JP3000990B2 - Discard priority control method and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a buffer discard priority control method, and more particularly to an ATM (Asynchronous Transfer) method.
Mode; Asynchronous Transfer Mode) The present invention relates to a method and system for controlling priority of discarding a buffer used in a communication device.

[0002]

2. Description of the Related Art Conventionally, as a discard priority control method of this type, for example, Japanese Patent Laid-Open Publication No. Hei 4-369139 discloses that a storage amount of cells stored in a buffer in a switch is determined by a discard level added to an input cell. (Class) is compared with a threshold value set in correspondence with the threshold value. Based on the comparison result, the input cell is written into the buffer only when the cell accumulation amount of the buffer is smaller than the threshold value. If it is larger than the threshold value, the input cells are discarded, and when the amount of cells stored in the buffer increases, the lower priority cells are sequentially discarded, and the control is performed so that the higher priority cells are not discarded. Control schemes have been proposed.

FIG. 4 is a block diagram for explaining a conventional discard priority control method. Referring to FIG. 4, an input cell 100 is a cell that is switched by a switch unit of an output buffer type ATM switch and is input to an output buffer unit for each output line. Discard class 1 threshold 1
.., And the threshold 101-N of the discard class N hold the threshold of each discard class.

A discard class detector 102 detects a discard class from header information added to an input cell and notifies the selector 103 of the discard class. The selector 103 sets the threshold of the discard class notified from the discard class detection unit 102 to the threshold 101-1 of the discard class 1, the threshold 101-2 of the discard class 2,
.., The write control unit 105 is selected from the threshold values 101-N of the discard class N and notified.

[0005] The cell storage amount detector 104 detects the number of cells stored in the buffer memory 106 and notifies the write controller 105. The write control unit 105 compares the cell storage amount of the buffer memory unit 106 notified from the cell storage amount detection unit 104 with the threshold value notified from the selector 103, and determines whether to write the input cell to the buffer memory unit 106. Judge and notify the buffer memory unit 106.

The buffer memory unit 106 writes an input cell in accordance with an instruction from the write control unit 105,
Cell reading is performed at regular intervals. Further, it notifies the cell storage amount detection unit 104 of information for detecting the cell storage amount.

Next, the operation of the conventional discard priority control method will be described. In the discard class detector 102, the input cell 10
The discard class is detected from the 0 header information, and the selector 10
Threshold values 101-1, 101 of each discard class set in 3
A threshold value corresponding to the discard class of the input cell is selected from -2, ..., 101-N. The selected threshold value is compared with the cell accumulation amount in the buffer memory unit 106. If the cell accumulation amount is smaller than the threshold value, the input cell is written into the buffer memory unit 106, and the accumulation number of the cell accumulation amount detection unit 104 is counted up. On the other hand, if the cell storage amount is larger than the threshold, the input cell is discarded.

[0008] Here, the threshold value 101-1 of each discard class,
.., 101-N according to the priority of the discarding class, the threshold value of the low-priority class is set to a low value, and the threshold value of the high-priority class is set to a high value. In this case, since the storage amount of the buffer memory unit 106 increases, control is performed such that input cells of a class having a lower priority of a discard class are discarded in order.

FIG. 5 is a diagram showing the relationship between the cell accumulation amount of the buffer and the threshold value.
If it is less than the discard class, the input cell is written into the buffer regardless of the discard class. If the cell accumulation amount of the buffer is equal to or larger than the threshold th1, only the cells of the class with high discard priority (discard class 2) are written into the buffer. This indicates that cells in a lower class (discard class 1) are discarded.

[0010]

However, in the above-described conventional discard priority control method, the sum of the accumulated amounts of cells of all discard classes stored in the buffer is compared with the threshold value of the discard class of the input cell. Then, it is determined whether to discard the input cell.

For this reason, the cell discard rate of the discard class is determined only by the traffic of the discard class.
In the above-mentioned conventional method, the influence of traffic of other discard classes is very large.

Further, in the above-mentioned conventional method, all cells having a low discard priority are all stored in cells of a high priority class while the threshold value of the class of a low discard priority is larger than the threshold value. There is also a problem of being discarded.

Accordingly, the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a discard priority control method for performing priority control of a plurality of discard classes using only one buffer. It is an object of the present invention to provide a discard priority control method and method which are hardly affected by the traffic.

Another object of the present invention is to provide a discard priority which guarantees a minimum band in which cells of a discard class having a low discard priority can pass through an ATM switch even when traffic of a discard class having a high discard priority is congested. It is to provide a control method and method.

[0015]

In order to achieve the above object, the present invention provides a method for controlling the discard priority of an output buffer type ATM switch , wherein a threshold value is set for each discard class,
If the accumulated amount of cells of the same discard class as the input cell exceeds the threshold, or if the buffer is full,
It is characterized in that input cells are discarded. Departure
The description is based on the discard class information added to the entered cell.
Buffer type ATM switch that performs priority control of cell discard
In the switch cell discard priority control method,
Discard class that detects the discard class for these input cells.
Output detection port, and the output port stores cells.
The buffer to be loaded and all cells stored in the buffer.
Counting means for counting the volume and provision corresponding to the disposal class
And the accumulated amount of cells in the buffer for each discard class.
Counting means for counting the number of cells, and discarding cells in the buffer.
Memory that stores the threshold value for determining
And the discard class detected by the discard class detecting means.
The count corresponding to the discard class selected based on
The same discard class as the discard class counted by the means
Based on the cell accumulation amount and the detected discard class
A threshold of the storage means corresponding to the selected discard class
Value and the comparison result, and the total cell accumulation of the buffer
Write the input cells into the buffer, taking into account the quantity
Means for determining whether or not to discard .

Another feature is that the area obtained by subtracting the threshold value of one discard class from the queue length of the buffer becomes the minimum buffer amount that can be used by the other discard class.

[Summary of the Invention] According to the present invention, the cell storage amount stored in the buffer is counted for all cells and two types for each discard class, and a threshold value is set for the cell storage amount for each discard class. Thus, cell discard due to the cell storage amount exceeding the threshold is not affected by traffic of other discard classes.

[0018]

Next, a preferred embodiment of the present invention will be described. In a preferred embodiment of the cell discard priority control method according to the present invention, A is a method for controlling cell discard based on discard class information added to an input cell.
In the cell switch priority control method of the TM switch, the accumulated amount of cells accumulated in the buffer is measured for each discard class,
A threshold value for the cell storage amount in the buffer is set for each discard class, and the current storage amount in the buffer of cells of the same class as the discard class is set for the input cell based on the discard class of the cell. , And a threshold value corresponding to the discard class, and based on the comparison result and the total cell storage amount of the buffer, it is determined whether the input cell is written / discarded in the buffer.

In a preferred embodiment of the cell discard priority control method according to the present invention, a buffer (7 in FIG. 1) for accumulating cells and a counting means for counting all cell accumulation amounts in the buffer (7 in FIG. 1). (3 in FIG. 1) and counting means (2 in FIG. 1) provided corresponding to the discard class and counting the amount of accumulated cells in the buffer (7 in FIG. 1) for each discard class.
-1, 2-2), and storage means (1-1, 1-2 in FIG. 1) storing a threshold for judging cell discard in the buffer (7 in FIG. 1) for each discard class. A means for detecting the discard class of the cell (5 in FIG. 1) and a selection means (4-2 in FIG. 1) based on the discard class detected by the discard class detection means (5 in FIG. 1). The selection means (4-1 in FIG. 1) based on the accumulated amount of cells of the same discard class as the discard class counted by the counting means corresponding to the discard class and the detected discard class. Means for writing or discarding the input cell in the buffer in consideration of the comparison result with the threshold value of the storage means corresponding to the discard class and the total cell storage amount of the buffer (7 in FIG. 1). (6 in FIG. 1).

[0020]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; FIG. 1 is a diagram showing the configuration of one embodiment of the present invention. Referring to FIG. 1, in one embodiment of the present invention, an input cell 8 is a cell that is switched by a switch unit of an output buffer type ATM switch and is input to an output buffer unit for each output line.

The discard class 1 threshold 1-1 stores the setting of the discard class 1 threshold. Discard class 2 threshold 1-2
Stores the setting of the threshold value of the discard class 2.

Cell discard amount detecting section 2-1 of discard class 1
Is the discard class 1 stored in the buffer memory unit 7.
The amount of accumulated cells is measured. The discard class 2 cell storage amount detector 2-2 measures the storage amount of the discard class 2 cells stored in the buffer memory unit 7.

The cell storage amount detector 3 measures the total storage amount of cells of all discard classes stored in the buffer memory unit 7.

The discard class detector 5 detects the discard class of the input cell from the header information of the input cell 8.

The selector 4-1 selects either the threshold 1-1 of the discard class 1 or the threshold 1-2 of the discard class 2 according to the discard class of the input cell detected by the discard class detector 5. The selector 4-2 selects either the cell storage amount 2-1 of the discard class 1 or the cell storage amount 2-2 of the discard class 2 according to the input cell discard class detected by the discard class detection unit 5.

The write / read control unit 6 determines the threshold of the same discard class as the input cell notified from the selectors 4-1 and 4-2, the cell storage amount of the same discard class as the input cell, and the buffer memory unit 7. It is determined whether or not the input cell is to be written into the buffer memory unit 7 based on the total cell storage amount.

When cells are stored in the buffer memory section 7, cell read control is performed in the order of writing.

The buffer memory section 7 is composed of storage means capable of temporarily storing cells and reading them out in the order of writing.

Next, the operation of the embodiment of the present invention will be described with reference to FIG.

The discard class detector 5 detects the discard class from the header information of the input cell 8. According to the detected discard class of the input cell, the selector 4-1 selects a threshold value of the same discard class as that of the input cell from the threshold values 1-1 and 1-2 of the set discard classes. 4-
In 2, the cell storage amount detection units 2-1 and 2-
From 2, the storage amount of the same discard class as the input cell is selected.

The write / read control unit 6 determines that the cell storage amount of the same discard class as the input cell is smaller than the selected threshold value and that the cell storage amount of the buffer memory unit 7 is smaller than the buffer amount. , Instructs the buffer memory unit 7 to write, writes the input cells into the buffer memory unit 7, and counts up the cell accumulation amount detection unit 3 and the cell accumulation amount detection unit 2-1 or 2-2 of the corresponding discard class. Instruct and count up the number of cells stored.

On the other hand, when the cell storage amount of the same discard class as the input cell is larger than the selected threshold value, or when the total cell storage amount of the buffer memory unit 7 is larger than the queue length of the buffer memory unit 7, Does not issue a write instruction to the buffer memory unit 7, discards the input cell, and stores the cell accumulation amount detection unit 3 and the cell accumulation amount detection unit 2-
No count-up instruction is issued to 1 or 2-2.

Further, while the cell storage amount of the cell storage amount detection unit 3 is not 0, the write / read control unit 6 instructs the buffer memory unit 7 to perform reading, and writes cells one by one in the order in which the cells are written from the buffer memory unit 7. The discarded class of the read cell is read out, and the countdown is instructed to the cell storage amount detection unit 3 and the cell storage amount detection unit 2-1 or 2-2 of the corresponding discard class, and the corresponding cell storage number is determined. Count down.

FIG. 2 is a diagram showing the relationship between the buffer accumulation amount and the threshold value in one embodiment of the present invention. A class having a high discard priority is referred to as a discard class 2 and a class having a low discard priority is referred to as a discard class 1.

When the input cell is of the discard class 1, only when the accumulation amount of the discard class 1 is less than the threshold thL and the sum of the accumulation amounts of the cells of all the discard classes of the buffer is smaller than the queue length of the buffer, The input cells are written to the buffer, and if the accumulated amount of the discard class 1 is equal to or larger than the threshold thL or the sum of the accumulated amounts of cells of all the discard classes of the buffer is equal to the queue length of the buffer, the input cells are discarded.

On the other hand, when the input cell is of the discard class 2, if the accumulation amount of the discard class 2 is less than the threshold thH and the sum of the accumulation amounts of the cells of all the discard classes of the buffer is smaller than the queue length of the buffer. Only when the input cell is written to the buffer, the input cell is discarded when the accumulated amount of the discard class 2 is equal to or larger than the threshold thH or when the sum of the accumulated amounts of cells of all discard classes of the buffer is equal to the queue length of the buffer.

Therefore, cells of the discard class 1 can be written in at least the area obtained by subtracting the threshold thH from the queue length of the buffer, and cells of the discard class 2 can be written in the area obtained by subtracting the threshold thL from the queue length of the buffer. Writable.

Next, the present invention is applied to an N × N output buffer type A.
An embodiment applied to a TM switch will be described with reference to FIG.

Referring to FIG. 3, the input cells 15-1, 1
,..., 15-N are switched by the switch unit 17 and output buffer units 19-
1, 19-2,..., 19-N.

The MUX (multiplex) unit 16 performs time division multiplexing on the input cells 15-1, 15-2,..., 15-N in order to process the cells one by one.

The discard class detection circuit 13 is provided with the input cell 15
, 15-2,..., 15-N, the discard class of the input cell is detected. The switch unit 17 sorts cells according to cell route information.

FIFO (First In First)
Out: a first-in first-out buffer memory) 18 is a memory for temporarily storing cells and reading out the cells in the order of writing.

The threshold register 10-1 of the discard class 1 is
The setting of the threshold value of the discard class 1 is stored. The discard class 2 threshold register 10-2 stores the setting of the discard class 2 threshold.

The cell accumulation counter 11- for the discard class 1
1 measures the storage amount of cells of the discard class 1 stored in the FIFO 18. The discard class 2 cell storage amount counter 11-2 measures the storage amount of the discard class 2 cells stored in the FIFO 18.

The cell storage amount counter 12 has a FIFO 18
The total amount of cells of all discard classes stored in the cell is measured.

The selector 4-1 includes a discard class detection circuit 1
According to the discard class of the input cell detected in step 3, either the value of the threshold register 10-1 of the discard class 1 or the value of the threshold register 10-2 of the discard class 2 is selected. The selector 4-2 determines whether the value of the cell accumulation counter 11-1 of the discard class 1 or the value of the cell accumulation counter 11-2 of the discard class 2 according to the discard class of the input cell detected by the discard class detection circuit 13. Select one or the other.

The write / read control circuit 14 determines the threshold value of the discard class of the input cell notified from the selectors 4-1 and 4-2, the cell storage amount of the same discard class as the input cell, and the total cell storage amount of the FIFO 18. It is determined from the output path information of the input cell notified from the switch (SW) unit 17 whether or not the input cell is to be written into the FIFO 18, and
If cells are stored in the cell 18, the cells are read out at regular intervals in the order in which they were written.

Output port sections 19-1, 19-2,..., 1
9-N are threshold registers 10- for discard classes 1 and 2, respectively.
1, 10-2 and the accumulation amount counter 11 for the discard classes 1 and 2.
-1, 11-2, the cell accumulation counter and the selector 4-1,
4-2, write / read control circuit 14 and FIFO 18
It is composed of The control unit 20 can read and write the threshold registers 10-1 and 10-2 of each discard class.

Next, the operation of this embodiment will be described with reference to FIG.

The input cells 15-1, 15-2,..., 15-
N is time-division multiplexed by the MUX unit 16. The discard class detection circuit 13 detects a discard class from the header information of the input cell. According to the discard class of the detected input cell,
The threshold value 10- of each discard class set by the selector 4-1
The threshold of the same discard class as that of the input cell is selected from 1, 10-2, and the selector 4-2 stores the same discard class as that of the input cell from the cell storage amount detection counters 11-1 and 11-2 of each discard class. Choose the amount.

The write / read control circuit 14 determines that the cell storage amount of the same discard class as the input cell is smaller than the selected threshold, the value of the cell storage counter 12 of the FIFO 18 is smaller than the buffer amount, and If the output destination of the input cell notified from the unit 17 matches its own port, a write enable is output to the FIFO 18,
The input cell is written into the FIFO 18, and the cell accumulation counter 12 and the cell accumulation counter 11-1 of the corresponding discard class are written.
Alternatively, a count-up enable is output to 11-2, and the number of stored cells is counted up.

On the other hand, if the cell storage amount of the same discard class as the input cell is larger than the selected threshold,
If the value of the total cell storage amount counter 12 of the FO 18 is
If the queue length is larger than the queue length of O18, or if the output destination of the input cell notified from the switch unit 17 is different from its own port, the write enable is not output to the FIFO 18, the input cell is discarded, and the cell accumulation amount Counter 12 and cell accumulation counters 11-1 and 11-2 for each discard class
Does not output a count-up instruction.

Further, the write / read control circuit 14
Outputs a read enable to the FIFO 18 at regular intervals while the cell accumulation amount of the cell accumulation amount counter 12 is not 0, reads out the cells one by one in the order of writing the cells from the FIFO 18, and detects the discard class of the read out cell. And
A countdown enable is output to the cell accumulation counter 12 and the cell accumulation counter 11-1 or 11-2 of the corresponding discard class to count down the cell accumulation number.

[0054]

As described above, according to the present invention, the following effects can be obtained.

A first effect of the present invention is that the cell discard rate of one discard class is hardly affected by traffic of another discard class.

The reason is that, in the present invention, the cell storage amount is measured for each discard class, a threshold value for the cell storage amount of each discard class is set, and the discard class storage amount is compared with the threshold value of the corresponding discard class. This is because whether to perform discarding is determined based on whether the discard class exceeds the threshold value for each discard class.

The second effect of the present invention is that even when the traffic of a cell of a class with a high discard priority is extremely congested, a minimum bandwidth can be guaranteed for cells of a class with a low discard priority. That's what it means.

The reason is that, in the present invention, the cell accumulation amount is measured for each discard class, and a threshold value is set for the cell accumulation amount of each discard class. This is because, by setting the value to be smaller than the length, the value obtained by subtracting the threshold value of the class with the higher discarding priority from the queue length of the buffer becomes the buffer area where the class with the lower discarding priority can always be used.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a relationship between a queue length and a threshold of a buffer memory unit in FIG. 1;

FIG. 3 is a block diagram showing a configuration of another embodiment of the present invention.

FIG. 4 is a block diagram for explaining a conventional output buffer type ATM switch discard priority control method.

5 is a diagram illustrating an example of a relationship between a queue length and a threshold of the buffer memory unit in FIG. 4;

[Explanation of symbols]

1-1, 1-2 Threshold of each discard class 2-1, 2-2 Cell storage amount measuring unit of each discard class 3 Cell storage amount detection unit 4-1, 4-2 Selector 5 Discard class detection unit 6 Write / read Control unit 7 Buffer memory unit 8 Input cell 10-1, 10-2 Threshold register of each discard class 11-1, 11-2 Cell accumulation counter of each discard class 12 Cell accumulation counter 13 Discard class detection circuit 14 Write / read Control circuit 15-1, 15-2, ..., 15-N Input cell 16 MUX unit 17 Switch unit 18 FIFO 19-1, 19-2, ..., 19-N Each output port 20 Control unit 100 Input cell 101-1 , 101-2,..., 101-N Threshold of each discard class 102 Discard class detector 103 Selector 104 Cell storage amount detector 105 Write controller 06 buffer memory unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04L 12/28 H04L 12/56

Claims (2)

(57) [Claims] An input cell is switched by a switch unit and input to an output buffer provided corresponding to an output port, and the output buffer has a plurality of discard classes.
In an output buffer type ATM switch cell discard priority control method in which an input cell is input and priority control of a plurality of discard classes is performed based on cell discard class information of the input cell, a plurality of types of discard input to the output buffer Has class
Output buffer for each discard class for input cells to be
May be set a threshold for the cell storage amount in the inner, counts all cells accumulated amount in the output buffer
Together with discarding the cell accumulation amount in the output buffer
Counted for each class, based on the cell discard class information of an input cell, compares the cell storage amount in the output buffer of the discard class of the same cell discard class, and a threshold value set with respect to the discard class If the result of comparison indicates that the cell storage amount exceeds the threshold value or that the output buffer is full,
A discard priority control method, wherein the input cell is controlled to be discarded. 2. An output buffer type A for performing priority control of cell discard based on discard class information added to an input cell.
A cell discard priority control method of a TM switch, comprising: a discard class detecting means for detecting a discard class of an input cell from an input port; and an output port for storing a cell having a plurality of types of discard classes ; Counting means for counting all cell accumulation amounts in the buffer; counting means provided corresponding to discard classes, for counting the cell accumulation amount in the buffer for each discard class; and judging cell discarding in the buffer. Storage means storing a threshold value for each discard class, and the same as the discard class selected by the discard class detected by the discard class detection means and counted by the counting means corresponding to the discard class. Corresponds to the accumulated amount of cells in the discard class and the discard class selected based on the detected discard class A threshold of the memory means that,
Means for judging whether to write or discard the input cell in the buffer in consideration of the comparison result of (1) and the total cell storage amount of the buffer.