JP2864049B2 - Call admission control method in ATM exchange - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] Regarding a call admission control method of an ATM exchange which does not accept a call which is expected to not obtain a required quality of service due to a large cell loss rate and delay, Calculating the load applied to the exchange by the call and the load fluctuation, predicting the possibility that the required service quality can be provided, and judging acceptance / rejection of the acceptance of the call, if the required service quality cannot be provided. For the purpose of enabling rejection of expected call acceptance, based on attribute parameters of the connection request call received at the time of a call connection request from a subscriber terminal, load of the connection request call and A load / load fluctuation calculating means for calculating a load fluctuation value; and a load / load fluctuation value calculated based on the attribute parameters of the connection request call of the accepted call, and updated by the load / load fluctuation value. An information management means for storing a load and a load change value; a load of the connection request call calculated by the load / load change calculation means, a load change value, and an outgoing route load and load managed by the information management means; Determining means for determining whether or not to accept the connection request for the call based on the fluctuation value.

[Industrial applications]

The present invention relates to a call admission control method for an ATM exchange, and more specifically, does not accept calls that are expected to not achieve the required quality of service due to a large cell loss rate and delay.
The present invention relates to a call admission control system for an ATM exchange.

[Conventional technology]

Broadband as a next-generation communication network integrating all information communication services such as voice, data, and moving images
ISDN research and development is currently underway. Among them, ATM (Asynchronous Transfer Mode) is based on continuous information such as audio and video, burst information such as CAD and CAM data, and without depending on the communication speed of each information. Is a technique of converting the information into fixed information called a cell and transferring the fixed information at a high speed. An ATM switch to realize this technology is currently under development and is expected to be commercialized around 1993.

In the ATM-compatible switching system, various traffics with different bearer speeds and burstiness of information such as voice, data, and moving images are handled in a unified manner, and these input information is converted into cells with fixed-length information and statistically processed. Multiplex exchange.

[Problems to be solved by the invention]

However, when traffic having a strong burst property is mixed, there is a problem that the load variation of the traffic applied to the exchange becomes large, and it becomes impossible to provide the required service quality with respect to the cell loss rate and the delay.

In other words, when data with strong burst characteristics, such as CAD or CAM data, enters the exchange, the load fluctuations during bursts and other than during bursts become very large, and during bursts the load becomes too large and Are discarded or delayed.

According to the present invention, for a call requesting connection, a load applied to an exchange by the call and a load fluctuation are calculated, and the possibility of providing a required quality of service is determined to determine management / rejection of call reception. It is an object of the present invention to be able to reject a call expected to be unable to provide a required quality of service.

[Means for solving the problem]

FIG. 1 is a functional block diagram of the present invention. The present invention is premised on an ATM exchange 1, a subscriber terminal 2 connected thereto, and an outgoing route 3 which is an output of the ATM exchange 1.

First, the subscriber terminal 2 has attribute parameter reporting means 4. The attribute parameter reporting means 4 is used when the subscriber terminal 2
When requesting a connection of a call to the M exchange 1, a parameter indicating the attribute of the call is declared together with the connection request. The attribute parameters include the peak speed of the call, the average speed, the duration of the burst, the number of cells generated during the burst duration, the interval between bursts, the burst rate, and the like. At least three of these attribute parameters are declared to the ATM exchange 1.

The ATM switch 1 has a load / load fluctuation calculating means 5.
The load / load fluctuation calculating means 5 calculates the load and the load fluctuation of the call based on the attribute parameters reported by the attribute parameter reporting means 4. The load and the load fluctuation can be calculated from three attribute parameter values.
That is, from the peak rate and the burst duration and the burst generation time interval, or from the average rate and the number of generated cells and the burst rate during the burst duration, or from the peak rate, the burst duration and the burst rate, or
The load and load fluctuation of the call are calculated from the peak speed, the average speed, and the burst duration, or from the peak speed, the average speed, and the number of generated cells during the burst duration.

The ATM exchange 1 has an information management means 6. The information management means 6 stores and manages the load and load fluctuation information of each outgoing route 3, and also stores each connected subscriber terminal 2.
Stores and manages information.

Information on the outgoing route 3 is stored as a database on a disk or the like. First, the outgoing route 3 for outputting the continuation request call is connected, and when the call is to be connected, the load and load fluctuation values of the outgoing route 3 before the connection of the call are updated, and the load / load fluctuation calculation is performed. The load and the load fluctuation value in consideration of the load and the load fluctuation value of the call obtained by the means 5 are stored. On the other hand, when disconnecting the connected call, the load and the load fluctuation value are updated with respect to the outgoing route 3 of the disconnected call, and the load and the load fluctuation of the disconnected call are removed.

On the other hand, the information of the subscriber terminal 2 is temporarily stored during the connection period of the call for which the memory subscriber terminal 2 in the ATM exchange 1 has requested connection. With respect to the subscriber terminal 2 to which the requested call is connected, the location, call number, outgoing route, load of the call and load fluctuation value of the subscriber terminal 2 are stored. When contacting the call,
The information about the subscriber terminal 2 of the call to be disconnected is deleted from the memory.

The ATM switch 1 further has a full load / load fluctuation calculation means 7. The full load / load change calculating means 7 calculates all loads and load changes on the selected outgoing route 3 when the subscriber terminal 2 requests connection of a call. In other words, the load and load fluctuation of the connection request call calculated by the load / load fluctuation calculating means 5 are added to all loads and load fluctuations of the outgoing route 3 stored by the information management means 6. Add influence.

Finally, the ATM switch 1 is provided with the cell loss rate / delay evaluation means 8.
Having. The cell discard rate / delay evaluating means 8 discards the connection request call from the load and load fluctuation value expected to be applied to the outgoing route 3 calculated by the full load / load fluctuation calculating means 7 by connecting the connection request call. The cell loss rate of the cell expected to be calculated and the delay expected to occur in information transmission are calculated, and by judging the value, it is determined whether or not to accept the connection of the connection request call. .

[Action]

When the subscriber terminal 2 accommodated in the ATM exchange 1 transmits information to another subscriber terminal 2, first, the subscriber terminal 2
Requests the ATM exchange 1 to connect a call. At this time, the attribute parameter reporting means 4 reports the parameter value indicating the attribute of the connection request call to the ATM exchange 1 together with the call connection request. The report parameters include the peak speed of the call, the average speed, the burst duration, the number of cells generated during the burst duration, the burst generation interval time, the burst rate, and the like. The attribute parameter declaration means 4 declares at least three parameter values among these attribute parameters.

The ATM exchange 1 receives from the subscriber terminal 2 a call connection request (calling signal) and attribute parameters of the connection request call.
First, the load / load variation calculating means 5 of the ATM exchange 1 receives at least three attribute parameter values sent from the attribute parameter reporting means 4 of the subscriber terminal 2 and calculates the load and the load variation value of the connection request call. I do. The load and load fluctuation values are derived from the peak speed, burst duration, and burst generation time interval, or from the average speed and the number of cells generated during the burst duration and burst rate, or from the peak speed, burst duration, and burst rate. Alternatively, it is calculated from the peak speed, the average speed, and the burst duration, or from the peak speed, the average speed, and the number of cells generated during the burst duration.

Next, the load and the load fluctuation value of the connection request call calculated by the load / load fluctuation calculating means 5 are sent to the total load / load fluctuation calculating means 7 in the ATM exchange 1. The ATM switch 1 selects the outgoing route 3 in response to the connection request call, and the load and the load fluctuation value expected to be applied to the outgoing route 3 are calculated by the full load / load fluctuation calculating means 7.

At this time, the total load / load change calculating means 7 receives the load of the outgoing route 3 and the load change data from the information managing means 6. This data is the load and load fluctuation data of the outgoing route 3 before the connection request call is connected. The full load / load fluctuation calculating means 7 adds the load data of the connection request call sent from the load / load fluctuation calculating means 5 to the load data of the outgoing route 3 to thereby execute the connection request call. When the connection is made, the load applied to the outgoing route 3 is calculated. Further, the total load / load change calculating means 7 includes the load data and the load change data of the outgoing route 3 obtained from the information managing means 6 and the load data of the connection request call received from the load / load change calculating means 5. And the load fluctuation data and the load data calculated by the total load / load fluctuation calculation means 7 which are expected to be applied to the outgoing route 3,
Calculate the load fluctuation value that is expected to occur.

The outgoing route 3 calculated by the full load / load variation calculating means 7
The load and load variation expected to be
It is sent to the cell discard rate / delay evaluation means 8.

The cell discard rate / delay evaluating means 8 first calculates a cell discard rate expected to be discarded when the connection request call is connected, based on the received load data and load fluctuation data. Then, a transmission delay expected when the connection request call is connected is calculated based on the received load data and load fluctuation data, similarly to the cell loss rate.

The ATM exchange 1 defines the service quality that must be satisfied for each service. The quality of service is determined by the cell loss rate and the magnitude of delay. That is, the ATM switch 1 determines the threshold values for the cell loss rate and the delay time for each service.

The cell discard rate / delay evaluating means 8 rejects the connection request call when it is expected that the specified service quality cannot be obtained. That is, if the calculated cell loss rate is greater than the threshold value or the delay time is greater than the threshold value, it is determined that the service quality is low, and the acceptance of the connection request call is rejected. To the subscriber terminal 2. On the other hand, when the calculated cell loss rate and the delay time are equal to or smaller than the predetermined threshold, it is determined that the required service quality is satisfied, and the one that accepts the connection request call and the ATM switch 1 perform the connection processing of the call. Execute.

When accepting the connection request call and executing the connection process, the information management means 6 executes a process for storing various information associated with the call. That is, information on the subscriber terminal of the call to be connected (subscriber terminal position, call number, outgoing route, load of the call, and load fluctuation data) is AT
The information is temporarily stored in a memory in the M exchange, and information on the outgoing route 3 (the load on the outgoing route 3 and the load fluctuation) to which the call is connected is updated. As for the information on the outgoing route 3, the load and load variation data for each outgoing route are managed as a database. Therefore, when the call is determined to be connected to a certain outgoing route 3, the information on the outgoing route in the database is updated.

On the other hand, also when ending the connected call, the information management means 6 executes information management processing. First, the database of the outgoing route 3 is updated. That is, the load and load fluctuation data stored in the database for the outgoing route 3 to which the call was connected, and the subscriber terminal information of the call temporarily stored in the memory in the ATM exchange 1 The load and the load fluctuation data are taken out, the load of the call is subtracted from the load data of the outgoing route 3, and the load fluctuation of the call is subtracted from the load fluctuation of the outgoing route 3. Then, for the outgoing route 3, the load and load fluctuation data from which the influence of the call is subtracted are stored in the database. And
Finally, the subscriber terminal information of the call temporarily stored in the ATM exchange 1 is deleted.

〔Example〕

The embodiment will be described below with reference to FIGS. 2 and 8.

FIG. 2 is a system configuration diagram of one embodiment of the present invention.

In the present embodiment, it is assumed that an ATM exchange 1 having an outgoing route 3 and a subscriber terminal 2 connected thereto. Each subscriber terminal 2 is connected to a network terminator (NT).
tor) 20 and connected to the ATM switch 1.

The ATM switch 1 includes a multiplexer 21 for multiplexing information input from each subscriber terminal 2 and an ATM for executing switching connection.
Switching device 22, subscriber terminal 2 and other ATM switch 1
A signal processing device 23 for transmitting / receiving a signal to / from, a call control device 24 for executing a call control such as traffic control, and a call processing device 25 for executing a call acceptance control. The multiplexing device 21 is connected to the subscriber terminal 2 via the network terminating device 20, and is also connected to the ATM switching device 22 and the signal processing device 23. ATM switching device 22 is multiplexing device 21
Outgoing line (outgoing route)
3 is connected to an external line. The signal processing device 23 is connected to the multiplexing device 21, the call control device 24, and the call processing device 25. The call control device 24 is connected to the ATM switching device 22, the signal processing device 23, and the call processing device 25. The call processing device 25 is connected to a database 26 that stores data necessary for call processing. This database 26 is composed of, for example, a magnetic disk device.

When making a call, each subscriber terminal 2 inputs a parameter value indicating the attribute of the call together with a call connection request signal to the ATM exchange 1 via the network terminating device 20. The connection request is sent to the signal processing device 23 via the multiplexing device 21, further sent to the call processing device 25 and the call control device 24, and the attribute parameter value is called via the multiplexing device 21 and the signal processing device 23. It is sent to the processing device 25.

The call control device 24 receives the connection request signal, selects the outgoing route 3 of the call, and notifies the call processing device 25 of the outgoing route number. The call processing device 25 determines whether or not to accept the connection request call in response to the connection request signal. This determination is based on the attribute parameter value declared by the subscriber terminal 2 and the call control device 24.
Is performed based on the selected outgoing route number and the load and load variation data for the outgoing route in the database connected to the call control device 25. The result of this determination is notified to the call control device 24. In the case of non-acceptance, a signal to the effect that resin cannot be sent to the subscriber terminal 2 is sent to the subscriber terminal 2 via the signal processing device 23, the multiplexing device 21, and the network terminating device 20.

The flow of the connection request acceptance determination process executed by the call processing device 25 will be described with reference to the operation flowchart of the embodiment of FIG.

First, the subscriber terminal 2 that is trying to communicate is an ATM.
A request is made to the exchange 1 for connection of a call, and a parameter indicating the attribute of the call is declared (S1).

FIG. 4 is an explanatory diagram of an example of types of attribute parameters declared by the subscriber terminal 2. For example, peak speed Vp, burst duration α ^-1 , burst occurrence time interval β ^-1 , average speed
Vav, the number Nc of cells generated during the burst duration, the burst rate Rb, and the like are attribute parameters. The subscriber terminal 2 does not need to declare all the values of these attribute parameters.
The values of the call load and the load fluctuation can be calculated if several of these attribute parameters are known.
The peak speed Vp is the average speed Vav and the burst duration α ^-1 ,
It can be obtained from the burst generation time interval β ^−1, and the number of cells Nc generated during the burst duration is obtained from the park speed Vp and the burst duration α ⁻¹ . further,
This is because the burst rate Rb can be obtained if the average speed Vav and the peak speed Vp or the burst duration α- ¹ and the burst generation time interval β- ¹ are known.

The call connection request and the attribute parameters sent to the ATM switch 1 by S1 are transmitted to the call processing device 25 and the call control device via the multiplexer 21 and the signal processor 23 of the ATM switch 1.
Sent to 24 and accepted (S2). Then, the call control device 24 selects the outgoing route 3 of the call (S3).

On the other hand, the call processing device 25 calculates the load and the load fluctuation value of the connection request call from the declared attribute parameters (S4).

FIG. 5 is an explanatory diagram of a calculation formula for obtaining a load and a load change. As mentioned above, call load and load variation are determined by using some of the declared attribute parameters.

FIG. 7A is a formula for calculating the load Aa and the load variation VARa when the declared attribute parameters are the peak speed Vp, the burst duration α ⁻¹ , and the burst occurrence time interval β ⁻¹ .
The load Aa is obtained from the peak speed Vp, the burst duration α ⁻¹ , and the burst generation time interval β ⁻¹ as in the equation (1). Where Vt is the maximum speed of the transmission line, this value is the ATM
It is known to the exchange 1. On the other hand, the load variation VARa is obtained by equation (2). Here, λ = Aa / h, h = Cl / Vt, and Cl is the cell length.

FIG. 7B is a calculation formula when the attribute parameters are the average speed Vav, the number of cells Nc occurring during the burst duration, and the burst rate (Formulas (3) and (4)). As in the case of FIG. 3A, the maximum speed Vt of the transmission line and the cell length Cl are used as known values.

Hereinafter, when the report parameters are the peak speed Vp and the burst duration time α ⁻¹ , and the burst rate, the load and the load fluctuation are calculated by the formulas (5) and (6) ((c) in the same figure), respectively. In the case of the peak speed Vp, the average speed Vav, and the burst duration α- ¹ , the calculation formulas of the load and the load fluctuation are the formulas (7) and (8) ((d) in FIG. 4), respectively. The calculation formulas of the load and the load variation twice as many as the average speed Vav and the number of cells Nc generated during the burst duration time are formulas (9) and (10), respectively ((e) in the same figure).

In S4, the formula is selected according to the type of the attribute parameter declared by the subscriber terminal 2 as described above, and the load Aa and the load variation VARa are obtained.

Next, the call processing device 25 receives the number of the outgoing route selected by the call control device 24, and calculates the total load and the load fluctuation value on the outgoing route (S5). At this time, the load Ad and the load fluctuation value VARd of the selected outgoing route are read from the database 26 connected to the call processing device 25, and the total load is read.
Used for calculating At and load fluctuation value VARt. The calculation formulas are: Total load At = Ad + Aa (11) Load fluctuation VARt VARt = VARd + VARa (12)

The total load At of the outgoing route is, as shown in equation (11), the load Ad before the connection request is read and the expected load of the connection request call.
It is obtained by adding Aa. Also, load fluctuation VARt
Is the load Ad and the load fluctuation VARd before the connection request call is connected, the expected load Aa and the expected load fluctuation VARa of the connection request call, and after connecting the connection request call to the outgoing route, as in equation (12). From the full load At. By calculating the above equation, the expected load At and the expected load fluctuation VARt when the connection request call is connected to the selected outgoing route are obtained.

Next, the cell loss rate and the delay of the ATM exchange 1 when the connection request call is accepted are calculated (S6). The cell loss rate and the delay are obtained by the following equations, respectively.

However, m: buffer capacity Here, Navt: average number of cells generated per unit time At = Navt · h When the cell loss rate OVF and the delay D are obtained by the equations (13) and (14), the cell loss rate OVF and the delay D are then calculated. It is determined whether the required service quality can be obtained from the value (S7). The call processing device 25 has a threshold value of the cell loss rate and the delay required for the service, and compares this value with the calculated value of the cell loss rate OVF and the delay D. If the values of both the cell loss rate OVF and the delay D are equal to or less than the threshold value, it is determined that the required service quality is obtained, and it is determined that the connection request call can be accepted. On the other hand, if one or both of the cell loss rate OVF and the delay D are larger than the threshold value, it is determined that the required service quality cannot be obtained, and it is determined that the connection request call cannot be accepted. .

In addition, the formula (1)
In addition to the method of calculating and calculating (3) and (14), the load Atr and the load fluctuation VARtr that satisfy the delay of the cell loss rate of the required quality in advance are calculated by equations (13) and (14). Off-line processing), there is a method of accepting a call if the load At and the load variation VARt obtained by the equations (11) and (12) are At ≦ Atr, VARt ≦ VARtr. For example, if the required cell loss rate is 10 ^-9
Then, Atr and VARtr are obtained from equation (13) as shown in FIG. The shaded portion indicates the acceptable load At and the load variation VARt, and the load At and the load variation VARt from the declared value at the time of calling.
And accept the call if it is within the shaded area.

If the connection cannot be accepted, the subscriber terminal 2 is notified that the connection request call cannot be accepted. on the other hand,
If it can be accepted, the process of S8 is executed.

That is, various information of the subscriber terminal 2 is transmitted to the call processing device 25.
(S8). The information of the subscriber terminal 2 includes position information of the subscriber terminal, call number, outgoing route number, load of the call and load fluctuation data.

Next, the database 26 for the outgoing route 3 connected to the call processing device 25 is updated (S9). That is, among the information on each outgoing route in the database 26, the information on the outgoing route connecting the current call is updated. The database 26 stores data of the load At and the load fluctuation VARt for each outgoing route. As a result, the total load and load fluctuation of the outgoing route when the connection request call is connected to the outgoing route are stored.

With the above processing, the reception determination control processing for the call connection request from the subscriber terminal 2 is completed. If it is determined by S7 that the connection request call can be accepted, S
8. After executing the processing of S9, a call is started.

Next, the processing when the subscriber terminal 2 ends the call will be described with reference to the flowchart of FIG.

First, a request signal for terminating a call is sent from the subscriber terminal 2.
It is sent to the ATM exchange 1 (S10). This request signal is sent to the call control device 24 and the call processing device 25 via the multiplexing device 21 and the signal processing device 23 of the ATM exchange 1 (S11). In response to the request signal, the call processing device 25 searches the temporary storage memory in the call processing device 25, and obtains information (the outgoing route number, the load Ax, and the load
VARx) is taken out (S12).

Next, the call processing device 25 updates information (load Ad and load variation VARd) corresponding to the outgoing route number in the subscriber terminal information from the database 26 (S13). This removes the effects of the load and load fluctuation of the call to be terminated from the total load and load fluctuation of the outgoing route. The updated load Ad and load fluctuation VARd are obtained by the following equations.

Load Ad ← Ad−Ax Load fluctuation VARd ← VARd−VARx After the update of the database 26 is completed, delete all the information of the subscriber terminal that has requested the termination stored in the temporary storage memory in the call processing device 25 ( S14).

FIG. 8 is a configuration diagram of the subscriber terminal information stored in the temporary storage memory in the call processing device 25.

The subscriber position number, call number, connection outgoing route number, load, and load variation are stored in order from the top of the memory. The above is the information for one subscriber terminal, and subsequently stores the information of the other subscriber terminals.

FIG. 9 is a configuration diagram of the outgoing route database of the database 26.

Outgoing route number, load, and load fluctuation are stored in order from the top of the database. The above is information on one outgoing route, and subsequently, loads and load fluctuations are stored for all outgoing routes.

〔The invention's effect〕

According to the present invention, the quality of service (cell loss rate and delay) that the ATM exchange can provide can be evaluated in advance by declaring the attribute parameters of the call from the subscriber terminal when the call is connected, and the required quality of service can be evaluated. If it is determined that the service quality cannot be satisfied, the reception of the call is rejected, and only the call satisfying the service quality is received, thereby making it possible to perform a switching connection that always satisfies the required service quality.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of the present invention, FIG. 2 is a system configuration diagram of an ATM exchange of one embodiment, FIG. 3 is an operation flowchart of one embodiment (acceptance judgment control at the time of a call connection request), FIG. Is an explanatory diagram of the types of report parameters, FIG. 5 is a calculation formula of a cell load and a load change, and FIG. 6 is a load (Atr) and a load change (V) indicating acceptance criteria.
ARtr), FIG. 7 is an operation flowchart of one embodiment (control at the time of a call termination request), FIG. 8 is a configuration diagram of subscriber information, and FIG. 9 is a database configuration diagram of an outgoing route. 1 ATM switch 2 Subscriber terminal 3 Outgoing route 4 Attribute parameter reporting means 5 Load / load fluctuation calculating means 6 Information management means 7 Full load Load fluctuation calculation means, 8: Cell discard rate / delay evaluation means.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-70330 (JP, A) JP-A-2-171061 (JP, A) 1990 IEICE Autumn National Convention B-379 IEICE Technical Research Report SE 87-138 IEICE Technical Research Report SE 87-108 IEICE Transactions J70-B, No. 3, p. 279-287 (58) Field surveyed (Int. Cl. ⁶ , DB name) H04L 12/28, 12/56

Claims (10)

(57) [Claims] 1. A load / load fluctuation calculating means for calculating a load and a load fluctuation value of the connection request call based on an attribute parameter of the connection request call received at the time of a call connection request from a subscriber terminal. Information management means for updating the load and the load fluctuation value calculated based on the attribute parameters of the received call connection request call and storing the load and the load fluctuation value of the outgoing route; and the load / load fluctuation calculation Means for determining whether to accept the connection request for the call based on the load and load fluctuation value of the connection request call calculated by the means and the load and load fluctuation value of the outgoing route managed by the information management means. A call admission control method in an ATM exchange, comprising: a judgment unit. 2. The attribute parameter includes a peak speed, an average speed, a burst duration time, a burst generation interval time, a number of cells generated during the burst duration time, and a peak speed of the connection request call.
2. A call admission control method in an ATM exchange according to claim 1, wherein the call admission control information comprises at least three pieces of information of a burst rate. 3. The load / load change calculating means calculates a load and a load change value of the connection request call based on attribute parameters of a peak speed, a burst duration time, and a burst occurrence interval time of the connection request call. 2. A call admission control method in an ATM exchange according to claim 1, wherein: 4. The load / load fluctuation calculating means calculates a load and a load fluctuation value of the connection request call based on attribute parameters of a peak speed, a burst duration, and a burst rate of the connection request call. The ATM according to claim 1, characterized in that:
Call admission control method in the exchange. 5. The load / load fluctuation calculating means calculates a load and a load fluctuation value of the connection request call based on attribute parameters of a peak speed, an average speed, and a burst duration of the connection request call. 2. A call admission control system in an ATM exchange according to claim 1, wherein: 6. The load determining unit determines the load of the connection request call determined by the load / load variation calculating unit, the load variation value, and the load and the load variation value of each outgoing route managed by the information managing unit. Based on the outgoing route to be selected for the call, a total load / load fluctuation calculating means for calculating a load and a load fluctuation value when the connection request call is added; The predicted value of the cell loss rate and the predicted value of the delay are determined based on the load and the load fluctuation value for the selected outgoing route, and the value of the cell loss rate and the value of the delay of the required quality of service are respectively determined. A cell discard rate / delay evaluating means for comparing a predicted value of the cell discard rate with the predicted value of the delay, and determining whether to accept the connection request call based on the comparison result. Call admission control in ATM switching system of claim 1,. 7. The information management means, if the cell discard rate / delay evaluation means determines that the connection request call is accepted, sends the information on the subscriber terminal which has made the connection request to the connection request. 7. The call admission control method in an ATM exchange according to claim 6, wherein the call is stored during a call connection period. 8. The information management means manages a database of loads and load fluctuation values of each outgoing route, and when the cell discard rate / delay evaluation means determines that the connection request call is accepted, the information management means performs the connection. The load and the load fluctuation value when the call is added to the outgoing route of the request call are stored,
7. The call admission control method in an ATM exchange according to claim 6, wherein when the connection request call is terminated, a load and a load variation value when the connection request call is lost are stored. 9. The load / load variation calculating means, based on an average speed of the connection request call, the number of cells generated during a burst duration, and an attribute parameter of a burst rate, the load and load variation value of the connection request call. The call admission control method in the ATM exchange according to claim 1, wherein 10. The load / load change value of the connection request call is calculated based on an attribute parameter of a peak speed, an average speed, and the number of cells generated during a burst duration of the connection request call. The call admission control method in the ATM exchange according to claim 1, wherein