JP3080357B2 - ATM communication network - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is used for ATM (Asynchronous Transfer Mode) communication. In particular, the present invention relates to an active / standby switching technique.

[0002]

2. Description of the Related Art An ATM communication network is physically composed of a virtual channel handler (switching) that performs switching in units of virtual channels (Virtual Channel, hereinafter referred to as VC) and a virtual path (Virtual Path, VC). A virtual path handler (Vir) that sets the information transfer route in units of VP
tual Path Handler: VPH or cross connect, X
And C) are connected by a transmission line. Logically, VCH is connected by VP, and VP is zero or one.
It is terminated at VCH via the above VPH.

[0005] A failure recovery method for a failure of a conventional communication device will be described with reference to FIG. FIG. 15 is a diagram showing a failure recovery method for a failure of a conventional communication device. Conventional failure recovery includes physical-level failure recovery shown in FIG. 15B and VP-level failure recovery shown in FIG. In order to realize physical-level failure recovery, the physical transmission path and the like are duplicated, and one 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, physical transmission paths and the like must always be duplicated, and network resources cannot be used efficiently.

Therefore, there is a VP-level failure recovery to which the concept of VP, which is a feature of the ATM communication network, is applied. VP is
V in the header area assigned to the cell as the information transfer unit
Identified by PI (Virtual Path Identifier), VP
In H, a route is set by a path connection (routing) table describing the connection destination of the path. VP-level failure recovery is realized by switching a VP disconnected due to a failure to a newly formed VP bypassing the failure by utilizing the fact that the path and capacity of the VP can be set independently. In particular, when a failure occurs, a centralized control system that centrally monitors the network controls each node (VCH, VPH, etc.) in the network based on preset bypass path information. A failure recovery method in which each node autonomously distributes and searches for a detour path and recovers it is called 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, as a conventional failure recovery, FIG.
As shown in (1), failure recovery using a combination of a physical level and a VP level is applied.

[0005]

However, in the conventional recovery from a failure at only the physical level and the VP level, a failure of the 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. However, the exchange is designed so as to satisfy the reliability in accordance with the highest required reliability. It was redundant for media that did not require reliability. FIG. 16 is a conceptual diagram of a highly reliable exchange. In a highly reliable exchange, a switch unit, an I / O unit, and a CPU unit are duplicated as shown in FIG. Units are connected by a cross route. The cost of a highly reliable switch due to such duplication is about four to six times higher than the cost of a switch having a simple configuration.

[0006] 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 that can use an exchange without redundant facilities for troubleshooting. SUMMARY OF THE INVENTION It is an object of the present invention to provide an ATM communication network capable of taking measures for relieving a VC connection during communication. An object of the present invention is to provide an ATM communication network that can effectively use network resources. An object of the present invention is to provide an ATM communication network with a high throughput. An object of the present invention is to provide an ATM communication network that can use an inexpensive exchange. SUMMARY OF THE INVENTION It is an object of the present invention to provide an ATM communication network capable of relieving a VC connection during communication without providing an apparatus for relieving VC connections intensively.

[0007]

When an exchange having a simple configuration is applied as a communication device, it is necessary to relieve a VC connection during communication at a high speed when the exchange fails. The present invention provides a call admission control (CAC) for a VC connection on a working route and a protection route.
And a routing table for setting a working and protection VC connection if the two routes can be accepted, and when a transit exchange on the working route fails, the failure information is transmitted to the originating exchange and the destination exchange. The main feature is that failure recovery at the VC level can be performed by switching the routing tables of the originating exchange and the destination exchange.

[0008] In the prior art, failure recovery up to the VP level has been performed.
By performing the level of failure recovery, it is possible to rescue the VC connection during communication when the exchange fails.

That is, the present invention comprises a plurality of exchanges, a virtual path is set between the plurality of exchanges,
This exchange is an ATM communication network provided with means for setting working and protection routes on a virtual path.

Here, the feature of the present invention resides in that a routing table in which a spare route to be switched to is designated is provided for each of the working routes.

Preferably, the portion is set for each virtual channel. Alternatively, the portion may be set in units of route identifiers assigned to a plurality of virtual channels.

[0012] The routing tables may be provided separately according to the grade of rescue performed when a failure occurs.

It is also possible to provide a means for observing the traffic of the working route and a means for adaptively setting the size of the backup route based on the observation result of this means. As a result, it follows the VC band fluctuation of the working route and the V of the route secured as the backup route.
The C band can also be varied. Therefore, at all times,
There is no need to secure the VC band of the backup route according to the peak value of the VC band of the working route, and the VC band can be used effectively.

Thus, in the ATM communication network of the present invention,
By performing the VC-level failure recovery, it is possible to rescue the VC connection during communication at the time of failure of the exchange, so that it is not necessary to use a highly reliable exchange, and by using an exchange having a simple configuration, The exchange cost can be reduced.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an overall configuration diagram of an embodiment of the present invention. FIG. 2 is a diagram showing a routing table.

The present invention comprises exchanges SW1 to SW4,
A VP is set between the exchanges SW1 to SW4, and the exchanges SW1 to SW4 are provided with an active VC setting unit VS0 and a backup VC setting unit VS1 as means for setting the active and standby routes on the VP. It is.

Here, the feature of the present invention resides in that a routing table TBL shown in FIG. 2 in which a spare route to be switched to is designated for each part of the working route is provided. The part is set in VC units.

In this specification, in order to make the description easy to understand, the exchanges SW1 to SW4 are respectively referred to as originating exchanges SW.
1. The destination exchange SW3 and the relay exchanges SW2 and SW4 are expressed as if they are different hardware. In practice, these functions are provided in each of the exchanges SW1 to SW4. .

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) In order to support a plurality of reliability classes, an ATM communication network according to the present invention prepares a VC route corresponding to each reliability class. When there is a request for setting a VC connection requesting a certain quality, a call admission judgment CAC is performed on the VC route, and if the judgment result is acceptable by the CAC, V
The C connection is set. The types of VC routes can be broadly classified into two types: a class that rescues a VC connection during communication (hereinafter, referred to as a rescue class) and a class that does not rescue (hereinafter, referred to as a non-rescue class) in the event of a network failure such as a switch failure. . The fact that the types of VC routes are different means that the reliability classes are different even if the routes are the same. VC connections belonging to the rescue class are not disconnected even when a failure occurs in an exchange or the like, and rescue the VC connection during communication by switching from the working route to the spare route at high speed. On the other hand, in the non-relief class, the VC connection during communication is disconnected at the time of failure. In an ATM communication network in which a plurality of media coexist, not all require a VC connection belonging to a rescue class. In particular, it is conceivable that a medium that does not require real-time properties sets a VC connection in the non-rescue class. In this way, a VC route is selected according to the degree of reliability required when setting up a VC connection. In the present invention, the communication V
The present invention relates to an ATM communication network for relieving a C connection.

In order to switch and rescue the VC connection during high-speed communication, a working VC connection and a spare VC connection are respectively set on the working route and the protection route at the time of accepting a call. In the first embodiment of the present invention,
A setting request is made so that a VC band of the backup route corresponding to the peak value of the VC band of the working route can be secured, and the working and protection VC connections are set. FIG. 3 is a diagram for explaining a procedure for securing a spare route band with respect to one working route band. As the VC route, there is a working route 1 and a corresponding backup route 1. The route of the working route 1 is the originating exchange SW1-the transit exchange SW2-the destination exchange SW3. The route of the backup route 1 is composed of the originating exchange SW1, the transit exchange SW4, and the destination exchange SW.
3, which is an independent route from the working route 1.

FIG. 4 shows the operation of call admission control (CAC) when setting a VC connection when a VC setting request occurs. FIG. 4 is a flowchart showing the operation of the call admission control (CAC). When a VC setting request occurs (S
1), CAC is performed for both the working route 1 and the protection route 1. If the acceptance determination is possible for both routes (S2), the VC is accepted (S3). Otherwise, a call loss occurs (S4). As a result, the VC connection is set on the working route, and the cell is transferred only on the working route. A backup VC connection is set on the backup route in case the working route fails. No actual cells are transferred on the spare route.

As a method of performing the CAC, there is a peak allocation method for determining whether to accept a VC based on the declaration of the peak value of the VC.
The peak allocation method determines whether or not a value obtained by adding the peak value of a new VC to the sum of the peak values of the VCs accommodated in the VP exceeds the VP capacity. If not, the VP can be accommodated. In other words, the CAC determines whether all VPs on the VC route can be accepted, and if all VPs on the VC route can be accepted, the requested VC is accepted.
Even if the cell is not actually transferred on the backup route, the bandwidth and the peak value of the backup VC connection are allocated in VP3 and VP4. That is, when a new VC occurs, the current VC connection or the backup VC
Whether the C connection can be accepted by the VP satisfies (the peak declared value of the new VC) + (the sum of the peak declared values of the working VC connection and the spare connection accommodated in the VP) <VP capacity. Then, it will be possible to accept.

FIG. 5 is a block diagram showing the principal parts of the relay exchanges SW2 and SW4. The relay exchanges SW2 and SW shown in FIG.
4, the new VC peak declared value is loaded into the requested VC bandwidth memory M2 and the VP
The sum of the peak declared values of the working VC connection and the spare connection accommodated in the memory is loaded into the accommodated VC band memory M1, and is added to the sum of these values added by the adder ADD and the VP capacity memory M3. The values are compared by the comparator CMP, and a reception determination is made.

As a result, an equivalent spare route band is secured with respect to the working route band. When the VC connection on the working route is disconnected by a normal process (end of communication), the setting of the bandwidth of the spare VC connection on the spare route is released at the same time.

Therefore, when the VC connection is switched, the bandwidth of the spare VC connection is secured, so that the quality of the cell loss rate in the switched VC connection can be maintained.

In addition, instead of securing the same spare route band as the working route band, the spare route band can be shared with a plurality of working route bands. . An example of sharing the bandwidth of the backup route will be described with reference to FIG. FIG. 6 is a diagram for explaining a procedure for securing a band of a spare route while sharing a band of a spare route with a band of one working route. The working route and the backup route correspond by numbers. For example, the active route 1 (the originating exchange SW1-the transit exchange SW2-the destination exchange SW3) corresponds to the backup route 1 (the originating exchange SW1-the transit exchange SW4-the destination exchange SW3). All working routes and backup routes are set as independent routes.

Focusing on VP1 between the relay exchange SW4 and the destination exchange SW3, three spare routes are accommodated. The working route 1 and the working route 2 are not independent routes because the switch SW2 is used as a transit exchange.
The current route 3 and the current route 2 and the current route 3 are independent routes. When the working route is an independent route, it is possible to share the band of the spare route, assuming that only one transit exchange fails. In the VP1, the backup route 1 can share the bandwidth with the backup route 3, but cannot share the bandwidth with the backup route 2.

When performing CAC of a spare VC connection on the spare route, a virtual band on the spare route that can be shared can be excluded. For example, a case is considered in which the above-described peak allocation method is applied and the exchange SW4 determines the acceptance of the backup VC connection on the backup route 1 in the VP1. V housed in VP1
When calculating the sum of the peak values of the C connection, the bandwidths of the backup route 1 and the backup route 3 can be shared, so the VC connection on the backup route 3 is excluded. In this case, the value obtained by adding the peak value of the new backup VC to the sum of the peak values of the VC connections of the backup route 1 and the backup route 2 is VP.
Judgment is made as to whether or not the capacity exceeds 1, and if the capacity is not exceeded, it is possible to accept, and if it is, it is determined as a call loss.

FIG. 7 is a block diagram of a main part of a transit exchange according to a procedure taking into account the sharing of the bandwidth of a backup route. The transit exchanges SW2 and SW4 will be described. Loaded into the band memory M2. Further, the housing VC bandwidth memory M1 ₁ to M1 _n for spare route k (k = 1 to n), spare route k
Of the VC connection is loaded. When there is a request for a VC on the spare route, the requested bandwidth memory M2 and the accommodated VC bandwidth memory M1 for the spare route
_The adder ADD calculates the sum of the VC bands from which the spare route that can share the band is excluded from _{1 to} M1 _n, is loaded to the comparator CMP and compared, and the reception determination is performed. In this way, by sharing the bandwidth of the spare route, network resources can be used efficiently.

As shown in FIG. 1, in the originating exchange SW1,
A spare outgoing VCI / V is stored in the routing table TBL.
The destination switch SW3 has a spare incoming VCI / VPI table in the routing table TBL. The spare tables of the originating exchange SW1 and the destination exchange SW3 are not used in a normal state. The backup VC connection table in the routing table TBL of the transit exchange SW4 is set as current and can be used even in normal operation. However, since the backup table on the outgoing side of the originating exchange SW1 is not used, the cell transmitted by the user is: It is not transferred to the backup VC connection, but is transferred only to the working VC connection. FIG. 2 shows an example of the table management on the outgoing side of the originating exchange SW1 (portion surrounded by a dotted frame in FIG. 1). There is no spare table for the non-relief class, but it has a spare table for the relief class.

FIG. 8 shows a transit exchange SW on a working route.
FIG. 4 is a diagram for explaining a procedure for relieving a VC connection when a failure occurs in a second connection; When a failure occurs in the transit exchange SW2 on the working route, the originating exchange SW1 and the destination exchange SW3 receive a VC connection failure notification. As a method of notifying a failure, there is a method based on a VC-AIS (Alarm Indification Signal, alarm display signal) using a failure notification cell. When the notified originating exchange SW1 and destination exchange SW3 recognize the failure of the VC connection by the failure notification, the VCI /
Switch table to VPI.

FIG. 9 shows the originating exchange SW1 and the destination exchange SW.
3 is a block diagram of a table switching device S for each VC connection according to the first embodiment of the present invention in FIG. When the VC connection failure detecting unit W receives the failure notification cell and detects a failure, the table switching control unit TS performs switching control of the routing table TBL for each VC connection.

As described above, when the relay exchanges SW2 and SW4 on the working route fail, the routing table TB
The switching of L switches the communicating VC connection from the working route to the backup route, so that the communicating V connection is switched.
Since the C connection can be relieved and an exchange having a simple configuration can be used without using a highly reliable exchange which is duplicated as in the related art, the cost of the exchange can be reduced.

(Second Embodiment) Another management example of the outgoing table of the exchange SW1 is shown in FIG.
0 will be described. FIG. 10 is a diagram showing a routing table TBL according to the second embodiment of the present invention (portion surrounded by a dotted frame in FIG. 1). VC communicating on the working route
A route identifier RI (Route Identifier) is newly defined for the purpose of quickly switching a connection to a spare route. RI is set for each VC route,
Like I, it is changed for each exchange. The RI uses the first 5 bits of the VCI in the second embodiment of the present invention. As shown in FIG. 8, when a failure occurs in the relay exchange SW2 of the active VC connection, the originating exchange SW1 and the destination exchange SW3 receive the failure notification of the VC connection.
As a method of notifying a failure, V using a failure notification cell is used.
There is a method based on C-AIS. At this time, the table is switched for each VC connection in the first embodiment of the present invention, but the table is switched for each VC route in the second embodiment of the present invention.

The timing of recognizing a fault in the VC route is, for example, when the VC-AIS of the VC connection belonging to the VC route exceeds a certain number. This is because the route information is loaded on the VC-AIS and the originating exchange S
This can be realized by counting for each route by W1 and destination exchange SW3. Also, the relay exchanges SW2, SW4
Is notified, and the failure of the VC route can be recognized.

After the originating exchange SW1 and the destination exchange SW3 recognize the failure of the VC route, the routing table TBL of the VC connection belonging to the VC route is identified by the RI, and the table is switched to the spare table for each VC route.

FIG. 11 shows the originating exchange SW1 and the destination exchange S.
FIG. 10 is a block diagram of a table switching device S for each VC route according to the second embodiment of the present invention in W3. When the VC connection failure detection unit W receives the failure notification cell and detects a failure, the table switching control unit TS performs switching control of the routing table TBL for each VC route. As described above, since the switching from the working table to the spare table is performed for each VC route, compared with the switching for each VC connection,
Switching can be performed at high speed. Therefore, the VC connection during communication can be relieved at a high speed, and the cell loss caused by the failure of the exchange can be reduced.

(Third Embodiment) A third embodiment of the present invention is shown in FIG.
This will be described with reference to FIG. FIG. 12 is a block diagram of the originating exchange SW1 of the third embodiment of the present invention. In the third embodiment of the present invention, the originating exchange SW1 is connected to the route-specific cell flow observation device RCo.
, And the change information of the VC band for each route is notified to the relay exchanges SW2 and SW4 on each spare route. As a result, each of the transit exchanges SW2 and SW4 takes in the VC band fluctuation information of the working route that changes every moment.
The VC band of the backup route can be adaptively set to the VC band of the working route (dynamic CAC). Therefore, in the first or second embodiment of the present invention, since the VC band of the backup route secured as the peak value of the VC band of the working route fluctuates according to the size of the VC band of the working route. Therefore, it is not necessary to secure a useless VC band, and the VC band can be effectively used.

FIG. 13 is a diagram showing a failure recovery method for a failure of a communication device according to the present invention. FIG. 13 described in the conventional example
As shown in FIG. 13A, in addition to the VP-level failure recovery of FIG. 13C and the physical-level failure recovery of FIG. On the other hand, it is possible to switch between the active and the standby while the communication is continued.

FIG. 14 is a diagram showing a network using a simplified (downsized) exchange. However, according to the present invention, it is not necessary to provide a redundant device for improving reliability in the exchange, and the downsizing is realized. Can be achieved.

[0041]

As described above, according to the present invention,
It is possible to use an exchange in which redundant equipment for troubleshooting is omitted. Further, it is possible to take measures against a failure to rescue the VC connection during communication. As a result, network resources can be effectively used and an ATM communication network with high throughput can be realized.

Further, the cost of the exchange can be reduced. Further, it is possible to relieve a VC connection during communication without providing a device for performing concentrated VC connection rescue.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a routing table.

FIG. 3 is a diagram for explaining a procedure for securing a band of a spare route with respect to a band of one working route;

FIG. 4 is a flowchart showing an operation of call admission control (CAC).

FIG. 5 is a block diagram of a main part of the relay exchange;

FIG. 6 is an exemplary view for explaining a procedure for securing a band of a spare route while sharing a band of a spare route with one band of an active route;

FIG. 7 is a block diagram of a main part of a transit exchange according to a procedure considering sharing of a band of a backup route.

FIG. 8 is a diagram for explaining a procedure for rescuing a VC connection when a failure occurs in a transit exchange on a working route;

FIG. 9 is a block diagram of a table switching device for each VC connection according to the first embodiment of the present invention in the originating exchange and the destination exchange;

FIG. 10 is a diagram showing a routing table according to the second embodiment of the present invention.

FIG. 11 is a block diagram of a main part of a table switching device for each VC route according to a second embodiment of the present invention in the originating exchange and the destination exchange;

FIG. 12 is a block diagram of an originating exchange according to a third embodiment of the present invention.

FIG. 13 is a diagram showing a failure recovery method for a failure of a communication device according to the present invention.

FIG. 14 is a diagram showing a network using a simplified (downsized) exchange.

FIG. 15 is a diagram showing a failure recovery method for a failure of a conventional communication device.

FIG. 16 is a conceptual diagram of a highly reliable exchange.

[Explanation of symbols]

TBL routing table VS0 working VC setting unit RCo route-specific cell flow monitoring device Co cell flow monitoring device S table switching device SW exchange SW1 (originating) exchange SW3 (destination) exchange SW2, SW4 (relay) exchange M1 accommodated VC band memory M2 request VC band memory M3 VP capacity memory ADD Adder CMP comparator VS1 Spare VC setting unit M11 _{1 to} M1 _n VC band memory accommodated in spare route k (K = 1 to n) TS table switching control unit W VC connection failure detecting unit

Continuation of the front page (56) References JP-A-62-242441 (JP, A) JP-A-5-153154 (JP, A) JP-A-7-143128 (JP, A) JP-A-8-251182 (JP) JP-A-9-93259 (JP, A) JP-A-6-164631 (JP, A) JP-A-9-18492 (JP, A) (58) Fields studied (Int. Cl. ⁷ , DB Name) H04L 12/28 H04L 12/56

Claims (4)

(57) [Claims] 1. A plurality of exchanges, the plurality of exchanges being provided.
A virtual path is set up between
A means to set up working and backup routes on the
In the provided ATM communication network, a spare route to be switched to is specified for each part of the working route.
With a routing table, How to monitor the traffic of the working route
Adaptive reserve route size based on stage observations
Means for setting ATM communication characterized by the following:
network. 2. The ATM communication network according to claim 1, wherein said portion is set for each virtual channel. 3. The ATM communication network according to claim 1, wherein said portion is set for each route identifier assigned to each of a plurality of virtual channels. 4. The ATM communication network according to claim 1, wherein said routing tables are provided separately according to a grade of rescue performed when a failure occurs.