KR20030016067A - Link diagnosis method of Asynchronous Transfer Mode switch system - Google Patents

Abstract

PURPOSE: A method of diagnosing a link of an ATM system is provided to estimate a section and a cause of fault by self-diagnosing when a segment loopback cell does not return to a switch, and to inform a system manager of an estimated result, thereby increasing system reliability. CONSTITUTION: An OAM processor transmits a segment loopback cell to a destination path(S501). If the segment loopback cell does not return, the OAM processor disables a segment loopback mode(S503), and converts an input SONET framer into a loopback mode. The OAM processor generates an input framer loopback cell to transmit the cell to the input SONET framer, to diagnose whether a fault is caused by an internal system problem or an external system problem(S504). If the input framer loopback cell returns, the OAM processor diagnoses the fault as the external system problem(S505). If the input framer loopback cell does not return, the OAM processor diagnoses the fault as the internal system problem(S509).

Description

Link diagnosis method of asynchronous transfer mode switch system

The present invention relates to a method for diagnosing a link in an asynchronous transfer mode (ATM) switch system, and in particular, by applying an ATM switch, diagnosing a link state for each section in a system to effectively find a part where an abnormality has occurred, thereby ensuring reliability of the system. The present invention relates to a link diagnosis method of an asynchronous transfer mode switch system.

The features of the Asynchronous Transfer Mode Layer (ATM Layer) are Asynchronous Transfer Mode / Cell and Virtual Path / Channel. In this asynchronous transmission mode, since multiplexing is performed by a block of fixed length (for example, a 5 byte header and a 48 byte information field) called a cell, the bandwidth of a communication channel (connection) is changed in time according to the number of communication of the cell. You can. In addition, the asynchronous transmission mode layer is composed of a virtual path (VP) that can vary the bandwidth capacity and a virtual channel (VC) that actually carries data on a virtual path established between user terminals.

In a network based on asynchronous transmission mode, operation, administration and maintenance (OAM) is divided into five hierarchical levels related to information flows, which are represented by 'F1' to 'F5'. In other words, the OAM of B-ISDN based on asynchronous transmission mode is divided into three categories: Performance Management, Fault Management, and Equipment Testing. This OAM function is defined on the management plane (M-Plane).

For this function, divide the network into five OAM levels and mark them as F1-F5. F1 is the playback section level, F2 is the digital section level, F3 is the OAM flow of the physical layer of the transmission path level, F4 is the virtual path (VP) level, F5 is the OAM of the ATM layer that handles the OAM of the virtual channel (VC). Flow. Here, the F1-F3 flow is performed in the sonnet framer block, and the F4 or F5 flow is processed in the OAM processing block.

1 is a diagram illustrating an F1-F3 flow, wherein the F1 (STE) flow is a repeater section level between sonnet section terminating equipment (STE) 101 and 111, and transmits a signal at a bit level by a transmission medium. The F2 (LTE) flow is the digital section level between the Sonnet Line Terminating Equipment (LTE) 102 and 112, which is transmitted between the network elements where the transmission frame terminates and is a continuous bit. Provides assembly and disassembly of flows or bite flows.

F3 (PTE) flow is a transmission path level between Sonnet Path Terminating Equipment (PTE) (103,113), which is transmitted between network elements where the cell flow is physically terminated, and uses cell synchronization, header error control, and empty cells. To adjust the cell speed. And, the upper ATE (104, 114) is an asynchronous transmission mode termination equipment.

(A) and (b) of FIG. 2 define F4 and F5 flows in an OAM cell format, and the F4 and F5 flows are divided into an ATM cell header and an ATM cell payload, and an ATM cell header. Contains generic flow control (GFC), VPI / VCI, payload type (PT), cell loss priority (CLP), and header error control (HEC) information, and ATM cell payload defines OAM cell type, function type, and function. Fields (Functions-Specific Fields), including CRC-10 information.

Here, GFC controls the traffic flow to mitigate short-term overload conditions, VPI / VCI is the routing bit, PT is the payload type, CLP defines the cell loss priority, and HEC is the cell Used in the physical layer for bit rare detection and modification of headers. The OAM cell type indicates types of OAM management functions such as fault management, performance management, activation / deactivation, the function type indicates the types of OAM functions actually performed in OAM management, and the CRC-10 indicates an error about OAM cell field information. It is to convey the detection code.

Information about the ATM layer is exchanged through an OAM cell. The service is divided into F4 and F5 flows according to whether a provided service is a virtual path (VP) level service or a virtual channel (VC) level service. Lose.

FIG. 3 is a diagram illustrating an F4 flow illustrating a virtual path level service in a user-network interface (UNI). The F4 flow is a virtual path level (Virtual Path-PT code pont 4 and 5). It is defined between the network elements 121, 122, and 123 that realize the termination function of, and is divided into one or several virtual paths.

In addition, the F5 flow represents a virtual channel level service in a user network interface (UNI), and the F5 flow is a virtual channel level (Virtual Channel-VCI Values 3 and 4). Exchanger, transmitter, etc.) (131, 132, 133), and is divided into one or several virtual paths.

4 is a diagram illustrating a general ATM switch, in which the F1 to F3 flows are performed in the sonnet framer, and the F4 and F5 flows are performed in the OAM processor.

In the case of a cell output from the outside to the local switching board (140) (Local Switching Board) 140 to the port in the same board, the local switch fabric (Local Switch Fabric) through the input SONET Framer (141) In the case of a cell that is forwarded to 142, the cell is switched in the local switch fabric 142 in the local switchboard 140, and the cell is output to an output port of another local switchboard. The switch is transferred to the central sonnet framer 151 of the central switch fabric 150 through), and is switched from the central switch fabric 152 to another local switchboard through the central sonnet framer 151.

In this case, when the connection between the local switch board 140 and the central switch board 150 is connected using a back plane, the number of the local switch boards 140 increases or the input cell rate of the local switch boards 140 is increased. If the cell rate is high, the number of lines in the back plan is increased or the transmission rate is increased, making implementation difficult.

Therefore, in order to implement a large capacity switch system, the local switch board 140 and the central switch board 150 are connected by using an optical line.

The input sonnet framer 140 of the local switchboard 140 processes the OAM for the physical layer and integrates and processes the OAM for the ATM layer in the OAM processor 153 of the central switchboard 150.

ATM layer management functions performed by the OAM processor 153 are classified into three failure management categories: alarm surveillance, connectivity verification, and invalid VPI / VCI detection. Dual connectivity authentication is verified using a well defined OAM loopback cell.

The OAM loopback feature has two loopbacks: end-to-end loopback and uni-loopback. End-to-end loopback uses end with loopback cell. Point-to-end loopback, and uni-loopback is loopback performed using segment loopback cells looped back from the virtual path connection (VPC) or virtual channel connection (VCC) segment ends. The segment is then defined as a link between ATM nodes.

Since the switch fabrics 142 and 152 correspond to segment terminations, the end-to-end loopback cells switch only according to VPI / VCI, and have a function of generating or looping back segment loopback cells. The switch system can use this function to diagnose the link connection status with other ATM nodes connected to the system (141, 142, 143, 151, 152), and if the segment loopback cell is not returned, the switch can know that the connection with the other node is boiled. Inform other nodes.

On the other hand, the reason that the loopback cell does not return can be divided into a problem inside the switch and an external problem. If it is an internal problem, it must be able to find out which part (141, 142, 143, 151, 152) is causing the abnormality and recover it. If the cell does not return, a method is needed to diagnose the inside of the switch.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. When the segmented loopback cell is not looped back, the present invention provides an ATM switch system for performing a loopback cell test that designates each node inside a switch to diagnose a failure. Its purpose is to provide a link diagnostic method.

Another purpose is for a loopback cell format specifying each node, specifying a specific virtual path identifier and virtual channel identifier in the ATM cell header to generate a loopback cell format and to perform tests on that node sequentially. It is an object of the present invention to provide a link diagnosis method of a mode switch system.

It is another object of the present invention to provide a link diagnosis method of an asynchronous transmission mode switch system, which has a loopback cell identifier of each node, so that loopback cell tests can be performed in any order or sequentially.

Another object of the present invention is to provide an asynchronous transmission mode switch system for diagnosing an abnormal operation from each node as a result of performing a loopback test, an utopian interface connecting each node, and OAM information of a framer's physical layer. To provide a link diagnostic method of the purpose.

1 is an OAM flow for ATM layer management.

2A is a flow format of a virtual path level identifier.

2B is a flow format of a virtual channel level identifier.

3 is a virtual path level service state diagram in a conventional user network interface and an ATM level service state diagram in a conventional user network interface.

4 is a block diagram illustrating a link diagnosis apparatus of an exchange switch system according to an exemplary embodiment of the present invention.

5 is a flowchart illustrating a link diagnosis method of an exchange switch system according to an exemplary embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

101,111 ... STE102,112 ... LTE

103,113 ... PTE104,114 ... ATE

140 ... Local switchboard 150 ... Central switchboard

141 .... input sonnet framer 142 ... local switch fabric

143 Local Sonnet Framer 151 Central Sonnet Framer

152 ... Central Switch Fabric 153 ... OAM Processor

In order to achieve the above object, the link diagnosis method of the asynchronous transmission mode switch system according to the present invention, in the OAM processor of the central switchboard to specify the virtual path identifier and virtual channel identifier to the specific node for diagnosing the interior of the switch Creating an internal loopback cell;

Transmitting each of the generated loopback cells on a sequential destination path;

According to a test result of the loopback cell on each sequentially transmitted node, it is possible to diagnose whether or not a failure occurs in a specific internal node of the switch depending on whether the loopback cell is looped back.

Preferably, in order to distinguish internal nodes of the switch, a loopback cell format in which a specific virtual path identifier and a virtual channel identifier is designated for each node is generated in a header of an ATM cell.

Preferably, the destination path is characterized by performing a loopback cell test from the smallest loop to the largest loop or the loopback cell loop from the largest loop to the smallest loop for the loopback loop created by the loopback cell from the OAM processor. do.

Preferably, the cause of the abnormal operation may be diagnosed by using the loopback test result and the physical layer OAM information of the specific framer.

Preferably, the test result of the loopback cell is characterized in that it detects the abnormality of the utopia interface connecting the node and the previous node when the abnormality in a particular node.

The test result of the loopback cell is to diagnose whether the internal or external abnormality of the switch is abnormal depending on whether the loopback cell is looped back from the node on the target path of the largest loop.

The link diagnosis method of the switch system in the asynchronous transmission mode according to the present invention as described above with reference to the accompanying drawings as follows.

4 and 5, the OAM processor 153 of the central switchboard 150 creates an internal loopback cell, each loopback cell being formatted by specifying a specific VPI / VCI of the ATM cell header. Are divided into a central switch fabric 152, a central sonnet framer 151, a local sonnet framer 143, a local switch fabric 142, and an input sonnet framer 141. Specify VPI / VCI separately.

That is, each loopback cell includes a central switch loopback (CSLB) cell, a central framer loopback (CFLB) cell, a local framer loopback (LFLB) cell, and a local switch loopback (LSLB). Switch Loopback (CLI) cell, Input Framer Loopback (IFLB) cell.

For link diagnosis on the destination path, the OAM processor 153 transmits the segment loopback cell on the destination path (S501), and disables the segment loopback mode when the segment loopback (LB) cell does not return. (S503), the input sonnet framer 141 is switched to the loopback mode.

First, an input framer loopback cell is generated and transmitted to an input sonnet 141 framer to diagnose whether the loopback (IFLB) cell is an internal problem or an external problem according to whether the loopback (IFLB) cell loops (S504). If the input framer loopback (IFLB) cell returns (loopback), it is an external problem (S505). If the input framer loopback cell does not return, it is an internal problem (S509).

In the case of an external problem, it is determined whether the problem is the physical layer or the ATM layer according to the physical layer OAM information of the input sonnet framer (S506). Table 1 summarizes the meanings of the OAM information of the physical layer.

Table 1 shows an alarm state among OAM information of a physical layer.

Sublayer Alarm state Session -Loss of Signal (LOS)-Out Of Frame (OOF)-Loss Of Frame (LOF) Line Alarm Indication Signal (AIS) -Remote Error Indication (REI) -Remote Defect Indication (RDI) Path -Loss of Pointer (LOP) -Remote Error Indication (REI) -Remote Defect Indication (RDI)

As shown in Table 1, signal loss (LOS) occurs when the signal level drops below a specified value, and when the cable is unplugged, when the signal is badly attenuated due to poor line conditions, or a framer failure. .

If OOF receives an invalid framing pattens for 4 to 5 sonnet frames, the Frame Loss (LOF) error occurs when the OOF state persists for milliseconds. It is a signal generated by substituting a normal frame to prevent a failure or an alarm that occurs when an existing frame is transmitted downstream.

In addition, a remote error indication (REI) is a signal for notifying a transmitting node when a block error is detected at a receiving node, and has the same meaning as a far end block error (FEBE), and RDI transmits a defect such as LOS, LOF, and AIS. It tells the node. Pointer loss (LOP) is a case where the pointer in the Synchronous Payload Envelope (SPE) cannot be found and the LCD fails to extract the cell boundary within the SPE.

That is, if LOS or RDI is activated, the cable is broken (S507). If LOS or RDI is not activated, the other system is bad (S509).

On the other hand, if the internal problem (S509) OAM processor 153 is a central switch fabric 152 in the central switchboard 150, the central sonnet framer 151, the local sonnet framer 143 in the local board 140, Loopback (CSLB, CFLB, LFLB, LSLB) cells are sent in the order of the local switch fabric 142 to find the node that has not returned and find the section that caused the abnormality.

In detail, the central switch loopback (CSLB) cell is transmitted to the central switch fabric 152, and when the central switch loopback cell does not return, the central switch fabric 152 is recognized as a failure (S510, In step S511, when the central switch fabric node is normal, the loopback cell CFLB is transmitted to the central sonnet framer 151.

If the loopback cell (CFLB) transmitted to the central sonnet framer 151 does not return, it is recognized as a failure of the central sonnet framer or an abnormal state of the Utopia interface (S512, S513). 151 recognizes that it operates normally.

If the central sonnet framer 151 is normal, the loopback cell LFLB is transmitted to the local sonnet framer 143 of the local switchboard 140.

Utopia interfaces are between each node and between nodes: between a central sonnet framer and a central switch fabric, between a local sonnet framer and a central sonnet framer, between a local sonnet framer and a local switch fabric, between a local switch fabric and an input sonnet framer, etc. It is an interface means to connect.

Here, the utopia interface is an interface for connecting nodes, such as.

After diagnosing whether the loopback cell LFLB transmitted to the sonnet framer has returned (S514), if the loopback cell LFLB does not return, the OAM information of the local sonnet framer 143 is analyzed to determine line loss ( LOS) or diagnosis of a state fault indication (RDI) state is activated (S515), and if a line loss state is a cable error (S516), if a state fault indication state is recognized as a central framer failure or a local framer failure (S517). Here, if the central sonnet framer is normal, there is a high probability that the local sonnet framer is abnormal.

When the loopback cell is returned from the local sonnet framer 141, the local sonnet framer 143 is normal, so that the loopback cell (LSLB) is transmitted to the local switch fabric 142, and it is diagnosed whether or not to return. S518).

When the loopback cell does not return from the local switch fabric 142, it is recognized as a local switch fabric failure or an utopian interface abnormal state (S520), and when it returns, it is recognized as an input framer failure or an utopian interface abnormal state (S520). ).

As described above, when the segment loopback cell does not return as described above, the OAM processor 153 generates a loopback cell for designating each node and performs a test sequentially or sequentially on each destination path, thereby causing a link or node error. Diagnosis can be made.

Another embodiment of the present invention can be tested by reversing the order of performing the inner loopback test. For example, starting with the smallest loop, the central switch fabric 152 loop, the largest loop is the input sonnet framer. The loopback test can be performed in the order of the loops to diagnose the internal and external problems at the end.In addition, starting from the largest loop, the input sonnet framer (141) loop, and then the smallest loop, the center switch loop. You may.

As described above, according to the link diagnosis method of the asynchronous transmission mode switch system according to the present invention, when the segment loopback cell does not return to the switch, the section and cause causing the failure are estimated by self-diagnosis, and the estimation thereof is performed. By informing the system administrator of the result, it is possible to improve the reliability of the system by quickly and effectively removing the cause of an error when a system error occurs.

Claims (7)

Generating a loopback cell specifying a virtual path identifier and a virtual channel identifier to a specific node for diagnosing the inside of the switch in an OAM processor of the central switchboard; Transmitting each of the generated loopback cells on a sequential destination path; And a method of diagnosing a failure in a specific internal node of a switch according to a test result of a loopback cell on each sequentially transmitted node, whether the loopback cell is loopbacked. The method of claim 1, And generating a loopback cell format in which a specific virtual path identifier and a virtual channel identifier are specified for each node in a header of an ATM cell to distinguish internal nodes of the switch. The method of claim 1, The destination path is a link diagnostic method of an asynchronous transfer mode switch system, characterized in that for performing the loopback cell test from the smallest loop to the largest loop loopback loop made by the loopback cell from the OAM processor. The method of claim 1, The destination path is a link diagnostic method of an asynchronous transmission mode switch system, characterized in that for performing a loopback cell test from the largest loop to the smallest loop loop loop cell loop generated during the transmission of the loop back cell from the OAM processor. The method of claim 1, And a loopback test result for diagnosing the cause of the abnormal operation using the physical layer OAM information of the specific framer and the loopback test result. The method of claim 1, And detecting an abnormality of a utopia interface connecting the node and the previous node when the loopback cell is abnormal at a specific node. The method of claim 1, And a test result of the loopback cell, to diagnose whether the internal or external abnormality of the switch is abnormal depending on whether the loopback cell is looped back from the node on the target path of the largest loop.