JP3196999B2 - ATM communication network and local exchange - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is used in an ATM (Asynchronous Transfer Mode) communication network. In particular, the present invention relates to a technology for restoring a failure of a communication device inserted in a transmission line.

[0002]

2. Description of the Related Art An ATM communication network is physically a virtual channel handler which performs switching on a virtual channel (VC) basis.
(Virtual Channel Handler, exchange) and a virtual path handler (Virtual P: VP) that sets a route for information transfer in units of a virtual path (Virtual Path: VP).
ath Handler: VPH or cross connect, XC) is connected by a transmission line. Theoretically, V
The CHs are connected by a VP, and the VP is terminated at the VCH via zero or one or more VPHs.

FIG. 12 shows a conventional method for restoring a failure of a communication device. FIG. 12 is a diagram showing the concept of a conventional failure recovery method. FIG. 12 shows a conventional failure recovery method.
There are physical-level failure recovery shown in (b) and VP-level failure recovery shown in FIG. In order to realize physical-level failure recovery, the physical transmission path link is duplicated, one of which is used as an active system and the other is used as a standby system. If a failure occurs in the active communication device, the active system is switched to the standby system, and the failure is recovered. However, in physical-level failure recovery, there is a problem that the physical transmission path link must always be duplicated, and network resources cannot be used efficiently.

Therefore, there is a VP-level failure recovery method that applies the concept of VP, which is a feature of the ATM communication network. VP
Is identified by a VPI (Virtual Path Identifier) in a header area given to a cell as an information transfer unit,
In the VPH, a route is set by a path connection (routing) table that describes a connection destination of the path. V
P-level failure recovery uses the fact that the VP path and capacity can be set independently,
This is realized by switching to a newly formed VP by bypassing the fault location. In particular, when a failure occurs, a centralized station that monitors the ATM communication network in a unified manner can access each node (VCH, VCH) in the network based on preset bypass path information.
Centralized control system,
A failure recovery method in which each node autonomously distributes and searches for a detour path is referred to as a self-healing method. The VP-level failure recovery is superior to the physical-level failure recovery in that the network resources of the transmission path can be used efficiently and that changes in the network can be flexibly handled. Therefore, a failure recovery method combining a physical level and a VP level is applied as a conventional failure recovery method.

[0005]

However, in the conventional method of restoring only the physical level and the VP level, a failure of a VCH (exchange) is not assumed, and a highly reliable exchange is required. In an ATM communication network in which a plurality of media coexist, the required reliability differs for each medium, but the exchange is designed to satisfy the reliability in accordance with the highest required reliability. It was redundant for media that did not require much reliability. FIG.
FIG. 3 is a conceptual diagram of a highly reliable exchange. In the highly reliable exchange, as shown in FIG.
The unit and the CPU unit are duplicated, and these units are connected by a cross route. The cost of a highly reliable switch due to such duplication is as follows:
The cost is about four to six times higher than the cost of a switch having a simple configuration.

The present invention has been made in view of such a background, and an object of the present invention is to provide an ATM communication network and a failure recovery method capable of performing a failure recovery measure on the premise of a failure of an exchange. SUMMARY OF THE INVENTION It is an object of the present invention to provide an ATM communication network and a failure recovery method which can omit a redundant hardware configuration for ensuring high reliability of an exchange. An object of the present invention is to provide an ATM communication network and a failure recovery method that can reduce the cost of an exchange. The present invention provides an AT that can perform a failure recovery without providing a device that performs a failure recovery intensively.
It is an object to provide an M communication network and a failure recovery method.

[0007]

When an exchange having a simple configuration is applied as a communication device, a VC at the time of failure of the exchange is used.
Route failures need to be quickly restored. Therefore, the present invention is characterized by providing a method for promptly recovering a VC route failure when a failure occurs in an exchange. As a method, in the event of a switch failure, a failure recovery message cell is sent from the destination exchange to recover the working route failure between the originating and destination exchanges, and the exchanges exchange information autonomously and notify the originating exchange of the network status. Then, the route is switched, and the route failure due to the switch failure is restored at the VC route level.
This is called self-healing at the VC root level.

In the prior art, self-healing at the VP level has been performed.
The VC root level self-healing makes it possible to recover a VC root failure at the time of an exchange failure.

That is, a first aspect of the present invention is that a plurality of local exchanges, a plurality of physical transmission lines connecting the plurality of local exchanges, and a relay interposed in the plurality of physical transmission lines. An ATM communication network comprising an exchange and a virtual path established between the plurality of subscriber exchanges.

Here, a feature of the present invention is that the subscriber exchange is provided with means for transmitting a failure recovery message cell to a virtual path, and the failure recovery message cell has a destination area and a message area. In the destination area, information for arriving at the other party's exchange via one or more transit exchanges is installed, and the transit exchange is provided with a message in the message area of the failure recovery message cell passing therethrough. There is a means for mounting the free band information of the exchange.

The message area is provided with a hop counter area in which the number of transit exchanges passing therethrough is provided. Each time a failure recovery message cell passes, the relay exchange has a transit exchange mounted in the hop counter area. Is desirably provided.

[0012] The local exchange has means for recognizing the possibility of a failure of the transit exchange inserted in the virtual path, and the means for transmitting the failure recovery message cell comprises:
It is desirable to send a failure recovery message cell in accordance with the output of this recognition means.

The local exchange is provided with means for receiving a failure recovery message cell arriving via a plurality of virtual paths, and is used in accordance with the available bandwidth information and the number of transit exchanges contained in the failure recovery message cell. It is desirable to have means for selecting a virtual path.

[0014] A second aspect of the present invention is a failure recovery method, which is characterized in that a plurality of virtual paths that can be used as an active virtual path and a backup virtual path are included in a virtual path set in a local exchange. Is set in advance, and when the possibility of failure is recognized in the transit exchange inserted in the working virtual path, the local exchange switches the failure recovery message cell to a plurality of virtual paths that can be the spare virtual path. The local exchange, which is the destination of the failure recovery message cell, sends any one of the plurality of virtual paths that can be the spare virtual path according to the available bandwidth information and the number of transit exchanges mounted in the failure recovery message cell. Where to choose.

This failure recovery method is characterized in that a large number of the local exchanges are dispersed in one communication network, and each of the local exchanges executes the failure recovery method autonomously and decentralized.

A third aspect of the present invention is a failure recovery standby method, which is characterized in that a plurality of virtual paths that can be used as an active virtual path and a backup virtual path are set as virtual paths set in the local exchange. The path is preset, and even if there is no failure of the transit exchange inserted in the working virtual path, the local exchange sends a failure recovery message cell to each of the plurality of virtual paths that can be the backup virtual path, In the local exchange that is the destination of the failure recovery message cell, one of the plurality of virtual paths that can be the backup virtual path is used as a backup according to the available bandwidth information and the number of transit exchanges that are mounted in the failure recovery message cell. It is to be pre-selected as a virtual path candidate.

This failure recovery standby method is characterized in that a large number of the local exchanges are dispersed in one communication network, and each of the local exchanges executes the failure recovery standby method autonomously and decentralized. is there.

A fourth aspect of the present invention is a failure recovery method, which is characterized in that a local exchange in one communication network establishes a virtual path for itself and / or belongs to the communication network. A fault recovery message cell is transmitted to the other local exchange on the virtual path.

In this specification, the terminating exchange and the transit exchange are expressed as if they are different communication devices, but this is for the sake of simplicity of explanation, and the same hardware is used. It can be realized by the communication device having the configuration.

[0020]

In the method of the present invention, a failure recovery message cell is transmitted from the destination exchange by self-healing at the VC root level, and the exchanges exchange information autonomously and decentralized.
Since the originating exchange can be notified of the network status, the route can be switched, and the VC route failure at the time of the exchange failure can be recovered, the necessity of using a highly reliable exchange is eliminated, and an exchange having a simple configuration is used. As a result, cost can be reduced.

The failure recovery message cell sent by the destination exchange reaches the originating exchange via a virtual path. This virtual path may be a virtual path determined in advance as a virtual path that can be a backup virtual path, or may be an unspecified virtual path in which a failure is not recognized.

The failure recovery message cell collects the free band information of the virtual path that passes while arriving from the destination exchange to the originating exchange. In other words, the transit exchange inserted in the passing virtual path, when passing the failure recovery message cell, mounts the free band information in its own transit exchange in, for example, a message area of the failure recovery message cell. The number of transit exchanges that have passed at the same time is also loaded as information. The originating exchange selects an optimal virtual path as a backup virtual path with reference to the information on the available bandwidth and the information on the number of transit exchanges that have passed. Thereafter, a virtual channel is set for this virtual path and communication is resumed.

The transmission of the failure recovery message cell may be controlled so that the failure recovery message cell is transmitted when any failure is recognized by the working virtual path or a transit exchange on the working virtual path. It is also possible to transmit a message cell and always select an optimal virtual path candidate as a backup virtual path.

According to the present invention, such a fault recovery control is referred to as A
The main feature is that each exchange included in the TM communication network performs autonomous decentralization.

[0025]

Embodiment (First Embodiment) The configuration of a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an overall configuration diagram of the present invention.
FIG. 2 is a block diagram of a principal part of the destination exchange. FIG. 3 is a configuration diagram of the failure recovery message cell. FIG. 4 is a block diagram of a main part of the transit exchange. FIG. 5 is a block diagram of a main part of the originating exchange.

The present invention relates to an originating exchange 1 which is a subscriber exchange.
And terminating exchange 6, and the originating exchange 1 and terminating exchange 6
Physical transmission lines P to R that connect each other, and relay exchanges 2, 3, 4, 5, 7,
This is an ATM communication network that includes virtual telephones 8 and 9 and in which a virtual path is set between the originating exchange 1 and the destination exchange 6.

Here, a feature of the present invention is that the destination exchange 6 is provided with a failure recovery message cell generation unit 12 as a means for transmitting a failure recovery message cell to a virtual path. , A destination area H and a message area M, and information for arriving at the originating exchange 1 via one or more transit exchanges 2, 3, 4, 5, 7, 8, and 9 is loaded in the destination area H. In addition, the relay exchanges 2, 3, 4, 5, 7, 8, 9 and 9 are provided in the message area M of the fault recovery message cell through which the exchanges 2, 3, 4, 5, 7, 8, 9 are available. Failure recovery message cell information mounting unit 14 as means for mounting information
It is located with.

In the embodiment of the present invention, the originating exchange 1, the destination exchange 6, the transit exchange 2,
Each of 3, 4, 5, 7, 8, and 9 is expressed as if it were a communication device having a different hardware configuration, but these are realized as one communication device having each function in common. Can be.

The message area M is provided with a hop counter area HC in which the number of transit exchanges 2, 3, 4, 5, 7, 8, and 9 that pass through is provided.
Each of 5, 7, 8, and 9 is provided with a unit for adding the number of transit exchanges mounted in the hop counter area HC each time the failure recovery message cell passes, in addition to the failure recovery message cell information mounting unit 14. I have.

The originating exchange 1 and the destination exchange 6 have relay exchanges 2, 3, 4, 5, 7,
A failure detection unit 10 is provided as means for recognizing the possibility of a failure in 8 or 9.
A failure recovery message cell is transmitted according to the output of the failure detection unit 10.

The originating exchange 1 is provided with a spare route setting unit 16 as means for receiving a failure restoration message cell arriving via a plurality of virtual paths, and the free band information and the relay exchange included in the failure restoration message cell. A means for selecting a virtual path to be used according to the number of backup routes is provided in the backup route setting unit 16.

The VC route is routed from the originating exchange 1 to one or more V
After P, the destination exchange 6 is set. In the originating exchange 1, when a call is generated, a certain route is selected from a plurality of VC routes, and a call admission judgment (Connection Admissio) is made.
n Control: CAC). For example, the route is selected at random. If a call is accepted by the CAC, a VC connection is set, and if the call is not accepted, a call is lost.

Next, the operation of the first embodiment of the present invention will be described with reference to FIG. FIG. 6 is a diagram for explaining the operation of the first embodiment of the present invention. As shown in FIG. 6, a failure recovery method according to the first embodiment of the present invention when a failure occurs in the transit exchange 5 focusing on only one working route will be described. Working route between originating exchange 1 and destination exchange 6 (1 → 4 → 5 → 6)
Are set via two transit exchanges, and the working route is currently using the B [Mbps] band.

With respect to this working route, a call is accepted after CAC, and a VC connection is set or disconnected. The used band of the working route is obtained, for example, by observing the number of cells used in the working route within a certain window size in the originating exchange 1. The windows used for observation include a jumping window and a sliding window.

Here, the jumping window is an observation method in which the window positions (observation positions) transition without overlapping at a fixed period, and the sliding window is a gradually changing window position at a constant period. This is a transition observation method. At a high level, jumping windows benefit from fast observations, while sliding windows benefit from accurate observations.

A plurality of backup routes are set in advance in case the working route becomes unavailable due to a failure. In FIG. 6, two backup routes (route P: 1 → 2 →) are set.
3 → 6, route R: 1 → 7 → 8 → 9 → 6). When a failure occurs, the originating exchange 1 and the destination exchange 6 recognize that the working route is in an unusable state by a cell or the like that notifies an alarm. The VC connection currently set in the working route is not rescued, but after the occurrence of a failure, a bypass route is searched so that a newly requested VC call can be received to the maximum.
Here, the destination exchange 6 serves as a sender for transmitting a failure recovery message cell, and the originating exchange 1 serves as a chooser which receives the failure recovery message cell and selects a switching route from among the spare routes. The destination exchange (sender) 6 sends a failure recovery message cell to check the state of the protection route. The fault recovery message cell is provided along the routes of the backup routes P and R along with the Vs on the routes of the backup routes P and R.
Check the state of P. A description will be given using the route R as an example. (1) Hop counter HC (2) Hop limit HL (3) Minimum value of VP unused band b _min (4) Route information RD is written in the message area M of the failure recovery message cell as a payload. The hop limit HL is set in advance in consideration of delay conditions and the like. The value of the minimum value b _min is set to ∞, and the value of the minimum value b _min is written in the failure recovery message cell. The failure recovery message cell via the route R is sent from the destination exchange 6 to the transit exchange 9, and in the transit exchange 9, if b <b _min , the value of the unused VP band b is set to b _min . In the transit exchange 9, for example, the VP unused band within a certain window size is obtained by observing the number of used cells. The windows used for observation include a jumping window and a sliding window. The hop counter HC is incremented by one each time the relay switch 9 → 8 → 7 passes, and the hop limit H
As long as it does not exceed L, it is sent to the next exchange. However, usually, the backup route is set in advance so as not to exceed the hop limit. In the next exchange 8, b = 2
Since b <b _min , b _min = 2. Similarly, the process of sending the failure recovery message cell is repeated, and the failure recovery message cell arrives at the originating exchange 1. The failure recovery message cell A transmitted on the backup route P also arrives at the originating exchange 1 in the same manner. Departure switch 1
Is the used bandwidth B of the working route and the backup route information (the minimum value b of the unused VP
_min , the number of hops) and one or more as the switching destination route. FIG. 7 is a diagram showing the route switching status in the first embodiment of the present invention. In the example of FIG. The route is selected as the previous route, and after the failure recovery, the route P is used as the working route.

Therefore, when a failure occurs in the exchange, the exchange exchanges information autonomously in a distributed manner by transmitting a failure recovery message cell, switches routes, and recovers from the failure. Because it is possible to use a switch with a simple configuration even if it is not a reliable switch,
The cost of the exchange can be reduced.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 8 is a diagram for explaining the operation of the second embodiment of the present invention. In the first embodiment of the present invention,
Although a failure recovery message cell is transmitted when a failure occurs, in the second embodiment of the present invention, as shown in FIG.
nt) Transmit cells to monitor the status of the backup routes P and R. The operation of the RM cell is the same as the operation of the failure recovery message cell of the first embodiment of the present invention. The originating exchange (chooser) 1 considers the used bandwidth B of the working route, the protection route information (minimum value b _min of the VP unused band, the number of hops) and the like from the protection route P or R, and Determine a switching destination route in case of a failure.

Here, the RM cell is periodically transmitted from the destination exchange (sender) 6 and the originating exchange (chooser) 1 which has received the RM cell updates the route of the switching destination according to the network state. . The transmission interval of the RM cell is determined from the degree of change in the network state.

When a failure occurs, the originating exchange 1 recognizes that the working route is in an unusable state by a cell for notifying an alarm or the like. The originating exchange 1 that has detected the failure of the working route is switched to the switching destination route normally prepared for the failure of the working route, and is used as the working route.

Therefore, in normal times, the RM (Resource Management) cell is transmitted from the destination exchange (sender) 6 to monitor the state of the protection route and determine the switching destination route in case of failure of the working route. Thereby, the failure recovery time can be shortened.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 9 is a diagram for explaining the operation of the third embodiment of the present invention. In the first embodiment of the present invention,
The backup routes P and R are set in advance, and a failure recovery message cell is transmitted on the backup routes P and R when a failure occurs. In the third embodiment of the present invention, the backup routes P and R are not set in advance, and a failure recovery message cell is transmitted by flooding as shown in FIG. The originating exchange 1 selects a backup route.

Here, flooding refers to “Flood”.
d ", that is, a term based on the image that cells are transmitted in an unspecified direction like" flood ", and means that a fault recovery message cell is transmitted to all exchanges that transmit VPs to the local exchange. Used for

As described in the first embodiment of the present invention, (1) hop counter HC (2) hop limit HL (3) VP unused band minimum value b _min (4) ) The route information RD is written. The hop limit HL is set in advance in consideration of delay conditions and the like. The value of the minimum value b _min is set to ∞, and the value of the minimum value b _min is written in the failure recovery message cell.

First, the destination exchange (sender) 6 sends a failure recovery message cell to all exchanges that send VPs to the own exchange. The exchange that has received the failure recovery message cell sets the value of the unused VP band b to b if b <b _min.
min . In the exchange b, for example, a VP unused band within a certain window size is obtained by observing the number of used cells. Information on the exchange that has passed is written as route information. The hop counter HC is incremented by one each time the signal passes through the exchange. If the hop counter HC exceeds the hop limit HL or the route information RD
, The failure recovery message cell is discarded if it has already passed through the same switch. Otherwise, the failure recovery message cell is further transmitted to all the exchanges that send VPs to the local exchange, and the exchange receiving the failure recovery message cell repeats the same operation, and the failure recovery message arrives at the originating exchange. I do.

The originating exchange (chooser) 1 uses the route information (V) based on the used bandwidth B of the working route and the arrived failure recovery message cell from the arrived failure recovery message cell.
In consideration of the minimum value b _min of the P unused band, the number of hops) and the like, one or a plurality of switching destination routes are selected.

Therefore, a failure recovery message cell is sent out by flooding and a failure recovery message cell arrives at the originating exchange 1 without setting a backup route in advance, so that it is flexible to changes in network topology, VP capacity, and the like. Can be restored.

FIGS. 10 and 11 show the concept of the fault recovery by the fault recovery method of the present invention. FIG. 10 is a diagram showing the concept of the failure recovery method of the present invention. FIG. 11 is a conceptual diagram of an ATM communication network to which the failure recovery method of the present invention is applied. FIG.
(B) and (c) are conventionally known VP-level and physical-level failure recovery concepts. In the present invention, as shown in FIG. 10A, by performing a fault recovery at the VC root level, as shown in FIG. 11, an ATM communication network can be configured without using a highly reliable exchange.

[0049]

As described above, according to the present invention,
Failure recovery control can be performed on the premise of a failure of the exchange. Therefore, a redundant hardware configuration for ensuring high reliability of the exchange can be omitted. Therefore, the cost of the exchange can be reduced. Further, failure recovery can be performed without providing a device for performing failure recovery intensively.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of the present invention.

FIG. 2 is a block diagram of a main part of the destination exchange;

FIG. 3 is a configuration diagram of a failure recovery message cell.

FIG. 4 is a block diagram of a main part of a transit exchange;

FIG. 5 is a block diagram of a main part of an originating exchange;

FIG. 6 is a diagram for explaining the operation of the first embodiment of the present invention.

FIG. 7 is a diagram showing a route switching status in the first embodiment of the present invention.

FIG. 8 is a diagram for explaining the operation of the second embodiment of the present invention.

FIG. 9 is a diagram for explaining the operation of the third embodiment of the present invention.

FIG. 10 is a diagram showing the concept of a failure recovery method according to the present invention.

FIG. 11 is a conceptual diagram of an ATM communication network to which the failure recovery method of the present invention is applied.

FIG. 12 is a diagram showing the concept of a conventional failure recovery method.

FIG. 13 is a conceptual diagram of a highly reliable exchange.

[Explanation of symbols]

Reference Signs List 1 originating exchange 2-5, 7-9 transit exchange 6 destination exchange 10 failure detection unit 12 failure recovery message cell generation unit 14 failure recovery message cell information loading unit 16 backup route setting unit H destination area HC hop counter HL hop limit M message Area RD Route information b _min Minimum value P, Q, R Route

Claims (6)

(57) [Claims] Claims 1.Virtual channel handler (V
CH)The local exchange and the multiple subscribers
A plurality of physical transmission lines connecting the exchanges, and
A relay exchange interposed in the physical transmission path of the
Number ofFor each physical transmission lineVirtual path is set
In an ATM communication network,As a virtual channel handlerSubscriber exchange
InVirtual channel supportFailure recovery message
Means for sending a message, the failure recovery message cell includes a destination area and a message.
Storage area, and one or more transit exchanges in the destination area.
Via the other sideAs a virtual channel handler
Reach the local exchangeLetInformation for carrying the fault recovery message through
In the message area of the cell, the free band information of the transit exchange is stored.
Information to includeEquipped with means for mounting, Local exchange as the virtual channel handler
From the information including the free band information to the virtual path
A means for recognizing the possibility of failure of the interposed exchange
Prepared, The means for transmitting the failure recovery message cell includes the acknowledgment.
Fault recovery message cell according to the output of the
Including means to create An ATM communication network, characterized in that: 2. The method according to claim 1, wherein the message area includes the empty band information.
A hop counter area is provided in which the number of transit exchanges that pass through is provided as one of the information including the information, and the transit exchange has the number of transit exchanges mounted in this hop counter area each time a failure recovery message cell passes. 2. The ATM communication network according to claim 1, further comprising means for adding 3. The virtual channel handler
Local exchanges via multiple virtual paths.
Means for receiving the incoming fault recovery message cell, and
Information including the free band information included in the failure recovery message cell
For selecting a virtual path to use according to the information
3. The ATM communication network according to claim 1, comprising: (4)As the virtual channel handler
In the local exchange, Active bar as a virtual path
Multiple that can be a Chall pass and a backup virtual pass
Virtual paths are set in advance, and this working path
-There is a possibility that the relay exchange inserted in the
When recognized, the local exchange will send a fault recovery message.
Multiple cells that can serve as the backup virtual path.
Means for sending to each of the virtual paths, The local exchange that is the destination of this failure recovery message cell
The empty band installed in this failure recovery message cell
Said spare bar according to the information and the number of transit exchanges
One of several virtual paths that can be a Chall pass
Means for selecting and setting a new virtual path To
Claim 3. ATM communication network. 5. The virtual channel handler
Subscriber exchanges are distributed in large numbers within one communication network.
Then, each local exchange sends the failure recovery message cell.
5. The apparatus according to claim 4, further comprising means for executing the reception in an autonomous decentralized manner.
ATM communication network. 6.Virtual channel in ATM communication network
A local exchange that is deployed as a handler (VCH)
What Send failure recovery message cell for virtual channel
Equipped with a means to issue This failure recovery message cell contains the destination area and message
Storage area, and one or more transit exchanges in the destination area.
Via the other side as a virtual channel handler
Information to reach the local exchange and relay via
Information including the vacant band information of the exchange is installed, Inserted into the virtual path from the information including the free band information
Means for recognizing the possibility of failure of the relay switch The means for sending the failure recovery message cell further comprises:
A failure recovery message is output according to the output of this recognition means.
Includes means to create dicel Subscriber exchange characterized by the fact that
Exchange.