JPH04258055A - Call reception controller for exchange in atm network - Google Patents

Abstract

PURPOSE:To estimate an abort rate with high quality and to evaluate the estimate at a high speed simply by accepting a connection request call when a cell abort rate of an output buffer is within a permissible abort state when a call having a maximum peak bit rate and a minimum burst is connected. CONSTITUTION:Let a maximum peak bit rate in a call in connection and a connection request call be Rmax4, a minimum burst be Bmin5 and a total sum of peak bit rates of the call in connection and the connection request call be R6, then a cell abort rate is evaluated when M sets (=R/Rmax)8 of calls whose peak bit rate is Rmax4 and whose burst is Bmin5 are connected. When the evaluated value is within a cell abort rate criterion 7 set optionally in advance, the input of the connection request call is allowed.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to ATM (Asynchronous
Transfer Mode (asynchronous transfer mode) is related to a call admission control device of an exchange in a network, and is particularly suitable for high-quality and high-speed determination of whether or not to accept a call.
This invention relates to a call admission control device for an exchange in a TM network.

0002

[Prior Art] Currently, ISDN (Integrate) is a system that aims to integrate data communication at a rate of about 64 kilobits/second.
d Services Digital Net
(Integrated Services Digital Network), with channel speeds of 1.5 megabits/second. On the other hand, in response to this, the development of broadband ISDN is underway, which allows not only telephone and personal computer communications, but also video conferencing with high-definition images and file transfers at tens of megabits per second using a single line interface.

[0003] The target of such broadband ISDN is multimedia information. To this end, broadband IS
DN is required to meet a wide variety of quality conditions as shown below. (1) Telephone calls, video conferences, etc. have strict requirements for transmission delay time. (2) In data communications, there are strict requirements against errors. (3) In image communication, in order to improve image quality, there is a requirement to store information in a bursty manner (the amount of information varies greatly over time, such as between moving and stationary parts of a moving image). Conventional switching methods such as circuit switching and packet switching cannot satisfy these requirements, and ATM (Asynchronous
transfer mode, asynchronous mode).

[0004] ATM divides a wide variety of information into short, fixed-length blocks with headers called "cells," and multiplexes each block using an efficient statistical multiplexing method. A cell is a concept similar to a time slot, but it does not appear periodically, but is allocated dynamically in response to time-varying requests for information transmission, and by changing the number of cells, the communication speed can be set variably. Therefore, ATM is a transfer mode that makes it possible to centrally transmit all kinds of digital information, from voice and data to images. Furthermore, since the beginning of a fixed-length cell appears at a specific timing, the channel can be identified at high speed using hardware or the like based on the label at the beginning, making it suitable for speeding up overall processing.

[0005] In this way, with ATM, it is only necessary to load the necessary number of cells onto a cell depending on the generation of information, and information can be transferred at any transmission speed. Furthermore, there is the advantage that the amount of generated information can be varied depending on changes in the image, and the image quality can be kept constant. A communication network that performs communications based on this ATM is called an ATM network.

FIG. 3 is a block diagram of a communication system that constitutes a conventional ATM network.

[0007] The ATM network consists of terminals 3 that users use for communication.
1 to 37, an ATM that controls connections between terminals 31 to 37
Exchanges 38-310 and ATM exchanges 38-31
It is constituted by a link 311 connecting 0. in this way,
The ATM exchanges 38 to 310 are connected to each other by a link 311, and the terminals 31 to 37 are connected to any one of the ATMs.
It is accommodated in M exchanges 38-310. Also, ATM
The exchanges 38 to 310, as represented by the ATM exchange 38 in the figure, are composed of a switch section 312, output buffers 313 to 314, and a call admission control section 315 as a call admission control device. Based on the control operation of the section 315, cells arriving from the input link are exchanged by the switch section 312, and sent to the output link via the output buffers 313-314.

FIG. 4 is a sequence diagram showing the operation of call admission control within the ATM network in FIG. 3.

This figure shows the terminal 31 in the ATM network of FIG.
3 shows a procedure for controlling connection of a call from to the exchange 38. That is, to connect a call, first, the terminal 31 makes a connection request 402 to the exchange 38 using the calling cell 401. Based on this connection request 402, the exchange 38 makes an acceptance determination 403. After the exchange 38 responds with a judgment result indicating that the call is acceptable 404 and the connection is permitted, cells 405 of the required amount corresponding to the call flow within the network. and,
The connection is terminated by sending open cell 406.

[0010] As shown in FIGS. 3 and 4, in an ATM network, when a call connection is requested, a cell containing information regarding the connection request is processed in a call admission control section in the exchange, and it is determined whether the call can be connected or not. It can be decided. After the call is accepted, the call flows through the network in the form of cells. However, at this time, since the output buffer within the exchange can accommodate only a certain number of cells or less, if the amount of incoming cells is excessive, cells will be discarded. Since this cell discard degrades communication quality, it is necessary in call admission control to determine whether the cell discard rate in the output buffer is within an allowable range for deterioration of communication quality.

FIG. 5 is a block diagram showing the internal configuration of the call admission control section in FIG. 3.

The call admission control section 315 includes a declared parameter receiving section 501 that takes in declared parameters sent at the time of a connection request from the terminal 31, and a cell discard rate that evaluates the cell discard rate based on the declared parameters taken in by the declared parameter receiving section 501. It is comprised of an evaluation section 502 and an acceptance determination section 503 that determines whether or not a call can be accepted based on the evaluation by the cell discard rate evaluation section 502. With such a configuration, when a call connection request is made from a terminal, the call admission control unit 315 accepts this connection request, and even if the cell in which the call occurs is added to the network, the call admission control unit 315 can still maintain the capacity of each output buffer. Whether or not the cell loss rate is within the allowable range is estimated and evaluated based on the declared parameters, using the cell loss rate after the call is accepted as a measure, and it is determined whether the call can be accepted.

[0013] That is, in call admission control, if
In order to determine whether the cell discard rate in each output buffer when a connection request call is accepted is less than or equal to a predetermined cell discard rate regulation value, the declaration parameters of the connection request call and the connection The cell discard rate at each output buffer after accepting a connection request call is estimated and evaluated from the declared parameters regarding the call or the measurement results regarding the amount of cells generated by the connected call.

[0014] Here, the declared parameters are information regarding the amount of cells in which the call in question occurs, and are assumed to include average bit rate, peak bit rate, burst, and the like. Also, the average bit rate is the bit length of one cell divided by the average cell generation interval, and
The peak bit rate is the bit length of one cell divided by the minimum cell generation interval. Further, although bursts may be declared directly, they can be obtained as "peak bit rate/average bit rate". Note that the declaration of parameters is made by the user of the terminal, and it is desirable for the network side to specify parameters that are easy to declare.

In call admission control, in order to quickly respond to a connection request call, it is necessary to quickly estimate and evaluate the cell discard rate if the connection request call is accepted. For example, the following formula can be considered to give an upper limit on the cell discard rate.

[Formula]

However, calculation of the cell discard rate based on this formula is complicated and time-consuming, resulting in poor call admission control efficiency.

Regarding call admission control in the ATM network as described above, for example, ``International
Teletraffic Congress, 7
th Specialist Seminar
1990, New dimensioning c
oncept for ATM network
s/H. Saito” and “IEICE Technical Report SSE89-155, 1990, Call
admission control in
an ATM network without
using traffic measure
nt/H. Saito”.

[0018]

The problem to be solved by the present invention is that call admission control cannot be performed efficiently with the conventional techniques. In other words, in call admission control, when responding to a connection request, the cell loss rate is estimated and evaluated if the connection request call were accepted, but in order to maintain the quality of this estimation and evaluation, it is necessary to perform complicated calculations. This results in a delay in responding to connection requests. The purpose of the present invention is to solve the problems of the prior art, to quickly and easily estimate and evaluate the cell loss rate with high quality, and to accept call reception by an exchange in an ATM network that can generate multiplexing gain. The purpose of the present invention is to provide a control device.

[0019]

[Means for Solving the Problems] In order to achieve the above object, the call admission control device of the exchange in the ATM network of the present invention receives call admission control equipment based on the declaration parameters of the calling cell from the terminal device accommodated in the ATM network. A call admission control device that estimates and evaluates the cell discard rate in the output buffer when a call connection request from a terminal device is accepted, and determines whether to accept a connection request from the terminal device. a peak bit rate memory that stores the peak bit rate, a burst memory that stores the burst of connected calls, a peak bit rate summation memory that stores the sum of the peak bit rates of the connected calls, and a peak bit rate memory that stores the sum of the peak bit rates of the connected calls; Based on the possible connection number reference table that shows the number of connectable calls corresponding to a call with a bit rate and burst, and the declared parameters of the calling cell from the terminal device, the peak bit rate and peak bits obtained with this declared parameter. A maximum peak bit rate extraction unit extracts the maximum peak bit rate from the peak bit rate stored in the rate memory, and similarly, based on the declared parameters of the calling cell from the terminal device,
A minimum burst extraction unit extracts the minimum burst from the burst obtained by the declared parameter and the burst stored in the burst memory, and the peak bit rate obtained from the declared parameter of the calling cell is stored in the peak bit rate sum memory. A call that connects a peak bit rate sum addition unit that adds to the total peak bit rate that is added to the total peak bit rate, and a call that has the maximum peak bit rate extracted by the maximum peak bit rate extraction unit and the minimum burst extracted by the minimum burst extraction unit. a virtual connection number calculation unit that calculates the number of calls, and a number of calls calculated by the virtual connection number calculation unit;
Compare the number of connectable calls corresponding to the maximum peak bit rate and minimum burst shown in the possible connection number reference table, and determine whether or not a calling cell from the terminal device can be accepted based on the result of this comparison. The present invention is characterized by being provided with a comparison and determination section.

[0020]

[Operation] In the present invention, the maximum peak bit rate and minimum burst of the connection requesting call and the connected call are extracted, and the call having the maximum peak bit rate and minimum burst is calculated as "sum of peak bit rates/maximum peak bit rate". Consider a hypothetical connection state in which the "rate" book is connected. Then, the connectable number corresponding to the call in this virtual connection state is extracted from the possible connectable number reference table and compared with the "sum of peak bit rates/maximum peak bit rate" book. As a result of the comparison, the sum of peak bit rates/
If the maximum peak bit rate is smaller than the connectable number extracted from the possible connection number reference table, the connection request call is allowed to be input. In this way, the maximum peak and minimum burst determine whether or not a connection can be made, so it can be controlled using a two-dimensional table. Also, the virtual connection state and the actual state are
The sum of the peak bit rates is saved, and in the virtual connection state, the peak bit rate and average bit rate are larger, and the number of connections is smaller. This leads to safe evaluation of cell discard and protects the quality of transferred data.

[0021] The number of connectable calls shown in the possible connection number reference table is the maximum connectable number that satisfies the specified value of cell loss rate. If more calls are connected than can be connected, more cells will be discarded, and the quality of transferred data will exceed the allowable range.

[0022]

Embodiments Hereinafter, embodiments of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the configuration of a call admission control section according to the present invention.

The call admission control unit 10 of this embodiment is a call admission control device of the present invention, and includes a peak bit rate memory 1 for storing the declared value of the peak bit rate of the connected call;
Burst memory 2 that stores the burst value of the connected call
, a peak bit rate summation memory 3 that stores the sum of declared peak bit rates of connected calls, a maximum peak bit rate calculation unit (denoted as Rmax in the figure) 4 that calculates the maximum peak bit rate, and a minimum A minimum burst calculation unit (indicated as Bmin in the figure) 5 calculates the burst, and a peak bit rate sum addition unit (in the figure) adds the declared value of the peak bit rate of the connection request call to the contents of the peak bit rate sum memory 3 , R) 6. Possible connection number reference table that stores a table showing how many calls can be connected based on the peak bit rate and burst of the connected call 7. Maximum pick bit rate and minimum burst The calculation results of the virtual connection number calculation unit (denoted as M in the figure) 8, which calculates the virtual connection state of how many calls are currently connected, and the calculation results of the post-acceptance call volume calculation unit 8 and the number of possible connections. It is comprised of a comparison and determination section 9 that determines whether or not a call can be accepted based on a reference table 7.

Note that the peak bit rate memory 1 includes:
The peak bit declared value of the connected call is memorized, but
In this example, only the maximum peak bit is used, so
Store in order of size to improve speed. In addition, the burst value of the connected call stored in the burst memory 2 is
Although it may be reported directly, it may also be determined by peak bit rate/average bit rate, or maximum number of arriving cells (integer)/average number of arriving cells in a certain period of time. Furthermore, in this embodiment, since only the minimum burst value is used for control, the values are stored in order of magnitude to speed up the processing. Further, the total sum of declared peak bit rates of connected calls stored in the peak bit rate total memory 3 is updated when a call is set up or released.

With such a configuration, the call admission control unit 10 of this embodiment can determine the maximum peak bit rate value, the minimum burst value, and the peak bit rate value from the call being connected and the call requesting connection. The total bit rate is determined, and the cell discard rate is evaluated based on these values to determine whether or not to permit input of a connection request call. For example, for a call currently connected and a call requesting a connection, the maximum peak bit is Rmax, and the minimum burst (peak/average, or maximum number of cells arriving within a certain period of time/average number of cells) is Bmi.
n, and let R be the sum of the peak bit rates of the connecting call and the connection requesting call. And the peak bit rate is Rmax,
M calls with burst Bmin (=R/Rmax)
Assuming that the connection is in progress, evaluate the cell loss rate. This evaluation value corresponds to the cell loss rate regulation arbitrarily set in advance, that is,
If the number of connections is smaller than the number of possible connections M' in the number of possible connections reference table 7 corresponding to a call in a virtual connection state where the peak bit rate is Rmax and the burst is Bmin, input of the connection request call is permitted. The operation will be explained in more detail below.

In the ATM network of this embodiment, when a connection request call is input, the maximum peak bit rate calculation unit 4 calculates
The maximum peak bit rate Rmax is obtained from the peak bit declared value of the connected call, which includes the peak bit rate declared at that time and is stored in the peak bit rate memory 1. At the same time, the minimum burst calculation unit 5 calculates the minimum burst Bm from the burst value of the connected call including the burst declared at that time and stored in the burst memory 2.
Get in.

Further, the peak bit rate sum addition section 6 adds the peak bit rate declared in the connection request call to the contents of the peak bit rate sum memory 3. Further, the virtual connection number calculation unit 8 divides the sum R of the peak bit rates calculated by the peak bit rate sum addition unit 6 by the maximum peak bit rate obtained by the maximum peak bit rate calculation unit 4, and calculates the maximum peak bit rate. A virtual connection state is calculated in which calls with the bit rate and minimum burst are connected for "sum of peak bit rates/maximum peak bit rate" (=R/Rmax=M). Note that between this virtual connection state and the actual state, the sum of peak bit rates is preserved, the peak and average are larger, and the number of connections is smaller.

Then, the comparison/judgment unit 9 determines the number of possible connections corresponding to the maximum peak bit rate Rmax and minimum burst Bmin obtained by the maximum peak bit rate calculating unit 4 and the minimum burst calculating unit 5 from the possible connection number reference table 7. M' is extracted, and the number of possible connections M' corresponding to the extracted maximum peak bit rate Rmax and minimum burst Bmin is compared with the number of possible connections M in a virtual connection state, and the connection is determined based on the comparison result. Sends acceptance determination of the requested call. Note that if M≦M', the connection request call is connected.

In this way, the call admission control unit 10 of this embodiment
Since connection availability is determined by the maximum peak and minimum burst, it can be controlled using a two-dimensional table, and for connection requests,
Fast response can be achieved without the need for complicated calculations.

[0031] Note that the total sum of peak bit rates is saved, and in the virtual connection state, the peak bit rate and average bit rate are larger and the number of connections is smaller than in the actual state. As a result, the virtual connection state is evaluated on the safer side than in the actual case, and the quality of the transferred data can be satisfied.

[0032] In other words, in the virtual connection state and the actual state, compared to the number of possible connections when considering only the peak bit rate, for example, the number of possible connections can be increased by taking into account the peak bit rate and the average and performing statistical multiplexing. To increase. The increase is the multiplexing gain resulting from consideration of the average. In this way, in the virtual connection state, a multiplexing gain occurs for the peak bit rate allocation, but since the sum of the peak bit rates is preserved, a multiplexing gain also occurs for the actual connection. The number of connections that can be made increases as the peak bit rate increases.
decreases as the average increases. Additionally, the multiplexing gain generally increases as the number of connections increases. for that,
Assuming a state with a smaller number of connections will result in a smaller estimate of the multiplexing gain, and the virtual connection state will be a safer estimate than in the actual case.

FIG. 2 is a flowchart showing the call admission control operation of the call admission control section in FIG. 1 according to the present invention.

First, the peak bit rate (Ro) of the connection request call and the declared burst value (Bo) are input from the calling cell (step 201). When declaring the average bit rate, "Bo=Ro/Ao" (Ao: average bit rate declared value), and if the defined interval length determined by the network is T and the cell length is L, "Bo=(P/Ao"). L)/(Ao×T/L
)” (P: rounded-up value of Ro×T/L).

Then, the peak bit rate memory 1 in FIG. 1 is searched, and the maximum peak bit rate (R'
o) (step 202), and the larger of Ro (peak bit rate of the connection request call) and R'o is set as Rmax.
(Step 203). Next, the burst memory 2 in FIG. This is set as Bmin (step 205). Further, the peak bit rate Ro of the connection request call is set to R in addition to the sum of the peak bit rates of the calls being connected, which is the content of the peak bit rate sum memory 3 in FIG. 1 (step 206). With the processing up to this point,
The maximum peak bit rate when a connection request call is added, the minimum burst, and the sum of the peak bit rate are Rmax, Bmin, and R, respectively.

Next, the (Rmax, Bmin) elements in the possible connection number reference table 7 in FIG. 1 are referred to, and the possible connection number (M') is extracted (step 207). The possible connection number reference table 7 in FIG. 1 shows, when a peak bit rate and burst are given, how many calls under that condition can be connected. Here, connection calls and connection request calls are calculated using peak bit rate (Rmax) and burst (B
min) calls, the (Rmax, Bmin) element of the possible connection number reference table 7 in FIG. 1 is referred to. Also, when converted to peak bit rate (Rmax) and burst (Bmin) calls, how many calls (M) are the total of connected calls and connection request calls?
Calculated using the formula “R/Rmax” (step 208
). Then, it is compared whether the calculated number of calls M is greater or less than the number of possible connections M' obtained from the number of possible connections reference table 7 in FIG. 1 (step 209). As a result of the comparison, if the calculated number of calls M is less than the number of possible connections M' obtained from the number of possible connections reference table 7 in FIG. 1, the call is accepted (step 210), and if it is greater, the call is rejected. (Step 211).

Note that the creation of the possible connection number reference table 7 shown in FIG. 1 is evaluated by, for example, the method described in the prior art. That is, the peak bit rate and burst need only be evaluated offline for the same call types, Rmax and Bmin.

Furthermore, the present invention does not use a reference table for the number of possible connections that indicates the number of connectable calls as shown in this embodiment, but rather uses a cell discard rate for a call with the maximum peak rate and minimum burst, for example. A table or the like indicating whether or not a specified value is satisfied may be used. Then, the cell loss rate is estimated and evaluated when the number of calls with the maximum peak rate and minimum burst are connected as many times as ``sum of peak bit rates/maximum peak bit rate'', and this evaluation value is calculated based on the preset cell If the discard rate is smaller than a specified value, input of a connection request call may be permitted.

As explained above using FIGS. 1 and 2, according to the call admission control method of the exchange in the ATM network of this embodiment, compared to the case where allocation (call admission judgment) is performed at the peak bit rate, This will improve the efficiency of resource use. In addition, acceptance can be determined only by searching the possible connection number reference table, and response speed is improved without impairing the quality of the cell discard rate.

[0040]

According to the present invention, it is possible to estimate and evaluate a high-quality cell discard rate quickly and easily.

[0041]

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the configuration of a call admission control unit according to the present invention;

FIG. 2 is a flowchart showing the call admission control operation of the call admission control unit in FIG. 1 according to the present invention.

FIG. 3 is a block diagram of a communication system that constitutes a conventional ATM network.

FIG. 4 is a sequence diagram showing the operation of call admission control within the ATM network in FIG. 3;

FIG. 5 is a block diagram showing the internal configuration of a call admission control section in FIG. 3;

[Explanation of symbols]

1. Memory for peak bit rate 2 Burst memory 3 Peak bit rate total memory 4 Maximum peak bit rate calculation section 5 Minimum burst calculation unit 6 Peak bit rate total addition section 7 Possible connection number reference table 8 Virtual connection number calculation unit 9 Comparison and judgment section 10 Call reception control unit 31-37 Terminal 38 ATM exchange machine 310 ATM switch 311 Link 312 Switch part 313-314 Output buffer 315 Call reception control unit 401 Calling cell 402 Connection request 403 Reception judgment 404 Acceptable 405 Cell 406 Open cell 501 Declaration parameter reception department 502 Cell discard rate evaluation department 503 Reception Judgment Department

Claims (1)

[Claims] 1. Estimating and evaluating the cell discard rate in an output buffer when a call connection request from a terminal device is accepted based on the declared parameters of a calling cell from a terminal device accommodated in an ATM network, The call admission control device of the exchange that determines whether to accept a connection request from the terminal device has a peak bit rate memory that stores the peak bit rate of the connected call, and a burst memory that stores the burst of the connected call. , a peak bit rate summation memory that stores the sum of the peak bit rates of the connected calls, and a possible connection number indicating the number of connectable calls corresponding to the calls having the respective predetermined peak bit rates and bursts. Based on the reference table and the declared parameters of the calling cell from the terminal device, the maximum peak bit rate is extracted from the peak bit rate obtained by the declared parameters and the peak bit rate stored in the peak bit rate memory. a peak bit rate extracting means; and a minimum burst extracting means for extracting a minimum burst based on the declared parameters of the calling cell from the terminal device from the bursts obtained by the declared parameters and the bursts stored in the burst memory; a peak bit rate total addition means for adding the peak bit rate obtained from the declared parameters of the calling cell to the total peak bit rate stored in the peak bit rate total memory; and a maximum peak bit rate extraction means. virtual connection number calculation means for calculating the number of calls when calls having the extracted maximum peak bit rate and the minimum burst extracted by the minimum burst extraction means are connected; The number of calls that can be connected is compared with the number of connectable calls corresponding to the call having the maximum peak bit rate and the minimum burst shown in the reference table for the number of possible connections, and based on the result of the comparison, the calling cell from the terminal device is 1. A call admission control device for an exchange in an ATM network, characterized in that a call admission control device for an exchange in an ATM network is provided.