JPH0993260A - ATM communication network - Google Patents

Abstract

(57) [Abstract] [Problem] In conventional failure recovery in an ATM communication network,
Since the failure of the exchange is not premised, the exchange becomes expensive to ensure high reliability. SOLUTION: Instead of using a simplified exchange, V
Enables C level failure recovery. For that purpose, a routing table is provided for promptly switching the working and protection of the VC connection. In addition, the VC connection is divided into a class that relieves the VC connection and a class that does not. [Effect] An ATM communication network can be constructed at low cost. When a failure occurs, the VC connection in communication is relieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for ATM (asynchronous transfer mode) communication. In particular, the present invention relates to an active / preliminary switching technique.

[0002]

2. Description of the Related Art An ATM communication network physically includes a virtual channel handler (switch) that performs switching in units of virtual channels (VC) and a virtual path (Virtual Path Handler). Hereinafter, a virtual path handler (Vir) that sets a route for information transfer in units of VP
tual Path Handler: VPH or cross connect, X
And C) are connected by a transmission line. Logically, VCHs are connected by VP, and VP is zero or 1
It is terminated in VCH via the above VPH.

A failure recovery method for a conventional communication device failure will be described with reference to FIG. FIG. 15 is a diagram showing a failure recovery method for a failure of a communication device of a conventional example. The conventional failure recovery includes physical level failure recovery shown in FIG. 15 (b) and VP level failure recovery shown in FIG. 15 (a). In order to realize physical level failure recovery, the physical transmission line and the like are duplicated and one is set as the working system and the other is set as the 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 the physical level failure recovery, the physical transmission lines and the like must be duplicated at all times, and network resources cannot be used efficiently.

Therefore, there is a VP level failure recovery to which the concept of VP, which is a characteristic of ATM communication networks, is applied. VP is
V in the header area added to the cell which is the information transfer unit
VP identified by PI (Virtual Path Identifier)
In H, a route is set by a path connection (routing) table that describes the connection destination of the path. The VP level failure recovery is realized by switching the VP disconnected by the failure to the VP newly formed by 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 station that centrally monitors the network controls each node (VCH, VPH, etc.) in the network based on preset bypass path information. The self-healing method is a failure recovery method in which each node autonomously disperses and searches for a detour path to recover. The failure recovery at the VP level is superior to the failure recovery at the physical level in that the network resources of the transmission path can be efficiently used and that the network can be flexibly dealt with. Therefore, as a conventional failure recovery, FIG.
As shown in, the failure recovery combining the physical level and the VP level is applied.

[0005]

However, in the conventional failure recovery only at the physical level and the VP level, a failure of the VCH (exchange) is not premised, so that a highly reliable exchange is required. Also, in an ATM communication network in which a plurality of media coexist, the reliability required for each medium is different, but 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 the highly reliable exchange, a switch section, an I / O section, and a CPU section are duplicated as shown in FIG. The units are connected by a cross route. The cost of an exchange that is highly reliable due to such duplexing is about 4 to 6 times higher than the cost of an exchange having a simple configuration.

The present invention has been made against such a background, and an object of the present invention is to provide an ATM communication network which can use an exchange in which redundant equipment for fault countermeasures is omitted. It is an object of the present invention to provide an ATM communication network capable of taking measures against a failure 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 high throughput. An object of the present invention is to provide an ATM communication network which can use an inexpensive exchange. It is an object of the present invention to provide an ATM communication network capable of repairing a VC connection during communication without providing a device for intensive VC connection repair.

[0007]

When an exchange having a simple structure is applied as a communication device, it is necessary to quickly relieve a VC connection during communication when the exchange is out of order. INDUSTRIAL APPLICABILITY The present invention is a call admission control (CAC) control of a VC connection on a working route and a backup route.
If a relay switch on the working route has a failure, it has a routing table for setting the working and standby VC connections if it can accept the two routes. The main feature is that the VC level failure recovery can be performed by notifying the caller and switching the routing tables of the originating switch and the destination switch.

In the prior art, the failure recovery up to the VP level was performed, but the feature of the present invention is that the VC is
By performing level failure recovery, it is possible to relieve the VC connection during communication at the time of failure of the exchange.

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

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

It is desirable that 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.

The routing tables may be separately provided according to the grade of repair performed when a failure occurs.

It is also possible to provide a means for observing the traffic of the current route and a means for adaptively setting the size of the spare route based on the observation result of this means. As a result, the VC band fluctuation of the current route is tracked and the V of the route secured as the backup route is
The C band can also be varied. Therefore, at all times,
It is not necessary to secure the VC band of the spare route in accordance with the peak value of the VC band of the working route, and the VC band can be effectively used.

As described above, in the ATM communication network of the present invention,
By performing VC level failure recovery, it is possible to relieve the VC connection during communication at the time of failure of the exchange, so there is no need to use a highly reliable exchange, and by using an exchange with a simple configuration, The exchange cost can be reduced.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION 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 each of the exchanges SW1 to SW4 is an ATM communication network including a working VC setting unit VS0 and a backup VC setting unit VS1 as means for setting a working route and a protection route on the VP. Is.

Here, the feature of the present invention resides in that the routing table TBL shown in FIG. 2 in which the spare route of the switching destination is designated for each part of the active route is provided. The portion is set in VC units.

In the present specification, in order to make the explanation easy to understand, each of the exchanges SW1 to SW4 is a source exchange SW.
1, the destination exchange SW3 and the relay exchanges SW2 and SW4 are expressed as if they are different hardware, but in reality, these functions are provided together with the respective exchanges SW1 to SW4. .

[0019]

【Example】

(First Embodiment) The ATM communication network of the present invention is provided with a VC route corresponding to each reliability class in order to support a plurality of reliability classes. When a VC connection setting request for requesting a certain quality is made, a call admission determination CAC is performed on the VC route, and if the determination result is acceptable by the CAC, the VC connection is set. The types of VC routes are roughly classified into two types: a class that rescues a VC connection in communication (hereinafter referred to as a rescue class) and a class that does not rescue a network (called a non-rescue class) when a network failure such as a switch failure occurs. . The different types of VC routes mean that the reliability classes are different even if the routes are the same. The VC connection belonging to the rescue class is not disconnected even when a failure occurs in the exchange or the like, and the VC connection in communication is rescued by switching from the working route to the protection route at high speed. On the other hand, in the non-relief class, VCs that are communicating during a failure are
The connection will be disconnected. In an ATM communication network in which a plurality of media coexist, not all VC connections belonging to the relief class are required. In particular, media that does not require real-time performance is VC for non-relief class.
It is possible to set up a connection. In this way, the VC route is selected according to the reliability required when setting the VC connection. The present invention relates to an ATM communication network that rescues a VC connection during communication that belongs to a rescue class.

In order to switch and rescue the VC connection in communication at high speed, a working VC connection and a spare VC connection are set on the working route and the protection route at the time of call acceptance. In the first embodiment of the present invention,
A setting request is made to secure the VC band of the spare route corresponding to the peak value of the VC band of the working route, and the working and spare VC connections are set. FIG. 3 is a diagram for explaining a procedure for securing a band of a spare route for a band of one working route. As the VC route, there are an active route 1 and a corresponding backup route 1. The route of the working route 1 is the originating exchange SW1-the relay exchange SW2-the destination exchange SW3. The route of the spare route 1 is the originating exchange SW1-the relay exchange SW4-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 is generated. FIG. 4 is a flowchart showing the operation of call admission control (CAC). When a VC setting request occurs (S
1), the CAC is performed on both the working route 1 and the backup route 1, and if the acceptance determination is possible for both routes (S2), the VC is accepted (S3). Otherwise, the call is lost (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 current route fails. No actual cells are transferred on the backup route.

As a method for performing CAC, there is a peak allocation method in which the acceptance of a VC is judged from the declaration of the peak value of the VC.
The peak allocation method judges whether or not the value obtained by adding the peak value of the new VC to the sum of the peak values of the VCs accommodated in the VP exceeds the VP capacity. If the VP is not exceeded, the VP can be accommodated. That is, 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 cells are not actually transferred on the backup route, the band and peak value of the backup VC connection are allocated in VP3 and VP4. That is, when a new VC occurs, the working VC connection or the backup V
Whether the C connection can be accepted by the VP satisfies (peak value of new VC) + (sum of peak value of working VC connection and backup connection accommodated in VP) <VP capacity If so, it will be possible to accept.

FIG. 5 is a block diagram of essential parts of the repeater exchanges SW2 and SW4. Relay switch SW2, SW of FIG.
4, the new VC's peak declared value is loaded into the requested VC band memory M2, and
The sum of the peak declared values of the working VC connection and the spare connection accommodated in (1) is loaded into the accommodated VC band memory M1, and the sum of these values added by the adder ADD and the VP capacity memory M3 are loaded. The present value is compared by the comparator CMP, and the acceptance decision is made.

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

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

Further, the bandwidth of the spare route may be shared with the bandwidth of the plurality of active routes, instead of securing the bandwidth of the spare route equivalent to the bandwidth of the active route. . An example of sharing the bandwidth of the spare route will be described with reference to FIG. FIG. 6 is a diagram for explaining a procedure of securing a band of a spare route for one active route band while sharing the band. The working route and the backup route are associated by number. For example, the backup route 1 (originating exchange SW1-repeater exchange SW4-terminating exchange SW3) corresponds to the active route 1 (originating exchange SW1-repeater exchange SW2-terminating 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. Working route 1 and working route 2 are not independent routes because SW2 is the transit exchange, but working route 1
The active route 3 and the active route 2 and the active route 3 are independent routes. When the working route is an independent route, the band of the spare route can be shared, assuming that only one transit exchange fails. In the VP1, the backup route 1 can share the band with the backup route 3, but cannot share the band with the backup route 2.

When CAC of the spare VC connection on the spare route is performed, the virtual band on the spare route that can be shared can be excluded. For example, let us consider a case in which the above-mentioned peak allocation method is applied and the exchange SW4 determines whether or not the spare VC connection on the spare route 1 is accepted by the VP1. V accommodated in VP1
When calculating the sum of the peak values of the C connections, the bands of the spare route 1 and the spare route 3 can be shared, so the VC connection on the spare route 3 is excluded. In this case, the value obtained by adding the peak value of the new spare VC to the sum of the peak values of the VC connections of the spare route 1 and the spare route 2 is VP.
It is judged whether or not the capacity exceeds the capacity of 1, and if the capacity is exceeded, it can be accepted.

FIG. 7 is a block diagram of a main part of a repeater exchange according to a procedure considering sharing of a band of a spare route. Explaining the repeater exchanges SW2 and SW4, the peak declared value of a new VC is a requested VC. The band memory M2 is loaded. Further, the housing VC bandwidth memory M1 ₁ to M1 _n for spare route k (k = 1 to n), spare route k
The VC's peak claim value is loaded. When there is a request for a VC on the spare route, the required 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 spare routes that can share the band are excluded from _{1 to} M1 _n, is loaded into the comparator CMP, is compared, and the acceptance determination is performed. By sharing the bandwidth of the spare route in this way, network resources can be used efficiently.

As shown in FIG. 1, in the originating exchange SW1,
VCI / V on the spare outgoing side in the routing table TBL
The destination exchange SW3 has a PI table, and the routing table TBL has a spare incoming VCI / VPI table. The spare tables of the originating exchange SW1 and the destination exchange SW3 are not normally used. The table for the backup VC connection of the routing table TBL of the repeater exchange SW4 is set as the current one and can be used even in the normal state, but since the backup table on the outgoing side of the originating exchange SW1 is not used, the cell sent by the user is It is not transferred to the backup VC connection, but only to the working VC connection. An example of table management on the outgoing side of the originating exchange SW1 is shown in FIG. 2 (portion surrounded by a dotted frame in FIG. 1). There is no spare table for the non-relief class, but I have a spare table for the rescue class.

FIG. 8 is a repeater exchange SW on the working route.
FIG. 6 is a diagram for explaining a procedure for relieving a VC connection when a failure occurs in 2; When a failure occurs in the transit switch SW2 on the working route, the originating switch SW1 and the destination switch SW3 receive the VC connection failure notification. As a method of notifying a failure, there is a method using VC-AIS (Alarm Indification Signal, alarm display signal) using a failure notification cell. The notified originating and terminating exchanges SW1 and SW3, when recognizing the fault of the VC connection by the fault notification, perform VCI / VCI for each VC connection.
Switch table to VPI.

FIG. 9 shows the originating exchange SW1 and the destination exchange SW.
3 is a block configuration diagram of a table switching device S for each VC connection of the first embodiment of the present invention in FIG. 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 in VC connection units.

As described above, when the relay exchanges SW2 and SW4 on the working route fail, the routing table TB
By switching L, the VC connection in communication is switched from the current route to the backup route, so V in communication is changed.
The C connection can be relieved, and an exchange having a simple structure can be used instead of the conventional dual and highly reliable exchange, so that the cost of the exchange can be reduced.

(Second Embodiment) Another management example of the table on the outgoing side of the exchange SW1 is shown in FIG.
This will be described with reference to 0. 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 in communication on the current route
A route identifier RI (Route Identifier) is newly defined for the purpose of switching a connection to a spare route at high speed. RI is set for each VC route, and VC
Similar to I, it is replaced 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 transit switch SW2 of the working VC connection, the originating switch SW1 and the destination switch SW3 receive the VC connection failure notification.
As a method of notifying a failure, V using a failure notification cell is used.
There is a method by C-AIS. At this time, in the first embodiment of the present invention, the table is switched for each VC connection, but in the second embodiment of the present invention, the table is switched for each VC route.

The timing of recognizing the failure of 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 to install route information in VC-AIS
This can be realized by counting each route in W1 and destination switch SW3. Also, the relay exchanges SW2 and SW4
Can be notified, and the failure of the VC route can be recognized.

After the originating switch SW1 and the destination switch SW3 recognize the failure of the VC route, the routing table TBL of the VC connection belonging to the relevant VC route is identified by 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.
It is a block block diagram of the table switching apparatus S for every VC route of 2nd Example of this 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 in VC route units. In this way, since the active table is switched to the backup table for each VC route, compared with the switching for each VC connection,
It can be switched at high speed. Therefore, the VC connection during communication can be relieved at high speed, and the cell loss caused by the failure of the exchange can be reduced.

(Third Embodiment) FIG. 12 shows a third embodiment of the present invention.
This will be described with reference to FIG. FIG. 12 is a block diagram of the originating exchange SW1 according to the third embodiment of the present invention. In the third embodiment of the present invention, a cell flow observing device RCo for each route is provided to the originating exchange SW1.
Is provided, and the VC band variation information for each route is notified to the relay exchanges SW2 and SW4 on each spare route. As a result, each of the repeater exchanges SW2 and SW4 incorporates the variation information of the VC band of the working route, which changes moment by 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, the VC band of the backup route, which is secured as the peak value of the VC band of the working route, changes following the size of the VC band of the working route. It is not necessary to secure a wasteful VC band, and the VC band can be effectively used.

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

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 enhancing reliability in the exchange, and downsizing is performed. Can be achieved.

[0041]

As described above, according to the present invention,
It is possible to use an exchange that omits redundant equipment for countermeasures against failures. Furthermore, it is possible to take a failure countermeasure to rescue the VC connection during communication. As a result, it is possible to effectively use network resources and realize an ATM communication network with high throughput.

Further, the cost of the exchange can be reduced. Further, the VC connection during communication can be rescued without providing a device for intensive VC connection rescue.

[Brief description of 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 for a band of one working route.

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

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

FIG. 6 is a diagram for explaining a procedure for securing a band of a spare route for one active route band while sharing the band;

FIG. 7 is a block diagram of a main part of a relay exchange according to a procedure that considers sharing of a bandwidth of a backup route.

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

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

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

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

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

FIG. 13 is a diagram showing a failure recovery method for a failure of the communication device of 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 communication device of a conventional example.

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

[Explanation of symbols]

TBL routing table VS0 active VC setting unit RCo route-specific cell flow observing device Co cell flow observing device S table switching device SW switch SW1 (departure) switch SW3 (arrival) switch SW2, SW4 (relay) switch M1 accommodated VC band memory M2 request VC band memory M3 VP capacity memory ADD adder CMP comparator VS1 spare VC setting unit M1 _{1 to} M1 _n accommodating spare route k (K = 1 to n) VC band memory TS table switching control unit W VC connection failure detection unit

Claims (5)

[Claims] 1. An ATM communication network comprising a plurality of exchanges, wherein a virtual path is established between the plurality of exchanges, and the exchange comprises a means for setting a working route and a spare route on the virtual path. A routing table in which a spare route to be switched to is designated for each part of the route is provided.
TM communication network. 2. The ATM communication network according to claim 1, wherein the portion is set for each virtual channel. 3. The ATM communication network according to claim 1, wherein the part is set in units of route identifiers assigned to a plurality of virtual channels. 4. The ATM communication network according to claim 1, wherein the routing table is provided separately according to a grade of relief performed when a failure occurs. 5. The method according to claim 1, further comprising means for observing traffic on a working route, and means for adaptively setting the size of the spare route based on the observation result of this means. The ATM communication network described.