JPH0496447A - Virtual path switching device - Google Patents

Abstract

PURPOSE:To prevent the rate of recovery from being lowered by adding information showing an identification number to specify a link generating a fault and the priority order of recovery to a recovery control signal, deciding the priority order of recovery based on this information when fetching the plural recovery control signals because of a multiple fault, and successively forming a detour path. CONSTITUTION:A recovery condition recording means A holds information showing the state of contributing fault recovery showing whether a self communication node is a communication node connected to the fault link or a communication node repeating the detour path, information showing the condition of advancing fault recovery, and information showing a decided result in the case of a preferential processing to the plural recovery control signals. A recovery preferential processing means B adds the identification number to specify the fault link or communication node and the information showing the priority order of recovery to the recovery control signal by detecting the cut-off of a virtual path with an upstream side communication node, decides the priority order of recovery based on this information when fetching the plural recovery control signals because of multiple fault, and successively forms the detour path. Thus, the high rate of recovery can be achieved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for relieving failures such as link failures that occur within an ATM (asynchronous transfer mode) transmission network by performing detour processing that switches virtual paths. This invention relates to a barge cell path switching device.

In particular, the present invention relates to a Hirch cell path switching device that can handle recovery processing from multiple failures using a distributed control method.

[Conventional technology]

As a conventional technology for switching paths when a failure occurs in an STM (Synchronous Transfer Mode) transmission network, there is a distributed control method (self-healing network method) in which each communication node behaves autonomously and decentrally to switch the path to a detour route. It has been known.

FIG. 5 is a diagram explaining the self-healing network method.

In the figure, the side to which information is transferred is considered to be the downstream side, and the side to which information is transferred is considered to be the upstream side. Communication node 51. ．． 51
If some kind of failure occurs in the path 52 between □,
Each communication notebook 511 to 515 sequentially switches from an upstream communication node to a downstream communication node for route search work (→
) and select the switching route to be used from among the searched routes to determine the detour route. Then, a path connection operation (<-) is performed to sequentially connect the selected switching route from the downstream communication node to the upstream communication node, thereby generating the switching route 55.

[Problem to be solved by the invention]

By the way, the distributed control method in the STM transmission network only deals with a failure of a single link within the network. Therefore, if another failure occurs in the network before recovery processing for one failure is completed, or if multiple failures occur simultaneously in the network, there are A plurality of types of recovery control signals are exchanged at the same time.

Communication nodes within the network that receive recovery control signals for such different failures secure spare capacity in connection links in order from the recovery control signal that arrives first. On the other hand, usable capacity may not be secured for recovery control signals corresponding to other failures that arrive late, and propagation of the recovery control signals stops at that communication node.

In other words, the spare capacity prepared in advance within the network is secured independently for multiple failure recovery operations.

Therefore, what was originally recoverable in terms of capacity,
Due to the scramble for spare capacity by each recovery control signal, it may become impossible to recover from any failure, and the failure recovery rate may be significantly lower than in the case of a single failure.

SUMMARY OF THE INVENTION An object of the present invention is to provide a virtual path switching device that can quickly and economically recover from a failure in an ATM transmission network, and can avoid a reduction in recovery rate even when multiple failures occur almost simultaneously. .

[Failure to solve the problem]

FIG. 1 is a block diagram showing the principle configuration of the system of the present invention.

In the present invention, a switch section reads a virtual path identification number included in the header area of an arriving cell transferred via a link, and logically connects the link according to a routing table that describes the transfer route of the cell. a path monitoring unit that is provided in a communication node that forms a Hirch cell path and detects that a virtual path between the upstream communication node and the upstream communication node is disconnected due to a failure in the link; In a virtual path switching device comprising a virtual path switching control unit that transmits and receives a recovery control signal between adjacent communication nodes and switches the virtual path to a Hirch cell path formed as a route that bypasses the failed link, the self communication node information indicating the involvement status of failure recovery indicating whether the node is a communication node connected to the failed link or a communication node relaying a detour route, information indicating the progress status of failure recovery, and information regarding a plurality of recovery control signals. A recovery status recording means that retains information indicating the determination result during priority processing and an identification number that identifies the failed link or communication node and recovery priority by detecting disconnection of the Hirch cell path between the upstream communication node. information indicating the above is added to the recovery control signal, and when multiple recovery control signals are captured due to multiple failures, recovery priorities are determined based on the information, and detour routes are sequentially formed according to the priorities. and recovery priority processing means.

[For production]

When a failure occurs in the downstream link of the own communication node, if the recovery status recording means of that communication node indicates that another failure recovery is currently in progress (if the own communication node If the occurrence of a failure is known), the communication node waits to send out a failure recovery control signal until the earlier failure recovery is completed, and starts the process after being notified of the termination of the earlier failure recovery.

If the downstream communication node of each of the multiple faulty links has no description in its recovery status recording means that another fault recovery is currently in progress (the time difference between occurrences is extremely small and each fault has failed due to non-arrival of each recovery control signal) (if the information is unknown), multiple recovery control signals are sent within the network.

In such a situation, multiple recovery control signals arrive at a given communication node, but the communication node that has received recovery control signals (with different identification numbers) for different failures uses the recovery priority processing means to decide which failure recovery should be prioritized. It determines whether to execute it first, and sends the result as a priority determination control signal to each communication node. The communication node on the downstream side of the failed link for non-priority side failure recovery, which has received this priority determination control signal, suspends recovery processing. Further, the upstream communication node sends a recovery end control signal to release the secured spare capacity to each communication node.

On the other hand, the downstream communication node of the failed link for prioritized failure recovery, which has received the priority determination control signal and the recovery end control signal for non-priority failure recovery, sends out the recovery control signal again. Furthermore, when the recovery process for the priority failure is completed, the upstream communication node sends out a recovery completion control signal.

In this way, the recovery process is first performed on the failed link for priority failure recovery, and then the non-priority failure recovery (for 3 or more failures, the next priority failure recovery) that receives the recovery end control signal sent out upon completion of the recovery process. The communication node on the downstream side of the failed link sends out a recovery control signal again to start the recovery process. That is, a plurality of failure recovery operations are performed in order of priority without duplication, and interruption and stoppage of failure recovery due to conflicts in multiple failure processing can be avoided.

Here, the control signals used in the device of the present invention include: (1) a recovery control signal used to form a detour virtual path, (2) a recovery control signal used to notify each communication node of the determination result of which of multiple failures should be restored first. There are priority determination control signals, and (1) a recovery completion control signal used to notify each communication node in the network that failure recovery has been completed.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 2 is a block diagram showing the configuration of an embodiment of the virtual path switching device of the present invention.

In the figure, when the side where the cell is input is called the downstream side and the side where the cell is output is called the upstream side, the cell is connected to the virtual path 22 accommodated in the link 21 set between the upstream side communication node. The signal is input and reaches the switch unit 24 via the path monitoring unit 23. The switch unit 24 refers to the routing table 27 and sends the arrived cell to the virtual path 25 accommodated in the link 26 set up with the downstream communication node.

Here, the virtual path switching device controls each link 21
Corresponding path monitoring unit 23, virtual path switching control unit 28, recovery status recording unit 30, and recovery priority processing unit 4
Consists of 0. In addition, the recovery status recording means 30
It has a communication node state recording section 31, a recovery state recording section 32, and a priority failure determination result recording section 33. The recovery priority processing means 40 includes a failure recovery identification number determination section 41 , a recovery priority processing section 42 , and a priority recovery determination section 43 .

The path monitoring unit 23 has a function of monitoring a failure in the Hirch cell path 22 on the receiving side, and notifies the virtual path switching control unit 28 of the occurrence of a failure. The virtual path switching control unit 28 refers to the communication node status recording unit 31 when the path monitoring unit 23 detects a failure in the link 21 to which the own communication node is downstream.

The communication node status recording unit 31 records whether or not the own communication node is currently involved in failure recovery, and if so, the role of the own communication node in the failure recovery (the node connected to the link where the failure occurred). or a relay node), and a failure recovery identification number that is uniquely determined within the network for failure recovery.

When the Hirch cell path switching control unit 28 refers to the communication node status recording unit 31, it learns that the own communication node is currently involved in other failure recovery and that other failure recovery is currently in progress within the network. Then, the state of the own communication node in the communication node state recording unit 31 is set to a recovery pending state, which waits until the recovery of the previous fault that has already been restored is completed, and the state of the own communication node is set to the recovery pending state, which waits until the recovery of the previous failure that has already been restored is completed, and the recovery for the fault recovery of the link to which the own communication node is connected is performed. Waits for control signal transmission. On the other hand, if the own communication node is not involved in failure recovery at the current location, the own communication node sends a recovery control signal to an adjacent node determined by the virtual path switching control unit 28.

At this time, the Hirch cell path switching control unit 28 determines a failure recovery identification number by a failure recovery identification number determination unit 41, and determines a recovery priority value by a recovery priority value determination unit 42, in order to cope with multiple failures. , and both are described in the recovery control signal sent out by the virtual path switching control unit 28 and transmitted.

The failure recovery identification number determining unit 41 determines a number uniquely determined within the network for the link in which the failure has occurred as the failure recovery identification number, and causes communication nodes within the network to recognize the failure to be restored by the recovery control signal. . This identification number may be, for example, a number defined for each link in the network, or any value that is unique within the network.

The recovery priority value determination unit 42 determines a recovery priority value for the purpose of determining which failure recovery should be performed first among a plurality of failure recovery processes that have occurred. This recovery priority value takes a value proportional to the capacity of the disconnected Hirch cell path, a value corresponding to the importance (priority) of the Hirch cell path, a value corresponding to the speed of failure occurrence, or other values.

When the virtual path switching control unit 28 provided in a communication node that is not the upstream communication node of the failed link receives the recovery control signal, the virtual path switching control unit 28 records the communication node status recording unit 31. refer. Here, the virtual path switching control unit 28
Normal operation is performed when the own communication node is not involved in failure recovery or is involved in the same failure as the failure recovery identification number written in the recovery control signal.

On the other hand, when referring to the communication node status recording unit 31, if the failure recovery identification number of which is different from the failure recovery identification number described in the recovery control signal is involved, the virtual path switching control unit 28 determines the priority determination result. Referring to the recording unit 33, it is investigated whether priority determination records for the two types of failure recovery identification numbers are written.

If the determination record has been written (if the communication node already knows that the type 2 failure has occurred), the virtual path switching control unit 28 discards the received recovery control signal. Also, if the judgment record is not written (if the communication node learns for the first time that the two types of failures have occurred in quick succession or at the same time, and recovery control signals for both are being sent within the network) In this case, the virtual path switching control unit 28 uses the priority recovery determination unit 43 to determine which failure recovery should be performed first and which one should be waited for - time based on the recovery priority values of the three. Further, the virtual path switching control unit 28 writes the result in the priority failure determination result recording unit 33, sends a priority determination control signal to all links connected upstream of the communication node, and outputs the determination result. Notify all communication nodes in the network.

Here, if the downstream communication node of the failed link for failure recovery described as non-priority (waiting side) recovery in the priority determination control signal receives the priority determination control signal, priority failure determination is performed. The determination result described in the priority determination control signal is recorded in the result recording unit 33, and the self-communication node status of the communication node status recording unit 31 is set to a recovery pending state to wait for completion of priority-side failure recovery.

In addition, if the upstream communication node of the failed link for failure recovery that is described as non-priority (waiting side) recovery in the priority determination control signal receives the priority determination control signal, The communication node stops sending out the recovery control signal that was sent out, sends a recovery end control signal to all links connected to the upstream side of the communication node, and releases the spare capacity secured for failure recovery.

In addition, when a communication node other than the above receives the priority determination control signal, if the priority result described in the priority determination control signal is already written in the priority determination result recording unit 33 of the own communication node, priority determination is made. Terminate propagation of control signals. On the other hand, if there is no description of the priority result described in the priority determination control signal in the priority determination result recording unit 33 of the own communication node, the priority result is written in the priority determination result recording unit 33, and further upstream of the own communication node The priority determination control signal is sent to all links connected to the link.

The downstream communication node for priority side failure recovery that has received the recovery end control signal for non-priority side failure recovery transmits the recovery control signal again.

When a communication node other than the above receives a recovery end control signal for non-priority side failure recovery, if the end of the non-priority side failure has already been written in the recovery status recording unit 32, the recovery end control signal is propagated. If there is no description, the end of the non-priority side failure is written in the recovery state recording unit 32, and the spare capacity reserved for the failure recovery described in the recovery end control signal is released.

Thereafter, the own communication node further sends out a restoration end control signal to all links connected to the upstream side.

The recovery status recording unit 32, which holds the failure recovery identification number of the failure for which recovery in the network has been completed, is referenced by the virtual path switching control unit 28, and is used to control the propagation of control signals after one day of recovery and the associated backup. Prohibits securing capacity.

When recovering from the preceding fault and the priority fault above, if all Hirch cell path switching is completed or the predetermined recovery time is exceeded and the fault recovery is completed, the upstream communication node of the faulty link will A recovery end control signal is sent to the communication node. This recovery end control signal is sent to the communication note on the downstream side of the faulty link of the above-mentioned subsequent fault that is in the recovery pending state, and the above-mentioned non-priority fault (
If the downstream communication node receives the message (failure recovery, which has the next priority in the case of three or more failures), it releases the pending state and starts the failure recovery process.

In addition, when a communication node other than the above receives the recovery end control signal, if the failure recovery identification number of the already completed failure recovery is registered in the recovery state recording unit 32, it ends the transmission of the recovery end control signal. do. In addition, if it is not registered, if the failure recovery identification number of the non-priority side failure recovery is registered in the recovery status recording section, the registration will be deleted, and the failure recovery identification number written in the recovery end control signal will be changed. Register and
The upstream communication node sends a recovery end control signal to all communication nodes in the network.

Hereinafter, with reference to FIGS. 3 and 4, the behavior of the mesh body according to the apparatus of this embodiment will be explained.

Note that the behavior differs depending on whether the downstream communication node of the link with the subsequent failure is aware of the preceding failure or the case where it is unknown, and will therefore be explained separately in FIG. 3 and FIG. 4, respectively.

(a) When it is known (FIG. 3) ■ An earlier failure occurs between the communication nodes C1 and Sl, and the downstream communication node S1 sends a recovery control signal into the network. Here, area C3I is an area for recovery control signals sent in response to a failure between communication nodes C1 and Sl.

■ A later failure occurs between communication nodes C2 and S2, but the recovery control signal for the earlier failure has already arrived at the communication node S2 on the downstream side of the later failure link, and the earlier failure is currently being recovered. is known. Therefore, the communication node S2 cannot send out a recovery control signal for fault recovery of its own communication node connection link and is in a pending state.

■ When the recovery from the preceding failure is completed, the upstream communication node F'CI of the preceding failure link sends a recovery end control signal R to the communication node in the network, and terminates the sending of the recovery 111 control signal for the preceding failure. , extra spare capacity C
Release 31'.

(2) The communication node S2, which has received the recovery end control signal R for the preceding failure, learns that the recovery from the preceding failure has ended, releases the pending state, sends out the recovery control signal I, and starts failure recovery.

Here, area C82 is an area for a recovery control signal sent in response to a failure between communication nodes C2 and S2. , ■ When the subsequent failure recovery is finally completed, the subsequent failure recovery completion control signal R is sent to the upstream communication node 1 of the subsequent failure link.
” Sent from C2 and restoration ends.

(b) When unknown (Figure 4) ■ Between communication nodes C1 and Sl, communication nodes C2 and S2
A plurality of failures occur in succession or simultaneously in a short period of time, and each sends a recovery control signal into the network because each party is unaware of the occurrence of the other failures. Here, area C3I is an area for a recovery control signal sent in response to a failure between communication nodes C1 and Sl. Area C32 is the communication node C2
, S2 is the area of the recovery control signal sent out in response to a failure.

(2) When communication node T receives the recovery control signal I7 from both communication nodes S1 and s2, it becomes clear that recovery from multiple failures is proceeding simultaneously.

■ Communication node T, which has learned that multiple failures are progressing simultaneously, uses the priority recovery determination unit to determine which failure should be prioritized (in this example, priority is given to failure recovery between communication nodes S1 and cl), and uses the result to perform priority determination control. It is written in signal J and transmitted to all communication nodes in the network.

■ The downstream side communication node S2 of the non-priority failed link that has received the priority determination control signal J goes into a hold state, and the secondary side communication node C2 stops sending out the recovery control signal and releases the secured spare capacity. Restoration end control signal R
Send out.

■ The downstream side communication node S1 of the priority side faulty link receives the priority determination control signal J and learns that its own failure recovery is on the priority side, and also receives the recovery end control signal R from the non-priority side and performs the non-priority recovery. When it learns that the spare capacity secured by the priority side has been released, it sends out a recovery control signal again.

■ When the failure recovery on the priority side is completed, the upstream communication node C1 of the failure link on the priority side sends a recovery end control signal R to notify the completion of recovery on the priority side, and also uses the extra reserved capacity C31'. unlock.

(2) When the non-priority side communication node S2 learns that recovery from the priority side failure has ended, it releases the hold and sends out the recovery control signal again.

■ Finally, when the non-priority side failure recovery is completed, the non-priority side failure recovery end control signal R is sent to the non-priority side failure link.
It is transmitted from the upstream communication node C2, and the recovery ends.

〔Effect of the invention〕

As described above, in the case where the communication node on the downstream side of a failed link is aware of the occurrence of another failure, the communication node performs failure recovery on the link to which the own communication node connects until the failure recovery is completed. Let's meet up.

Also, the communication node is unknown to other failure recovery,
When recovery control signals for recovery from multiple failures are sent within the network, a communication node that learns that recovery from multiple failures is proceeding at the same time determines recovery priorities and performs failure recovery in sequence according to that priority. Control what you do.

In this way, when multiple faulty links occur in succession in a short period of time or at the same time, the device of the present invention performs recovery processing for multiple failures one after another without conflict, resulting in a high recovery rate. can be achieved. In other words, AT with high reliability for failure recovery
M transmission network can be realized.

Processing means, 41... Failure recovery identification number determination unit, 42.
. . . Recovery priority value determination unit, 43 . . . Priority recovery determination unit.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the basic configuration of the present invention. FIG. 2 is a block diagram showing the configuration of an embodiment of the present invention. FIGS. 3 and 4 are diagrams for explaining the behavior of the wire mesh body according to the apparatus of this embodiment. FIG. 5 is a diagram explaining the self-healing network method.

Claims (1)

[Claims] (1) The switch unit reads the virtual path identification number included in the header area of the arriving cell transferred via the link, and logically connects the link according to the routing table that describes the transfer route of the cell. a path monitoring unit that is provided in a communication node that forms a virtual path by detecting that the virtual path between the upstream communication node and the upstream communication node is disconnected due to a failure in the link; A virtual path switching device comprising a virtual path switching control unit that transmits and receives a recovery control signal between adjacent communication nodes and switches the virtual path to a virtual path formed on a route that bypasses the failed link. Information indicating the involvement status of failure recovery indicating whether the node is a communication node connected to the failed link or a communication node relaying a detour route, information indicating the progress status of failure recovery, and a plurality of recovery control signals. recovery status recording means that retains information indicating the determination result of priority processing for Information indicating the priority is added to the recovery control signal, and when multiple recovery control signals are captured due to multiple failures, the recovery priority is determined based on the information, and a detour route is sequentially determined according to the priority. A virtual path switching device comprising a recovery priority processing means for forming a virtual path.