KR20020054466A - Method for continuity check of ATM OAM - Google Patents

Abstract

PURPOSE: A method for checking the continuity of an ATM(Asynchronous Transfer Mode) OAM(Operation And Maintenance) is provided to generate activation and deactivation cells setting continuity checking of virtual connection in ATM OAM function, and efficiently create a continuity cell and detect a continuity error in checking the continuity. CONSTITUTION: A list of continuity checking nodes is divided into a list of CC(Continuity Check) cell transmitting nodes and a list of CC cell receiving nodes(ST11). The received OAM cell is processed(ST12). A continuity checking of the OAM cell is performed(ST13). A CC cell or an OAM cell reporting LOC alarm is created according to the current state of state variables(ST14).

Description

Method for continuity check of ATM OAM

The present invention relates to a method for checking the continuity of an ATM (Asynchronous Transfer Mode) operation and maintenance (OAM), and particularly, to set up a continuity check of a virtual connection among ATM OAM functions. Activation / Deactivation The present invention relates to a method for checking continuity of ATM OAM, which is suitable for generating a continuity check cell and efficiently performing continuity error detection during continuity check.

In general, asynchronous transmission mode (ATM) is determined by ITU-T (formerly CCITT) as a transmission method of B-ISDN (broadband ISDN) in 1988, and is a core transmission and switching technology of B-ISDN. This method divides all information into fixed length blocks called ATM cells and transmits them sequentially.

The ATM cell has 53 bytes, of which the header is 5 bytes and the information field is 48 bytes. This fixed-length data stream is the unit of multiple exchanges. The header contains a Virtual Channel Identifier (VCI) for identifying the connection to which the cell belongs, and a Cell Loss Priority that indicates whether the cell should be discarded during congestion. , CLP), cell information identification (Payload Type, PT) for distinguishing network control information, header error detection and control (Header Error Control, HEC), and the like. The characteristic of ATM multiplexing is that multiplexing efficiency higher than L division can be achieved by statistical multiplexing, and the transmission band allocated to individual communication can be freely set.

In the ATM exchange, since the routine information is stored in the header, each ATM exchanger can independently relay and exchange cells, and the exchange processing can be realized in hardware, thereby improving the exchange speed.

The ATM switching network consists of two levels of networks called virtual paths (VPs) and virtual channels (VCs). As described above, ATM inherits high transmission efficiency of packet switching and corrects a decrease in switching delay line use efficiency, which is a disadvantage of circuit switching, so that various information can be processed at high speed.

And according to ITU-T I.610 Recommendations, ATM OAM functions have fault management and performance management functions, among which fault management detects physical failures on the network and generates alarms and sends information on failures to other nodes on the network. It will perform the function of delivering.

1 illustrates a hierarchical structure of a general ATM OAM.

1, the OAM layer is divided into F1 to F5, and F4 of the Virtual Path Connection (VPC) layer and F5 of the Virtual Channel Connection (VCC) layer correspond to the ATM OAM layer. OAM information generated in the ATM OAM layer is transmitted through Alarm Indication Signal (AIS), Remote Defect Indication (RDI), Continuity Check (CC), and LoopBack (LB) cells. It is divided into end-to-end.

2 is a flowchart illustrating a continuity check method of a conventional ATM OAM.

As shown therein, if the continuity check is activated, step (ST1) (ST2) of setting the directionality, interval, and layer of the CC; Checking the continuity with the Confirm cell when the Confirm cell or the Deny cell is transmitted in response to an endpoint or a connection point within the set interval receiving the activation cell after the setting (ST3); Generating a CC cell in the execution interval in the continuity check and notifying that the continuity is maintained, and then determining whether the user cell and the CC cell exist for a predetermined time in the execution interval (ST5) (ST6); If there is no user cell and CC cell for the predetermined time, generating an AIS and transmitting one cell per second downward, and generating an RDI cell upward and transmitting one cell per second (ST7) (ST8); If there is a user cell or CC cell for the predetermined time, the continuity check is continued, and the continuity check is terminated by deactivation (ST9).

Therefore, continuity check among ATM OAM defect management functions is executed by the user through CC activation / deactivation process arbitrarily to determine the abnormality of ATM virtual connection. In this case, the direction, interval, and layer of CC are determined and executed.

An endpoint or a connection point within a set interval receiving an activation cell sends a Confirm cell or a Deny cell in response to the continuity check.

If the continuity check is performed, it should be noted that the continuity is maintained by generating a CC cell in the execution interval.

If there is no user cell and CC cell in the execution interval for about 3 seconds, LOC (Loss of Continuity) has occurred. Therefore, AIS is generated and transmitted one cell per second downward (direction of user cell flow), and the RDI cell is upward. Generated and sent one cell per second. At this time, if a user cell or CC cell is received, AIS / RDI cell generation is immediately stopped and continuity is checked again.

In Deactivation, the continuity check is completed by sending the same parameters that were given during activation.

However, such a conventional technology has a limitation that the continuity check can be performed only by supporting the OAM continuity check in the hardware of the ATM equipment, and the continuity check cannot be performed when the hardware of the ATM equipment does not support the OAM continuity check.

In addition, the loopback or performance monitoring OAM function can not be used along with the continuity check, and accordingly, there is a problem in that information such as the occurrence location and duration according to the occurrence of the alarm and the transmission efficiency of the node cannot be managed.

In addition, it is dependent on the multiple channels in the equipment, there was a limit to consider the number of channels in the expansion.

Accordingly, the present invention has been proposed to solve the above-mentioned conventional problems, and an object of the present invention is to create an activation / deactivation cell for setting a continuity check of a virtual connection among ATM OAM functions and to check the continuity check cell during continuity check. An object of the present invention is to provide a continuity check method for ATM OAM that can efficiently generate and detect continuity errors.

In order to achieve the above object, the method for continuity check of ATM OAM according to an embodiment of the present invention,

Separating a list of continuity check nodes into a 'CC cell transmission node list' and a 'CC cell reception list'; A second step of processing the received OAM cell after performing the first step; A third step of performing a continuity test after performing the second step; And a fourth step of generating an OAM cell for notifying the CC cell or the LOC alarm according to the current state of the state variable after performing the third step.

1 is a diagram showing a hierarchical structure of a general ATM OAM,

2 is a flowchart illustrating a continuity checking method of a conventional ATM OAM.

3 is a flowchart illustrating a method for checking continuity of ATM OAM according to the present invention;

4 is a configuration diagram of the software module of FIG.

5 is a detailed flowchart of an OAM cell receiving processing step in FIG. 3;

FIG. 6 is a detailed flowchart of an OAM continuity checking step in FIG. 3.

7 is a detailed flowchart of an OAM cell generation step in FIG. 3;

FIG. 8 is a diagram illustrating an operation when Activation and Deactivation are requested from an DSL multiplexer to an ATM switch in FIG. 3.

FIG. 9 is a diagram illustrating an operation when Activation and Deactivation are requested to a DSL multiplexer from an ATM switch in FIG. 3.

FIG. 10 is a diagram illustrating an operation when a CC cell is sent from a ATM switch to a DSL multiplexer in FIG. 3.

** Description of symbols for the main parts of the drawing **

10: DSL Multiplexer 11: OAM API

12: OAM cell reception processing task 13: OAM continuity check processing task

14: OAM cell generation processing task 15: State variable

20: ATM switch 30: ATU-R

Hereinafter, an embodiment according to the present invention as described above, the technical idea of the method for checking the continuity of ATM OAM with reference to the drawings as follows.

3 is a flowchart illustrating a method for checking continuity of ATM OAM according to the present invention.

As shown therein, a first step ST11 of dividing the list of continuity check nodes into a 'CC cell transmission node list' and a 'CC cell reception list'; A second step (ST12) of processing the received OAM cell after performing the first step; A third step (ST13) of performing a continuity test after performing the second step; And performing a fourth step (ST14) of generating an OAM cell for notifying the CC cell or LOC alarm according to the current state of the state variable after performing the third step.

FIG. 5 is a detailed flowchart of the OAM cell receiving processing step, which is the second step in FIG. 3.

As shown in the figure, waiting for the OAM cell data to enter the message queue and reading the data from the queue, determining whether the received OAM cell is a normal OAM cell (ST21 to ST23); If the received OAM cell is a normal OAM cell, determining an OAM type (ST24); If the shape of the OAM is a continuity check cell, performing the third step (ST25); If the form of the OAM is an activation / deactivation cell, a step of calling and processing a function corresponding to a corresponding function (Function) is performed.

FIG. 6 is a detailed flowchart of the OAM continuity check step, which is the third step in FIG. 3.

As shown therein, determining whether the OAM cell is a 'CC cell transmitting node list' (ST31); If the OAM cell is a 'CC cell transmitting node list', transmitting a CC cell and then returning a value, and determining whether the OAM cell is a 'CC cell receiving node list' (ST32 to ST34); Determining whether the user cell and the CC cell exist for a predetermined time when the OAM cell is a 'CC cell receiving node list' (ST35) (ST36); If there is a user cell and a CC cell for the predetermined time, a step (ST37) (ST38) of generating, transmitting and returning an RDI cell after LOC setting is performed.

FIG. 7 is a detailed flowchart of an OAM cell generation step, which is the fourth step in FIG. 3.

As shown therein, steps ST41 and ST42 bringing a state variable to check the F4 level LOC state variable of the hierarchical structure of the ATM OAM; Transmitting RDI, which is an alarm cell, to the corresponding node according to the LOC state variable of the F4 level, and checking the LOC state variable of the F5 level of the hierarchical structure of the ATM OAM (ST43) (ST44); And transmitting the AIS, the alarm cell, to the corresponding node (ST45) (ST46) according to the LOC state variable of the F5 level.

The operation of the ATM OAM continuity checking method according to the present invention configured as described above will be described in detail with reference to the accompanying drawings.

First, the present invention efficiently performs ATM OAM continuity check functions of F4 and F5 levels for a plurality of channels in a transmission device such as a FLC (Fiber Loop Carrier) or DSLAM (DSL Access Multiplexer). I could do it.

3 is a flowchart illustrating a method for checking continuity of ATM OAM according to the present invention, and FIG. 4 is a configuration diagram of the software module of FIG. 3.

So, when looking at the software configuration through Figure 4, there is an OAM application programming interface (OAM) to command the execution of continuity check (OAM Cell Receive Process Task) to process the received OAM cells '(12),' OAM Permanent Process Task 'which will perform continuity check (13),' OAM cell that generates OAM cell to inform CC cell or LOC alarm depending on the current state of state variable OAM Cell Creation ProcessTask'14, and 'State variables'15 protected by Critical Sections.

State Variables (15) are the parts that contain the state variables of each node and a list of nodes that are performing continuity checks. They are protected by the Critical Section and are shared by the following three tasks.

The OAM Permanent Process Task (13) receives an Activation / Deactivation command input by the user and executes a 'State Variables' ( 15) List them in to monitor the nodes in the list. After that, the side set to send the CC cell checks whether there is a user cell, and if not, generates a CC cell. In addition, since the continuity check is performed between two endpoints in the test interval, the two endpoints are set differently so that the receiving side of the CC cell can declare a LOC state and generate an alarm cell if there is neither a user cell nor a CC cell on the node. do.

'OAM Cell Receive Process Task' (12) receives a request / confirm / deny cell and CC cell according to Activation / Deactivation of continuity check and receives the corresponding CC cell. It is the part that handles by passing it to me function.

The OAM Cell Creation Process Task 14 creates a CC cell by the command of the OAM Continuity Check Processing Task 13 when there is no user cell, or when in the LOC state. Alarm cell according to the change of the block 15 '.

This operation of the present invention will be described in more detail.

FIG. 5 is a detailed flowchart of the OAM cell receiving processing step, which is the second step in FIG. 3.

Waiting for OAM cell data to enter the message queue, and then reading the data from the queue, it is determined whether the received OAM cell is a normal OAM cell.

Qpost (putting data in queue) is done by ATM layer of B-ISDN Reference Model when OAM Cell is received.

If the received OAM cell is a normal OAM cell, the type of OAM is determined.

If the form of the OAM is a continuity check cell, a third step, the OAM continuity check step, is performed.

If the OAM type is an activation / deactivation cell, a function corresponding to the function is called and processed. At this time, when receiving the Confirm Cell corresponding to the activation process, the node is recorded in the list of nodes that perform the continuity check, and the Deny cell resets and deactivates. When you receive the corresponding Deact Cell, remove the node from the list.

FIG. 6 is a detailed flowchart of the OAM continuity check step, which is the third step in FIG. 3.

It is determined whether the OAM cell is the 'CC cell transmission node list'.

If the OAM cell is the 'CC cell send node list', the CC cell is transmitted and then the value is returned.

In this case, the Spend is a list taken from the State Variable (15) area which is managed as a critical section by a semaphore. After executing the check routine, the value is returned by Spost.

In addition, it is determined whether the OAM cell is a 'CC cell receiving node list'.

Here, the list named 'continuity check list 1' is a 'CC cell transmission list' for a node that is to send a CC cell in the multiplexer according to the direction of the continuity check. The list named 'Continuity Checklist 2' is a 'CC Cell Receive List' for a node that is supposed to receive a CC cell from an ATM switch according to the direction of the continuity check.

If the OAM cell is a 'CC cell receiving node list', it is determined whether there is a user cell and a CC cell for a predetermined time.

If there is a user cell and a CC cell for a certain period of time, after setting the LOC, the RDI cell is generated, transmitted, and returned.

Here, if there is no user cell and CC cell for 3 seconds through the timer, it is determined as LOC state.

FIG. 7 is a detailed flowchart of an OAM cell generation step, which is the fourth step in FIG. 3.

Spend the State Variable to examine the LOC state variable at the F4 level of the hierarchical structure of the ATM OAM. At this time, the node in which the state variable is set to LOC in the 'OAM continuity check processing task' 13 is inspected.

According to the LOC status variable of F4 level, RDI, an alarm cell, is transmitted to the corresponding node.

And we check the F5 level LOC state variable of the hierarchical structure of ATM OAM.

According to LOC status variable of F5 level, AIS, an alarm cell, is transmitted to the corresponding node.

So, in case of F4 level, RDI is sent to the corresponding node, and AIS is sent to the node of F5 level belonging to the node. In case of F5 level, AIS is also sent to the node.

Meanwhile, in the present invention, each node must be managed in software, so that 'State Variables' (15) is set as a critical section, so that three tasks 12 to 14 share each node according to the principle of mutual exclusion. Use semaphores to manage state information. In addition, this section not only has status information of each node, but also has a list of nodes executing continuity checks, thereby reducing the load of unnecessary state checks.

The CC Activation / Deactivation Request function is called according to the user's CC command. The type of continuity check is divided as follows. First, depending on the VP / VC layer, second, according to the segment / end-to-end interval, third, A-> B, B-> between the requesting side (A) and the responding side (B). It is divided according to the directionality of A and A <-> B.

The activation / deactivation process of the continuity test will be described with reference to FIGS. 8 and 9.

First, referring to FIG. 8 showing an activation / deactivation process from the DSL multiplexer (A) 10 to the ATM switch (B) 20, a request cell is sent by a CC command, and the ATM switch ( B) (20) side, Confirm comes in response to Request. Then, after recording on the continuity check list, the continuity check is performed by the 'OAM Permanent Process Task' (13). When Deny comes, the state is reset.

Next, referring to FIG. 9 showing an activation / deactivation process from an ATM switch (A) 20 to a DSL multiplexer (DSL Mux) (B) 10, when the request is received, If there is no problem by checking the status of, record in the continuity check list and send Confirm cell.

And if there is a problem, it sends a Deny cell.

In this case, if a request for the end-to-end interval of the VC layer is received, this cell is used in the DSL multiplexer (B) 10 because the ATU-R 30, which is a terminal, becomes an end point of the end of the VC layer, that is, a node. Will bypass.

In addition, according to the directionality, which is the third condition that distinguishes the types of continuity check mentioned above during confirmation, bidirectional continuity check by creating different continuity check lists when receiving CC cells and sending CC cells in the continuity section. Do not overdo the setting of.

Thus, in FIG. 5, the OAM Cell Receive Process Task 12 performs a While Loop, and when there is a received OAM cell, the OAM cell part is read and processed according to the cell type.

In addition to other OAM cells, such as AIS and RDI cells, Request / Confirm / Deny cells and CC cells according to CC Activation / Deactivation are distinguished and processed.The CC Activation / Deactivation cell calls the corresponding function. Permanent Process Task '(13) is used to check the continuity.

In FIG. 6, the OAM cell continuity process task 13 is divided into a part for generating a CC cell and a part for receiving a CC cell.

'Part generating CC cell' reports the nodes recorded in 'CC generation node list' in 'State Variables' (15) among the nodes that execute continuity check by receiving Activation / Deactivation command inputted by user. Generate a CC cell once.

In the 'receiving CC cell' section, the nodes recorded in the 'CC receiving node list' in the 'State Variables' (15) are monitored and if there is no user cell and the CC cell on the node for 3 seconds, the LOC status is displayed for the node. Declare and trigger an alarm cell.

In FIG. 7, the 'OAM Cell Creation Process Task' 14 checks the 'State Variables' 15 every 1 second to check the user cell during the continuity check in the 'OAM Permanent Process Task' 13. If there is a node in LOC state that is recorded when there is no CC cell, it plays a role of generating alarm cell. At this time, refer to FIG. 10 for generating an alarm cell.

As such, the present invention generates an activation / deactivation cell for setting the continuity check of the virtual connection among the ATM OAM functions, and efficiently generates the continuity check cell and detects the continuity error during continuity check.

Although the preferred embodiment of the present invention has been described above, the present invention may use various changes, modifications, and equivalents. It is clear that the present invention can be applied in the same manner by appropriately modifying the above embodiments. Accordingly, the above description does not limit the scope of the invention as defined by the limitations of the following claims.

As described above, the ATM OAM continuity checking method according to the present invention generates an activation / deactivation cell for setting the continuity check of a virtual connection among ATM OAM functions, and efficiently generates the continuity check cell and detects the continuity error during the continuity check. There is an effect that can be performed with.

In addition, the present invention can effectively perform the continuity check when the hardware of the ATM equipment does not support the OAM continuity check, and if the loopback or performance monitoring OAM function is used together with the continuity check, then the occurrence location and continuity according to the alarm occurrence Information such as time and transmission efficiency of nodes can be managed simply and effectively, and can operate independently for multiple channels in the equipment, and can be easily expanded regardless of the number of channels.

Claims (5)

A first step of processing a list of continuity check nodes; A second step of processing the received OAM cell after performing the first step; A third step of performing a continuity test after performing the second step; And a fourth step of generating an OAM cell for notifying the CC cell or the LOC alarm according to the current state of the state variable after performing the third step. The method of claim 1, The first step of the continuity check method of ATM OAM, characterized in that for processing the list of continuity check nodes divided into 'CC cell transmission node list' and 'CC cell reception list'. The method of claim 1, wherein the second step, Waiting for OAM cell data to enter the message queue, and then reading the data from the queue, determining whether the received OAM cell is a normal OAM cell; If the received OAM cell is a normal OAM cell, determining the type of OAM; If the shape of the OAM is a continuity check cell, performing the third step; If the type of the OAM is an activation / deactivation cell, calling and processing a function suitable for a corresponding function. The method of claim 1, wherein the third step, Determining whether the OAM cell is a 'CC cell transmitting node list'; If the OAM cell is a 'CC cell transmitting node list', transmitting a CC cell and then returning a value, and determining whether the OAM cell is a 'CC cell receiving node list'; If the OAM cell is a 'CC cell receiving node list', determining whether a user cell and a CC cell exist for a predetermined time; If there is a user cell and a CC cell for the predetermined time, generating and transmitting an RDI cell after setting up a LOC, and returning a value. The method of claim 1, wherein the fourth step, Examining the LOC state variable at the F4 level of the hierarchical structure of the ATM OAM by taking a state variable; Transmitting an RDI, which is an alarm cell, to a corresponding node according to the LOC state variable of the F4 level, and checking the LOC state variable of the F5 level of the hierarchical structure of the ATM OAM; And transmitting the AIS, which is an alarm cell, to the corresponding node according to the LOC state variable of the F5 level.