JP3087943B2 - 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, call admission control (dynamic CAC: Call Admission Cont
rol) technology.

[0002]

2. Description of the Related Art An ATM communication network physically includes an exchange (SW) that performs switching in units of a virtual channel (Virtual Channel, hereinafter referred to as VC) and a virtual path (Virtual Path, hereinafter referred to as VP). Cross connect (XC) that sets the information transfer route as a unit
Are connected by a transmission line. Logically,
VCHs (Virtual Channel Handlers) are connected by VPs, and VPs have zero or one or more VPHs (Virtual Path Ha
ndler) and terminated on VCH.

[0003] In the ATM communication network, when a VC setting request is made so that the required VC quality can be provided,
It performs call admission control (CAC). A
In the TM communication network, the information on the set VC is transferred in the form of a fixed-length packet called a cell, and the number of transferred cells varies depending on the amount of information. It is necessary to consider what cell transfer quality is degraded due to this.

One of the CAC methods is a method of declaring a peak value of a VC band, observing a cell arrival distribution arriving at a buffer, and estimating a cell loss rate after reception (dynamic CAC).
There is. The dynamic CAC method is described in H. Saito and K. Shiomoto, "Dy
namic Call Admission Control in ATM Networks ", IEEE
Journal of Selected Areas in Communications, Vol.
9, No. 7, pp. 982-989, September, 1991. The dynamic CAC has an advantage that a statistical multiplexing effect can be expected and network resources can be effectively used. VC
Is set via one or more VPs, so that it is determined whether the cell loss rate required for end-to-end is satisfied or not for each VP to be accommodated. A determination is made whether it is possible.

[0005] This conventional example will be described with reference to FIGS. 9 to 11. FIG. 9 is a block diagram of a main part of a conventional exchange. FIG. 10 is a flowchart showing the procedure of a conventional dynamic CAC. FIG. 11 is a conceptual diagram of a reception judgment based on a cell arrival distribution in a conventional dynamic CAC. Here, for the sake of simplicity, attention is focused on one VP. As shown in FIG. 9, the exchange SW is provided with an output buffer Bu for temporarily storing incoming cells, and a cell flow observation device Co for observing a cell flow flowing into the output buffer Bu. In the cell flow observation device Co,
A cell arrival distribution is determined. The cell arrival distribution has the number of cells on the horizontal axis and the frequency on the vertical axis. As a result, it is possible to observe how many cells have arrived per unit time and how many cells are currently stored in the output buffer Bu.

As shown in FIG. 10, in the dynamic CAC, first, a cell flow transferred to the output buffer Bu is observed (S1). Cell arrival distribution obtained by observation (S2)
From the declared peak value of the requested VC band (S3), the cell arrival distribution after receiving the requested VC is estimated (S4).
Further, based on the cell arrival distribution, the cell loss rate after reception is estimated (S5), and it is determined whether or not the estimated value satisfies the cell loss rate specified value of the requested VC in the exchange (S6). ). If satisfied, the VP can be accepted (S7), and if not satisfied, a call loss occurs (S7).
8).

[0007] Based on the cell arrival distribution observed as shown in FIG. 11 (a), as shown in FIG.
The cell arrival distribution after C reception is estimated. As a result,
It turns out that the cell at the first position along the horizontal axis is discarded,
An estimate of the cell loss rate is determined.

[0008] Since dynamic CAC performs CAC based on observations, it is possible to make a reception decision according to the state of use of network resources, and to effectively utilize network resources with the expectation of a statistical multiplexing effect. There is an advantage that can be.

Next, a conventional example of a specific ATM communication network will be described. FIG. 12 is a diagram showing a specific example of the ATM communication network. FIG. 12 shows a case where a spare route is set in addition to the working route in preparation for a failure of the exchanges SW1 to SW4. A working VC is set on the working route, and a protection VC is set on the protection route. Cell transfer is performed on the working route, but cell transfer is not performed on the protection route. The cell transfer is performed on the spare route when the working route becomes unavailable due to a failure. For example, the route of the working route 1 is the originating exchange SW.
1-relay switch SW2-destination switch SW3. The route of the backup route 1 to the working route 1 is the originating exchange SW1.
The relay exchange SW4—the destination exchange SW3, which is an independent route (a route that does not share the relay exchanges SW2 and SW4) from the working route 1; When a VC is set by a request, dynamic CAC needs to be performed for both the working route 1 and the protection route 1 in order to secure the bandwidth of the working VC and the protection VC.

[0010]

However, in the dynamic CAC based on the observation of the cell flow, the cell transfer is not actually performed on the backup VC on the backup route.
Dynamic CA considering backup VC band on backup route
C cannot be performed. Therefore, if the dynamic CAC is performed only for the working route and the reception determination is possible,
The working VC is set on the working route, and the protection VC is set on the protection route without considering the available VC band. Therefore, for example, the relay exchange SW2
And a cell transfer from the working VC to the spare V
When switching to C, in the spare VC,
The required cell loss rate may not be guaranteed. Further, in the VP4 between the transit exchange SW4 and the destination exchange SW3, the working VCs of the working route 2 are set, but the cell loss rate of these working VCs may not be guaranteed.

The present invention has been made in such a background. A spare VC band is reserved according to the working VC band, and the cell transfer is switched from the working VC to the spare VC. It is another object of the present invention to provide an ATM communication network capable of guaranteeing a required cell loss rate. The present invention
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.

[0012]

According to the present invention, a plurality of exchanges are provided, and a virtual path is set between the plurality of exchanges. The exchange includes means for setting working and protection routes on the virtual paths. ATM communication network.

Here, the features of the present invention are as follows: means for observing the traffic of the working route for one exchange, and adaptively setting the size of the spare route based on the observation result of this means. And means.

[0014] With this, a spare VC band can be set according to the working VC band, so that when a failure occurs in the working route and switching to the spare route, the cell loss rate on the spare route is defined. Value can be satisfied. Furthermore, if the working VC band is reduced, the spare VC band is also reduced accordingly, so that unnecessary V wastes.
Network resources can be effectively used without occupying the C band.

When there are a plurality of working routes, it is preferable that the means for observing is provided separately for each corresponding backup route. This makes it possible to finely control the call admission of the backup route for each of the plurality of working routes.

The traffic may have a cell arrival distribution. Since the cell arrival distribution is convenient for indicating, for example, the accumulation state of cells in the output buffer of the exchange, the cell loss rate after receiving the request VC can be accurately estimated.

[0017] A spare band on a spare route may be provided in common with a plurality of working routes that are independent of each other. In other words, by providing a spare route in common for independent working routes that are not interrupted by both due to the same fault location, it is possible to save the VC band provided as a spare route.
In the ATM communication network according to the present invention, the size of the backup route may be set as the backup route for the working route, which is an independent route, based on the observation result of any of the working routes.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 and FIG. 2 are block diagrams showing the principal parts of the exchange of the present invention. In particular, FIG. 1 is a block diagram of a main part of the originating exchange SW1, and FIG. 2 is a block diagram of a main part of the relay exchanges SW2 and SW4. ATM
See FIG. 12 for the communication network configuration.

According to the present invention, as shown in FIG.
1 to SW4, and a VP between the exchanges SW1 to SW4.
1 to VP4 are set, and the exchanges SW1 to SW4 are
This is an ATM communication network including a working VC setting unit VS0 and a protection VC setting unit VS1 as means for setting working and protection routes on VP1 to VP4.

Here, the feature of the present invention is that, for each exchange SW1, a route-specific cell flow observation device RCo as a means for individually observing traffic of a plurality of working routes passing through the exchange SW1 is provided. ,
Preliminary root cell arrival distribution memory CM1 ₁ ~CM1 _n as means for setting the size of the spare routes adaptively based on the observation result of the route-cell flow observation device RCo,
Convolution integrator CI, virtual cell arrival distribution memory CMV
And where it is.

In the embodiment of the present invention, the originating exchange SW1, the transit exchange SW2, and the
4. The destination exchange SW3 is divided and expressed as if it were different hardware. However, in actuality, all the functions are provided together in one exchange.

The transit exchange SW2, SW4 is the preliminary root cell arrival distribution memory CM1 ₁ ~CM1 _n, holds information transferred from the originating exchange SW1 as cell arrival distribution routes working to the root of the reserve.

[0023]

【Example】

(First Embodiment) As shown in FIG. 12, an ATM communication network has an active 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. The route of the backup route 1 does not share the transit switch SW2 or SW4 with the working route 1 and is therefore an independent route. When a VC setting request is generated, dynamic CAC is performed at the time of VC setting on the working route 1. The dynamic CAC is performed for both the working route 1 and the backup route 1. If the acceptance determination is possible for both routes, the VC setting request is accepted. Thereby, the VC is set on the working route, and the cell is transferred only on the working route. No actual cells are transferred on the backup route. However, assuming that cells of the VC on the working route are also transferred on the protection route, the dynamic CAC on the protection route is performed.

When the dynamic CAC method is performed, regarding the working route, each of the exchanges SW1, SW on the working route is used.
2. According to the normal dynamic CAC process in SW3, the cell arrival distribution arriving at the output buffer Bu is observed, the cell loss rate after receiving the requested VC setting is estimated, and the reception is determined. At this time, the actual cell is not transferred on the spare route. Therefore, when performing the reception determination on the spare route, the originating exchange SW1 observes the cell arrival distribution for each working route for each route. FIG. 1 shows the configuration of the originating switch SW1 on the working route. It is characterized by having a per-route cell flow observation device RCo, in which the local exchange observes the cell flow for each working route for the working route to be the originating exchange, and holds the cell arrival distribution of each working route. And transfers the per-route cell arrival distribution to a transit exchange (eg, SW4) on each backup route. The transfer timing is when the per-route cell arrival distribution changes. The transfer cycle is short when the variation in the cell arrival distribution is large, and long when the variation in the cell arrival distribution is small. The exchange receiving the transfer performs dynamic CAC each time, and sets a VC band of a spare route corresponding to the fluctuation. Further, the cell arrival distribution may be transferred periodically.

In FIG. 12, the cell arrival distribution of the working route 1 is observed by the SW1 of the originating exchange, and the cell arrival distribution of the working route 1 is transferred to the transit exchange SW4 on the protection route 1. In the VP4 between the relay exchange SW4 and the destination exchange SW3 on the protection route 1, the cell arrival distribution of the protection route 1 in which no cell transfer is actually performed in the relay switching SW4 and the working route 2 in which the cell transfer is performed is It is necessary to perform dynamic CAC in consideration of this.

FIG. 3 shows a dynamic CA according to the first embodiment of the present invention.
It is a flowchart of C. FIG. 4 is a diagram showing a state of estimation of convolution integration, virtual cell arrival distribution, and cell loss rate. As shown in FIG. 3, for the route that is used as the backup route 1 and has no actual cell arrival distribution, the cell arrival distribution of the working route 1 transferred from the originating exchange SW1 is received and used (S12). In addition, for the route from which the actual cell arrival distribution can be observed, the cell arrival distribution observed by the destination exchange SW3 or the cell arrival distribution observed by the transit exchange SW4 is used (S11). The convolution integrator CI performs convolution integration of the cell arrival distributions of the working route 2 and the backup route 1 accommodated in these VPs 4 (S13, FIG. 4A), and relays as shown in FIG. 4B. The virtual cell arrival distribution in the exchange SW4 is calculated (S14). In consideration of the peak declared value of the required VC band in the virtual cell arrival distribution (S15), the virtual cell arrival distribution after receiving the requested VC is estimated (S16, FIG. 4).
(C)) Further, the cell loss rate after reception is estimated (S1).
7, FIG. 4 (c)), it is determined whether or not the estimated value of the cell loss rate after reception satisfies a specified value (S18). As a result, if the specified value is satisfied, it can be accepted to the VP (S19), and if not, it is determined as a call loss (S20).
Make a reception decision. As a result, an equivalent band of the backup route 1 is secured with respect to the band of the working route 1. Even if a failure occurs in the transit exchange SW2 on the working route 1 and the working VC becomes unusable and the cell transfer is switched to the protection VC on the protection route 1, the protection VC band is considered. As a result, the required cell loss rate can be guaranteed.

As described above, the dynamic CAC can be performed in consideration of the VC band on the backup route, so that the required cell loss rate is guaranteed even when the cell transfer is switched from the working VC to the backup VC. be able to.

(Second Embodiment) In the first embodiment of the present invention, a VC band of a spare route equivalent to the VC band of the working route is secured, but in the second embodiment of the present invention, The VC band of the spare route is shared with the VC bands of the plurality of working routes. FIG. 5 shows the configuration of an ATM communication network for explaining the second embodiment of the present invention. FIG. 5 is an overall configuration diagram of an ATM communication network according to a second embodiment of the present invention. In FIG. 5, the working route and the backup route correspond by numbers. For example, for the active route 1 (the originating exchange SW1-the transit exchange SW2-the destination exchange SW3), the backup route 1 (the originating exchange SW1-the transit exchange SW4-the destination exchange S)
W3) corresponds. All working routes and backup routes are set as independent routes.

V between the relay exchange SW4 and the destination exchange SW3
Focusing on P1, three spare routes are accommodated. The working route 1 and the working route 2 are connected to the transit switch SW2.
Route is not an independent route because it shares
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, the VC band of the spare route can be shared, assuming that only one transit exchange fails. VP1
, The backup route 1 can share the VC band with the backup route 3, but cannot share the VC band with the backup route 2.

Dynamic CAC of spare VC on spare route
Is performed, the virtual V on the spare route that can be shared
The C band can be excluded. Applying the dynamic CAC method, the VC on the protection route 1
The current route 1
And the cell arrival distribution of the working route 2 are convoluted and integrated to calculate the virtual cell arrival distribution in the VP1.
However, since the band of the protection route 3 can be shared, the cell arrival distribution of the working route 3 is excluded. As a method of determining whether the spare band can be shared, for example, each switch SW1
SW7 has the route information of the working route for the accommodated spare route, and the working route for the spare route for performing the dynamic CAC is different from the working route for the spare route housed in the same VP. Judgment is made based on whether the path is an independent path. If the path is an independent path, a spare VC band can be shared. If the path is not an independent path, the spare VC band cannot be shared.

FIG. 6 is a flowchart of the dynamic CAC according to the second embodiment of the present invention. This is a generalization of the contents described with reference to FIG. 5, including those in which the working route is accommodated in the target VP, and there is a process of observing the actual cell flow. First, the cell arrival distribution of the working route for each backup route is received (S21). From the cell arrival distribution of the working route to each backup route, those that can share the VC band are excluded and selected (S22). Observe the cell flow actually passing through its own switch (S2
3). These are subjected to convolution integration by the convolution integrator CI (S24). Thereby, a virtual cell arrival distribution is obtained (S25). The declared peak value of the requested VC call is input (S26), and the virtual cell arrival distribution after receiving the VC is estimated (S27). From this, the cell loss rate after receiving the VC is estimated (S28). It is determined whether this cell loss ratio satisfies a specified value (S29). As a result,
If the specified value is satisfied, it can be accepted by the VP (S3
0). If it is not satisfied, it is determined as a call loss (S31).

The features of the second embodiment of the present invention are as follows.
It is characterized by a process of selecting a cell arrival distribution of a working route with respect to each backup route, excluding those that can share a VC band. The targets of the convolution integration are the actually observed cell arrival distribution and the cell arrival distribution of the selected spare route.

FIG. 7 shows a transit exchange S according to a second embodiment of the present invention.
FIG. 3 is a block diagram of a main part of W2, SW4, and SW7. The present invention transit exchange SW2 of the second embodiment, SW4, SW7 features of the pre-root cell arrival distribution memory CM1 ₁ ~CM
1 _n holds the cell arrival distribution information of the working route for the protection route transferred from the originating exchanges SW1 and SW6, and can share the VC band from the cell arrival distribution of the working route for each protection route. Is provided with a selector SL for excluding and selecting.
As described above, by performing dynamic CAC in consideration of sharing the VC band of the spare route, network resources can be used efficiently.

(Third Embodiment) A third embodiment of the present invention will be described with reference to FIG. FIG. 8 is a diagram showing a routing table used in the third embodiment of the present invention. In the third embodiment of the present invention, a routing table as shown in FIG. 8 is used for switching between the working and the standby shown in the first or second embodiment of the present invention. As a result, the VC that is communicating on the working route is switched to the backup route without interrupting the communication. As described in the first or second embodiment of the present invention, the current VC band and the spare VC band are adaptively and equally secured, so that there is no cell loss after switching.

Further, at the time of switching between working and standby,
For routes that transfer information that may be interrupted (for example, information that does not require real-time processing), the routing table is not set as a non-relief class, thereby providing flexibility in route setting. It is.

[0036]

As described above, according to the present invention,
A spare VC band is reserved according to the working VC band, and when the cell transfer is switched from the working VC to the spare VC,
The required cell loss rate can be guaranteed. As a result, network resources can be effectively used, and an ATM communication network with high throughput can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a main part of an originating exchange.

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

FIG. 3 is a flowchart of a dynamic CAC in the first embodiment of the present invention.

FIG. 4 is a diagram showing a situation of convolution integration, virtual cell arrival distribution, and estimation of a cell loss rate.

FIG. 5 is an overall configuration diagram of an ATM communication network according to a second embodiment of the present invention.

FIG. 6 is a flowchart of a dynamic CAC according to a second embodiment of the present invention.

FIG. 7 is a block diagram of a main part of a transit exchange according to a second embodiment of the present invention.

FIG. 8 is a diagram showing a routing table used in a third embodiment of the present invention.

FIG. 9 is a block diagram of a main part of a conventional exchange.

FIG. 10 is a flowchart illustrating a procedure of a conventional dynamic CAC.

FIG. 11 is a conceptual diagram of a reception determination based on a cell arrival distribution in a conventional dynamic CAC.

FIG. 12 is a diagram showing a specific example of an ATM communication network.

[Explanation of symbols]

Bu output buffer CI convolution device CMV virtual cell arrival distribution memory CM1 ₁ ~CM1 _n preliminary root cell arrival distribution memory Co cell flow observation device RCo route-cell flow observation device SL selectors SW1, SW6 (originating) exchange SW2, SW4, SW7 ( Relay) exchange SW3, SW5 (Destination) exchange VS0 Working VC setting unit VS1 Spare VC setting unit

────────────────────────────────────────────────── ─── Continued on the front page (56) References IEICE Technical Report SS E95-60 (September 28, 1995) 1995 IEICE Communication Society Conference SB-6-1 (August 1995 15) 1995 IEICE Communications Society Conference B-350 (August 15, 1995) IEICE Technical Report SS E93-43 (September 30, 1993) (58) (Int.Cl. ⁷ , DB name) H04L 12/28 H04L 12/56

Claims (3)

(57) [Claims] 1. An ATM communication network comprising a plurality of exchanges, wherein a virtual path is set between the plurality of exchanges, and wherein the exchange has means for setting working and protection routes on the virtual path. Means for observing the cell arrival distribution of the current route, and the cell arrival distribution observed by this means and
Perform convolution integral operation based on the declared bandwidth peak value
Estimate the cell loss rate after accepting the request, and specify this cell loss rate
Judge whether the value satisfies
Means for setting a spare route of a band requested to be acceptable . 2. The ATM communication network according to claim 1, wherein when there are a plurality of working routes, said means for observing is provided separately for each corresponding backup route. 3. The ATM band restricting apparatus according to claim 1, wherein a spare band on a spare route is provided in common for a plurality of working routes independent of each other.