JP2845352B2 - Call admission control device for exchange in ATM network - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ATM (Asynchronous T) for realizing a high-speed broadband service integrated network.
The present invention relates to a call admission control device of an exchange in a transfer mode (asynchronous transfer mode) network, and more particularly to an ATM suitable for making a high-quality and high-speed judgment of call admission.
The present invention relates to a call admission control device for an exchange in a network.

[0002]

2. Description of the Related Art At present, ISDN (Integrate) is aimed at integrating data communication of about 64 kbit / s.
d Services Digital Network
k, integrated service digital network), communication is performed at a channel speed of 1.5 Mbit / sec. On the other hand, in addition to telephone and personal computer communication, high-definition video teleconferencing and file transfer at several tens of megabits / second are possible with a single line interface.
SDN is under development.

[0003] The target of such a broadband ISDN is multimedia information. Therefore, the broadband IS
The DN is required to have various quality conditions as described below. (1) In telephones, TV conferences, and the like, requirements for transmission delay time are severe. (2) In data communication, requirements for errors are severe. (3) In image communication, there is a requirement for storing information burstiness (a large change in the amount of information over time, such as a moving part and a non-moving part of a moving image) in order to improve image quality. Conventional switching methods such as circuit switching and packet switching cannot satisfy such requirements, and one of the methods for uniformly and efficiently transmitting such various kinds of information is ATM (Asynchronous).
nousTransfer Mode, asynchronous mode)
There is.

[0004] ATM divides various kinds of information into short fixed-length blocks with headers called "cells", and multiplexes the blocks in units of an efficient statistical multiplexing system. The cell is a concept of a time slot, but does not appear in a time-periodic manner, but is dynamically allocated according to a time-varying information transmission request, and the communication speed can be variably set by changing the number of cells. Therefore, the ATM is a transfer mode in which all digital information from voice and data to images can be transmitted in a unified manner. In addition, since the head of a fixed-length cell appears at a specific timing, the channel can be identified at high speed by hardware or the like based on the head label, which is suitable for speeding up the entire processing.

[0005] As described above, in the ATM, only a necessary number of cells need to be loaded in a cell in accordance with the generation of information, and information can be transferred at an arbitrary transmission rate. Further, there is an advantage that the amount of generated information can be varied according to a change in the image and the image quality can be kept constant. A communication network that performs communication based on this ATM is called an ATM network.

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

The ATM network is a terminal 3 used by a user for communication.
ATM for controlling connection between terminals 1-37 and terminals 31-37
Exchanges 38-310 and ATM exchanges 38-31
It is configured by a link 311 connecting 0. in this way,
The ATM exchanges 38 to 310 are interconnected by a link 311, and the terminals 31 to 37 are connected to any of the ATs.
M exchanges 38 to 310 are accommodated. Also, ATM
Each of the exchanges 38 to 310 includes a switch unit 312, output buffers 313 to 314, and a call admission control unit 315 as a call admission control device, as represented by the ATM exchange 38 in FIG. Based on the control operation of the unit 315, the cells arriving from the input link are exchanged by the switch unit 312 and transmitted to the output link via the output buffers 313 to 314.

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

FIG. 1 shows a terminal 31 in the ATM network of FIG.
The procedure for controlling the connection of a call from the to the exchange 38 will now be described. That is, when connecting a call, first, the terminal 31 sends the exchange 38
, A connection request 402 is made by the calling cell 401. On the basis of the connection request 402, the exchange 38 makes an acceptance judgment 403. After the exchange 39 responds with the determination result indicating that the call can be accepted 404 and the connection is permitted, the required number of cells 405 corresponding to the call flow in the network. The connection is terminated by sending the release cell 406.

As shown in FIGS. 3 and 4, in an ATM network, when a call connection request is made, a cell having information on the connection request is processed in a call admission control unit in the exchange to determine whether or not the call can be connected. I can decide. Then, after the call is accepted, the call flows through the network in the form of a cell. However, at this time, since the output buffer in the exchange can accommodate only a certain number of cells or less, if the inflowing cell amount is excessive, the cell is discarded. Since the cell discarding deteriorates the communication quality, it is necessary in the call admission control to determine whether or not the cell discard rate in the output buffer is within an allowable range for the communication quality deterioration.

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

The call admission control unit 315 receives a report parameter sent at the time of a connection request from the terminal 31, a report parameter reception unit 501, and a cell discard rate for evaluating a cell discard rate based on the report parameter received by the report parameter reception unit 501. The evaluation unit 502 includes a reception determination unit 503 that determines whether a call can be received based on the evaluation of the cell loss rate evaluation unit 502. With such a configuration, the call admission control unit 315 accepts this connection request at the time of a call connection request from the terminal, so that even if a cell in which the call is added to the network is added, each output buffer Is evaluated and evaluated based on the report parameters to determine whether or not the cell discard rate in the above is within an allowable range, using the cell discard rate after accepting the call as a scale, and decide whether or not to accept the call.

That is, in the call admission control, temporarily
In order to determine whether the cell loss rate at each output buffer when accepting a connection request call is equal to or less than a predetermined cell loss rate specified value, a report parameter of the connection request call, The cell discard rate in each output buffer after accepting the connection request call is estimated and evaluated from the report parameters for the call or the measurement result regarding the cell amount generated by the connected call.

Here, the report parameter is information on the amount of cells in which the call concerned occurs, and an average bit rate, a peak bit rate, a burst, and the like are assumed. The average bit rate is the bit length of one cell divided by the minimum cell generation interval, and
The peak bit rate is obtained by dividing the bit length of one cell by the minimum cell generation interval. Also, the burst may be declared directly, but is obtained at “peak bit rate / average bit rate”. It should be noted that the parameter is declared by the user of the terminal, and it is desirable for the network to specify a parameter that is easily declared.

In the call admission control, in order to promptly respond to a connection request call, it is necessary to quickly estimate and evaluate the cell loss rate when the connection request call is accepted. For example, the following equation can be used to give the upper limit of the cell loss rate.

[Formula]

However, the calculation of the cell discard rate based on this equation is complicated and time-consuming, and the efficiency of call admission control deteriorates.

With respect to the call admission control in the ATM network as described above, for example, “International
Teletraffic Congress, 7th
Specialist Seminar 1990,
New dimensioning concept
for ATM networks / H. Sait
o "and" IEICE Technical Report SSE8 "
9-155, 1990, Call advertisement
control in an ATM Network
with using traffic me
assurement / H. Saito ".

[0018]

The problem to be solved is that the conventional technology cannot efficiently perform call admission control. That is, in the call admission control, when responding to a connection request, the cell loss rate is temporarily estimated and evaluated when the connection request call is accepted. However, in order to maintain the quality of the estimation / evaluation, it is necessary to perform complicated calculations. And the response to the connection request is delayed. The object of the present invention is to solve these problems of the prior art, perform high-speed and simple estimation and evaluation of high-quality cell loss rate,
Another object of the present invention is to provide a call admission control device for an exchange in an ATM network capable of generating a multiplexing gain.

[0019]

In order to achieve the above object, a call admission control device for an exchange in an ATM network according to the present invention, based on a report parameter of a call cell from a terminal device accommodated in the ATM network, is used. A call admission control device that estimates and evaluates a cell loss rate in an output buffer when a call connection request of a terminal device is accepted, and determines whether or not to accept the connection request of the terminal device. , A burst bit memory for storing a burst of a connected call, a peak bit rate sum memory for storing a sum of peak bit rates of a connected call, and a predetermined peak Based on a possible connection number reference table indicating the number of connectable calls corresponding to a call having a bit rate and a burst, and a declaration parameter of a calling cell from the terminal device. A maximum bit rate extraction unit for extracting the maximum bit rate from the peak bit rate obtained in the declaration parameter and the peak bit rate stored in the peak bit rate memory, and similarly, a calling cell from the terminal device. The minimum burst extraction unit that extracts the minimum burst from the burst obtained by this report parameter and the burst stored in the burst memory based on the report parameter of the report cell, and the peak bit rate obtained from the report parameter of the calling cell, A call having a peak bit rate sum adding section for adding to the sum of the peak bit rates stored in the rate sum memory, and a call having a maximum peak bit rate extracted by the maximum peak bit rate extracting section and a minimum burst extracted by the minimum burst extracting section. the number of calls in the case of connecting the upper Peak bit
Peak bit rate sum obtained by rate sum adding means
From the maximum peak bit rate extraction means
Has a virtual connection number calculating section to output calculated by dividing the peak bit rate, the number of calls is calculated by the virtual connection number calculating section, the maximum peak bit rate and a minimum burst indicated by connectable number reference table A comparison / determination unit is provided for comparing the number of connectable calls corresponding to the call and determining whether or not the terminal device can accept a calling cell based on the result of the comparison.

[0020]

According to the present invention, the maximum peak bit rate and the minimum burst of the connection request call and the connection call are extracted, and the call having the maximum peak bit rate and the minimum burst is defined as "sum of peak bit rates / maximum peak bit." Consider a virtual connection state in which a "rate" book is being connected. Then, the connectable number corresponding to the call in the virtual connection state is extracted from the possible connection number reference table, and is compared with “the sum of the peak bit rates / the maximum peak bit rate”. As a result of the comparison, “the sum of the peak bit rates /
When the “maximum peak bit rate” book is smaller than the connectable number extracted from the possible connection number reference table, the input of the connection request call is permitted. As described above, since the connection is determined by the maximum peak and the minimum burst, control is possible using a two-dimensional table. Also, in the virtual connection state and the actual state,
The sum of the peak bit rates is stored, and in the virtual connection state, the peak bit rate and the average bit rate are larger and the number of connections is smaller. This leads to a safe evaluation of cell discard and protects the quality of transfer data.

The number of connectable calls shown in the possible connection number reference table is the maximum connectable number that satisfies the cell discard rate prescribed value. When a call exceeding the connectable number is connected, the number of cells to be discarded increases, and the quality of transfer data exceeds an allowable range.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings.

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

The call admission control unit 10 of the present embodiment is a call admission control device of the present invention, and stores a peak bit rate memory 1 for storing a declared value of a peak bit rate of a connected call.
A burst memory 2 for storing a burst value of a connected call, a peak bit rate total memory 3 for storing a sum of declared values of peak bit rates of a connected call, and a maximum peak bit rate for calculating a maximum peak bit rate. A calculating unit (described as Rmax in the figure) 4, a minimum burst calculating unit (described as Bmin in the figure) 5 for calculating a minimum burst,
A peak bit rate sum adder (shown as R in the figure) 6 for adding the declared value of the peak bit rate of the connection request call to the contents of the peak bit rate sum memory 3; Based on this, a possible connection number reference table 7 storing a table indicating how many calls can be connected, and a virtual connection state of how many calls having the maximum peak bit rate and the minimum burst are being connected are calculated. A virtual connection number calculation unit (denoted by M in the figure) 8, and
A comparison determination unit 9 that determines whether a call can be accepted based on the calculation result of the post-acceptance call volume calculation unit 8 and the possible connection number reference table 7.
It consists of.

The peak bit rate memory 1 has:
The peak bit report value of the connected call is stored,
In this embodiment, since only the maximum peak bit is used,
The data is stored in the order of the size to improve the speed. The burst value of the connected call stored in the burst memory 2 is:
Although it may be declared directly, it may be calculated by peak bit rate / average bit rate, or maximum number of cells (integer) / average number of cells arriving for a certain period of time. Further, in this embodiment, since only the minimum burst value is used for control, the values are stored in order of magnitude, thereby speeding up the processing. The sum of the declared values of the peak bit rate of the currently connected call stored in the peak bit rate sum memory 3 is updated when the call is set and released .

With such a configuration, the call admission control unit 10 according to the present embodiment calculates the maximum peak bit rate value, the minimum burst value, and the peak burst value from the connected call and the call requesting the connection. The sum of the bit rates is obtained, and the cell discard rate is evaluated based on these values to determine whether the connection request call input is permitted or not. For example, in a connection call and a connection request call, the maximum peak bit is Rmax, the minimum burst (peak / average, or the maximum number of cells / average number of cells arriving within a certain period of time) is Bmin,
The sum of the peak bit rates of the connecting call and the connection request call is R
And Then, assuming that M (= R / Rmax) calls with a peak bit rate of Rmax and a burst of Bmin are being connected, the cell loss rate is evaluated. This evaluation value is smaller than the arbitrarily settable cell discard rate, that is, smaller than the connectable number M ′ in the possible connection number reference table 7 corresponding to the call in the virtual connection state in which the peak bit rate is Rmax and the burst is Bmin. In this case, the input of the connection request call is permitted. Hereinafter, the operation will be described in more detail.

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

Further, the peak bit rate summation 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 to obtain the maximum peak bit rate. A virtual connection state is calculated in which a call having a bit rate and a minimum burst is connected to “sum of peak bit rates / maximum peak bit rate” (= R / Rmax = M). In the virtual connection state and the actual state, the sum of the peak bit rates is stored, and the peak and average are relatively large, and the number of connections is relatively small.

Then, the comparison / determination unit 9 obtains the maximum number of connectable bits corresponding to the maximum peak bit rate Rmax and the minimum burst Bmin obtained by the maximum peak bit rate calculation unit 4 and the minimum burst calculation unit 5 from the possible connection number reference table 7. M ′, and the extracted maximum peak bit rate R
max and the connectable number M ′ corresponding to the minimum burst Bmin,
It compares the connectable number M in the virtual connection state and sends a connection request call acceptance determination based on the comparison result. Note that M ≦
In the case of M ', a connection request call is connected.

As described above, the call admission control unit 10 of this embodiment
In, since the connection availability is determined by the maximum peak and the minimum burst, it can be controlled with a two-dimensional table.
A high-speed response can be performed without requiring complicated calculations.

The sum of the peak bit rates is stored, and in the virtual connection state, the peak bit rate and the average bit rate are larger than those in the actual state.
The number of connections is smaller. As a result, the virtual connection state is evaluated on the safe side as compared with the actual case, and the quality of transfer data can be satisfied.

That is, in the virtual connection state and the actual state, the number of connectables is statistically multiplexed in consideration of the peak bit rate and the average with respect to the number of connectables in consideration of only the peak bit rate. To increase.
The increase is a multiplexing gain due to consideration of the average. As described above, in the virtual connection state, the multiplexing gain is generated for the peak bit rate allocation, but since the sum of the peak bit rates is stored, the multiplexing gain is generated for the actual connection. And, as the peak bit rate increases, the number of connectable
It decreases as the average increases. Also, the multiplexing gain generally increases as the number of connections increases. for that reason,
Assuming a state in which the number of connections is small means that the multiplexing gain is estimated to be small, and the virtual connection state is a safe estimate compared to the actual case.

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

First, a peak bit rate (Ro) of a connection request call and a burst report value (Bo) are input from the calling cell (step 201). When the average bit rate is declared, “Bo = Ro / Ao” (Ao: average bit rate reported value), and when the defined section length defined by the network is T and the cell length is L, “Bo = (P / L) / (Ao × T / L) "
(P: round-up value of Ro × T / L).

Then, the peak bit rate memory 1 shown in FIG. 1 is searched, and the maximum peak bit rate (R ') is stored therein.
o) is extracted (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 shown in FIG.
And the minimum burst (B'o) is extracted (step 204), and the smaller of Bo (the declared value of the burst of the connection request call) and B'o is set as Bmin (step 20).
5). Furthermore, the peak bit rate Ro of the connection request call
Is added to the sum of the peak bit rates of the currently connected calls, which is the contents of the peak bit rate sum memory 3 in FIG. 1 (step 206). In the processing up to this point, the sum of the maximum peak bit rate, the minimum burst, and the peak bit rate when a connection request call is added is Rmax, Bmin, and R, respectively.

Next, the connectable number (M ') is extracted by referring to the (Rmax, Bmin) element in the possible connection number reference table 7 of FIG. 1 (step 207). The number-of-possible-connections reference table 7 in FIG. 1 shows, when a peak bit rate and a burst are given, how many calls under the condition are connected. Here, the connection call and the connection request call are divided into a peak bit rate (Rmax) and a burst (Bmin).
Therefore, the (Rmax, Bmin) element of the possible connection number reference table 7 in FIG. 1 is referred to. In addition, when converted to a call of a peak bit rate (Rmax) and a burst (Bmin), the number of calls (M) including the connected call and the connection request call is represented by “R”. / Rmax ”(step 208). Then, it is compared whether the calculated number M of calls is larger or smaller than the connectable number M ′ obtained from the possible connection number 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 connectables M ′ obtained from the possible connection number reference table 7 in FIG. 1, the call is accepted (step 210). (Step 211).

The creation of the possible connection number reference table 7 in FIG. 1 is evaluated by, for example, the method described in the prior art. In other words, the peak bit rate and the burst need only be evaluated for the same call type of Rmax and Bmin, and also off-line.

Further, according to the present invention, instead of the possible connection number lookup table indicating the number of connectable calls as shown in the present embodiment, for example, the cell discard rate for a call having a maximum peak rate and a minimum burst is determined. A table or the like indicating whether or not the specified value is satisfied may be used. Then, a cell having a maximum peak rate and a minimum burst is estimated and evaluated for a cell loss rate when the number of connections is equal to the “sum of peak bit rates / maximum peak bit rate”. If the value is smaller than the prescribed value of the discard rate, input of a connection request call may be permitted.

As described above with reference to FIG. 1 and FIG. 2, according to the call admission control method of the exchange in the ATM network of the present embodiment, compared with the case where the allocation (call admission judgment) is performed at the peak bit rate. As a result, resource use efficiency is improved. In addition, the reception determination can be made only by searching the possible connection number reference table, and the response speed can be improved without impairing the quality of the cell loss rate.

[0040]

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

[0041]

[Brief description of the drawings]

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

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

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

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

FIG. 5 is a block diagram showing an internal configuration of a call admission control unit in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Memory for peak bit rate 2 Memory for burst 3 Memory for sum total of peak bit rate 4 Maximum peak bit rate calculation unit 5 Minimum burst calculation unit 6 Peak bit rate sum total addition unit 7 Reference table of possible connection number 8 Virtual connection number calculation unit 9 Comparison Judgment unit 10 Call admission control unit 31-37 Terminal 38 ATM exchange 310 ATM exchange 311 Link 312 Switch unit 313-314 Output buffer 315 Call admission control unit 401 Calling cell 402 Connection request 403 Acceptance judgment 404 Acceptable 405 Cell 406 Open cell 501 Declaration parameter receiving unit 502 Cell loss rate evaluating unit 503 Receiving determining unit

Claims (1)

(57) [Claims] 1. A method for estimating and evaluating a cell loss rate in an output buffer when a call connection request of a terminal device is accepted based on a declaration parameter of a calling cell from a terminal device accommodated in an ATM network. In the call admission control device of the exchange which performs the reception judgment of the connection request of the terminal device, a memory for a peak bit rate storing a peak bit rate of a connected call, a burst memory for storing a burst of a connected call, A peak bit rate sum memory for storing the sum of the peak bit rates of the currently connected calls, and the number of possible connections indicating the number of connectable calls corresponding to the calls having the predetermined peak bit rates and bursts, respectively. Based on the lookup table and the report parameters of the calling cell from the terminal device, the peak bit rate obtained by the report parameters and the peak A maximum peak bit rate extracting means for extracting a maximum peak bit rate from the peak bit rate stored in the memory for the bit rate, a burst obtained by the declaration parameter based on the declaration parameter of the calling cell from the terminal device, and the burst The minimum burst extracting means for extracting the minimum burst from the burst stored in the memory for use, and the peak bit rate obtained from the report parameter of the calling cell are calculated by summing the peak bit rates stored in the peak bit rate sum memory. the peak bit rate sum adder for adding the number of calls in the case of connecting a call having a minimum burst extracted with maximum peak bit rate and a minimum burst extracting means extracted by the maximum peak bit rate extracting unit, the Pikubi
The bit rate obtained by the sum total
The sum was extracted by the above maximum peak bit rate extraction means
And virtual connections calculation means for output calculated by dividing a maximum peak bit rate, the number of calls is calculated by the virtual connection number calculating means, the maximum peak bit rate and the minimum indicated by the connectable number reference table Comparing means for comparing the number of connectable calls corresponding to a call having a burst, and determining whether or not to accept a calling cell from the terminal device based on a result of the comparison. A call admission control device for an exchange in an ATM network.