JP2001053754A - ATM network two-way continuity check method and two-way continuity check test device - Google Patents

Abstract

(57) Abstract: The present invention relates to a method and an apparatus for confirming bidirectional continuity by a test cell in an ATM network, and aims to greatly reduce the traffic of the test cell without lowering the conventional confirmation accuracy. I do. A test for confirming bidirectional continuity of a desired check section in an ATM network is issued at the start side end with one of the devices in one of the check sections as a start end and the other device as a start end. The test end is transmitted by transmitting the test cell to the actuated end, and the actuating end issues a test cell that is looped back by the partner using the loopback cell function of the monitoring control cells, and Send to initiator end. The actuated end monitors the reception of the test cell, and returns to the actuated end when the test cell is successfully received. The initiating end monitors the reception of the returned self-issued test cell.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for confirming bidirectional continuity by using test cells in an ATM network.

ATM technology is being established as a means for realizing high speed and high bandwidth, and high reliability is required in addition to its speed and bandwidth. OA for network monitoring and control is one of the means to ensure its reliability
An M (Operation And Maintenance) cell is used.
Among the OAM cells, a continuity check (Continuity Check) cell is used as a means for confirming continuity between segments of an ATM connection or end-to-end. A loopback (Loopback) cell is used as a means for specifying the location when a failure occurs on a connection. The present invention relates to a method of applying the continuous check cell and loopback cell technologies to efficiently check continuity as compared with the conventional method.

[0003]

2. Description of the Related Art FIG. 14 shows a conventional conduction checking method for checking conduction in a section between stations A and B. As shown in FIG. 14, in the conventional conduction check, when starting from one of the target sections, only one-way checking from the starting side is possible. Here, it is assumed that the station A starts up. First, it is necessary to transmit an activation cell from the activation station (station A) to the partner station (station B) at the start of the test so that the partner station B recognizes the start of the test. Startup confirmation (Activatio
(n Confirmed) When the cell is returned, the test cell (in this case, a continuous check cell is used) can be transmitted from the activation station A.

[0004] The continuous check cells are transmitted to the B station at an interval of 1 cell / second. The normality of continuity is confirmed by whether or not the test cell is received by the station B. That is, as a normality check method, one OAM cell (here, a continuous check cell as a test cell) is transmitted for a nominal one second, and the receiving side receives a user message within a monitoring time of 3.5 ± 0.5 seconds.
If at least one (user) cell or this continuous check cell can be received, it is determined that the conduction is normal. The monitoring time is measured by a monitoring timer, and the monitoring timer is cleared and restarted each time a user cell or a continuous check cell is received. Conversely, if even one cell cannot be received, it is determined that the conduction is abnormal. The user cell is a cell used for normal communication from the station A to the station B. If this is received, it can be determined that there is continuity between the stations A and B. Also, it is determined that the conduction is normal.

[0005] To end the test, a deactivation cell is transmitted from the test activation side (station A in this case). Confirmation of deactivation from the other party (station B in this case) (Deactivat
(ionconfirmed) cell is received, and the test is completed.

As described above, normality / abnormality of conduction from the station A to the station B can be tested. However, in order to conduct a conduction test from the station B to the station A, the station B must be tested. Becomes the station that starts the test and performs the same processing as described above.

FIG. 15 shows, in the form of a functional block diagram, a device configuration of the stations A and B (mainly a configuration of a continuity check function) for performing the above-described continuity check method.
The function of each component will be described below.

The continuous check cell generator 1 generates continuous check cells at a rate of 1 cell / second. The OAM cell insertion device 2 inserts a continuous check cell generated by the continuous check cell generator 1 onto a connection in a test section. The OAM cell extraction device 3 transmits the cell header information (VC
The user cell and the OAM cell are identified based on the I value or the PTI value, and only the OAM cell is extracted. A continuous check cell, which is one of the OAM cells, is extracted here. The monitoring timer 4 is cleared each time a cell arrives. If it is not cleared for 3.5 seconds or more, a timeout occurs and a continuity error is reported to the management system. At the same time, an AIS signal is sent to the downstream of the connection (or RIS signal is sent to the upstream).
DI signal). After checking the content of the received continuous check cells, the continuous check cell inspection device 5 discards them.

FIG. 16 shows the OAM type and the function type of the OAM cell. As shown, OA
The M type includes failure management, performance management, test start / stop, system management, and the like. The function types include AIS, RDI, continuous check, loopback, forward monitoring, backward reporting, performance monitoring, and the like, and different codes are attached to each of them.

[0010]

In the conventional conduction confirmation method, when conducting conduction in two directions (that is, in the direction of A → B station and in the direction of B → A station), independent test cells (at both ends of the target section) are used. (Continuous check cells) must be generated. In this case, the amount of test cells is twice as large as that in one-way confirmation, and as a result, there is a problem that traffic in the confirmation section is greatly increased. Was.

The present invention has been made in view of such a problem, and by applying a technique for identifying a faulty section using a loopback cell to a test cell, only a test cell generated from one of the sections to be confirmed is used. An object of the present invention is to significantly reduce the traffic of a test cell without lowering the conventional confirmation accuracy based on the idea of enabling bidirectional conduction confirmation.

[0012]

In the present invention, the AT is used.
The test for bidirectional continuity check of a desired check section in the M network is performed by using a test cell issued by the above-mentioned start end with one of the devices in the above-mentioned check section as an activation end and the other device as an actuation end. This is performed by transmitting to the above-mentioned activated end. In this test, by applying a conventional technique for identifying a faulty section using a loopback cell to a test cell, bidirectional continuity can be checked only with a test cell generated from one of the check sections to be checked. .

That is, in order to solve the above-mentioned problems,
The bidirectional continuity check test device according to the present invention is installed at the end of the check section, issues a test cell that is looped back by the partner using the loopback cell function of the monitoring control cells, and transmits the test cell to the partner. Test cell transmitting means, a first monitoring means for monitoring the reception of the test cell issued by the other party and returning to the other party when the test cell can be received, and a second monitoring means for monitoring the reception of the self-issued test cell returned by the other party. 2 monitoring means. The activating end issues a test cell by the test cell transmitting means and transmits the test cell to the activated end. The activated end monitors the reception of the test cell by the first monitoring means, and returns to the activated end when the test cell is successfully received. The initiating end monitors, by the second monitoring means, the reception of the returned self-issued test cell. As a result, it is possible to confirm bidirectional continuity in the check section with one test cell issued by the activation-side end.

In the above-described apparatus of the present invention, the operation state of the self side is currently in the "activated" state in which test cells are issued and transmitted, or in the "activated" state in which the test cells issued by the other party are received and looped back. Is stored as a current state, and when a reception abnormality is detected while monitoring reception of a test cell issued by the other party, a state change signal is sent to the other party and the current state of the own side is also sent. First state switching means for switching the state from "activated" to "activated" to issue and transmit a test cell, and upon receiving a state change signal, changing the current state of its own side from "activated" to "activated". Second state switching means for switching to stop issue / transmission of test cells and monitoring reception of test cells issued by the other party. The actuated end monitors the reception of the test cell issued by the actuated end by the first state switching means, and if a conduction abnormality is detected, sends a state change signal to the actuated end. Is switched from "activated" to "activated" to issue / transmit a test cell. Upon receiving the state change signal, the starting end switches its current state from "starting" to "activated" by the second state switching means to stop issuing / transmitting the test cell and issue the other party. Monitor the reception of the test cell. Thus, even if there is a conduction abnormality in the path from the activation side to the activation side, the activation side end and the activation side end are switched, and a test for confirming the conduction of the opposite path can be performed.

Further, the above-described apparatus of the present invention detects an abnormal "two-sided start" in which both ends of the check section are both start-ends by detecting that the received test cell is a test cell issued by the other party. The apparatus further includes a two-sided abnormality detecting means for detecting a state. The starting end detects the received test cell as a partner-issued test cell by means of the both-side abnormality detection means, so that both ends of the check section are both the starting end. Is detected. As a result, it is possible to take a countermeasure against the abnormal state of the “both-side start”.

Further, the above-mentioned apparatus of the present invention comprises an initial state storage means for storing the initial operation state of the apparatus at the start of the continuity check test as an initial state, and "two-sided activation".
State detection means for setting the content of the initial state on the own side to the current state on the own side when the occurrence of the abnormal state is detected. The starting end is controlled by the abnormality detection means on both sides.
When the occurrence of the abnormal state of “both-side activation” is detected, the contents of the initial state of the own side are set as the current state of the own side. As a result, in response to the occurrence of the abnormal state of “both-sided activation”, the activation-side end, which was initially the activated-side end, returns to its initial state, that is, the activated-side end, whereby the “both-sided activation” abnormality You can recover the condition.

Further, the above-described apparatus of the present invention issues a test stop request signal to the other party when ending the test from the own side when the current state of the own side is "activated".
It further includes a test stop requesting means for transmitting, and a stop signal transmitting means for issuing a test stop signal when receiving the test stop request signal and transmitting it to the other party. When the actuated end terminates the test from itself, the actuated end issues and transmits a test stop request signal to the actuated end by the test stop requesting means. In response to this, the starting end issues and transmits a test stop signal to the driven end by the stop signal transmitting means, and ends the test. Thus, even if the activation-side end that has started the test is subsequently switched to the actuation-side end, the test can be ended from the actuation-side end (that is, the side that started the test).

The monitoring of the reception of the test cell is performed when a test cell or a user cell from the same path as the test cell cannot be received within a predetermined monitoring time during the test. It can be determined.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an outline of a procedure of a bidirectional conduction confirmation method according to an embodiment of the present invention. FIG. 2 shows a format of a continuous LB start / stop cell used in this embodiment, and FIG. 3 shows a format of a continuous LB check cell similarly. FIG. 4 shows, in the form of a functional block diagram, a schematic configuration of a switching system including the stations A and B for implementing the method of checking continuity.

First, the outline of the conduction confirmation procedure will be described with reference to FIG. The role of the start / stop cell and the start / stop confirmation cell used for the test start / stop is almost the same as that of the conventional method, but it is necessary to indicate and terminate the continuity check method according to the present invention. Since these cells are strictly different in that they are cells used for the first time (cells that have not been used in the conventional method), these cells are used here as continuous L cells.
The cells are referred to as B start / stop cells and continuous LB start / stop confirmation cells. After transmitting the continuous LB activation cell and returning the continuous LB activation confirmation cell, a test cell is generated and transmitted from the A station on the activation side. The test cell used for the test according to the present invention is a continuous LB check cell (Continuous Loopback Check C).
ell). In the conventional method, in order to perform bidirectional confirmation, it is necessary to separately transmit a starting cell from both the A station and the B station to start the test. However, in the method of the present invention,
By using a loop-back cell for conduction confirmation, bidirectional conduction can be confirmed only by starting a test from one side (here, the A station side). By setting the transmission interval of the continuous LB check cells to 1 cell / 2 seconds, the test cell traffic used for the bidirectional test is reduced to half of the conventional method.

Next, a description will be given of a schematic configuration of an exchange system for implementing the bidirectional conduction confirmation method. Each station at both ends of the test section consists of components having the following functions.

The continuous LB check cell generator 1 generates continuous LB check cells at a rate of 1 cell / 2 seconds. Here, the test cell used for the test according to the present invention is a continuous LB
It is called a check cell. The continuous LB check cell generator 1 also generates a continuous LB start / stop cell and a continuous LB start confirmation / stop confirmation cell as needed.
The configuration of these cells is as follows.

[Continuous LB start / stop cell (Continuous Lo
opback Activation / DeactivationCell)] In this embodiment, a cell used to start / stop (end) bidirectional conduction confirmation is referred to as a continuous LB start / stop cell (continuous LB start cell / continuous LB stop cell). FIG. 2 shows the cell structure. This continuous LB
Since the start / stop cell is a kind of start / stop cell among the OAM cells (see FIG. 16), the OAM type value is “1000”. On the other hand, since there is no conventional function type, the function type value is an undefined value (eg, 0).
010).

[Continuous LB check cell (Continuous Loop check cell)
back Check Cell) FIG. 3 shows a structure of a test cell used for performing bidirectional conduction confirmation according to the present invention. The present cell is positioned as a kind of a failure management cell (a function type is similar to a loopback) among the OAM cells (see FIG. 16),
Although the OAM type value is “0001”, there is no conventional function type, so the function type value is an undefined value (eg, 1100). Function-specific fields (Fu
nction Specific Field) is a conventional loopback OAM
Use the same feature-specific fields that are used for the cells. As a result, the continuous LB check cells can be turned back, and bidirectional check can be performed.

The OAM cell insertion device 2 inserts the cells generated by the continuous LB check cell generator 1, the state change cell generator 9, and the test stop request cell generator 10 onto the connection in the test section.

The OAM cell extracting device 3 identifies a user cell and an OAM cell based on cell header information (VCI value or PTI value), and extracts only the OAM cell. The continuous LB check cells are extracted here.

The monitoring timer 4 is a timer that always counts up and is cleared each time a cell arrives. If it is not cleared for more than 4 seconds, a timeout occurs and a continuity error is reported to the management system. At the same time, it generates and transmits an AIS signal to the downstream of the connection (or an RDI signal to the upstream).

The continuous LB check cell inspection device 5 checks the contents of the continuous LB check cells, returns the cells as necessary, and determines whether or not the cells are to be discarded. The check cell folding device 6 inserts a continuous LB check cell determined to require folding by the continuous LB check cell inspection device 5 in the upstream direction by the present device.

The initial state memory 7 stores a starting state at the start of a test. In this state, there is a master / slave, and the contents set once are not changed until the end of the test.

The current state memory 8 stores a start state during a test. This state includes a master / slave, and the contents are changed (updated) each time the state at both ends of the test section changes in the course of this test.

The state change cell generator 9 is a device for generating a state change cell. This state change cell changes the activation state to the slave side with respect to the other side when the slave side detects an abnormality (therefore, the state change cell itself). Is a signal requesting to be a master).

The test stop request cell generator 10 is a device that generates a test stop request (Test Stop Request) cell. The test stop request cell is a signal for requesting the master to generate a continuous LB stop cell from the slave when the user or the management system instructs the slave to end the test.

Hereinafter, the method for confirming bidirectional conduction will be described in detail. [Starting and stopping the bidirectional continuity check test] First, in this bidirectional continuity check method, a continuous LB start / stop is performed to start / stop the bidirectional continuity test between the ATM exchange and the ATM terminal.
Use stop cells. This confirmation test can be initiated from the management system or from the end user.

Specifically, when starting (or ending) this test, as shown in FIG. 1, the continuous LB start cell (or the continuous LB stop cell) is called one of the monitoring sections (called the start end). ), And transmits it to the other end of the section (referred to as the activated end). As described above, since these continuous LB start / stop cells are a kind of start / stop cells as shown in FIG. 2, the OAM type value is “10”.
00 ”, the function type value is a conventionally undefined value (example = 001)
0) is used.

The starting end is "the starting side at the start of the test".
Is stored in the initial state memory 7, and the activation state at that time is stored in the current state memory 8. Specifically, as shown in FIG. 5, "0" (= master) is set in each of the initial state memory 7 and the current state memory 8. Thereafter, a continuous LB activation cell is issued and transmitted.

On the side receiving this continuous LB activation cell,
At that time, the fact that it is the "activation side at the start of the test" is stored in the initial state memory 7, and the activation state at that time is stored in the current state memory 8. Specifically, as shown in FIG. 5, the initial state memory 7 and the current state memory 8
Is set to “1” (= slave). The activated end activates the monitoring timer 4 and then confirms activation to the activated end, that is, sends back a continuous LB activation confirmation cell.

On the other hand, when ending the bidirectional continuity test, the test is completed by sending a continuous LB stop cell to the other party and returning the continuous LB stop confirmation cell to the other party.

The function-specific fields in these continuous LB start / stop cells and their confirmation cells are the same as those used for the conventional conduction confirmation (continuous check) start / stop and its confirmation. In addition, a conventional method is also used for processing for continuous LB start / stop cells (start cell retransmission processing, confirmation processing interruption due to start error, etc.).

[Confirmation of bidirectional conduction by continuous LB check cells and monitoring timer] Bidirectional conduction confirmation by continuous LB check cells is to continuously generate and transmit continuous LB check cells at a rate of one cell every 2 seconds, and to check both ends of the check section. Efficient two-way checking by monitoring using a 4-second timer (with approximately half the test cell traffic compared to conventional)
Do.

More specifically, as shown in FIG. 5, the activated side (station B) that has received the continuous LB activation cell from the activation side (station A) transmits a continuous LB activation confirmation cell as a response thereto. (A station), and at that time, the monitoring timer 4 is started at the same time.

On the other hand, continuous L from the actuated end (station B)
Upon receiving the B activation confirmation cell, the activation end (station A) activates the monitoring timer 4, generates a continuous LB check cell, and sends it to the activated end.

The monitoring timer operation on both sides of the A / B stations is independent, and the monitoring timer 4 times out in 4 ± 0.5 seconds. User cell or continuous LB within this time
When the check cell arrives, the monitoring timer 4 is cleared and restarts counting (timer restart).
I do.

As shown in FIG. 1, the activating end (station A) continuously sends out continuous LB check cells at an interval of once every 2 seconds of the nominal value. As described above (see FIG. 4), since the continuous LB check cell is a kind of the fault management cell (see FIG. 16), the OAM type value is “0001”, and the function type value is a conventionally undefined value ( Example: 1100) is used. The function-specific field of this cell is the same as that used in the conventional loop-back OAM cell.

As shown in FIG. 5, the actuation-side end (station B) activates the monitoring timer 4 on its own side, and at least a predetermined monitoring time (in this case, 4.0 ± 0.5 sec.) It monitors whether any user cells or continuous LB check cells are received. If at least one cell is received, the monitoring timer 4 is cleared immediately, and the counting of 4 seconds is started again therefrom. If no cell can be received in 4 seconds, a timeout occurs and it is determined that there is a conduction abnormality in the A → B station direction path.

When this abnormality is detected, as in the conventional conduction check, VP / VCAIS is applied to the downstream (if this is the connection end, VP / VC
RDI). It also reports to the management system the continuity abnormality in the A → B station direction. This state of conduction abnormality is released when the actuated end (station B) receives the next user cell or continuous LB check cell,
The management system is notified of the abnormal termination of conduction in the direction of the A → B station.

On the other hand, the activated side (station B) normally continues LB
If a check cell is received, the actuated side (station B)
Returns it to the activation side (station A) within 1 second after receiving it.

The activation side (station A) starts the monitoring timer 4 on its own side in the same manner as the activation side (station B), and then sets 4.0.
It monitors whether at least one user cell or continuous LB check cell is received within a monitoring time of ± 0.5 seconds. If at least one cell has been received normally, the monitoring timer 4 is cleared immediately, and the counting of 4 seconds is started again therefrom. In the event that no cell can be received in 4 seconds, a timeout occurs, and it is determined that there is a conduction abnormality in the B → A station direction path, and the activation side (station A) generates and sends VP / VCAIS to the downstream. . If this is the connection end, VP / VC RDI is generated and transmitted to the upstream. In addition, it reports the conduction abnormality in the direction of the B → A station to the management system. This state of abnormal conduction is released when the activation end (station A) next receives a user cell or a continuous LB check cell, and the management system is notified of abnormal termination of conduction in the direction from station B to station A.

On the other hand, the activation side (station A) confirms the contents of the continuous LB check cell when receiving it, and determines that the continuous LB check cell is clearly transmitted by the activation side itself. , It is determined that bidirectional conduction is normal.

At the end of the test, the monitoring timer 4 of the station B is cleared when the continuous LB stop confirmation cell is transmitted to the station A, and the monitoring timer of the station A is cleared when the activation stop confirmation cell is received.・ Operation stops.

[Switching of Master / Slave] In the example of FIG. 5, the station A performs generation and transmission of a continuous LB check cell. That is, the initiating side (master). On the other hand, the station B side is an actuated side <slave> that returns the continuous LB check cell. This state is recorded in the current state memory 8 of each A / B. Next, a method of switching between the master and the slave will be described.

In this switching method, the current state memory 8 is used to store the activation state at that time, the activation state / activation side is clarified by referring to the current state memory 8, and the activation state is determined. If the person who has detected the conduction abnormality detects the conduction abnormality by using the state change cell to the activation side, the activated side until then becomes the activation side and issues and transmits the check cell. That is.

With the occurrence and transmission of this state change cell, the contents of the current state memory 8 at both ends of the test section are reversed. Regarding the contents of the state, the activation side (the side that generates and transmits the continuous LB check cells) is the master (= 0), and the activated side (the side that returns the continuous LB check cells) is the slave (= 1). At the start of the test, the current state memory 8 is set, and the contents are changed depending on the state during the test. This reveals the active and inactive sides at that point in the test. The contents of the current state memory 8 are cleared at the end of the test.

More specifically, in the test for confirming continuity,
Start / stop is instructed from the connection end subscriber terminal or the management system of the station used for connection connection. During the test, the initiating side (master) continues to issue and transmit the continuous LB check cell until the test stop is instructed, regardless of the result. Further, “monitoring of the cell” is continued until the start and the activated sides are instructed to stop the test.

At the start of the test, the starting state at that time at both ends of the test section is stored in the current state memory 8. As shown in FIG. 5, the current state memory 8 on the activation side A at the start of the test is “0” (= master), and the current state memory 8 on the activation side B at the start of the test is “1” (= slave). And When the state transition between the master and the slave occurs due to the detection of the conduction abnormality during the test, a new activation state is written in the current state memory 8 by the overwriting method each time.

FIG. 6 shows an outline of the processing when a conduction abnormality occurs in the direction B → A (processing when NG occurs only in B → A). As shown in FIG. 6, when the conduction failure is only in the B → A direction, the cell reaches the station B, so that the monitoring timer 4 of the station B is always cleared. However, since the cell does not reach the station A due to the conduction abnormality in the direction B → A (of course, the continuous LB check cell issued by the own side does not return).
The monitoring timer 4 of the station A is not cleared, and if no cell can be received within 4 seconds, a timeout occurs,
An alarm of “B → A direction conduction abnormality” is reported to the management system. However, station A keeps issuing and transmitting continuous LB check cells. This is because the normality in the A → B direction can be confirmed at least by the continuous LB check cell. Therefore, the current states on both sides A and B do not change.

FIG. 7 shows the outline of the processing when the conduction abnormality in the A → B direction occurs (processing when NG occurs only in A → B). It is assumed that the station A was the master (the station B was a slave) before the occurrence of the abnormality. As shown in FIG.
→ If there is a continuity abnormality only in the B direction, since no cell enters the B station, the monitoring timer 4 of the B station cannot be cleared, a timeout state occurs, and an alarm of the continuity abnormality is reported to the management system.

Due to the conduction abnormality in the direction A → B,
The continuous LB check cell generated and transmitted by the station A is not returned to the station A. Therefore, when there is no user cell in the B → A direction, the monitoring timer 4 of the station A also times out. However, due to the difference between the timings at which the A / B stations time out, the monitoring timer 4 at the B station always times out first.

Therefore, when the station B on the slave side detects a conduction abnormality, the station B changes its activation state, that is, the current state to "0" (master), and makes a state change to the partner (station A). Send the cell.

This state change cell is used to change the activation state of the master to a slave when an abnormality is detected. FIG. 8 shows the cell structure of this state change cell. Since this is a special cell used only for bidirectional conduction confirmation by the continuous LB check cell of the present invention, the OAM type value is a conventionally undefined value (eg, 1001).
(Continuous LB specific Type
), Function type value is also undefined value (ex: 0000)
(= State change type).

Thereafter, the station B starts transmitting the continuous LB check cells issued by itself to the station A. This is because at the time of this abnormality and when there is no user cell in the B → A direction,
This is because there is no means for confirming the normality in the B → A direction using the continuous LB check cell issued by the A station.

The station A receiving the state change cell
Recognizing "A to B direction conduction abnormality", changes its activation state, that is, the current state, to "1" (= slave).
As a result, the issuance / transmission of the continuous LB check cell at the station A is stopped. According to this method, even in the case of abnormal conduction in the direction A → B, the normality of conduction in the direction B → A can be confirmed at least.

[Detection of "Both Masters" Abnormality] Next, a method of detecting an abnormal state of the "both masters" in this embodiment will be described. This method uses a loopback indication (Loopback Indic) of received continuous LB check cells.
ation) is inconsistent with the operation indicated in the contents of the current state memory 8, thereby detecting an abnormal state of "two-sided master" in which both stations A and B are masters. As a result, the state of "continuous LB check cell transmission from both sides" caused by the abnormal conduction state can be recognized, and the action can be shifted to an action for returning the state to normal.

At the time of the "two-way conduction abnormality", since both stations A and B have determined that "their own side is the master", A and B
Both sides issue and transmit continuous LB check cells. Therefore, when the abnormal termination of conduction is detected, A,
It is necessary to stop the continuous LB check cell transmission from one of the stations B. Because continuous LB from both directions
This is because check cell transmission is useless.

FIG. 10 shows a process performed when a conduction abnormality occurs in both directions and then the direction A → B recovers (bidirectional abnormality, A →
B recovery process). When a conduction abnormality occurs in both directions, as a result, both A / B stations generate and transmit a continuous LB check cell. However, the generation and transmission of the continuous LB check cells from both sides are useless, and it is sufficient only from one side (either the A station or the B station).

Therefore, as shown in FIG. 10, when conduction is abnormal in both directions and the A → B direction recovers first, the continuous LB check cells from the A station reach the B station, so that the B station changes the cell. The monitoring timer 4 of the station B is cleared, and the monitoring time is restarted (Restart). At the same time, the abnormal termination of conduction in the A → B direction is reported to the management system.

When the station B receives the continuous LB check cells, it checks whether the contents are correct. However, B
→ At the point in time when the direction A has not yet recovered, the continuous LB check cell issued by the station B itself cannot return to the station B. On the other hand, continuous LB check cells issued and transmitted by the A station can be received. However, since the B → A direction has not been recovered, this does not return to the A station normally. Therefore,
When the master station B receives the continuous LB check cell issued by the other party (station A), the loopback indication (ID) in the cell is "1". LB check cells, that is, “the other side is also a master”.

Since the station B determines that the current state memory 8 is "0" (= master) after detecting the conduction abnormality in the direction of the station A → B, that is, "it is the master station". Think that it is unlikely that a continuous LB check cell issued by station A will arrive. Therefore, the station B that has detected the continuous LB check cell issued by the station A detects that the "double-sided master" abnormality has occurred.

In this case, as described later in detail, B
The station refers to the contents of its own initial state memory 7 and resets the state stored therein. That is, the station B becomes a slave and stops issuing and transmitting continuous LB check cells.

FIG. 11 shows a process when a conduction abnormality occurs in both directions and the direction B → A recovers thereafter (bidirectional abnormality, B →
A recovery process). As described above, when the conduction is abnormal in both directions and the direction B → A recovers first, the monitoring timer 4 is cleared and the abnormal termination of the conduction is reported to the management system because the station A can receive the cell.

When the station A receives the continuous LB check cells, it checks whether the contents are correct. However, A →
When the direction of B has not yet recovered, the continuous LB check cell issued by the station A itself cannot return to the station A. On the other hand, continuous LB check cells issued and transmitted by the station B can be received. However, since the A → B direction has not recovered, the continuous LB check cell does not return to the B station normally. When the station A receives the continuous LB check cell, the loopback indication (ID) in the continuous LB check cell is “1”, so that it is a continuous LB check cell issued by the station B. That is, the user realizes that the other party is also a master. When the station A detects a conduction abnormality in the B → A direction, the current state memory 8 stores “0”.
(Master). That is, it is determined that "the self is the master." For this reason, it is considered that a continuous LB check cell issued by the station B should not arrive. Therefore, B
When a continuous LB check cell issued by the station arrives, the station A detects that the "master on both sides" error has occurred.

In this case, as described later in detail, A
The station refers to the contents of its own initial state memory 7 and resets the state stored therein. That is, the station A maintains the master state and continuously issues and transmits the continuous LB check cells.

[Resetting of master / slave] Next, upon detection of the "both-side master" abnormality by the above-described method,
The method of resetting the activation side and the activation side will be described in more detail. In this method, in each station, an initial activation state at the start of the test is stored in the initial state memory 7 and the contents of the initial state memory 7 are referred to in order to eliminate the "double-sided master" state at the time of an abnormality, and activated accordingly. The side and the actuated side are reset, that is, set to the same state as at the start of the test.

Here, the contents of the initial state of the initial state memory 7 are such that the activation side is a master (= "0"),
The actuated side is defined as a slave (= "1"). The contents of the initial state memory 7 are not changed during the test and are cleared at the end of the test.

More specifically, the starting state of each station at the start of the test is stored in the initial state memory 7. The initial state memory 7 is different from the current state memory 8, and the information once stored is not rewritten during the test and is cleared at the end of the test. The method of expressing the initial state is the same as that of the current state memory 8. The initial state memory 7 is used for the purpose of returning the “both-side master” state to the “one-side master / one-side slave normal state”.

As shown in FIG. 10, when the "Both-side master" abnormality is detected at the station B, the current state of itself is checked. Since the initial state of the station B is “slave”, the station B changes the current state memory 8 to “slave” and thereafter stops issuing and transmitting the continuous LB check cells. At this point, the "two-sided master" state is cleared. Station B is in the slave state, so "master on both sides"
Continuous L issued by station A used as a trigger for abnormality detection
The B check cell is returned to the A station.

On the other hand, as shown in FIG. 11, when the "double-sided master" abnormality is detected at the station A, the own own initial state is similarly observed. Since the initial state of the station A is “master”, the station A keeps issuing and transmitting continuous LB check cells without changing the current state. In addition, since station A is the "master", "stations on both sides"
Continuous L issued by station B used as a trigger for abnormality detection
The B check cell is discarded and is not returned to the B station.

When the station A detects the "two-sided master" abnormality before the station B, the abnormality is recognized at the station A, but the continuity in the direction A → B is restored, and the station B also detects the abnormality. Until an abnormality is recognized and its current state is changed to "slave", the "master on both sides" state is not cleared.

[Test Termination Action from Activated Side] Next, a description will be given of a method of performing a test end action from the activated side when the activation side that has started the continuity test is subsequently changed in state to the activated side. . In this method, a test stop request (Test Stop Request
) Issue and transmit cells. After receiving the test stop request cell, the start-up side issues and transmits the start-stop cell, and ends the test.

FIG. 12 shows an outline of a procedure for terminating the continuity test according to the present invention (test termination procedure). As described above, in the process of the bidirectional continuity test, the current state of both stations A and B may be switched. Therefore, the side that has received the test end request by a command or the like checks the current state prior to the conventionally used start / stop processing.

More specifically, as shown in FIG. 12, when an end of the test is instructed by a command or the like to the A station which has become a slave in the course of the test, the A station receiving the test end request Checks its current state. At this time,
Since the current state is “slave”, it is known that “the other party (station B) is the master”, and station A issues and transmits a test stop request cell to station B.

The test stop request cell requests the slave to issue a continuous LB stop cell for terminating the continuity test from the slave side. FIG. 9 shows the structure of the test stop request cell. . Since this test stop request cell is a special cell used only for bidirectional conduction confirmation by a continuous LB check cell, the OAM type value is a value that has not been defined conventionally (eg, 1001) (= continuous LB specific type), a function type. The value is also a conventionally undefined value (eg, 0001) (= test stop request type).

The station B (master station) receiving the test stop request by receiving the test stop request cell generates a continuous LB stop cell and transmits it to the station A. Continuous LB
Station A that has received the stop cell issues and transmits a continuous LB stop confirmation cell to station B, and the test ends. When the side whose current state is “master” receives the test termination request, it immediately issues and transmits a continuous LB stop cell to the partner station.

[Comparison of Traffic Volume between New System and Conventional System] FIG. 13 shows the effectiveness of the traffic volume according to the present invention in comparison with the conventional system. In the case of performing the bidirectional conduction check in the test section by the conventional method, it is necessary to generate test cells (continuous check cells) independently from both ends of the section. The generation / transmission interval is 1 cell / second. Therefore, as shown in FIG.
Cell traffic occurs in the test section.

On the other hand, in the method (new method) according to the present invention,
A test cell (continuous L
Only by generating the B check cell), bidirectional conduction confirmation is possible. In addition, in the new method, the abnormality monitoring time is set to be 0.5 seconds longer than the conventional 3.5 ± 0.5 seconds, and the interval between generation and transmission of the continuous LB check cell is 2 seconds (twice that of the conventional method). And As a result, the test can be performed with a traffic volume that is half (10 cells in a 10-second test) compared to the conventional method without lowering the conventional accuracy.

[0085]

As described above, according to the present invention, by applying a technique for identifying a faulty section using a loopback cell to a test cell, only a test cell generated from one of the sections to be confirmed can be used. Direction can be confirmed, and the traffic of the test cell can be greatly reduced without lowering the conventional confirmation accuracy.

[Brief description of the drawings]

FIG. 1 shows an outline of a conduction confirmation procedure in a bidirectional conduction confirmation system according to the present invention.

FIG. 2 shows a continuous LB start / stop cell (Continu) used to start / stop (end) the bidirectional continuity check test of the present invention.
ous Loopback Activation / Deactivation Cell).

FIG. 3 shows a cell structure of a continuous LB check cell used for performing bidirectional conduction confirmation according to the present invention.

FIG. 4 is a functional block diagram showing an exchange system for realizing the bidirectional conduction confirmation method of the present invention.

FIG. 5 shows the operation of a monitoring timer used for conducting a continuity test according to the present invention.

FIG. 6 shows an outline of a process performed when a conduction abnormality in the B → A direction occurs (process performed when NG occurs only in B → A).

FIG. 7 shows an outline of a process in the case where a conduction abnormality in the A → B direction occurs (a process in which NG occurs only in A → B).

FIG. 8 shows a cell structure of a state change cell for changing the activation state on the master side to a slave when an abnormality is detected.

FIG. 9 shows the structure of a test stop request cell in which the slave requests the master to issue a continuous LB stop cell for ending the continuity test.

FIG. 10: A conduction abnormality occurs in both directions, and then A → B
The processing when the direction is recovered (bidirectional abnormality, processing when A → B recovers) is shown.

FIG. 11: A conduction abnormality occurs in both directions, and then B → A
The processing when the direction is recovered (bidirectional abnormality, processing when B → A is recovered) is shown.

FIG. 12 shows an outline of a procedure for terminating a continuity test (test termination procedure) according to the present invention.

FIG. 13 shows the effectiveness in traffic volume according to the present invention in comparison with the conventional method.

FIG. 14 shows a conventional continuity test system between the exchanges of the A station and the B station.

FIG. 15 is a functional block diagram showing a switching system for realizing the conventional method.

FIG. 16 is a table showing conventional OAM types and function types.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Continuous LB check cell generator 2 OAM cell insertion device 3 OAM cell extraction device 4 Monitoring timer 5 Continuous loopback cell inspection device 6 Check cell return device 6 7 Initial state memory 8 Current state memory 9 State change signal generator 10 Test stop Request signal generator

Claims (13)

[Claims] 1. A test for confirming bidirectional continuity of a desired check section in an ATM network is performed by setting the apparatus at one end of the check section to the start end and the apparatus at the other end to the start end. A method in which the issued test cell is transmitted to the actuation-side end, wherein the test cell is set as a test control cell that is looped back by the other party using a loopback cell function among the monitoring control cells, The initiating end issues the test cell and sends it to the initiating end. The initiating end monitors the reception of the test cell and returns to the initiating end if it can receive the test cell. The end monitors the reception of the returned self-issued test cell, thereby confirming the bidirectional continuity of the check section. Direction continuity check method. 2. The device at both ends of the above-mentioned check section has a current operation state of its own side in an "activated" state for issuing / transmitting a test cell, or a device for receiving / returning a test cell issued by a partner. The current state storage means for storing the current state as the current state is provided.The activated end monitors the reception of the test cell issued by the activated end and detects a conduction abnormality. A state change signal is sent to the initiating end, and the current state of the own side is switched from “activated” to “activated” so that test cells are issued and transmitted. The initiating end transmits the state change signal. Upon receiving, a contract is made to switch the current state of the self side from “start” to “activated” to stop issuing / transmitting test cells and to monitor reception of test cells issued by the other party. Bidirectional connection confirmation method of the ATM network of claim 1, wherein. 3. The start-side end detects an abnormal state of "two-sided start" in which both ends of a check section are both start-ends by detecting that a received test cell is a test cell issued by the other party. 3. The method according to claim 2, wherein the two-way connection is detected. 4. The apparatus at both ends of the check section includes initial state storage means for storing an initial operation state of the apparatus at the start of a continuity check test as an initial state. 4. The method for confirming bidirectional conduction of an ATM network according to claim 3, wherein when the occurrence of an abnormal state of "both-side activation" is detected, the contents of the initial state of the own side are set to the current state of the own side. 5. The actuated end issues and transmits a test stop request signal to the activator end when terminating the test from itself, and in response thereto, the activator end activates the test stop signal. The AT according to any one of claims 1 to 4, wherein the test is terminated by issuing / transmitting to the side end.
A method for confirming the bidirectional conduction of the M network. 6. The monitoring of the reception of a test cell is performed when a test cell or a user cell from the same path as the test cell cannot be received within a predetermined monitoring time, and it is determined that there is a conduction abnormality in the path. The method for confirming bidirectional conduction of an ATM network according to claim 1. 7. A bidirectional continuity check test device installed at an end of a check section for performing a test of a bidirectional continuity check in a desired check section in an ATM network, the test control section comprising: A test cell transmitting means for issuing a test cell to be looped back by the partner using the loopback cell function and transmitting the test cell to the partner, and monitoring the reception of the test cell issued by the partner and returning to the partner when successful. A bidirectional continuity check device for an ATM network, comprising: a monitoring means for monitoring the reception of a self-issued test cell returned by the other party. 8. The current state is stored as to whether the operating state of its own side is an "activated" state in which a test cell is issued and transmitted or a "activated" state in which a test cell issued by a partner is received and looped back. When the current state storage means and the reception of the test cell issued by the other party are monitored and a conduction abnormality is detected, a state change signal is sent to the other party, and the current state of the own side is changed from "activated" to " First state switching means for issuing / transmitting a test cell by switching to "activation"; and when receiving the state change signal, switching the current state of its own side from "activation" to "activated" to issue / test a test cell. 8. The ATM network bidirectional continuity check test device according to claim 7, further comprising second state switching means for stopping transmission and monitoring reception of a test cell issued by the other party. 9. A two-sided abnormality detection means for detecting an abnormal state of "two-sided activation" in which both ends of a check section are both activated ends by detecting that a received test cell is a test cell issued by a partner. The test apparatus for bidirectional continuity check of an ATM network according to claim 8, further comprising: 10. An initial state storage means for storing an initial operation state of the own side at the start of the continuity check test as an initial state; 10. The test apparatus for bidirectional continuity check of an ATM network according to claim 9, further comprising a state return means for setting the contents to the current state of the own side. 11. A test stop requesting means for issuing and transmitting a test stop request signal to the other side when ending the test from the own side when the current state of the own side is "activated", and a test stop request signal. The ATM network bidirectional continuity check test device according to any one of claims 7 to 10, further comprising: a stop signal transmitting means for issuing a test stop signal when receiving the test signal and transmitting the test stop signal to the other party. 12. The monitoring of the reception of a test cell is performed when a test cell or a user cell from the same path as that of the test cell cannot be received within a predetermined monitoring time during the test. An ATM network bidirectional continuity check test device according to any one of claims 7 to 11, wherein the test is performed. 13. A bidirectional continuity check test device provided at an end of the check section, for performing the bidirectional continuity check method according to claim 1.