JP2970573B2 - ATM virtual path switching node and failure notification method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ATM (Asyn)
AT that performs recovery from a failure by bypassing a virtual path affected by various failures occurring in a network to another virtual path (chronous transfer mode; asynchronous transfer mode).
M virtual path switching node.

[0002]

2. Description of the Related Art Broadband ISDN (Integrated)
ATM technology is a promising network technology for realizing Service Digital Network (“BISDN”). The traffic accommodated in the ATM network is transmitted on a virtual path (virtual path; also referred to as "VP") in which connections and bands are virtually allocated on physical links such as optical fibers and coaxial cables. A plurality of virtual paths can be set on each physical link.

In such an ATM network,
If a physical link or node failure occurs, the LCD
(LOss of Cell Delineatio
n) and SDH (Synchronous Digital Hierarchy;
AT using synchronous digital hierarchy) frames
When transmitting M cells, LINE AIS of SDH
(Alarm Indication Signal; alarm display signal) L
OF (Loss of Frame), LOS (Loss of Frame)
ATM, etc. as link failures such as
The node can detect the failure.

When a virtual path affected by a failure is detoured to another virtual path between its endpoints based on the detected failure information, information for activating a virtual path switching process is transmitted to another ATM. Must be transferred to node.

For example, Japanese Patent Application Laid-Open No. 4-257143 discloses that a communication node on the downstream side of a troubled link performs a capacity check via communication means facilitated between communication nodes involved in switching, and reports the result of the troubled link. A switching path is determined by integrating the upstream communication nodes and switching is executed after confirming the formation of the switching path, and a small number of signals are exchanged by distributed control for a link failure or a link failure in response to an intentional link disconnection request. A virtual path switching device capable of performing the switching process at a higher speed has been proposed.
Also, for example, Japanese Patent Application Laid-Open No. Hei 5-235983 discloses an ATM.
As a virtual path switching device that rescues failures by detour processing that switches virtual paths for failures such as link failures and node failures that occur in the transmission network, when a failure occurs in the virtual path being used, switching is performed The switching control signal is propagated on the path of the switching virtual path set in advance between the switching end nodes to secure the capacity to perform switching, recover from the failure, and switch the switching virtual path to the switching virtual path. Therefore, the number is relatively small, and a method has been proposed which realizes a high-speed recovery without using a centralized control station.

Reference (1) (Transactions of the Institute of Electronics, Information and Communication Engineers, V
ol. J77-BI No. 3pp. 115-123
1994/3, "Path switching method by centralized control in ATM transmission network", IEICE CS94-151
IN94-123 1994/11) proposes an ATM self-healing algorithm and describes its failure recovery characteristics. In the virtual path switching process when the same cell flowing on the working virtual path is not flown to the backup virtual path in advance, the virtual path A switching control method between an ATM node at a transmitting end and a receiving end is described. However, a method of detecting a link failure and starting a switching process at an ATM node at a virtual path receiving end after a link failure occurs is clarified. Not.

Conventionally, as starting information of such a virtual path switching process, reference (2) (Proceedings of International Switching Symposium, Yoshitaka Fujita et al., And ATM Virtual Path Protection Switching and Application (Yoshitaka Fujitaet)
al. , “ATM VP Protection S
switchingand Application
s ", Proceedings of Internationala
Tional Switching Symposiu
m, P. g20, pp. 82-86, April 19
95) As described in the ATM virtual path switching method described in
ITU-TI. There is a method of using a VP AIS cell specified in 610.

FIG. 5 is a diagram for explaining such an ATM virtual path switching method. Referring to FIG.
The TM nodes AD include links 502, 503, 505,
The links 501 and 502 are connected to ATM nodes A and B, respectively, and the links 507 and 508 are connected to ATM nodes C and D, respectively.

The virtual paths 511 and 512 are set so as to pass through the links 501 to 503 and to be terminated at the ATM node D, and the cell is transmitted to the node D via the virtual path. Then, the node D outputs the cells on the virtual paths 511 and 512 to the virtual paths 519 and 520 of the link 508, respectively.

The virtual paths 513 and 514 are
The cell is set to be terminated at the ATM node C through the links 501 and 502, and the cell is transmitted to the node C via the virtual path. And node C
Outputs the cells on the virtual paths 513 and 514 to the virtual paths 521 and 522 of the link 507, respectively.

Each of the virtual paths 515 to 518 is set in advance as a backup virtual path for the virtual paths 511 to 514 in preparation for a failure in the network.
04-506 and is terminated at the ATM node D, and virtual paths 517 and 518 are set.
Is set to pass through the links 504 and 505 and be terminated at the ATM node C.

Next, a description will be given of a method of activating a switching process in which a failure occurs in the link 501 and a cell transmitted by the virtual path 511-514 is bypassed by the backup virtual path 515-518.

When a failure occurs in the link 501, the ATM node A detects the failure of the link 501 and
It detects that a failure has occurred in the virtual paths 511-514.

Next, the ATM node A sends VP AI to the ATM node D, which is a terminal node downstream of the virtual paths 511, 512, and the ATM node C, which is a terminal node downstream of the virtual paths 513 and 514, as VP AI as alarm information.
Generate and transfer S cells.

The ATM nodes C and D are connected to virtual paths 513 and 514 and virtual paths 511 and 5 respectively.
12, a VP AIS cell is received, and it is recognized that a fault has occurred in each of the virtual paths 511 and 514, and switching processing to the backup virtual path is started.

Thereafter, when the same cell flowing on the virtual path 511-514 is also transmitted to the backup virtual path 515-518 at the transmitting end ATM node in advance, the processing for switching to the backup virtual path is performed by the virtual path transmission. This can be performed without using message communication for switching control with the end ATM node.

In the above conventional method, the link 501 is used.
When a failure occurs in the virtual path, a failure is detected for each virtual path by the VP AIS cell received for each virtual path in the link 501, and switching processing to the backup virtual path is started.

Reference (3) (ANSI T1S1.
5 / 96-110 ATM Virtual Path
Group Protection Switchi
As described in ng (by Lucent)), the ATM nodes that start the virtual path switching process by grouping the virtual paths in which the ATM nodes at the transmission end and the reception end of the virtual path are the same are grouped. VP received earliest in virtual path
There is a method in which a virtual path grouped by an AIS cell is specified and switching processing is started collectively.

Reference (4) (ANSI T1X)
1.5 / 96-044 ATM VP Fault Re
configuration Proposal for
Uni-Ring Networks (by ALC
As described in ATEL)), when a link failure is detected, the switching process of each virtual path is activated, not by using the VP AIS cell received from each virtual path, but by notifying the link failure. There is a method for performing this in a cell for the purpose.

[0020] The payload of this cell contains an identifier for indicating the position of the link where the failure has occurred. Therefore, the downstream AT that starts the virtual path switching process
The M node receives the cell from one virtual path, and collectively activates a process of switching the virtual path that is accommodated in the failed link and terminates at the own node to the backup virtual path. Can be.

Referring to FIG. 5, a method for starting a process of switching a cell transmitted by the virtual path 511-514 to be bypassed by the backup virtual path 515-518 after a failure in the link 501 will be described below.

When a failure occurs in the link 501, the ATM node A detects the failure in the link 501 and, after detecting the failure in the link 501, terminates the ATM which is the terminal node downstream of the virtual paths 511 and 512.
A link failure notification cell including an identifier indicating a failed link position is generated and transferred to the node D and the ATM node C which is a downstream terminal node of the virtual paths 513 and 514.
ATM nodes C and D each have a virtual path 5
11-514, the link failure notification cell is received from any of the virtual paths 511 and 512, and the link 50 is determined based on information indicating the location of the failed link included in the cell.
1 recognizes that a failure has occurred.

Each of the ATM nodes C and D previously stores information on which link each virtual path terminating at the own node passes through, and checks the information with the fault link position information in the fault notification cell. By the matching process, the process of switching the virtual path accommodated in the link 501 to the backup virtual path is started.

Thereafter, when the same cell flowing on the virtual path 511-514 is also transmitted to the backup virtual path 515-518 at the transmitting end ATM node in advance, the processing for switching to the backup virtual path is performed by transmitting the virtual path. This can be performed without using message communication for switching control with the end ATM node.

[0025]

As described above, in the conventional system, when a virtual path affected by a failure is detoured to another virtual path between its termination points based on a detected link failure, The virtual path switching process can be started by the VP AIS cell.

However, such a conventional method has the following problems.

That is, when the number of virtual paths passing through the failed link and terminating at the downstream ATM node is large, the VP AI to each virtual path is
There is a problem that the processing load for generating and transmitting the S cell increases, and it takes time for the VP AIS cell to be received from all the virtual paths in the ATM node that starts the virtual path switching process. .

In addition, each ATM node receives a VP AIS cell for every virtual path to be switched and starts switching processing of the virtual path, so that the processing load increases.

Therefore, the time required from the occurrence of a link failure to the recovery of all virtual paths increases.

The above processing load can be reduced by grouping virtual paths having the same ATM node at the transmitting end and the receiving end. However, when the purpose is to notify a link failure, It is not a link failure notification method that minimizes the processing load.

Further, in order to speed up the activation of the virtual path switching process, the generation of VP AIS cells is accelerated, and transmission delay is suppressed by assigning a VP AIS cell to the highest priority queue when the VP AIS cell passes at each ATM node. In this case, if the number of virtual paths for transferring VP AIS cells increases, the effect on user cells due to cell loss, cell delay, and the like increases.

In the conventional method of notifying a fault notifying cell including position information of a link in which a fault has occurred, a conventional method of generating a link fault notifying cell in an ATM node which has detected a link fault, and a process of transfer in each ATM node. Although the load can be suppressed, it is necessary to notify each ATM node that starts the virtual path switching processing of the link position where the failure has occurred. In addition, each ATM node uses the received link failure notification cell to determine whether to activate the virtual path switching process.
It is necessary to hold the information of the passing link for each virtual path, and to determine whether or not the switching process can be activated, it is necessary to perform a process of comparing the passing link information with the fault link position information in the received fault notification cell. is there.

Accordingly, the present invention has been made in view of the above-mentioned problems, and has as its object to provide a link failure notification cell in which a VP AIS cell can be used as a link failure notification cell. The generated link position information is unnecessary, and it is not necessary for each ATM node to hold the passing link information of the virtual path.
Further, a link failure notification method and an ATM virtual path switching node capable of reducing the processing load of generating, transmitting and switching virtual paths for cells for notifying a link failure and capable of recovering the failure of the virtual path in a relatively short time. To provide.

[0034]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention generates and sends information for notifying a link failure.
Virtual path for link failure notification transfer
Most virtual paths with the same node at the end
Select one or more virtual paths passing through the node
ATM virtual machine that detects and detects link failure
The switch node switches the link failure notification specified in advance.
Generation of a failure notification cell for the virtual path for transmission and
Sending out .

The ATM virtual path switching node of the present invention is connected by a plurality of links through which cells are transmitted in an ATM network, and provides a service provided in advance in the plurality of links when a failure occurs in the ATM network. An ATM virtual path switching node for switching a working virtual path used for a standby virtual path to a protection virtual path preset for bypassing, wherein a switch for switching between the working virtual path and the protection virtual path; A virtual path routing table referred to by a virtual path switching control unit when switching between the working virtual path and the backup virtual path; a link failure detection unit that monitors the link for each link; and a link failure notification. Selected to transfer cells A link failure notification cell transfer virtual path management unit that holds information about a virtual path, and when a link in which a failure has occurred is notified from the link failure detection unit, the link failure notification cell transfer virtual path management unit is notified. The link failure notification cell is generated between the failure notification cell generation unit that generates and transfers the link failure notification cell to the failure notification cell transfer unit according to the received information, and another ATM virtual path node via a virtual path. Transmitting and receiving, the content of the received link failure notification cell, the failure notification cell transfer unit to notify a virtual path switching activation determination unit, comprising, the virtual path switching activation determination unit, from the failure notification cell transfer unit According to the information of the received failure notification cell and the virtual path manager for transferring the referenced link failure notification cell. A virtual path switching control unit that determines switching activation of a virtual path, and further controls the switch with reference to the virtual path routing table according to information from the link failure detection unit and the virtual path switching activation determination unit. in ATM virtual path switching node with the Li
Link failure notification
Of a virtual path for transferring the link failure notification to be transmitted
Is the highest among the virtual paths where the transmitting end is the same node.
Of virtual paths passing through many nodes
It is performed by selecting several pieces .

[0036] In the present invention, the failure notification cell transfer unit may be configured to transmit a designated link failure notification transfer according to the information of the link failure notification transfer virtual path notified from the link failure notification cell transfer virtual path management unit. The link failure notification cell transmitting on the virtual path may be preferentially transmitted to the switch.

According to the present invention, the virtual path switching start-up determining unit determines that the same VPI value as the VPI value of the link failure notification cell transfer virtual path held in the link failure notification cell transfer virtual path management unit. When the link failure notification cell having a value is received from the failure notification cell transfer unit, a plurality of the working virtual paths that pass through the working link in which a failure has occurred, and that are to be switched by the own node are a plurality of the working virtual paths. The virtual path switching control unit may be configured to notify the virtual path switching control unit so as to switch to the backup virtual path at once .

[0038]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below. According to a preferred embodiment of the present invention, a link failure detection unit (101 in FIG. 1) for detecting a failure of a link terminated at its own node, a link failure notification cell transmitted to a virtual path, and a virtual path , A switch for switching between the working virtual path and the backup virtual path (103 in FIG. 1), and when a link failure detection unit notifies the end link of a failure. A failure notification cell generation unit (104 in FIG. 1) for generating a cell for notifying the link failure, and activation of virtual path switching processing according to the link failure notification cell notified from the failure notification cell transfer unit. The virtual path switching activation determining unit (105 in FIG. 1) that determines the link and the link that manages the virtual path for transferring the link failure notification cell Virtual path management unit for fault notification cell transfer (106 of FIG. 1), virtual path switching control unit which controls the switch to switch the current virtual path to the protection Virtual Path (Figure 1
107), and a virtual path routing table (108 in FIG. 1) referred to in the switching control.

In a preferred embodiment of the present invention, the virtual path manager for transferring a link failure notification cell (106 in FIG. 1) stores the VPI value of the virtual path selected to transfer the link failure notification cell. to manage.
The failure notification cell generation unit (104 in FIG. 1) is a virtual path management unit (10 in FIG. 1) for transferring a link failure notification cell.
6) Generates a link failure notification cell for the failure notification transfer virtual path notified by priority, and transmits it to the failure notification cell transfer unit (102 in FIG. 1).

The failure notification cell transfer unit (102 in FIG. 1)
The failure notification cell transmitted on the virtual path for link failure notification cell transfer is preferentially transmitted to the switch (103 in FIG. 1), and the input virtual path (130 _{1 to} 130 in FIG. 1) is transmitted.
_k ), the contents of the link failure notification cell received are notified to the virtual path switching activation determination unit (105 in FIG. 1).

The virtual path switching activation determining unit (105 in FIG. 1) is the same as the link failure notification cell transfer virtual path held in the link failure notification cell transfer virtual path management unit (106 in FIG. 1). When a failure notification cell having the VPI value is received from the failure notification cell transfer unit (102 in FIG. 1), a plurality of working virtual paths that pass through the link in which the failure has occurred and are to be switched by the own node are set as backup virtual paths. It is determined that the processes for switching to paths are to be activated collectively, and the switching activation information is notified to the virtual path switching control unit (107 in FIG. 1).

The virtual path switching control unit (FIG. 1)
107) is transmitted to the virtual path routing table (109 in FIG. 1) when the virtual path switching activation determining unit (105 in FIG. 1) notifies the virtual path switching processing to activate in a lump. Batch switching control of the switch (103 in FIG. 1) is performed according to the stored information.

In the link failure notification method of the present invention, in a preferred embodiment, one or more virtual paths passing through the most nodes among the virtual paths whose transmitting ends are the same node are linked. This is a virtual path for transferring the failure notification cell.

For this reason, according to the embodiment of the present invention,
Since the number of link failure notification virtual paths can be reduced as compared with a method in which the transmitting end and the receiving end select a virtual path for notifying a link failure from a virtual path of the same node, generation and transmission of a link failure notification cell The load can be further reduced.

Further, the virtual path switching activation determining unit (105 in FIG. 1) stores information on a plurality of virtual path groups to be switched for each virtual path for link failure transfer, and thereby, the virtual path for link failure transfer. Based on the VPI value of the link failure notification cell received from the path, it is possible to easily determine a plurality of virtual paths that pass through the failed link and are to be switched by the own node. Therefore, information on the location of the failed link in the link failure notification cell is unnecessary, and it is not necessary for each ATM node to hold the passing link information of the virtual path.

[0046]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention;

FIG. 1 is a block diagram showing an embodiment of an ATM virtual path switching node according to the present invention. In FIG. 1, reference numeral 100 denotes an ATM virtual path switching node, and 120 ₁ -120 _j denote input links, 1
40 ₁ -140 _j is an output link, 130 ₁ -130 _k is an input virtual path, 150 ₁ -150 _k is an output virtual path, and the ATM virtual path switching node 100
Input link 120 ₁ -120 _j and output link 140 ₁ -1
The virtual path is switched between 40 _j .

The ATM virtual path switching node 1
00 is a link failure detection unit 101, a failure notification cell transfer unit 102, a switch 103, a failure notification cell generation unit 104,
The configuration includes a virtual path switching start-up determining unit 105, a link failure notification cell transfer virtual path managing unit 106, a virtual path switching control unit 107, and a virtual path routing table 108.

The link failure notification cell transfer virtual path management unit 106 sets a virtual path for notifying a link failure in the failure notification cell generation unit 104 and the failure notification cell transfer unit 102 in advance.

The link failure detection unit 101 detects a failure of each input link, and notifies the failed link to the failure notification cell generation unit 104.

The fault notifying cell generating unit 104 generates a link fault notifying cell to a virtual path set in advance with high priority and transfers it to the fault notifying cell transfer unit 102, and the fault notifying cell transfer unit 102 , The link failure notification cell transmitted on the virtual path for link failure notification transfer is sent to the switch 103 with priority.

Next, a link failure notification cell is received from the ATM virtual path switching node that has detected the link failure,
The operation of the ATM virtual path switching node 100 that starts the virtual path switching process will be described with reference to FIG.

The failure notification cell transfer unit 102 of the ATM virtual path switching node notifies the virtual path switching activation determination unit 105 of the contents of the link failure notification cell received from the input virtual path.

The virtual path switching start determination unit 105
Link failure notification cell transfer virtual path manager 106
The VPI value and the failure notification cell transfer unit 10 are referred to by referring to the link failure notification transfer virtual path information held by the
When the VPI values of the link failure notification cells received from the second node coincide with each other, it is determined that a plurality of working virtual paths that pass through the failed link and that are to be switched by the own node are faulty, and are designated as backup virtual paths. It is determined that the switching processes are to be activated collectively, and the switching activation information is notified to the virtual path switching control unit 107.

When the virtual path switching control section 107 is notified by the virtual path switching start determining section 105 to start a plurality of virtual path switching processes collectively, the virtual path switching table 107 refers to the virtual path routing table 108 and the switch 103. Is performed.

The failure notification cell transfer unit 102 of the ATM virtual path switching node located between the ATM virtual path switching node that detects the link failure and the ATM virtual path switching node that starts the virtual path switching process is The link failure notification cell received from the link failure notification transfer virtual path in the input virtual path is preferentially transmitted to the switch.

Next, a method of switching a virtual path using the ATM virtual path switching node according to the embodiment of the present invention shown in FIG. 1 will be described with reference to FIG. A link failure notification method according to an embodiment of the present invention will be described with reference to FIGS.

In FIG. 2, reference numerals 280 to 284 denote ATM virtual path switching nodes of the present embodiment shown in FIG. 201-214 are links, 220 ₁ -220 _j , 22
11 ₁ -221 _k , 222 ₁ -222 ₁ , 230 ₁ -230 _j ,
231 ₁ -231 _k , 232 ₁ -232 ₁ , 240 ₁ -24
_{0 j, 241 1 -214 k,} 242 1 -242 1, 250 1 -
250 _j , 251 ₁ -251 _k , and 252 ₁ -252
₁ is a virtual path showing a plurality of virtual paths as one for the sake of convenience, and the working virtual path 230 ₁ -23
0 _j, 231 ₁ -231 _k and 232 ₁ -232 _per preliminary virtual path 240 ₁ -240 _j, 241 ₁ -
241 _k and 242 ₁ -242 ₁ are provided respectively.

ATM virtual path switching node 280
Are 220 ₁ -220 _j , 221 ₁ -221 _k and 222 ₁
Transmitting -222 ₁ inputted from the virtual path cells same cell and to each working virtual path and the protection virtual path.

270 is a link failure notification signal;
0 is a failure that occurs in the link 201.

The virtual paths 250 ₁ -250 _j , 251
₁ -251 _k and 252 ₁ is connected to a working virtual path in an ATM virtual path switching nodes 282, 283 and 284, respectively.

FIG. 3 shows a working virtual path connected between ATM virtual path switching nodes, which is not shown in FIG. 2 for convenience.

FIG. 4 shows one or more of the working virtual paths shown in FIG. 3 in which one or more of the virtual paths passing through the most nodes among the virtual paths of the same node are notified of the link failure. FIG. 5 is a diagram for explaining an embodiment of a link failure notification method using a virtual path for cell transfer. In the example shown in FIG. 4, 230 _1-2 in FIG.
Against 30 _j, 231 ₁ -231 _k and 232 ₁ -232 ₁ virtual path, and the 232 _first virtual path link failure notification cell transfer virtual path.

Here, the link 260 in FIG.
Occurs, the ATM virtual path switching node 282
Detects a link failure and generates and transfers a link failure notification cell to an ATM virtual path switching node downstream only for a virtual path for link failure notification at high speed. Incidentally, the virtual path link failure notification is 232 ₁ of the virtual path as described above.

The ATM virtual path switching node 2
Reference numerals 82 and 283 denote failure notification cells input from a virtual path for link failure notification transfer not terminated at the own node,
High-speed transfer to the downstream ATM virtual path switching nodes 283 and 284 is performed.

On the other hand, the ATM virtual path switching node 2
When the link failure notification cell is received from the virtual path 232 ₁ , the working virtual path 230 ₁ -230 _j
Are switched collectively so as to connect the virtual paths 250 ₁ -250 _j connected to the backup virtual paths 240 ₁ -240 _j .

[0067] Similarly, ATM virtual path switching node 283 receives the link failure notification cell from the virtual path 232 _1, working virtual path 231 ₁ -23
It switched collectively virtual path 251 ₁ -251 _k connected to 1 _k to connect to the backup virtual path 241 ₁ -241 _k.

Further, when the ATM virtual path switching node 284 receives the link failure notification cell from the virtual path 232 ₁ , the ATM virtual path switching node 284 receives the active virtual path 232 ₁ -23.
Switches the virtual paths 252 ₁ -252 ₁ connected to 2 ₁ collectively to connect to the backup virtual path 242 ₁ -242 _1.

[0069]

As described above, according to the present invention,
When a virtual path affected by a failure based on a detected link failure is diverted to another virtual path between its termination points, the node that detects the link failure uses a small number of virtual Since the configuration is such that the high-speed generation and transfer of the link failure notification cell is performed only for the path, the processing load of the generation and transfer of the link failure notification cell can be reduced.

Further, according to the present invention, a node that transfers a failure notification cell from an input link to an output link preferentially transfers only a failure notification cell flowing on a set virtual path, and thus gives the failure notification cell to a user cell. The effect has an advantage that the effect can be reduced as compared with the method of transferring the failure notification cell for each virtual path.

Further, according to the present invention, in the node that activates the virtual path switching process, a failure occurs only by the VPI value of the failure notification cell received from the selected small number of link failure notification virtual paths. By specifying a virtual path group accommodated in the link and terminating at the own node, activation of virtual path switching processing and switch control processing can be performed collectively.

Therefore, according to the present invention, each ATM node passes through each virtual path necessary for specifying a virtual path group accommodated in the failed link and terminated at its own node. Without retaining the link position information, a high-speed virtual path restoration process can be performed when a node or link failure occurs.

According to the present invention, it is not necessary to include information indicating the position of the link where a failure has occurred in the information of the failure notification cell. Therefore, the VP AIS cell, which is alarm information, is used as the link failure notification cell. In addition to the VP AIS cell, the present invention can be easily applied to a link failure notification cell that does not include information on the position of a failed link.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an ATM virtual path switching node according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a virtual path switching operation by an ATM virtual path switching node according to one embodiment of the present invention.

FIG. 3 is a diagram showing a working virtual path connected between ATM virtual path switching nodes in FIG. 2;

FIG. 4 is a diagram showing a virtual path for link failure notification cell transfer in FIG. 3;

FIG. 5 is a diagram illustrating conventional virtual path switching.

[Explanation of symbols]

100, 280-284 ATM virtual path switching node 101 Link failure detection unit 102 Failure notification cell transfer unit 103 Switch 104 Failure notification cell generation unit 105 Virtual path switching activation determination unit 106 Link failure notification cell transfer virtual path management unit 107 Virtual path Switching control unit 108 Virtual path routing table 120 ₁ -120 _j input link 130 ₁ -130 _k input virtual path 140 ₁ -140 _j output link 150 ₁ -150 _k output virtual path 201-214, 501-508 link 220 ₁ -220 _j , 221 ₁ -221 _k , 222 ₁ -22
_{2 1, 230 1 -230 j,} 231 1 -231 k, 232 1 -
_{232 1, 233 1 -233 m,} 234 1 -234 n, 23
_{5 1 -235 o, 240 1 -240} j, 241 1 -241 k,
242 ₁ -242 ₁ , 250 ₁ -250 _j , 251 ₁ -25
_{1 k, 252 1 -252 1,} 511-522 virtual path 260 link failure 270 link failure notification cell

Claims (2)

(57) [Claims] 1. An active virtual network connected by a plurality of links through which cells are transmitted in an ATM network and used for providing a service preset in the plurality of links when a failure occurs in the ATM network. An ATM virtual path switching node for switching a path to a backup virtual path set in advance for bypassing, comprising: a switch for switching between the working virtual path and the backup virtual path; and wherein the switch includes the working virtual path and the backup virtual path. When a path is switched, a virtual path routing table referred to by a virtual path switching control unit, a link failure detection unit that monitors the link failure for each link, and a link failure notification cell that is selected to be transferred. That holds information about the virtual path When a link in which a fault has occurred is notified from the link fault detection unit, a fault notification cell is transferred according to the information notified from the link fault notification cell transfer virtual path management unit. A link failure notification cell that generates and transfers a link failure notification cell to a transfer unit; and a link failure notification cell that is transmitted and received between the ATM virtual path node and another ATM virtual path node via a virtual path. The failure notification cell transfer unit that notifies the contents of the failure notification cell to a virtual path switching activation determination unit.The virtual path switching activation determination unit includes the failure notification cell and the failure notification cell received from the failure notification cell transfer unit. Determines whether to start switching virtual paths according to the information of the virtual path manager for cell failure notification cell transfer referred to Further, according to information from the link fault detecting unit and the virtual path switching activation determination unit, the virtual path routing tables refer to ATM virtual path switching with a virtual path switching control unit for controlling the switch to
In the replacement node, the link failure notification cell transfer virtual path management unit
Of the virtual path for link transfer
The decision is made in the virtual path where the sender is the same node.
One or more virtual paths through the most nodes in
Is an ATM virtual path switching node performed by selecting a plurality of nodes. 2. A virtual path for link failure notification transfer for generating and transmitting information for notifying a link failure, a virtual path passing through the most nodes among the virtual paths whose transmitting ends are the same node. The ATM virtual switching node that selects and determines one or a plurality of link failures and detects a link failure generates and sends a failure notification cell to a prespecified virtual path for link failure notification transfer. ,
A failure notification method, characterized in that: