JPH10150447A - Congestion avoidance system for periodic traffic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid congestion without degrading communication quality and image quality and increasing a network resource. SOLUTION: Information of each of ATM communication equipments 2-4 is registered to a terminal registration section 8 in an ATM exchange 1. A synchronization ATM cell generating section 10 generates a synchronization ATM cell addressed to each communication equipment at the same interval of a traffic period according to information of the registration section 8 and transmits the ATM cell so that the transmission time differs from each communication equipment. Synchronization ATM cell identification sections 11-13 in each communication equipment inform the reception of the synchronization ATM cell and transmission timing control sections 14-16 make a peak of a transmission traffic synchronously with a notice time. Thus, duplicate traffic peak of the ATM cells arrived from a plurality of paths to the ATM exchange 1 is prevented from being overlapped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for avoiding congestion in a network system for communicating a signal having a constant periodicity in traffic, such as a real-time moving image signal, in an ATM (Asynchronous Transfer Mode) cell. .

[0002]

2. Description of the Related Art When a moving image signal is communicated via a network, in order to reduce the communication cost, usually, various image compression methods are used to reduce the amount of data before transmission. M
As in the case of the PEG system, a system that uses a different compression system for each frame of a moving image inserts a relatively low compression rate frame (I-picture in the MPEG system) for each fixed number of frames. When this signal is transmitted in real time, data to be transmitted per unit time is large in a frame with a low compression ratio, and small in a frame with a high compression ratio. This is performed in real time by ATM (Asynchronous Transfer Mo
de: Asynchronous Transfer Mode) In the case of transmission using cells, the density of ATM cells per unit time is high in a frame with a low compression ratio, and low in other frames. If this is viewed in a continuous time, the traffic pattern has a peak at a constant period.

[0003] Although the ATM network absorbs the traffic fluctuation to some extent in the buffer memory in the exchange, when the ATM cell traffic input from a plurality of routes goes to the same route, the input cell traffic is reduced. If the peaks overlap, congestion occurs in the exchange. Since the capacity of the buffer memory is finite, when such congestion occurs, the arrival ATM exceeding the capacity is received.
Cells are discarded, which significantly reduces communication quality.

[0004] As a method of solving this problem of congestion,
A method of increasing the capacity of the line, a method of increasing the buffer memory in the exchange, and a method of distributing peaks by providing a buffer in the transmitting terminal device are conceivable. Of these, increasing the line capacity is the most effective, but increases the communication cost, and reduces the cost advantage of statistical multiplexing, which is a feature of the ATM network. In addition, an increase in the buffer memory capacity of the ATM exchange or the communication terminal device not only increases the cost of communication equipment, but also increases the communication delay time.

Therefore, as another method, a notifying means for generating a resource management ATM cell indicating congestion detection and transmitting it to the transmitting terminal device is provided.
The transmitting terminal device is notified by the resource management ATM cell, and the transmitting terminal device that has received the notification switches to a compression method having a higher compression ratio (however, in this case, the degree of restoration is reduced), By lowering the resolution,
A method of reducing the amount of data at that time and controlling so as to lower the peak of traffic has been considered. Further, the methods proposed in Japanese Patent Application Nos. 3-003452 and 4-059866 do not limit the application target to the ATM network, and the methods of predicting and detecting the congestion state are different.
Similarly, the coding parameter is changed to adapt the amount of transmission data. However, with these methods,
Temporarily degraded quality of the restored image, complicated control due to the fact that the encoding circuit on the transmitting side must change the operation mode in real time, and multiple similar traffic with peaks overlapping in the same cycle In such a case, congestion is always encountered, and there is a problem that image quality is suppressed to a low level.

[0006]

As described above, in the conventional congestion avoidance system in which the line capacity and the buffer memory on the route are enlarged, the communication cost increases, and in the system in which the buffer memory is further enlarged, the communication quality deteriorates. There was a problem of doing it. Further, in the conventional congestion avoidance method that adapts the amount of transmission data, there is a problem that image quality is deteriorated and control of an encoding circuit on a transmission side becomes complicated. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and when a signal having a certain periodicity in traffic such as a real-time moving image signal is transmitted by an ATM cell, a circuit capacity such as a line capacity or a buffer memory on a path is required. An object of the present invention is to provide a congestion avoidance method capable of avoiding congestion without increasing network resources (communication cost) and without reducing communication quality and image quality.

[0007]

According to the present invention, there is provided a plurality of ATM communication apparatuses in which transmission traffic fluctuates greatly at a predetermined traffic cycle.
With an ATM switch that accommodates the lines connected to them,
The ATM exchange continuously generates ATM cells for synchronization destined for each ATM communication device at the same interval as the traffic cycle, and transmits the ATM cells to each communication device such that the transmission time differs for each ATM communication device. Each ATM communication device synchronizes the peak of transmission traffic with the arrival time of the received synchronization ATM cell. As described above, the ATM exchange generates ATM cells for synchronization addressed to each ATM communication device at the same interval as the traffic cycle, and transmits these ATM cells at different transmission times for each ATM communication device.
Each of the ATM communication devices synchronizes the peak of the transmission traffic with the arrival time of the ATM cell for synchronization, thereby preventing the traffic peaks of the ATM cells arriving at the ATM switch from a plurality of routes from overlapping. Further, as described in claim 2, the ATM exchange is provided with each AT.
A terminal registration unit for registering information of the M communication device, and a synchronization ATM cell destined for each ATM communication device is continuously generated at the same interval as the traffic cycle in accordance with the information registered in the registration unit. Synchronization AT for transmitting to each communication device so that the time is different for each ATM communication device
Each ATM communication device has M cell generation means, and each ATM communication device has a synchronization ATM cell identification means for notifying reception of a synchronization ATM cell, and a transmission timing control means for synchronizing a peak of transmission traffic at the notification time. Things.

[0008] As described in claim 3, a plurality of A
The first ATM communication device, which is one of the TM communication devices, continuously generates a synchronization signal destined for itself and a synchronization ATM cell destined for another ATM communication device at the same interval as the traffic cycle. The transmission is performed to each communication device so that the transmission time differs for each ATM communication device, and the peak of the transmission traffic is synchronized with the time of the synchronization signal. The other second ATM communication device is connected via the ATM switch. The peak of the transmission traffic is synchronized with the arrival time of the synchronization ATM cell received. Thus, the first AT
The M communication device generates a synchronization signal addressed to itself and a synchronization ATM cell addressed to another ATM communication device at the same interval as the traffic cycle, and transmits these at different transmission times for each ATM communication device. Synchronizes the peak of the transmission traffic at the time of
By synchronizing the peak of the transmission traffic with the arrival time of the ATM cell for synchronization received via the exchange, it is possible to prevent the traffic peaks of the ATM cells arriving at the ATM exchange from a plurality of routes from overlapping. According to a fourth aspect of the present invention, the first ATM communication device includes a terminal registration unit for registering information of each ATM communication device, and each ATM communication device according to the information registered in the registration unit.
Synchronization ATM cells for synchronization destined for the TM communication device and synchronization signals destined for itself are continuously generated at the same interval as the traffic cycle, and transmitted to each communication device such that their transmission times are different for each ATM communication device. Second ATM cell generating means, and a transmission timing control means for synchronizing the peak of transmission traffic with the time of the synchronization signal.
The communication apparatus includes a synchronization ATM cell identification unit for notifying the reception of the synchronization ATM cell, and a transmission timing control unit for synchronizing the peak of the transmission traffic at the notification time.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION

1. Embodiment 1. Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a network system according to a first embodiment of the present invention. In the present embodiment, the transmission traffic characteristics of the ATM communication devices 2 to 4 are as follows:
Each of them has a characteristic in which a peak appears at a period t as shown in FIG. Such an assumption can actually occur in the case of a terminal or the like transmitting a compressed moving image. In addition,
It does not matter whether the data is transmitted while the compression is performed in real time or the already compressed image data is continuously transmitted.

The ATM exchange 1 has ATM communication devices 2 to 4
Are directly connected by bidirectional links 5-7. This A
In the terminal registration unit 8 in the TM exchange 1, information such as a port number indicating to which input port of the ATM exchange 1 each ATM communication device 2-4 is connected and a destination identifier of the ATM communication devices 2-4 are registered. In addition, information such as the above-described cycle t and the generation timing of a synchronization ATM cell described later is registered.

These information can be registered and referred to by the control console 9. Then, the ATM cell generator 10 for synchronization in the ATM exchange 1
According to the information registered in the terminal registration unit 8, each ATM
An ATM cell for synchronization with the communication device is generated for each cycle t. FIG. 3 is a diagram showing the generation timing of the ATM cell for synchronization.

FIG. 3A shows the timing of generation of a synchronization ATM cell addressed to the ATM communication device 2. That is,
The synchronization ATM cell generation unit 10 registers the synchronization ATM cell to which the destination identifier of the communication device 2 registered in the registration unit 8 is added as the destination identifier in the cell header in the registration unit 8 in FIG. Generated according to generation timing. Similarly, FIG. 3B shows a timing of generating a synchronization ATM cell addressed to the ATM communication device 3. The synchronization ATM cell generation unit 10 converts the synchronization ATM cell to which the destination identifier of the communication device 3 is added as the destination identifier in the cell header as shown in FIG.
It is generated according to the generation timing of (b).

FIG. 3C shows the timing of generation of a synchronization ATM cell addressed to the ATM communication device 4. The synchronization ATM cell generator 10 generates a synchronization AT with the destination identifier of the communication device 4 added as the destination identifier in the cell header.
M cells are generated according to the generation timing of FIG. As can be seen from FIG. 3, the synchronization AT for each communication device is used.
The generation timings of the M cells are registered in the terminal registration unit 8 with their phases shifted so that they do not coincide with each other.

The ATM exchange 1 distributes the generated ATM cell for synchronization to each route according to the destination identifier in the cell header. Thereby, the ATM communication devices 2 to 4
The ATM cell for synchronization destined is transmitted to the ATM communication devices 2 to 4 via the bidirectional links 5 to 7, respectively.

Next, the synchronization A in the ATM communication devices 2 to 4
Upon receiving the ATM cells for synchronization from the bidirectional links 5 to 7, the TM cell identification units 11 to 13 send a notification signal to the transmission timing control units 14 to 16 in the communication device to notify that the ATM cells for synchronization have arrived. Output. This notification signal has a meaning as a timing for recommending peak traffic transmission.

When receiving the notification signals from the synchronization ATM cell identification units 11 to 13, the transmission timing control units 14 to 16 synchronize the transmission traffic peaks with the arrival times of the notification signals. When transmitting image data while compressing the image data in real time, this processing can be realized by generating the compressed image data so that the peak of the transmission traffic (a frame with a low compression ratio) is synchronized with the arrival time of the notification signal.

When transmitting the compressed image data after temporarily storing it in the buffer memory, it can be realized by reading the compressed image data from the buffer memory so that the peak of the transmission traffic is synchronized with the arrival time of the notification signal. In this way, it is possible to prevent traffic peaks of ATM cells arriving at the ATM switch 1 from a plurality of routes from overlapping, and to avoid congestion.

Embodiment 2 FIG. 4 is a block diagram of a network system showing another embodiment of the present invention, and the same components as those in FIG. 1 are denoted by the same reference numerals. In the present embodiment, as in Embodiment 1, AT
The transmission traffic characteristics of the M communication devices 2a, 3 and 4 are such that a peak appears at a period t as shown in FIG.

The ATM exchange 1a is connected to the ATM communication device 2
a, 3, 4 are directly connected by bidirectional links 5-7. In the terminal registration unit 18 in the ATM communication device 2a, information such as the destination identifier of the other ATM communication devices 3 and 4 is registered, and further information such as the cycle t and the generation timing of the ATM cell for synchronization is registered. .

These pieces of information can be registered and referenced by the control console 19. Then, the synchronization ATM cell generation unit 20 in the ATM communication device 2a generates a synchronization ATM cell to each ATM communication device for each cycle t according to the information registered in the terminal registration unit 18. The generation timing of the synchronization ATM cell is the same as that in FIG. However, as a signal addressed to itself, an internal synchronization signal is generated instead of a synchronization ATM cell.

That is, the synchronization ATM cell generator 20
FIG. 3 shows an internal synchronization signal registered in the terminal registration unit 18.
It is generated according to the generation timing of (a) and is output to the transmission timing control unit 21. Further, the synchronization ATM cell generation unit 20 uses the communication device 3 as the destination identifier in the cell header.
FIG. 3B shows a synchronization ATM cell to which the destination identifier of FIG.
, And a synchronization ATM cell to which the destination identifier of the communication device 4 is added as the destination identifier in the cell header according to the generation timing of FIG.

As in the first embodiment, the generation timings of the synchronization ATM cell and the internal synchronization signal for each communication device are registered in the terminal registration unit 18 with their phases shifted so that they do not coincide with each other. And the ATM communication device 3,
4 is transmitted to the transmission timing control unit 21.
To the bidirectional link 5. ATM exchange 1a
Distributes the ATM cell for synchronization received from the bidirectional link 5 to each route according to the destination identifier in the cell header.
As a result, the ATM cells for synchronization destined for the ATM communication devices 3 and 4 are transmitted to the ATM communication devices 3 and 4 via the bidirectional links 6 and 7, respectively.

The transmission timing control units 15 and 16 in the ATM communication devices 3 and 4 include the synchronization ATM cell identification units 12 and 1.
When the notification signal is received from No. 3, a process for synchronizing the peak of the transmission traffic with the arrival time of the notification signal is performed.
The transmission timing control unit 2 in the ATM communication device 2a
Upon receiving the internal synchronization signal from the synchronization ATM cell generator 20, the 1 performs a process of synchronizing the peak of the transmission traffic with the arrival time of the synchronization signal. These synchronization processes can be realized in the same manner as in the first embodiment. Thus, by providing the terminal registration unit 18 and the synchronization ATM cell generation unit 20 in the first ATM communication device 2a, the ATM
An effect similar to that of the first embodiment can be obtained without providing the exchange with a special function.

[0024]

According to the present invention, according to the first aspect, the ATM exchange is provided with a synchronization AT for each ATM communication device.
M cells are generated and transmitted such that their transmission times are different for each ATM communication device, and each ATM communication device synchronizes the peak of transmission traffic with the arrival time of the synchronization ATM cell, so that a plurality of cells are transmitted. It is possible to prevent the traffic peaks of the ATM cells arriving from the road to the ATM exchange from overlapping. As a result, in the transfer of a data flow having a periodic transmission traffic peak, avoiding congestion without impairing communication quality and image quality and without increasing network resources such as line capacity and buffer memory capacity. Can be.

Further, as described in claim 2, the ATM exchange is provided with terminal registration means and synchronization ATM cell generation means, and each ATM communication device is provided with synchronization ATM cell identification means and transmission timing control means. In addition, a congestion avoidance method capable of avoiding congestion without impairing communication quality and image quality and without increasing network resources such as line capacity and buffer memory capacity can be realized with a simple configuration.

[0026] According to a third aspect of the present invention, the first A
The TM communication device generates a synchronization signal addressed to itself and a synchronization ATM cell addressed to another ATM communication device, and transmits these at different transmission times for each ATM communication device. Synchronize the peak of the second
ATM communication device synchronizes the peak of the transmission traffic with the arrival time of the ATM cell for synchronization received via the ATM switch, so that the traffic peaks of the ATM cells arriving from the plurality of routes to the ATM switch overlap. Can be prevented. As a result, the same effect as described above can be obtained without having a special function in the ATM exchange.

[0027] Further, as described in claim 4, the first A
By providing the TM communication device with terminal registration means, synchronization ATM cell generation means and transmission timing control means, and providing the second ATM communication device with synchronization ATM cell identification means and transmission timing control means, communication quality and image quality can be improved. A congestion avoidance method capable of avoiding congestion can be realized with a simple configuration without deteriorating the traffic and without increasing network resources such as a line capacity and a buffer memory capacity.

[Brief description of the drawings]

FIG. 1 is a block diagram of a network system according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating transmission traffic characteristics of an ATM communication device.

FIG. 3 is a diagram showing generation timing of a synchronization ATM cell.

FIG. 4 is a block diagram of a network system showing another embodiment of the present invention.

[Explanation of symbols]

1, 1a ATM switch, 2-4, 2a ATM communication device, 5-7 bidirectional link, 8, 18 terminal registration unit,
9, 19 ... control console, 10, 20 ... ATM for synchronization
Cell generation units, 11 to 13... ATM cell identification units for synchronization, 1
4 to 16, 21 ... Transmission timing control unit.

Claims (4)

[Claims] 1. A congestion avoidance system in a network system comprising a plurality of ATM communication devices whose transmission traffic fluctuates greatly at a predetermined traffic cycle, and an ATM exchange accommodating a line connected thereto. Is to generate ATM cells for synchronization destined for each ATM communication device continuously at the same interval as the traffic cycle, and to transmit the ATM cells to each communication device such that the transmission time differs for each ATM communication device. A method for avoiding congestion of periodic traffic, wherein each ATM communication device synchronizes a peak of transmission traffic with an arrival time of a received ATM cell for synchronization. 2. The congestion avoiding system for periodic traffic according to claim 1, wherein the ATM switch comprises: a terminal registration unit for registering information of each ATM communication device; and an ATM exchange according to the information registered in the registration unit. Synchronous ATM cell generation for generating ATM cells for synchronization destined for each ATM communication device continuously at the same interval as the traffic cycle, and transmitting the ATM cells to each communication device such that the transmission time differs for each ATM communication device. Each ATM communication device has a synchronization ATM cell identification means for notifying the reception of the synchronization ATM cell, and a transmission timing control means for synchronizing the peak of the transmission traffic at the notification time. A method for avoiding congestion of periodic traffic. 3. A congestion avoidance method in a network system comprising a plurality of ATM communication devices whose transmission traffic fluctuates greatly at a predetermined traffic cycle and an ATM switch accommodating a line connected thereto. A first ATM communication device, which is one of the ATM communication devices, continuously generates a synchronization signal addressed to itself and a synchronization ATM cell addressed to another ATM communication device at the same interval as the traffic cycle. Is transmitted to each communication device such that the transmission time of each communication device is different for each ATM communication device, and the peak of transmission traffic is synchronized with the time of the synchronization signal. The other second ATM communication device is an ATM switch. Wherein the peak of the transmission traffic is synchronized with the arrival time of the ATM cell for synchronization received via the transmission line. Congestion Avoidance Method of traffic. 4. The congestion avoidance system for periodic traffic according to claim 3, wherein the first ATM communication device is a terminal registration unit for registering information of each ATM communication device, and is registered in the registration unit. In accordance with the received information, the ATM cells for synchronization destined for each ATM communication device and the synchronization signal destined for itself are continuously generated at the same interval as the traffic cycle, and each communication device is set such that the transmission time differs for each ATM communication device. And a transmission timing control means for synchronizing the peak of the transmission traffic with the time of the synchronization signal. The second ATM communication apparatus receives the synchronization ATM cell. It has ATM cell identification means for synchronization for notifying, and transmission timing control means for synchronizing the peak of transmission traffic at the notification time. Congestion avoidance scheme periodicity traffic characterized.