JPH0514388A - Band control system for atm network - Google Patents

Abstract

PURPOSE:To control the increase of momentary traffic to reduce abandonment of cells by reading out cells in a storage means with periods of proportions corresponding to declared bands to smooth and output burst cells. CONSTITUTION:Input cells from a communication line are separated in accordance with set VCI numbers by a separating means 1 and are stored in cell storage means 2. Data corresponding to band declaration values declared for respective VCI numbers are preliminarily set to a control means 5, and cells are read out from cell storage means 2 at each timing and are multiplexed by a cell multiplexing means 4 and are outputted to the communication line. Since cells are read out with periods of proportions corresponding to declared bands in this manner, cells are outputted at speeds in declared bands and burst cells are smoothed and outputted. Consequently, the increase of momentary traffic is controlled to reduce abandonment of cells. Further, a maximum cell storage value setting means 3 is added to adjust the abandonment volume of cells.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a band control system in an ATM network, and more particularly to a band control system provided with a policing mechanism for monitoring whether or not the band of cells transmitted to the communication path of the ATM network is protected according to a declared value. Regarding

In ATM (Asynchronous Transfer Mode) communication, information such as variable speed images and burst data is handled in addition to constant speed voice and data, so it is very difficult for the network side to grasp the communication band. Is. Therefore,
Traffic that is larger than the declared bandwidth may be input instantaneously. As a result, the network may become overloaded and the quality of service may deteriorate (cell discard, etc.).

In order to deal with such a problem, it is necessary to perform bandwidth control by monitoring the traffic volume at the input part of the network and performing some kind of restriction processing.

[0004]

2. Description of the Related Art FIG. 8 shows a configuration of a first conventional example. In FIG. 8, 80 is V included in the header of each cell of the input communication path.
CI (Virtual channel number assigned to each call: Vi
rtual channel identifire), VCI identification means, 81 is a cell passage counting means provided corresponding to each VCI number # 1 to #n, and 82 is a band declared in advance for a call corresponding to each VCI (for example, , A peak value) and a value of the number of cells (the number of cells within a certain time period) corresponding to the peak value).
5 is a disposal means.

To explain the operation, when a plurality of call cells are multiplexed and input on the input communication path, the VCI identifying means 8
0, the VCI of each cell is identified, and the identified VC
Outputs (VCI # 1 to #n) corresponding to I are generated. As a result, the cell passage counting means 81 for each VCI number to which the output is supplied counts. The comparison means 83 compares the count value (denoted as A) of the cell passage counting means 81 corresponding to each VCI with the declared number (denoted as B) set in the declared count holding means 82. And the value of A is B
When the value of is exceeded, an output for displaying the VCI is generated, and the logical sum means 84 sends this VC to the discard means 85.
An instruction is given to discard the cell with I. As a result, the discarding unit discards the cell having the corresponding VCI and does not send it to the output communication path.

Next, the configuration of the conventional example 2 shown in FIG. 9 will be described. In FIG. 9, 90 is a band monitoring means, 91 is a mark adding means, and 92 is an ATM network. This conventional example 2 is called a marked cell system and is a band monitoring means 90.
In the same manner as in Conventional Example 1 above, the cells on the input communication path are
The number of arrivals within a fixed time is counted for each time, and when the number of arriving cells exceeds the declared value by comparing with the declared value (input from the control unit) for each VCI, the mark adding means 91 indicates that the corresponding VCI is violated. Instruct. Thereby, the mark adding means 9
The numeral 1 attaches a mark (for example, "1" is set to a predetermined specific bit in the header) to the cell having the corresponding VCI, and sends it to the ATM network 92. In the ATM network 92,
When congestion occurs in the network, the marked cells are preferentially discarded.

[0007]

In the method of the prior art 1 described above, since the number of arrivals of cells within a fixed time is monitored, only the fluctuation of average traffic can be dealt with, and the traffic increases instantaneously. There was a problem that it could not be controlled.

In the system of the second conventional example, in the case of a cell in which the burst property is instantaneously increased by some influence despite the band being protected on average, the traffic characteristic of the cell output from the policing controller is ATM because there is no change
There has been a problem that cells are discarded in the network and the quality of service deteriorates.

It is an object of the present invention to provide a band control method in an ATM network which can control a cell whose traffic is instantaneously increased so as to reduce cell discard and not to exceed a declared band. To do.

[0010]

FIG. 1 is a block diagram showing the principle of the present invention, FIG. 2 is a block diagram showing the first principle of read control means, and FIG. 3 is a block diagram showing the second principle of read control means.

In FIG. 1, 1 is a cell separating means for separating cells according to VCI, 2 is a cell accumulating means provided corresponding to each VCI, and 3 is a number of cells accumulating in the cell accumulating means 2. Maximum cell storage amount setting means, 4 is cell multiplexing means, and 5 is read control means for reading cells from the cell storage means in accordance with the declared band.

In FIGS. 2 and 3, 20 is a selection number accumulating means, 21 is a cycle counter, and 22 is a random counter. According to the present invention, input cells are stored in the cell storage means provided for each VCI, and cells of each VCI are stored. At this time, cells having a cell amount equal to or larger than the cell amount set in the maximum cell storage amount setting means are discarded, while storing each cell. The cells stored in the means are read out at a cycle corresponding to each VCI declared band.

[0013]

In FIG. 1, cells from the input communication path are input to the cell separation means 1 and separated according to the VCI number set in the cell header, and stored in each cell storage means 2 corresponding to each VCI. It Each cell storage means 2 has a FIFO (Firs
t In First Out) type memory having a certain capacity, and the accumulated data is read out from the head cell of one cell accumulating means 2 selected by the cell multiplexing means 4 The cell accumulating means 2 is selected, and the first cell in the cell accumulating means 2 is read and multiplexed on the output communication path and output.

Reading is performed by the read control means 5,
Data corresponding to a band declaration value previously declared for each VCI (call) is set in the read control means 5 from a control unit (not shown), and the read control means 5 sets cells at each timing. When a signal for selecting the storage means 2 is generated, a cell is read from the corresponding cell storage means 2.

In this way, by reading out each cell accumulating means 2 in a cycle corresponding to each declared band according to each VCI, the cells of each VCI are at the speed within the declared band on the output communication path. Burst cells can be smoothed and output.

In FIG. 1, maximum cell storage amount setting means 3 is provided corresponding to each cell storage means 2. The maximum cell storage amount setting means 3 controls the cell storage amount by setting the number of cells (maximum value) that can be stored and stored in the cell storage means 2 according to the band declared value declared for each VCI from the control unit. Used when possible. When the maximum value is supplied from the maximum cell storage amount setting means 3 to the cell storage means 2, the cell storage means 2
When the number of accumulated cells reaches the maximum value, does not accumulate even if more cells are input (cell discard). Therefore, even if a large number of cells arrive instantaneously in a burst, it can be suppressed at this stage.

The first principle configuration of the read control means (5 in FIG. 1) shown in FIG. 2 will be described. Data of the VCI number (or the cell storage unit 2 number) is written to each address of the selection number storage unit 20 from the control unit. This data is stored in addresses that are evenly spaced by the number proportional to the declared bandwidth of each VCI stored in each cell storage unit 2. The selection number accumulating means 20 is read with the count value of the cycle counter 21 as a read address, and the read data is supplied to the cell multiplexing means 4. In this example,
Each address of the selection number storage means 20 has a cycle counter 21.
Are read in the order of addresses.

Next, the second principle configuration of the read control means shown in FIG. 3 will be described. In the selection number accumulating means 20 of FIG. 3, the VCI number (or the cell accumulating means 2 number) data is written to each address from the control section as in the first principle configuration of FIG. Optional (no need to be evenly spaced). The address for reading this data is generated from the random counter 22. Therefore, the cell accumulating means 2 is read out in an order not related to the position of the write address of the selection number accumulating means 20.

[0019]

FIG. 4 is a block diagram of the first embodiment, FIG. 5 is a block diagram of the second embodiment, FIG. 6 is a configuration example of a FIFO, and FIG. 7 is a diagram showing a portion to which the present invention is applied in an ATM network. .

In the configuration of the first embodiment shown in FIG. 4, the input communication path is 8
It has a bandwidth of Mbps (megabits per second), and the VCI is the first on the input communication path (displayed as # 1).
Cell (report band is 4 Mbps) and VCI is number 4 (#
It is assumed that the cell of 4) (declared band is 1 Mbps) is currently input.

In FIG. 4, reference numeral 40 denotes a VCI extraction unit, 41
Is a decoder, 42 is a FIFO (two-port memory for writing and reading simultaneously) which is a buffer for cell storage provided for each VCI, and 43 is a threshold of the cell storage amount (cell storage amount corresponding to each FIFO). The maximum value of the threshold), 44 is a selector for multiplexing cells,
Reference numeral 45 is a decoder, and 46 is a RAM (Random Access Memo) in which data for controlling the selection operation of the selector is stored.
ry) and 47 are 8-cycle counters. The RAM is 8
It has a data storage capacity corresponding to each address.

The operation of the embodiment shown in FIG. 4 will be described. 8 Mb
VCI # 1 with declared bandwidth of 4 Mbps on ps input communication path
, And the cell of VCI # 4 having the declared band of 1 Mbps are statistically multiplexed and sent to the input communication path, but these cells do not always arrive in the band of the declared value.

The VCI extraction unit 40 extracts the VCI from the header of the cell on the input communication path and identifies it in the decoder 41. According to the identification result of the decoder 41, the FIFO 42 having a corresponding number is write-driven, and the arriving cell is written in the corresponding FIFO 42, that is, FIFO # 1 and FIFO # 4.

For the FIFO 42 corresponding to each VCI,
When controlling the storage amount by setting the maximum storage cell amount, a threshold value is set in advance by the control unit (not shown).
Set to 3. This output is supplied to the corresponding FIFO 42, and each FIFO 42 performs the accumulation operation of the input cell within the range not exceeding the threshold value.

FIG. 6 shows an example of the structure of the FIFO. This operation will be described. The cell input to the FIFO is written in the cell buffer when the write signal is supplied, the cell number counter 61 counts up (+1), and the read signal is input to add one cell. When read, the cell number counter 61 counts down (-1). Therefore, the count number of the cell number counter 61 represents the number of cells accumulated in the cell buffer 60.

The count value of the cell number counter 61 is compared with the threshold value output from the threshold value setting section (43 in FIG. 4) in the comparison circuit 62, and when the counter value exceeds the threshold value, it is "0". Occurs, otherwise "1" occurs. Therefore, the write signal of the cell buffer 60 is
The AND circuit 63 is supplied to the cell buffer when "1" is supplied from the comparison circuit 62, and is not supplied to the cell buffer when "0", and the input cell is not written (discarded) at this time. .

The communication quality such as cell discard for the input traffic characteristics is adjusted according to the threshold value set in the threshold value setting / setting section 43. For example, if the threshold value is set higher, the cell discard rate for an instantaneous burst can be reduced.

In the case of FIG. 6, one FIFO buffer is provided corresponding to one VCI, but in reality, one buffer is physically separated for each VCI and a plurality of buffers are provided. A configuration of accumulating cells of VCI can be adopted.

Returning to the explanation of FIG. 4, in the RAM 46, according to the declared bandwidths 4 Mbps and 1 Mbps of VCI # 1 and VCI # 4 from the control unit, as shown in FIG. A VCI number is assigned (written). That is, since the band of the cell of VCI # 1 is 4 Mbps, 1/1 / the band of the communication path is 8 Mbps.
2 and 4 out of 8 total addresses in RAM 46 (A
DDR1, 3, 5, 7) are used, and the allocation method is every other address. Similarly, since the cell band of VCI # 4 is 1 Mbps, 1 / of the communication channel band of 8 Mbps is used.
8, that is, 1 address (ADDR2) is allocated.

The RAM 46 is sequentially read by using the counter value output from the 8-cycle counter 47 as an address, the VCI number read from the RAM 46 is identified by the decoder 45, and a read signal is output to the FIFO 42 corresponding to the number. On the other hand, the read VCI number is also supplied to the selector 44. The selector 44 selects the read FIFO 42 and sends the read cell to the output communication path.

Even if the number of cells arriving in this manner has a burst-like traffic characteristic and the number of cells arriving momentarily increases, the declared band can be protected after being read from the FIFO, and the traffic can be further protected. The characteristics are smoothed.

Explaining the configuration of the second embodiment shown in FIG. 5,
Reference numerals 50 to 56 in FIG. 5 are circuits or devices similar to those in 40 to 46 in FIG. Reference numeral 57 is an 8-period pseudo random number generation counter.

In the case of the second embodiment, the addresses of the RAM 56 are assigned to the RAM 56 in accordance with the instruction from the control unit at the rate of the band in which each VCI in the band of the communication path is declared. At this time, unlike the case of the first embodiment, the allocation method of each VCI can be freely set to an empty address of the RAM 56.

This RAM 56 is read by using the output of the 8-period pseudo random number generation counter 57 as an address, takes out a cell from the FIFO 52 of the VCI number outputted, and sends it to the output communication path. As a result, even if the arriving cell has a bursty traffic characteristic, the declared band can be protected after being read from the FIFO 52, and the traffic characteristic can be smoothed.

Next, the part of the ATM network to which the present invention is applied will be described with reference to FIG. A. of FIG. Is a layout diagram of the central exchange, and a mechanism (for example, a polishing mechanism) according to the bandwidth control method of the present invention can be provided at a position where input communication paths from a plurality of remote concentrators input to the exchange. In addition, in FIG. In the above case, a mechanism is provided by the bandwidth control system of the present invention at the portion where each subscriber line is input in each remote concentrator. Similarly, other VCs
It can be applied to the part for transmitting I cells.

[0036]

According to the present invention, even if a cell in which traffic is instantaneously increased occurs, the traffic characteristic after being output from the cell accumulating means is smoothed within the declared band (Traffic shap).
Therefore, it is possible to control even when the traffic increases instantaneously, and it is possible to improve the service quality such as cell discard.

Further, as a result of smoothing traffic characteristics, the buffer amount can be reduced when setting a network, which is economical. Further, by adding a maximum cell storage amount setting means which can freely set the queue length of the cell storage means provided for each VCI, even if a burst occurs in the input traffic characteristic, the amount of cells discarded from the cell storage means. Can be adjusted.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is a first principle configuration diagram of a read control unit.

FIG. 3 is a second principle configuration diagram of the read control means.

FIG. 4 is a configuration diagram of a first embodiment.

FIG. 5 is a configuration diagram of a second embodiment.

FIG. 6 is a structural example of a FIFO.

FIG. 7 is a diagram showing a portion to which the present invention is applied in an ATM network.

FIG. 8 is a configuration diagram of Conventional Example 1.

FIG. 9 is a configuration diagram of Conventional Example 2.

[Explanation of symbols]

1 cell separation means 2 cell storage means 3 Maximum cell storage amount setting means 4 cell multiplexing means 5 Read control means

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Ryuichi Takechi             1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture             Within Fujitsu Limited (72) Inventor Ken Kawasaki             1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture             Within Fujitsu Limited

Claims (4)

[Claims] 1. A band control method for a cell transmitted on a communication path of an ATM network, wherein a cell having a plurality of different VCIs (virtual channel numbers) for call identification is statistically multiplexed from a communication path to a cell for each VCI. Cell separating means for allocating, cell accumulating means for accumulating cells for each VCI, read control means for controlling reading of cells from the cell accumulating means, and cells read from the cell accumulating means under control of the read controlling means. The read control means is provided with a cell multiplexing means for multiplexing, and the read control means reads the read from the cell storage means corresponding to each VCI in accordance with the ratio of the band previously declared for each VCI in the band of the communication path transmitting the cell. A bandwidth control method in an ATM network. 2. The cell storage means for each VCI according to claim 1, wherein a maximum storage amount setting means for setting a queue length that can be stored is provided, and an input traffic characteristic is set according to a set value of the maximum storage amount setting means. A band control system in an ATM network, characterized in that the amount of cell discard in a cell storage means when a burst occurs is adjusted. 3. The read control means for controlling the reading of a cell from the cell storage means according to claim 1, comprising a selection number storage means for storing a selection number of the cell storage means to be read, and a selection number storage means. The selection number accumulating means is configured by a cycle counter that sequentially specifies addresses, and the selection number accumulating means allocates each VCI in the band of the communication path for transmitting cells so that the VCI has a pre-declared band ratio and the address intervals are even. Characteristic AT
Bandwidth control method in M network. 4. The read control means for controlling reading of a cell from the cell storage means according to claim 1, comprising a selection number storage means for storing a selection number of the cell storage means for reading and a selection number storage means. The selection number accumulating means is configured by a counter that randomly designates addresses, and the selection number accumulating means allocates at a rate of the band previously declared by each VCI in the band of the communication path for transmitting cells, and reads from the selection number accumulating means at random. A bandwidth control method in an ATM network characterized by performing.