 includes a plurality of node matching modules 7-2 and 7-3, a plurality of switch matching modules 8-1 and 8-2, a cell switching module 5-2, and a node. It consists of a management module 6-2.

Cell switching module 5-1 of RSN is connected to subscriber module 4-1, 4-2, node matching module 7-1, and node management module 6-1. Cell switching is performed according to the routing tag, and subscriber matching modules 4-1 and 4-2 interface subscribers of DS3 or DS1E speed. HSN cell switching module (5-2) is a node matching module (7-2, 7-3), switch matching module (8-1, 8-2), node management module (6-2) is connected to each module Switch cells input from

3 is a format diagram showing the structure of the data flow between modules of an ATM network system, that is, the structure of an ATM cell. An ATM cell composed of a total of 53 bytes includes a 5-byte header and a 48-byte payload. In the header structure of 5 bytes, the first byte consists of 4 bits of Generic Flow Control (GFC) and 4 bits of Virtual Path Identifier (VPI). The byte consists of a 4-bit Virtual Path Identifier (VPI) and a 4-bit Virtual Channel Identifier (VCI). The third byte consists of an 8-bit Virtual Channel Identifier (VCI). Consists of a 4-bit Virtual Channel Identifier (VCI), a 3-bit Payload Type Identifier (PTI) and a 1-bit Cell Loss Priority (CLP). It consists of Header Error Control (HEC).

Here, the ATM cell is largely divided into a user cell and an IPC cell. The user cell refers to a cell intended to be output from each subscriber and transmitted to another subscriber. An IPC (Inter-Processor Communication) cell is mainly a node management module 6-1 or 6-2. It refers to a cell containing a kind of management message for the purpose of managing the message, the node matching module, the exchange matching module and the subscriber matching module received the management message sent to the node management module (6-1, 6-2) It also means. IPC cells are generated in the processor of each module.

The management message periodically searches the board state of other modules and processes the failure when it is determined that a failure has occurred, and detects the degradation of performance to occur in the future to prevent failure and analyzes the performance to evaluate the performance of the entire network. Take appropriate action to drive performance improvements, while setting and releasing point-to-point paths and channels.

These IPC cells enter the matching modules 4-1, 4-2, 7-1, 7-2, 7-3, 8-1, 8-2 from the node management modules 6-1, 6-2. Then, the processor of the matching module analyzes the IPC cell, forms an OAM cell for performing the maintenance and maintenance of the module, and inserts it into the flow of cells flowing in the system.

Accordingly, each of the matching modules needs to extract and process an OAM cell and a user cell of a corresponding connection that should perform the OAM from a cell stream flowing in the system, and also the OAM cell generated as a result of the OAM processing and the It is necessary to insert the user cell after the OAM processing is completed and insert it into the cell flow.

Accordingly, in order to satisfy the above necessity, the present invention provides an OAM cell which extracts an OAM cell from a received cell flow and inserts the OAM cell generated as a result of the OAM processing into a transmitting cell flow. Its purpose is to provide an OAM calculation processor.

OAM cell processing apparatus of the ATM network system of the present invention for achieving the above object, the first receiver for inputting the multiplexed cell stream from the subscriber or another node, and the OAM cell receiving the cell stream from the first receiver Extracts, analyzes, and separates each function by function, and extracts the user cell of the OAM processing target, OAM processing the extracted user cell by the extracted OAM cell, and based on the processing result, the OAM cell. A first processing unit for generating a first input unit, the first insertion unit for receiving the generated OAM cell and the OAM processing user cell is inserted into the user cell stream bypassed from the first extraction unit, the cell from the first cell insertion unit A first transmitter for receiving the signal and transmitting the cell stream to the cell switching module; a second receiver for inputting the multiplexed cell stream from the cell switching module; and a cell stream from the second receiver. A second extraction unit which extracts and analyzes the OAM cells and extracts them by function, extracts the user cells of the OAM processing target, OAM processes the extracted user cells by the extracted OAM cells, and processes the results. A second processing unit for generating an OAM cell based on the input, a second inserting unit for receiving the generated OAM cell and the OAM processed user cell and inserting it into a user cell stream bypassed from the second extracting unit and inserting the second cell And a second transmitter for receiving a cell from the unit and transmitting the cell to the cell switching module.

According to the apparatus of the present invention, an OAM cell and a corresponding user cell are extracted from the flow of the received cell and OAM processing, and the OAM cell and the user cell generated as a result of the OAM processing are inserted into a transmitting cell flow and transmitted.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 is a block diagram of an OAM cell processing apparatus of an ATM network system according to the present invention. As shown in FIG. 4, the apparatus of the present invention extracts an OAM cell by receiving a cell stream from the first receiver 10 and the first receiver 10 for inputting a multiplexed cell stream from a subscriber or another node. The first extraction unit 20 for analyzing and separating the functions by function, and extracting the user cell of the OAM processing target, OAM processing the extracted user cell by the extracted OAM cell, and based on the processing result, OAM The first processor 30 for generating a cell, the first inserter 40 for receiving the generated OAM cell and the OAM processed user cell and inserting the cell into the bypassed user cell stream from the first extractor 20. The first transmitter 50 receives the cell from the first inserter 40 and transmits the cell stream to the cell switching module (5-1 of FIG. 2) and the multiplexed cell stream from the cell switching module 5-1. Receiving the second receiver 60, the cell strip from the second receiver 60 A second extraction unit 70 for extracting and analyzing the OAM cell to extract and analyze the function, and extracts the user cell of the OAM processing target, OAM processing the extracted user cell by the extracted OAM cell, Based on the processing result, the second processor 80 generating the OAM cell, the generated OAM cell, and the OAM processed user cell are received and inserted into the user cell stream bypassed from the second extractor 70. The second inserter 90 and the second inserter 90 are configured to receive a cell and transmit it to a subscriber or another node 100.

Here, the first processor 30 reads the OAM cell and the user cell of the corresponding function from the first extractor 20 to perform transmission coefficients or error detection for each connection of the extracted user cell, and as a result Based on the first operation monitoring unit 31 for generating an OAM cell and the OAM cell and the user cell of the corresponding function is read from the first extraction unit 20, the transmission of the user cell for a predetermined time for the connection is performed. If it does not occur, the OAM cell is read from the first continuous signal detector 32 and the first extractor 20 which generates the OAM cell, and the OAM cell is checked to check whether there is an abnormal connection with the set receiving node. After generating the cell and transmitting it to the receiving node through the second inserting unit 90, the loopbacked OAM cell is received again through the first extracting unit 20, and the received OAM cell is compared with the received OAM cell. First loop check unit 33, and the first weight The OAM cell is input from the output unit 20, the error bit is checked, and the cell in which the error is detected is discarded and transmitted to the first operation monitoring unit 31 or the first continuous signal detection unit 32, and the first operation monitoring. The first error bit detector 34 which receives the OAM cell from the unit 31 or the first continuous signal detector 32, generates an error detection bit, transmits the error detection bit to the first inserter 40 in addition to the corresponding part of the cell. It consists of.

In addition, the second processing unit 80 reads the OAM cell and the user cell of the corresponding function from the second extracting unit 70 and performs transmission coefficients or error detection for each connection of the extracted user cell, and outputs the result. Based on the second operation monitoring unit 81 that generates the OAM cell and the OAM cell and the user cell of the corresponding function from the second extraction unit 70, transmission of the user cell occurs for a predetermined time for the corresponding connection. If not, the OAM cell of the corresponding function is read from the second continuous signal detection unit 82 and the second extraction unit 70 generating the OAM cell, and to check whether there is an abnormal connection with the set cell switching module side. After generating the OAM cell and transmitting it to the cell switching module through the first inserting unit 40, the OAM cell is received again from the cell switching module through the second extracting unit 70, and the received OAM cell is received. Second base to compare OAM cells The OAM cell from the second checker 83 and the second extractor 70 and check the error bit to discard the cell in which the error is detected, and the second operation monitor 81 or the second continuous signal detector. And transmits an OAM cell from the second operation monitoring unit 81 or the second continuous signal detection unit 82, generates an error detection bit, and adds the error detection bit to the corresponding portion of the cell. A second error bit detector 84 for transmitting

Next, the operation and effects of the present invention configured as described above will be described in detail.

First of all, the functions of OAM (Operation And Manintenance) include PM (Performance Management), CC (Continue Check) and Loopback.

The first PM function is to monitor the performance of the number of cells transmitted and the error detection during cell transmission for the user cell stream per connection.

Second, the CC function is to ensure the continuous flow of the cell by transmitting a CC OAM cell when the user cell for each connection does not pass for a predetermined time.

Third, the loopback function is to verify the connection status of the connection and check the cell processing delay of the network.

Each of the above OAM function requests is executed by the EMS and the designated master and slave nodes.

In addition, there is a Fault Managemant (FM) function. If a node in the serving network fails at the physical layer or the ATM layer, the node informs the other node that may be affected by the fault. You must inform. In other words, if a service cannot be supported for all VPC / VCC connections accommodated in the port, the function creates and transmits an FM cell every 1 second for all VPC / VCCs in the port.

At this time, the CPU provides information about the connection to transmit the FM cell, that is, the defect, the cause and location, the destination to which the OAM cell is transmitted, and writes it in the form of a cell to the memory, and then transmits the cell together with the start position of the memory to the OAM processing apparatus. It will pass the instructions. Even when the PM cell is received, the device notifies the CPU of the PM cell reception and delivers it through the memory. The memory not shown here is a place for storing data necessary for inserting / extracting cells and performing OAM functions. The memory may be extracted from a cell stream and recorded in a memory, and a cell requested from the memory may be read and inserted into a user cell stream. . That is, by using the OAM dedicated memory, by sending and receiving data with the CPU through this memory can receive the data required to perform the OAM function and report the result of the OAM function execution to the CPU. The memory is configured to separate and manage memory for cell insertion / extraction function and OAM function, and to store 53 bytes of complete OAM cell data per connection.

In the memory arrangement, the first two cell areas are used for receiving and transmitting active / diacbit cells as common use areas. The next active maximum capacity stores the 32-cell monitoring PM OAM cell information and reporting PM OAM cell, then stores the 32-cell CC information, and stores the next 8 cell-sized loopback-related OAM cells. Finally, it stores information about FM. Other memory spaces are intended for use by other devices.

At this time, the memory interface unit is set aside, and the bus is output by outputting a control signal for preventing a collision caused by a simultaneous memory access request between the CPU and two functional blocks (i.e., the first and second operational monitoring units and the first and second continuous signal detectors). You can approve.

In addition, the CPU (not shown) accesses the memory for providing information and results for the OAM, and prevents signal collision with the functional blocks (first and second operational monitoring units and first and second continuous signal detection units) and efficiently. In order to operate the memory, memory access is mainly performed by a function block, and the arbitration unit is externally set so that the memory access permission can be performed. That is, the memory can be accessed only while the functional device is not accessing the memory.

In this case, the CPU interface unit may be set aside to establish a interface relationship compatible with an external CPU in order to perform functions required by the CPU, that is, performing OAM and inserting and extracting arbitrary connection cells.

In FIG. 4, the controller 110 controls the overall control function of the OAM processing apparatus of the present invention under the control of the CPU, and generates control signals necessary for interfacing with other external function elements. That is, the controller 110 generates a control signal for recognizing reception of a cell by inspecting a start of cell (SOC) of an external interface, and generates a control signal when receiving an OAM cell to operate another function module. In addition, the controller 110 includes a control function for maintaining and managing cell synchronization from cell synchronization loss that may occur when processing one cell among internal functional blocks, and in a cell stream or node of a connection that does not perform OAM. Bypass the OAM cells that are not processed.

As shown in FIG. 4, the input / output interface for input / output of a cell includes four input / output ports for the first and second receivers 10 and 60 and the first and second transmitters 50 and 100. Accordingly, the ATM cell is transmitted and received using the cell synchronization signal and the control signal.

Each transmit / receive port 10, 50, 60, 100 has a FIFO to operate independently of the inside of the device. In addition, each transmit / receive port (10, 50, 60, 100) has a register indicating the state of the port to control traffic according to the FIFO and the change of the state of the port, The register indicating the status has a bit indicating that the FIFO is full and used as a control signal for inputting a cell from the outside, and the register indicating the status of the transmission ports 50 and 100 can receive an enable signal from the outside. In addition to outputting a control signal to output a cell only when an overflow occurs in the FIFO, an interrupt is generated. At this time, the data widths transmitted and received at the transmission and reception ports 10, 50, 60, and 100 are 8 bits in parallel.

The extractors 20 and 70 receiving the cell streams from the receivers 10 and 60 analyze the header 4 bytes for all cells and select OAM cells belonging to a connection and user cells of the connection to perform the OAM function. The extracted OAM cell checks the value of the first byte of the payload again, identifies the type of OAM cell, and stores it in memory for transmission to the corresponding function block. The user cell is also sent to the block to perform the OAM.

That is, when the first byte value of the extracted OAM cell payload is '0001', it is determined as an FM OAM cell and transmitted to the CPU. If it is '0100', it is determined as a CC OAM cell and transmitted to the continuous signal detectors 32 and 82, and '1000'. ', It is determined that the loopback OAM cell is transmitted to the loop checker (33, 83).

The extracted OAM cell belonging to an arbitrary connection should be written to the memory area and inform the CPU of the cell extraction so that the CPU can read it. The error bit detection units 34 and 84 which check the error detection bits (for example, CRC-10) for the payloads of all the received OAM cells discard all of the cells in which the error has occurred without performing the OAM. In addition, for the OAM cell generated as a result of the OAM process, CRC-10 is calculated to generate one completed OAM cell in addition to the corresponding part of the payload, that is, the error detection bit.

The operation monitoring units 31 and 81 are designated as the master node and the slate node, and the node designated as the master performs PM calculation on the user cell for each connection inputted from the extracting units 20 and 70 to the OAM cell. The node designated as the slave performs the same calculation as the master for the connection, stores the result in memory and transmits the result to the master so that the master compares the two data values.

The continuous signal detectors 32 and 83 transmit a CC OAM cell when a user cell for each connection does not pass for a predetermined time or more. The continuous signal detection unit 32 and 83 transmits a CC OAM cell. May require execution. Like the PM function, it is designated and operated as a master node and a slave node. The node designated as the master has a timer and transmits a CC OAM cell to the inserter 40 or 90 by an internal interrupt when a limited time elapses.

In other words, the timer is operated by a reference clock and has one timer for each connection, and is implemented to increase at regular time intervals. Whenever a user cell of the connection arrives, the timer for each connection is set to '0' and driven again.

At this time, if the timer passes the specified time, an internal interrupt is generated and the CC OAM cell is transmitted. If the user cell is received within the specified time, the timer is set to '0' to start the timer again from the beginning.

Like a master node, if a node designated as a slave arrives within the time limit of the user cell or CC OAM cell of the corresponding connection, the timer of the slave is set to '0'. Otherwise, a continuity failure occurs for the connection. Send a 'FERF OAM' cell to inform.

The loopback checker 33 and 83 are divided into a master node and a slave node similarly to the operation monitors 31 and 81 or the continuous signal detectors 32 and 82. In order to check whether there is a loopback OAM cell to the transmitting node, the transmitting node receives the cell and transmits it back to the receiving node to check whether there is an abnormal connection.

As described above, the user cell that has completed the corresponding OAM process and the generated OAM cell are transmitted to the inserting units 40 and 90, so that the inserting units 40 and 90 transmit the cells to the extracting units 20 and 70. Insert into the bypassed cell stream. Cell insertion is based on the principle that one complete OAM cell and user cell stored in the memory are read and inserted into an empty time slot (one cell transmission period) when the user cell is not transmitted in the user stream. The start address of the cell to be transferred is received from the CPU or OAM function device, and the cell is read from the memory and inserted into the cell stream.

In order to prevent cell loss that may occur during the cell insertion process, that is, the cell insertion process that may occur when there is no empty time slot, a buffer of about 3 cells may be placed in the device.

The apparatus according to the present invention may be divided into a case of receiving a cell from a matching module of a subscriber or another node and a case of receiving a cell from a cell switching module.

First, when receiving a cell from the matching module of the subscriber or another node, first, the cell stream is input from the first receiver 10 and transmitted to the first extractor 20, so that the first extractor 20 receives the OAM. The cell and the corresponding user cell requiring OAM processing are extracted and sent to the first processor 30, and the remaining cells are bypassed.

The OAM cell and the user cell OAM-processed by the first processor 30 are input to the first inserter 40 and inserted into the bypassed cell stream, and then the cell switching module through the first transmitter 50. Is sent to.

On the other hand, when receiving a cell from the cell switching module, by first transmitting the cell stream from the second receiver 60 to the second extraction unit 70, the second extractor 70 is OAM cell and OAM processing Extracts the corresponding user cell and sends the second processing unit 80 to bypass the remaining cells.

The OAM cell and the user cell OAM processed by the second processor 80 are input to the second inserter 90 and inserted into the bypassed cell stream, and then the subscriber or another node through the second transmitter 100. Is sent to.

As described above, the apparatus of the present invention extracts an OAM cell and a user cell of a connection requested by a user, performs OAM processing, and inserts and outputs the resulting OAM cell ALC user cell into a transmitting cell flow. There is an effect that can be performed more effectively than the treatment.

Claims (3)

After extracting the maintenance (OAM) cell from the cell received from the subscriber or another node and transmitting it to the cell switching module, and extracting the maintenance (OAM) cell from the cell received from the cell switching module, the subscriber and the other In the matching device of an ATM network system transmitting to a node, the OAM cell is extracted by receiving a cell stream from the first receiver 10 and the first receiver 10 that receives the popularized cell stream from the subscriber or another node. The first extraction unit 20 for analyzing and separating the functions by function, and extracting the user cell of the OAM processing target, OAM processing the extracted user cell by the extracted OAM cell, and based on the processing result, OAM A first processing unit 30 for generating a cell, the first OAM cell and the first receiving the OAM processing user cell is received and inserted into the user cell stream bypassed from the first extraction unit 20 An inserter 40, a first transmitter 50 that receives a cell from the first inserter 40 and transmits the cell to the cell switching module, and a second receiver 60 that receives a multiplexed cell stream from the cell switching module. ), Receiving the cell stream from the second receiver 60, extracting and analyzing the OAM cells, and separating them by function, and extracting the user cells of the OAM processing target, the second extracting unit 70 and the extracted OAM cells. OAM processing the extracted user cell by the second processing unit 80 to generate an OAM cell based on the processing result, the generated OAM cell and the OAM processing user cell received the second extraction unit ( A second insertion unit 90 for inserting the user cell stream bypassed from 70 and the second transmission unit 100 for receiving a cell from the second insertion unit 90 and transmitting it to the subscriber or another node. Maintenance Cell Treatment of TEM Network System Device. The method of claim 1, wherein the first processor 30 reads an OAM cell and a user cell of a corresponding function from the first extractor 20 to perform transmission coefficients or error detection for each connection of the extracted user cell. The OAM cell and the user cell of the corresponding function are read from the first operation monitoring unit 31 and the first extraction unit 20 based on the result, and the user is connected to the connection for a predetermined time. If no cell transmission occurs, the OAM cell of the corresponding function is read from the first continuous signal detector 32 and the first extractor 20, which generates an OAM cell, to check whether there is an abnormal connection with the set receiving node. To this end, after generating an OAM cell and transmitting it to the receiving node through the second inserting unit 90, the loopbacked OAM cell is received again through the first extracting unit 20, and the received OAM cell is received. A first loop checker 33 for comparing the OAM cells, and a phase The OAM cell is input from the first extraction unit 20, the error bit is inspected, and the cell in which the error is detected is discarded and transmitted to the first operation monitoring unit 31 or the first continuous signal detection unit 32. 1 The first error bit detection unit receiving the OAM cell from the operation monitoring unit 31 or the first continuous signal detection unit 32 to generate an error detection bit, and transmit the generated error detection bit to the first insertion unit 40 in addition to the corresponding part of the cell. Maintenance cell processing apparatus of the AT network system, characterized in that consisting of (34). The method of claim 1, wherein the second processor 80 reads an OAM cell and a user cell of a corresponding function from the second extractor 70 and performs transmission coefficients or error detection for each connection of the extracted user cell. The second operation monitoring unit 81 generates an OAM cell based on the result, and the OAM cell and the user cell of the corresponding function are read from the second extraction unit 70 and the user is connected to the connection for a predetermined time. If no cell transmission occurs, the OAM cell of the corresponding function is read from the second continuous signal detector 82 and the second extractor 70 which generates the OAM cell, and there is an abnormal connection with the set cell switching module side. In order to check, the OAM cell is generated and transmitted to the cell switching module through the first inserting unit 40, and then the OAM cell is received again from the cell switching module through the second extracting unit 70, and the transmission is performed. Compare one OAM cell with a received OAM cell The second loop checker 83 receives the OAM cell from the second extractor 70, checks the error bit, discards the cell in which the error is detected, and discards the second operation monitor 81 or the second. Transmits to the continuous signal detector 82, receives the OAM cell from the second operation monitor 81 or the second continuous signal detector 82, generates an error detection bit, and adds the second detection bit to the corresponding part of the cell. And a second error bit detection unit (84) for transmitting to the unit (90).