JPH1084348A - Cell transmitter and cell transmission control method for asynchronous transfer mode communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent cell intervals from being shortened due to contention delay. SOLUTION: Upon the receipt of a transmission request REQ from each cell transmission section 810, a contention control section 850 returns a transmission acknowledgement ACK to the cell transmission section 810. In this case, when the transmission requests REQ are in contention, any cell transmission section 810 is selected and the transmission acknowledgement ACK is returned to the selected cell transmission section 810 and the transmission acknowledgement ACK is returned sequentially to all the remaining transmission sections 810 every time a unit time required for cell transmission elapses. The respective cell transmission sections 810 wait the transmission acknowledgement ACK is received and the cell transmission section 810 receiving the transmission acknowledgement ACK reads a cell from a memory 814 and the transmission section 816 sends the cell. In this case, a cell time interval setting section 822 sets a prescribed cell time interval to a transmission counter 820. Thus, contention delay is caused more for the cell transmission section 810 receiving the transmission acknowledgement ACK with a delay, but since the time interval is set after the transmission acknowledgement ACK is received, the cell interval is not made short for the transmission of succeeding cells.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cell transmission apparatus and a cell transmission control method in an asynchronous transfer mode communication system, and more particularly, to an ATM switch for multiplexing calls from a plurality of routes and transmitting them at high speed. The present invention relates to a cell transmission device and a cell transmission control method in an asynchronous transfer mode communication system suitable for use.

[0002]

2. Description of the Related Art In recent years, digitalization of public telecommunication networks has been advanced.
It is expected that efficient and high-performance services will be realized by integration, and a broadband digital integrated service network capable of transmitting various information including voice information and data transmission, as well as still image information and moving image information. Research on (B-ISDN) has been carried out in various fields, and its practical application has been progressing sequentially.

[0003] A transfer technique called an asynchronous transfer mode (hereinafter referred to as ATM) is effectively applied to this broadband digital integrated service network. In an ATM communication network,
Information such as voice, data, and images are all divided into fixed-length blocks, and a header indicating the destination is attached to each block, so-called fixed-length cells are formed.
Information transmission is performed in these unified length ATM cells.

In such an ATM switching system, at the time of calling, a terminal transmits a signaling cell including destination information of a connection destination, information of a requested service type and a cell speed to the ATM network. The ATM network determines the transmission route based on the signaling cells. At this time, the ATM network determines whether it is possible to sequentially transfer control cells to each node forming the network, for example, an ATM switch or a virtual channel handler (VCH), and pass the cells under the required service conditions. Check if. For example, it is determined whether or not the requested traffic does not exceed the transmission capacity. Thereafter, the terminal is notified that communication is possible, and the mode shifts to the communication mode.

However, in each node, a large number of calls are connected at the same time, so that cells are concentrated on a specific route, and as a result, the capacity of the virtual channel (VC) or virtual path (VP) is exceeded. It may happen that cells have to be sent at a high instantaneous rate. For this reason, each node performs control to temporarily store each cell in a buffer memory and read and transmit the cell so that the instantaneous speed of the cell does not exceed a certain value.

Conventionally, for example, in a cell transmitting apparatus including a buffer memory as described above, a cell transmitting section of a plurality of speeds is prepared according to each user's request, and cells are transmitted at predetermined time intervals. Is sent. The cell transmission unit has a transmission counter, and measures a time interval determined by using the counter. The time required for the cell transmission unit to transmit a cell is defined as one unit time, and a determined time interval, that is, how many unit times the cell time interval corresponds to, is set as a cell time interval value,
Set it in the transmission counter.

[0007] The transmission counter decrements the counter value every unit time, for example, by a trigger from a unit time timer. When the counter value becomes zero, the cell transmission unit sends a transmission request REQ to the contention control unit. At the same time, a cell time interval value is newly set in the transmission counter.

[0008] The contention control unit transmits a transmission request from the cell transmission unit.
Upon receiving the REQ, it performs contention control and transmits a transmission permission ACK to the cell transmission unit. The cell processing unit that has received the transmission permission ACK transmits the cell.

For example, assuming that a cell transmission time is one unit time, a certain cell processing unit A transmits a cell every five unit times, and another certain cell processing unit B transmits a cell every eight units. Set each. That is, the cell processing unit A
Sends a transmission request REQ to the contention control unit every 5 unit time,
When a transmission permission ACK is received from the contention control unit, the cell is transmitted. Similarly, the cell processing unit B sends the transmission request REQ to 8
The cell is transmitted to the contention control unit every unit time, and the cell is transmitted when the transmission permission ACK is received.

As described above, by preparing a plurality of cell transmission devices of different speeds in each node and controlling them in a coordinated manner, cells can be transmitted smoothly without exceeding the capacity of a virtual channel or a virtual path. Can be.

[0011]

However, in the above-mentioned prior art, since a plurality of cell transmission units exist, there is a case where the cell interval becomes narrower than a predetermined time interval due to competition between them. There was a problem.

For example, as shown in FIG. 4, it is assumed that the transmission requests REQ of the cell transmission units A and B compete with each other. It is assumed that the contention control unit returns a transmission permission ACK by giving priority to the transmission request REQ of the cell transmission unit B and returns a transmission permission ACK to the cell transmission unit A with a delay of one unit time. Then, the cell from the cell transmission unit A is delayed by one unit time from the original. Thereafter, the cell processing unit A sends the next transmission request REQ to 5
The transmission is performed after a unit time, and at this time, since there is no competition with the cell transmission unit B, the transmission permission ACK for the transmission request REQ is received without delay. The cells are also transmitted without delay. Here, since the previous cell is delayed by one unit time,
As a result, the cell interval is narrowed to 4 unit times. As a result, in the cell transmitting unit A, the time interval of the determined 5 unit time is not guaranteed, and a problem such that the cells are discarded by the subsequent nodes or the like occurs.

The present invention solves the above-mentioned drawbacks of the prior art, and enables cell transmission in an asynchronous transfer mode communication system in which a cell transmission interval can be maintained at a predetermined time interval or more even when a conflict occurs during cell transmission. It is an object to provide an apparatus and a cell transmission control method.

[0014]

According to the present invention, there is provided a cell transmitting apparatus in an asynchronous transfer mode communication system, in which information divided into fixed-length cells each having a predetermined length is transmitted for a predetermined time. In the cell transmission device in the asynchronous transfer mode communication system for sequentially transmitting at intervals or more,
Processing means for creating and processing the fixed-length cells, storage means for sequentially storing the fixed-length cells processed by the processing means, and transmission means for sequentially reading and transmitting the fixed-length cells stored in the storage means. A plurality of cell transmission units, including a control unit including contention control means for controlling contention of fixed length cells transmitted from the cell transmission unit, each cell transmission unit, when transmitting a fixed length cell A request signal indicating a transmission request is sent to the control unit, and when a permission signal indicating transmission permission is received from the contention control means of the control unit, the fixed-length cell is transmitted in a predetermined unit time. A predetermined time interval value is set, and after the time interval has elapsed, a request signal indicating a transmission request for the next fixed-length cell is transmitted to the control unit.

In this case, the cell transmission unit further includes an interval value setting means for setting a predetermined time interval when transmitting the request signal, a timer for measuring a unit time, and an interval value for counting the unit time from the timer. A transmission counter that counts a time interval set by the setting unit, wherein the interval value setting unit sets a predetermined time interval value in the transmission counter when receiving the permission signal from the contention control unit.

The unit time is a time required for transmitting a fixed-length cell, and the time interval value is preferably set to be an integral multiple of the unit time. Further, the contention control means sends a permission signal to any one of the cell transmission units when simultaneously receiving request signals from a plurality of cell transmission units, and thereafter, a unit time for cell transmission in the cell transmission unit is After the lapse of time, the permission signal may be transmitted to any one of the cell transmission units, and the permission signal may be sequentially transmitted to any of the cell transmission units after a lapse of a unit time.

Further, the cell transmitting apparatus according to the present invention provides a virtual channel handler or an ATM for setting a plurality of virtual channels in response to a call from each user.
It is advantageous to provide it at the node of the ATM network including the exchange. Further, it may be provided in a user / network interface to which a plurality of terminals are connected.

On the other hand, according to the cell control method of the present invention, when a plurality of fixed-length cells divided into a predetermined length are sequentially transmitted from a plurality of cell transmission units, a predetermined time interval or more is controlled based on the control of each control unit. In the cell transmission control method in the asynchronous mode communication system for transmitting fixed-length cells, a first step in which a time interval value for transmitting fixed-length cells is determined in advance by each cell transmission unit, and A second step of transmitting a request signal indicating a transmission request to the control unit when transmitting a fixed-length cell by the control unit, and a third step of transmitting a permission signal indicating transmission permission to the cell transmitting unit which has transmitted the transmission request by the control unit. And a fourth step of transmitting a fixed-length cell within a unit time by the cell transmitting unit that has received the permission signal.
A fifth step of repeating the second to fourth steps at a predetermined time interval value in the first step;
The step of, when a transmission request is simultaneously transmitted from the plurality of cell transmission units to the control unit, a step of selecting any one of the cell transmission units that transmitted the transmission request in the control unit and transmitting a permission signal, This step is repeated for each unit time, and a permission signal is sequentially transmitted to all the cell transmission units that have transmitted the transmission request. The fifth step includes the steps of: A step of waiting for a permission signal from the control unit in the cell transmission unit, and thereafter, setting a predetermined time interval value in the first step after receiving the permission signal, and setting a second time interval value after the time interval elapses. And returning to the step.

In a fifth step, when the permission signal is received from the control unit, the time interval value determined in the first step is set in a predetermined counter, and the unit time is counted by the counter. A predetermined time interval may be counted. further,
The unit time is a time required for transmitting a fixed-length cell, and the time interval value may be set to an integral multiple of the unit time.

[0020]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a cell transmission apparatus and a cell transmission control method in an asynchronous transfer mode communication system according to the present invention; FIG. 1 shows an embodiment of a cell transmission device to which a cell transmission control method according to the present invention is applied. FIG. 2 shows an example of a network to which the cell transmission device of the present embodiment is applied. The cell transmitting device in the present embodiment is an ATM network 100 including an ATM switch or a virtual channel handler (VCH) for switching calls from the respective user premises devices 10 to 50 to respective routes in response to the request. Effectively applied to each node 60,60.

The user premises devices 10 to 50 sequentially transmit signaling cells including information such as the destination, service type, and cell speed to the ATM network 100 when setting up a call. In the case of the present embodiment, the user premises equipment 10 to 50 is a user premises equipment 20 of a plurality of terminals accommodated in a private branch exchange or the like, or a LAN (Lo
cal Area Network) A plurality of connected user premises devices 40 and the like, and each terminal includes an ATM terminal capable of simultaneously setting a plurality of channels such as voice, video, or data transmission. Although FIG. 2 shows a simple example of the ATM network 100, a large number of nodes 60 are installed in each region, and these are connected to each other by virtual paths and virtual channels to form the ATM network 100. Node
Various terminals and subscriber networks are connected to 60, and illustration thereof is omitted for convenience of explanation.

When the ATM network 100 receives the signal cell, the ATM cell 100 sequentially transfers the control cells to the respective nodes 60, 60 based on the signal cell, and transmits the requested service condition, for example,
It is determined whether or not the requested traffic does not exceed the transmission capacity, and whether or not the cell can be passed is confirmed. As a result, virtual channels VC satisfying the service and cell rate required by the user are respectively set. Thereafter, the terminal is notified that communication is possible, and the mode is shifted to the communication mode.

Each of the nodes 60, 60 is a switching node that physically accommodates a plurality of subscriber lines, multiplexes them, and exchanges each call. Logically, each node 60, 60 Accordingly, the virtual channel handler sets a virtual channel VC with another node 60 and transfers the cell as shown by a dotted line in the figure. In the present embodiment, each node 60 has, for example, the cell transmitting device of the present embodiment including a buffer memory on its output side, and at a predetermined time interval or more so that the instantaneous speed of the cell does not exceed a fixed value. The cells are read from the buffer memory and transmitted sequentially.

More specifically, as shown in FIG. 3, the ATM switch or virtual channel handler applied to the node 60 of the present embodiment includes an input device 62, an ATM switch 64,
An output device 66 and a control device 68 are included. Input device 62 includes a plurality of receiving devices 70 that receive cells from virtual path VP and virtual channel VC. Each receiving device
Reference numeral 70 denotes a line termination device having a function of detecting a signal cell upon a call from a user and transferring the signal cell to the control device 68, and a function of monitoring the flow rate of each path and channel.

In particular, at the time of flow rate monitoring, when a call is set, a band is allocated to each of the receiving devices 70 under the control of the control unit 68, and whether the cell of each user is transmitted with the declared capacity. If a cell exceeding the specified value is detected, processing such as discarding the cell is performed.

The ATM switch 64 switches cells from the input device 62 by hardware based on the header thereof,
A switch circuit for supplying to the output device 66 of a predetermined route, for example, a switch such as a batcher banyan type combining a sorting circuit and a routing switch or a buffer type combining a routing switch and a memory is effectively applied. . In this embodiment, switches of various configurations capable of self-routing can be applied regardless of the type.

The output device 66 is an output circuit for outputting each cell routed by the ATM switch 64 to each route. In this embodiment, the cell is connected to a virtual channel and a virtual path at a predetermined time interval or more. A plurality of cell transmitting devices 80 for transmitting each are effectively applied.

More specifically, the cell transmitting apparatus 80 according to the present embodiment
Is, for example, as shown in FIG.
0 and a conflict control unit 850. The cell transmission unit 810 is a transmission circuit connected to each line via the common bus 824 and transmitting cells from the ATM switch 64 according to the respective speeds, and includes a processing unit 812, a buffer memory 814, It includes a transmission section 816, a unit time timer 818, a transmission counter 820, and a cell time interval value setting circuit 822. The processing unit 812 of this embodiment is a cell processing circuit that mainly deletes and generates the header of a cell received from the ATM switch 64 to form a cell at the next node. The processed cells are supplied to a buffer memory 814.

The buffer memory 814 is, for example, a first-in first-out storage circuit, and includes a processing unit 81
2 are sequentially stored, and the stored cells are sequentially output in accordance with the read signal from the interval value setting circuit 822. The read cell is supplied to the transmission unit 816. Transmission section 816
Is a transmission circuit for sequentially transmitting cells read out from the buffer memory 814 via the common bus 824 connected to the line at a predetermined speed.
The time required for cell transmission from 616 is treated as a unit time.

The unit time timer 818 is a time counting circuit for sequentially counting the above unit time, and the counted value is supplied to the transmission counter 820 as a subtraction value. Transmission counter 820
Is a counting circuit for counting a time interval value at the time of cell transmission. In this embodiment, when the set time interval value is counted, a request signal for requesting the contention control unit 850 to transmit a cell is provided.
Outputs REQ.

The cell time interval value setting circuit 822 is a setting circuit for sequentially setting the time interval value at the time of cell transmission to the transmission counter 820. In this embodiment, when a permission signal ACK is received from the contention control unit 850. The respective time interval values are set in the transmission counter 820. At this time, a cell read signal is supplied to the buffer memory 814, and the cell is transmitted from the transmission unit 816. In the present embodiment, the time interval value is an integral multiple of the unit time, and is a value determined in advance for each cell transmission unit 810.

The contention control unit 850 is a control circuit for controlling contention between the cell transmission units 810. When there is no contention between the cell transmission units, the transmission request is transmitted from any of the cell transmission units 810.
Upon receiving the REQ, the controller sequentially returns an acknowledgment signal ACK in response to the REQ. When a contention occurs, the ACK is sent to one of the cell transmission units 810 including the priority cell, for example. Is a priority control circuit for sequentially returning the permission signal ACK to the cell transmission unit 810 of FIG.

On the other hand, returning to FIG. 3, the control device 68 is a main control device for controlling the input device 62, the ATM switch 64 and the output device 66, respectively. Controls such as routing control, connection control, usage parameter control, priority control, congestion control, and resource management are respectively performed. For example, a signal cell received via the input device 62 at the time of call setting is decoded, and destination information, a service type, a cell speed, and the like displayed on the cell are detected, and a cell route is determined based on the information. I do. When the route is determined, a control cell is created and sequentially transmitted through the ATM switch 64 and the output device 66, and it is confirmed whether or not the cell can be passed under the service condition. In particular, it checks whether or not the speed from the cell transmission device 80 satisfies the transmission capacity of the virtual channel.
When the condition is satisfied, the band is allocated to the cell receiving device 70, the terminal is permitted to perform communication, and the terminal enters the communication mode. When the communication mode is entered, the cell receiving device 70 is controlled to monitor whether the actual cell inflow amount matches the declared transmission capacity. If the actual traffic exceeds a prescribed value, a process such as attaching a violation tag or the like and discarding is performed.

When the cells passing through the ATM switch 64 are concentrated on a specific route and the data amount becomes excessive at the output side, the control device 68 detects the priority cell and outputs the priority cell. , Etc., is controlled. In particular, in the present embodiment, the traffic data that sequentially changes from each cell transmission device 80 is detected, the quality target of the communication speed is determined, and the time interval value of cell transmission to each cell transmission device 80 is sequentially determined. Decide and set. further,
When traffic is congested, various controls such as limiting a request for a new connection connection or changing a parameter value of usage parameter control are performed.

In the above configuration, the operation of the cell transmission apparatus according to the present embodiment will be described together with the cell transmission control method. In the present embodiment, for ease of explanation, each cell transmitting section 810 in the cell transmitting apparatus shown in FIG. 1 will be described as cell transmitting sections A, B, and C in order from the left. First, in a state where some calls are occurring, the control device 68 determines a time interval value at the time of cell transmission in the cell transmission units A, B and C based on the cell speed and traffic state of each call. To determine
The respective time interval values are set in the time interval setting circuits 822 of the cell transmission units A, B, and C, respectively.

For example, in this embodiment, the time interval setting circuit 822 of the cell transmitting section A has 5 unit times, the time interval setting circuit 822 of the cell transmitting section B has 8 unit times, and the time interval setting circuit 822 of the cell transmitting section C has Set 10 unit times respectively. Thereby, if the cell transmission units A, B, and C execute cell transmission for the time interval value or more set, the service request for the generated call, for example, the conditions such as the cell rate and the transmission capacity are satisfied and the setting is performed. It enables cell transmission that satisfies the transmission capacity of virtual channels and virtual paths.

Next, when the setting of the time interval value is completed, the control device 86 notifies each user that communication is possible and shifts to the communication mode. As a result, when each user starts communication, the information is divided into cells of a fixed length, and the ATM network 10 is divided via the respective subscriber lines.
0 and arrives at node 60 via the configured virtual channel and virtual path.

Next, in the node 60, when each cell is received by the input device 62, while monitoring whether or not the inflow amount of the cell matches the value declared by the user, the received valid cell is monitored. Is transferred to the ATM switch 64. As a result, the ATM switch 64 switches the cells by hardware based on the header of each cell and distributes the cells to the cell transmission device 80 on a predetermined route of the output device 66.

The cells switched by the ATM switch 64 are supplied to the cell transmission units A, B, and C of the cell transmission device 80 according to the respective speeds. Cell transmission units A, B,
C decomposes cells in the processing unit 812, removes the header, and adds a newly generated header to each cell to form a cell in the next route.

The processed cells are sequentially supplied to and stored in a buffer memory, that is, a storage unit 814. During this time, the cell time interval value is set in the transmission counter 820 by the cell time interval value setting circuit 822. The value of the transmission counter 820 is decremented by one every unit time, and when the value becomes zero,
Each of the cell transmission units A, B, and C sends a transmission request REQ to the contention control unit 850. In this case, if there is no conflict between the cell transmitters A, B, and C, the contention controller 850 immediately permits transmission.
An ACK is returned to each of the cell transmission units A, B, and C.

Next, the cell transmission units A, B,
C reads out the cells stored in the buffer memory 814 and supplies them to the transmission unit 816. This allows the buffer memory
The cell read from 814 is transmitted to a predetermined line via common bus 824. At this time, each cell transmission unit
In A, B, and C, the transmission interval 820 is sent from the time interval setting unit 822.
Set the time interval value again.

Next, the value of the set transmission counter 820 is sequentially decremented by the value from the unit time timer 818.
During this time, the next cell is processed and stored in the buffer memory 814 again. Next, when the value of the transmission counter becomes zero again, the cell transmission units A, B, and C again transmit transmission request REQ.
Is sent to the conflict control unit 850.

In this case as well, if there is no contention between the cell transmission units A, B, and C, a transmission permission ACK is immediately received from the contention control unit 850, and the cell is read from the buffer memory 814. Send Next, the time interval value is set in the transmission counter 820. Thereafter, if there is no contention in the cell transmission units A, B, and C, the cells from the ATM switch 64 are sequentially processed and processed.
The data can be accumulated and transmitted sequentially with the time interval value set in the time interval value setting section 822.

On the other hand, when contention occurs in the cell transmission units A, B, and C and a plurality of transmission requests REQ are supplied to the contention control unit 850 at the same time, the contention control unit 850 performs contention control and One of the cell transmitting units A, B, and C, for example, a cell transmitting unit 810 that transmits a cell including a priority cell, for example, a cell transmitting unit B is selected, and a transmission permission ACK is transmitted to the cell transmitting unit B. Upon receiving the transmission permission ACK, the cell transmitting section B reads out the cells stored in the buffer memory 814 in the same manner as described above, and
Transmitted from transmitting section 816. Then, the time interval value is set in the transmission counter 820, and the above operation is repeated.

Next, the contention control unit 850 sets the cell transmission unit B
After sending the permission signal ACK to
After the time for transmitting the cell in the cell transmission unit B has elapsed,
At the time of contention, one of the remaining cell transmitting units 810 that transmitted the transmission request REQ, for example, the cell transmitting unit A, is selected and a transmission permission ACK is returned. During this time, the remaining cell transmission units 81
0 waits while holding the state until receiving the permission signal ACK. Of course, the cell processing in the processing unit 812 is sequentially continued, and the processed cells are sequentially stored in the buffer memory 814.

Next, the cell transmission unit A receiving the permission signal ACK
Reads cells from the buffer memory 814 and
Send from 6. At this time, the time interval setting unit 822 sets the time interval value in the transmission counter 820. Then, the unit time is counted by the transmission counter 820, and the above operation is repeated.

Next, when one unit time elapses after returning the permission signal ACK to the cell transmission unit A, the contention control unit 850 transmits the remaining cell transmission unit C that has transmitted the transmission request REQ.
ACK signal is returned. As a result, the cell transmitting section C reads out the cell from the buffer memory 814, and
Sent from 816. At this time, similar to the cell transmission units A and B,
The time interval value is set in the transmission counter 820 and the above operation is repeated.

When a conflict occurs as described above, the conflict control unit
850 is a cell transmission unit 810 that has transmitted the transmission request REQ.
One of them is selected, and a transmission permission ACK is first given to the cell transmission unit 810. When one unit time for ending the cell transmission in the cell transmission unit 810 elapses, the next cell transmission unit 810 is selected.
Give 810 a permission signal.

Then, the permission signals are sequentially transmitted to all the cell transmission units 810 that have transmitted the transmission request REQ for each unit time.
When ACK is given, the contention control at that time ends. The competing cell transmitting section 810 waits until receiving the permission signal ACK, and then transmits the cell when receiving the permission signal ACK,
Set the time interval.

By this means, even if the return of the permission signal ACK is delayed due to contention, the transmission time of the next transmission request REQ can be delayed by that much, so that the cell interval is not narrowed until the next cell transmission. The time interval can be kept longer than the set time interval.

For example, FIG. 4 shows an example of cell transmission control in a conventional cell transmission device. In this figure, a cell transmitting unit A transmits a cell in five unit times. The cell transmission unit B transmits a cell in eight unit times. Assuming that the third transmission request REQ of the cell transmission unit A shown in the figure and the second transmission request REQ of the cell transmission unit B compete with each other, the contention control unit firstly transmits the transmission permission ACK to the cell transmission unit B.
give. Thereby, the cell transmission unit B transmits the cell.

Next, when one unit time elapses after giving the transmission permission to the cell processing section B, the contention control section gives a transmission permission ACK to the cell transmission section A. As a result, the cell processing unit A transmits a cell one unit time later than when there is no contention. Then, when five unit times have elapsed since the transmission of the previous transmission request REQ3, the next transmission request REQ4 is transmitted to the contention control unit. Upon receiving the transmission request, the contention control unit immediately returns the permission signal ACK to the cell transmission unit A because there is no contention with the cell processing unit B at this time. The cell transmission unit A having received the transmission permission transmits the cell.

As a result, the interval between the previous cell transmission timing and the current cell transmission becomes 4 unit times shorter than 5 unit times. Therefore, at the time of cell reception at the next node 60 or the like, cells may be discarded due to an overcapacity or the like.

However, as described above, in this embodiment, after each cell transmitting section 810 receives the transmission permission ACK from the contention control section 850, the time interval setting section 822 stores the predetermined time interval value in the transmission counter 820. Is set, the time interval value of the cell transmission is not narrowed even if the contention occurs and the return of the transmission permission from the contention control unit 850 is delayed. As a result, each cell can be accurately received by the next node 60, and reliable transmission that does not cause cell discard or the like can be performed.

In the description of the above embodiment, the case where the cell transmitting apparatus according to the present invention is applied to an ATM exchange or a virtual channel handler is taken as an example. In the present invention, for example, the user premises apparatus 20 shown in FIG. Applicable to user-network interfaces such as private branch exchanges, or network terminating devices of user private units 40 that connect multiple channels such as LANs to ATM networks, or network terminating devices that connect terminals that can set multiple channels simultaneously. May be.

In the above embodiment, the unit time timer 81
Although the unit time measured at 8 is the time required for cell transmission, another time may be used as the unit time in the present invention. Further, in the above embodiment, the interval value set in the transmission counter 820 from the time interval setting circuit 822 is an integral multiple of the time required for cell transmission, but the present invention is not limited to this. However, it is advantageous to set the count value of the transmission counter to the time required for cell transmission.

[0057]

As described above, according to the cell transmission apparatus and the cell transmission control method of the present invention, a transmission request is transmitted from a plurality of cell transmission units to the control unit, and then, after waiting for transmission permission from the control unit. Since the predetermined time interval value is set when the transmission permission is received, it is possible to prevent the interval between cells transmitted by the cell transmission unit from being narrowed by the contention delay caused by the contention control, and The time interval can always be kept above that interval value. As a result, an excellent effect such as accurate transmission of the cell to the next stage can be achieved without causing the transmission capacity to be exceeded or the cell to be discarded when receiving the subsequent nodes.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing one embodiment of a cell transmission device in an asynchronous transfer mode communication system according to the present invention.

FIG. 2 is a diagram to which the cell transmitting apparatus according to the embodiment of FIG. 1 is applied;
FIG. 2 is a diagram illustrating an example of an ATM communication network.

FIG. 3 is a diagram to which the cell transmitting apparatus according to the embodiment of FIG. 1 is applied;
FIG. 2 is a block diagram illustrating an example of an ATM switch or a virtual channel handler.

FIG. 4 is a time chart for explaining a race condition at the time of conventional cell transmission.

[Explanation of symbols]

60 node (ATM switch, virtual channel handler) 62 input device 64 ATM switch 66 output device 68 control device 70 cell receiving device 80 cell transmitting device 810 cell transmitting unit 812 processing unit 814 buffer memory 816 transmitting unit 818 unit time timer 820 transmission counter 822 Cell time interval value setting section 850 Contention control section

Continuation of front page (72) Inventor Satoshi Takahashi 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd.

Claims (9)

[Claims] 1. A cell transmission apparatus in an asynchronous transfer mode communication system for sequentially transmitting information divided into fixed-length cells of a predetermined length at a predetermined time interval or more, the apparatus includes: A plurality of cells including processing means for performing processing, storage means for sequentially storing fixed-length cells processed by the processing means, and transmission means for sequentially reading and transmitting the fixed-length cells stored in the storage means A transmitting unit, and a control unit including contention control means for controlling contention of fixed-length cells transmitted from the cell transmitting unit. Each of the cell transmitting units transmits the fixed-length cell. And transmits a fixed-length cell at a predetermined unit time when receiving a permission signal indicating transmission permission from the competition control means of the control unit. A cell transmission device in an asynchronous transfer mode communication system, wherein a predetermined time interval value is set, and a request signal indicating a transmission request for the next fixed-length cell is sent to the control unit after the elapse of the time interval. . 2. The apparatus according to claim 1, further comprising: an interval value setting means for setting a predetermined time interval when transmitting the request signal; a timer for measuring a unit time; A transmission counter which counts a unit time from a timer and counts a time interval set by the interval value setting means, wherein the interval value setting means, upon receiving a permission signal from the contention control means, A cell transmission device in an asynchronous transfer mode communication system, wherein a predetermined time interval value is set in a transmission counter. 3. The apparatus according to claim 2, wherein the unit time is a time required for transmitting a fixed-length cell, and the time interval value is set to be an integral multiple of the unit time. A cell transmission device in an asynchronous transfer mode communication method, which is characterized by the following. 4. The apparatus according to claim 1, wherein the contention control means sends a permission signal to any one of the cell transmission units when the request signals are simultaneously received from a plurality of cell transmission units. After that, after the unit time at the time of cell transmission in the cell transmission unit has elapsed, the permission signal is transmitted to any one of the other cell transmission units, and the permission signal is sequentially transmitted to any one of the cell transmission units after the unit time elapses. A cell transmission device in an asynchronous transfer mode communication method, characterized by transmitting. 5. The apparatus according to claim 1, wherein said apparatus is a virtual channel handler for setting up a plurality of virtual channels in response to a call from each user or an ATM network including an ATM switch. A cell transmission device in an asynchronous transfer mode communication system, which is provided in a node. 6. The cell transmitting apparatus according to claim 1, wherein said apparatus is provided in a user network interface to which a plurality of terminals are connected. 7. Asynchronous transmission of fixed-length cells divided by a predetermined length from a plurality of cell transmission units and transmitting the fixed-length cells at a predetermined time interval or more under control of a control unit when sequentially transmitting the fixed-length cells. In the cell transmission control method in the mode communication system, the method includes: a first step of determining in advance a time interval value for transmitting a fixed-length cell in each cell transmission unit; and a fixed-length cell in each cell transmission unit. A second step of transmitting a request signal indicating a transmission request to the control unit when transmitting the transmission request, and a third step of transmitting a permission signal indicating transmission permission to the cell transmission unit that has transmitted the transmission request in the control unit. A fourth step of transmitting a fixed-length cell within a unit time by the cell transmitting unit having received the permission signal, and a time interval determined in advance in the first step by following the second to fourth steps. 5th to repeat at And the third step, when a transmission request is simultaneously transmitted from the plurality of cell transmission units to the control unit, any one of the cell transmission units that have transmitted the transmission request in the control unit. Selecting and transmitting a permission signal; and repeating the step for each unit time to sequentially transmit a permission signal to all the cell transmission units that have transmitted the transmission request. The fifth step includes the third step. And c) waiting for a permission signal from the control unit in the cell transmission unit when a conflict occurs in the step, and then lapse of a time interval determined in the first step after receiving the permission signal. And returning to the second step after performing the method. 8. The method according to claim 7, wherein the fifth step sets a time interval value determined in the first step to a predetermined counter when receiving a permission signal from the control unit. A cell transmission control method in the asynchronous transfer mode communication system, wherein a unit time is counted by the counter and a predetermined time interval is counted. 9. The method according to claim 7, wherein the unit time is a time required for transmitting a fixed-length cell, and the time interval values are respectively integral multiples of the unit time. A cell transmission control method in the asynchronous transfer mode communication method.