JP3652966B2 - Back pressure threshold automatic change method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a back pressure threshold automatic change system, and more particularly to a back pressure threshold automatic change system of an ATM switching system.
[0002]
[Prior art]
Conventionally, this type of back pressure threshold automatic change method is used for the purpose of reducing discard of high-quality ATM cells, as in, for example, a buffer threshold control system for an ATM network described in Japanese Patent Laid-Open No. 6-244858. .
[0003]
FIG. 10 is a block diagram showing a configuration of a conventional back pressure threshold automatic changing method. Referring to FIG. 10, the conventional back pressure threshold automatic change method is different from the buffer 10 for accumulating arriving ATM cells, the queue length measuring means 11 for measuring the queue length of the buffer 10, and the output of the queue length measuring means 11 separately. The comparison means 12 for comparing the input threshold value, the control unit 20 for giving the optimum threshold value to the comparison means 12 every time a call is received based on the information given from the signal message, and the comparison result of the comparison means 12 Correspondingly, cell discarding means 13 for performing discard control of ATM cells arriving at the buffer 10 is provided.
[0004]
Next, the operation will be described. An ATM cell and a signal message are received from the input line. In the control unit 20, the CLP detection unit 21 detects the value of the CLP bit for each ATM cell from the signal message and notifies the CPU 22 of the value. Further, the CPU 22 calculates the CLP ratio for each call, reads the corresponding threshold value from the threshold value table 23 a in the memory 23, and gives it to the input of the comparison means 12 as a queue length threshold value.
[0005]
The comparison unit 12 compares the buffer usage rate from the queue length measurement unit 11 with the threshold value. When there are many arrivals of low quality ATM cells, the threshold value is decreased. Then, the cell discarding means 13 discards the low-quality ATM cell, and minimizes the discard of the high-quality ATM cell.
[0006]
Thus, when a high-quality ATM cell arrives, the cell is stored as long as there is a vacancy in the buffer 10, but when a low-quality ATM cell arrives, if the queue length exceeds the threshold, the cell discarding means 13 To discard the ATM cell.
[0007]
[Problems to be solved by the invention]
In the above-described prior art, only the reduction of discard of high-quality ATM cells is taken into consideration, so that there are problems such as cell loss due to delay and fluctuation of high-quality ATM cells, PCR (PEAK CELL RATE) excess, echo, and the like. was there.
[0008]
Further, the conventional technique has a problem that a cell discarding means must be newly provided in order to discard a low-quality ATM cell.
[0009]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a back pressure threshold automatic setting method capable of reducing delay and fluctuation of a high-quality ATM cell.
[0010]
Another object of the present invention is to provide a back pressure threshold automatic setting method capable of discarding low-quality ATM cells without using cell discarding means.
[0011]
[Means for Solving the Problems]
The invention according to claim 1 is a backpressure threshold automatic change system, wherein an input buffer unit that temporarily stores input cells, an ATM switch unit that exchanges and connects cells sent from the input buffer unit, and An output buffer unit that temporarily stores cells transmitted from the ATM switch unit, and suppresses cell transmission to the input buffer unit when the cell accumulation amount exceeds a preset threshold; and the input buffer unit A fluctuation measurement unit that measures fluctuation of an input cell and outputs a threshold value change request signal that requests the change of the threshold value when the measurement result is out of an allowable range, and a threshold value that should be changed according to a request from the fluctuation measurement unit And a threshold value control unit that changes the threshold value of the output buffer unit.
[0012]
The invention according to claim 2 is characterized in that the fluctuation measuring unit includes a threshold change timer unit that notifies threshold change timing, and a high-quality ATM cell that is input to the input buffer unit at a timing notified from the threshold change timer unit. A fluctuation monitoring unit that monitors an arrival interval, a fluctuation value calculation unit that calculates a fluctuation value from the arrival interval, and the fluctuation value is compared with a preset allowable fluctuation value. And a fluctuation value comparison unit that outputs a threshold value change request signal.
[0013]
According to a third aspect of the present invention, the threshold control unit determines a new threshold by receiving the threshold change request signal, and a threshold for setting the threshold determined by the threshold determination unit in the output buffer unit And a change function.
[0014]
The invention according to claim 4 is a back pressure threshold automatic change system, wherein an input buffer unit that temporarily stores input cells, an ATM switch unit that exchanges and connects cells sent from the input buffer unit, and An output buffer unit that temporarily stores cells transmitted from the ATM switch unit, and suppresses cell transmission to the input buffer unit when the cell accumulation amount exceeds a preset threshold; and the input buffer unit A delay and fluctuation measuring unit for measuring a fluctuation value and a delay value of an input cell, and outputting a threshold value change request signal for requesting the change of the threshold value when the fluctuation value or the delay value is out of an allowable range; And a threshold value control unit that determines a threshold value to be changed according to a request from the delay and fluctuation measurement unit and changes the threshold value of the output buffer unit.
[0015]
According to a fifth aspect of the present invention, the delay and fluctuation measurement unit is a threshold change timer unit that notifies a threshold change timing, and a high-quality ATM that is input to the input buffer unit at a timing notified from the threshold change timer unit. A delay and fluctuation monitoring unit for monitoring the arrival interval of cells; a delay and fluctuation value calculating unit for calculating a fluctuation value and a delay value from the arrival interval; an allowable fluctuation value in which the fluctuation value and the delay value are set in advance; and And a delay and fluctuation value comparison unit that outputs a threshold value change request signal when the fluctuation value or the delay value is outside the allowable range in comparison with an allowable delay value.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an embodiment of an automatic back pressure threshold change system according to the present invention. Referring to FIG. 1, the embodiment of the present invention includes an input buffer unit 1, an ATM switch unit 2, an output buffer unit 3, a fluctuation measurement unit 4, a threshold control unit 5, and a line output unit 6.
[0017]
The input buffer unit 1 temporarily accumulates input cells for each service class and outputs them to the ATM switch unit 2. When a back pressure request is received from the output buffer unit 3, transmission of low quality ATM cells is suppressed, and when the input buffer for low quality ATM cells is full, the low quality ATM cells are discarded.
[0018]
The ATM switch unit 2 is connected between the input buffer unit 1 and the output buffer unit 3 to perform cell exchange connection. Normally, cells are input from the line cell input 100 to the ATM switch unit 2 and stored in the output buffer unit 3 through the output buffer input line 110. The cells output from the output buffer unit 3 are output from the output buffer output line 150 via the line output unit 6.
[0019]
The output buffer unit 3 temporarily accumulates the cells output from the ATM switch unit 2 and outputs the cells to the line via the line output unit 6. The number of cells that can be stored in the output buffer unit 3 is set in advance as a queue length threshold value. When the cell storage amount exceeds the threshold value, back pressure is generated for the input buffer unit 1 to suppress cell transmission. The queue length threshold can be changed from the outside. The output buffer unit 3 outputs a service class notification signal 120 indicating the service class of the received cell to the fluctuation measuring unit 4.
[0020]
The fluctuation measuring unit 4 measures the fluctuation of the high-quality ATM cell at a predetermined timing from the service class notification signal 120 received from the output buffer unit 3, and outputs a threshold value change request signal 130 when the measured value is outside the allowable range. To do.
[0021]
Here, the service class refers to a traffic type determined for each path, and in the present embodiment, two classes of a high-quality ATM cell having a high priority and a low-quality ATM cell having a low priority at the time of congestion will be described. Note that the number of service classes in the present invention is not limited to two, and two or more service classes may be provided.
[0022]
Upon receiving the threshold change request signal 130 from the fluctuation measuring unit 4, the threshold control unit 5 determines an appropriate queue length threshold and outputs the threshold change signal 140 to the output buffer unit 3.
[0023]
FIG. 2 is a block diagram showing an internal configuration of the fluctuation measuring unit 4 in FIG.
Referring to FIG. 2, the fluctuation measurement unit 4 includes a threshold change timer function 41, a fluctuation monitoring function 42, a fluctuation value calculation function 43, a maximum allowable fluctuation value storage function 44, a minimum allowable fluctuation value storage function 45, And a fluctuation value comparison function 46.
[0024]
The threshold change timer function 41 is connected to the fluctuation monitoring function 42 and outputs a monitoring timing notification signal indicating the execution timing of the threshold change. A timer value is set in advance in the threshold change timer function 41, and a monitoring timing notification signal is output based on this timer value. As an example of setting the timer value, there is a setting only at the initial stage of system start-up or for every fixed cycle.
[0025]
When the monitoring timing notification signal is notified from the threshold change timer function 41, the fluctuation monitoring function 42 monitors the arrival interval of high-quality ATM cells from the service class notification signal 120 and outputs the monitoring result to the fluctuation value calculation function 43. To do. The fluctuation value calculation function 43 calculates the fluctuation value of the high-quality ATM cell from the monitoring result received from the fluctuation monitoring function 42 and outputs it to the fluctuation value comparison function 46.
[0026]
The maximum allowable fluctuation value storage function 44 is connected to the fluctuation value comparison function 46, and the maximum allowable fluctuation value of the high-quality ATM cell is stored in advance. The maximum fluctuation value is the maximum fluctuation value that can be taken in a range where no cell is lost. This value can be changed from the outside. In addition, for each change, setting for each VPI / VCI is also possible.
[0027]
The minimum allowable fluctuation value storage function 45 is connected to the fluctuation value comparison function 46, and the minimum allowable fluctuation value of the high-quality ATM cell is stored in advance. The minimum allowable fluctuation value is the minimum fluctuation value that can be taken within the range not exceeding the allowable maximum speed on the output line side, and this value can be changed from the outside. In addition, for each change, setting for each VPI / VCI is also possible.
[0028]
The fluctuation value comparison function 46 determines whether or not the fluctuation value received from the fluctuation value calculation function 43 is within the allowable range, and outputs a threshold value change request signal 130 to the threshold value control unit 5 when the fluctuation value is outside the allowable range. As the upper limit value and the lower limit value at the time of determination, the maximum allowable value stored in the maximum allowable fluctuation value storage function 44 and the minimum allowable value stored in the minimum allowable fluctuation value storage function 45 are used.
[0029]
FIG. 3 is a block diagram showing the internal configuration of the threshold control unit 5 in FIG.
Referring to FIG. 3, the threshold control unit 5 includes a threshold determination function 51, a threshold increase value storage function 52, a threshold decrease value storage function 53, and a threshold change function 54.
[0030]
When the threshold value determining function 51 receives the threshold value change request signal 130, the threshold value determining function 51 determines whether the fluctuation measurement value is above or below the allowable range, and decreases or increases the threshold value. The threshold increase value storage function 52 is connected to the threshold determination function 51, and stores an increase amount when the threshold determination function 51 increases the threshold. The threshold decrease value storage function 53 is connected to the threshold determination function 51, and stores a decrease amount when the threshold determination function 51 decreases the threshold.
[0031]
The threshold value change function 54 receives the threshold value determined by the threshold value determination function 51, sends a back pressure threshold value change processing procedure to the output buffer unit 3, and receives the threshold value of the output buffer unit 3 from the threshold value determination function 51. Change to
[0032]
Next, the operation of the embodiment of FIG. 1 will be described in detail.
The input cell is temporarily stored in the input buffer unit 1 and then output to the ATM switch unit 2 via the input buffer output line 100. The ATM switch unit 2 performs an exchange process of the input cell and outputs it to a predetermined output buffer unit 3. The output buffer unit 3 temporarily stores the received cells, and then outputs the cells via the line output unit 6.
On the other hand, the fluctuation measuring unit 4 always receives the service class notification signal 120 from the output buffer unit 3 and measures fluctuations according to the following procedure.
[0033]
FIG. 4 is a flowchart showing a procedure for measuring fluctuations in the fluctuation measuring unit 4.
The fluctuation measuring unit 4 outputs a monitoring timing signal to the fluctuation monitoring function 42 when it is determined that it is time to change the threshold from the timer value preset by the threshold changing timer function 41 (for example, timer value overflow). (Step 401). When receiving the monitoring timing signal, the fluctuation monitoring function 42 immediately monitors the arrival interval of the high-quality ATM cell for each VPI / VCI, and outputs the result to the fluctuation value calculation function 43 (step 402).
[0034]
When the fluctuation value calculation function 43 receives the result of the arrival interval from the fluctuation monitoring function 42, it calculates a fluctuation value for each high-quality ATM cell and outputs it to the fluctuation value comparison function 46 (step 403). The fluctuation value comparison function 46 compares the input value from the fluctuation value calculation function 43 with the input values from the maximum allowable fluctuation value storage function 44 and the minimum allowable fluctuation value storage function 45, and the measured value falls within this allowable range. It is determined whether it is within the range (step 404).
[0035]
If it is within the range, it is determined that there is no problem in the fluctuation of the high-quality ATM cell, and the fluctuation measuring unit 4 is in a state of waiting for the monitoring timing signal reception. If it is out of range, the fluctuation value comparison function 46 sends a threshold value change request signal 130 to the threshold value control unit 5 (step 405). The threshold control unit 5 that has received the threshold change request signal 130 changes the threshold in the following procedure.
[0036]
FIG. 5 is a flowchart showing a threshold changing procedure in the threshold controller 5.
When the threshold value determination function 51 receives the threshold value change request signal 130 (step 501), the threshold value control unit 5 determines whether or not the fluctuation measurement value exceeds the allowable range (step 502). If the threshold value determining function 51 determines that the threshold value is exceeded, the threshold value to be changed from the threshold decrease amount received from the threshold decrease value storage function 53 and the threshold value set in the output buffer unit 3 is determined. It is determined (step 503).
[0037]
If the threshold value determining function 51 determines that the threshold value is below the allowable range, it should be changed from the threshold increase amount received from the threshold value increase value storage function 52 and the threshold value set in the output buffer unit 3. A threshold is determined (step 504). Based on the threshold value determined by the threshold value determination function 51, the threshold value change function 54 sends a threshold value change processing procedure to the output buffer unit 3, and changes the threshold value of the output buffer unit 3 (step 505).
[0038]
When the threshold value of the output buffer unit 3 is changed in a series of these procedures and the threshold value decreases, back pressure is likely to occur, and it is possible to suppress low-quality ATM cells and reduce fluctuations in high-quality ATM cells. Become. The suppressed low-quality ATM cells start to be discarded when the low-quality ATM cell buffer is full. On the other hand, when the threshold value increases, back pressure hardly occurs and the quality of the low quality ATM cell is improved.
[0039]
As described above, in the first embodiment, by monitoring the fluctuation and optimizing the threshold value of the output buffer unit 3, the quality or delay of the low-quality ATM cell is ensured while ensuring the quality of the high-quality ATM cell. Processing can be reduced.
[0040]
Next, a second embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 6 is a block diagram showing the configuration of the second embodiment, and is characterized in that a delay and fluctuation measuring unit 7 is provided instead of the fluctuation measuring unit 4 in the first embodiment. The delay and fluctuation measurement unit 7 measures the delay value in addition to the measurement of the fluctuation value. In FIG. 6, the same reference numerals as those shown in FIG. 1 have the same functions, and detailed description thereof is omitted.
[0041]
FIG. 7 is a block diagram showing an internal configuration of the delay and fluctuation measuring unit 7. Referring to FIG. 7, the delay and fluctuation measuring unit 7 includes a delay and fluctuation monitoring function 71, a threshold change timer function 41, a delay and fluctuation value calculation function 72, a maximum allowable fluctuation value storage function 44, and a minimum allowable fluctuation. A value storage function 45, a maximum allowable delay value storage function 73, and a delay and fluctuation value comparison function 74 are provided. Details will be described assuming that the same reference numerals as those shown in FIG. 2 have the same functions.
[0042]
When the monitoring timing notification signal is notified from the threshold change timer function 41, the delay and fluctuation monitoring function 71 monitors the arrival interval of high-quality ATM cells from the service class notification signal 120, and calculates the delay and fluctuation value from the monitoring result. Output to function 72. The delay and fluctuation value calculation function 72 calculates the delay value and fluctuation value of the high-quality ATM cell from the monitoring result received from the delay and fluctuation monitoring function 71, and outputs them to the delay and fluctuation value comparison function 74.
[0043]
The maximum allowable delay value storage function 73 is connected to the delay and fluctuation value comparison function 74, and the maximum allowable delay value of the high quality ATM cell is stored in advance. The maximum allowable delay value is the maximum delay value that can be taken within a range where no echo occurs, and this value can be changed from the outside. In addition, for each change, setting for each VPI / VCI is also possible.
[0044]
The delay and fluctuation value comparison function 74 determines whether or not the delay value and fluctuation value received from the delay and fluctuation value calculation function 72 are within the allowable range. A request signal 130 is output. Further, the upper limit value and the lower limit value of the allowable range use the maximum allowable value stored in the maximum allowable fluctuation value storage function 44 and the minimum allowable value stored in the minimum allowable fluctuation value storage function 45, and the upper limit when determining the delay value. As the value, the maximum delay value stored in the maximum allowable delay value storage function 73 is used.
[0045]
Next, the operation of the second embodiment will be described in detail with reference to the drawings. Note that the second embodiment differs from the first embodiment only in some of the operations of the delay and fluctuation measurement unit 7 and the threshold control unit 5, so only these points will be described and other parts will be described. Description of is omitted.
[0046]
The delay and fluctuation measurement unit 7 always receives the service class notification signal 120 from the output buffer unit 3, and measures delay and fluctuation in the following procedure.
[0047]
FIG. 8 is a flowchart showing a delay and fluctuation measurement procedure in the delay and fluctuation measurement unit 7.
The delay and fluctuation measuring unit 7 monitors the delay and fluctuation monitoring function 71 when it is determined that it is time to change the threshold from the timer value preset by the threshold change timer function 41 (for example, timer value overflow). A timing signal is output (step 801). Upon receiving the monitoring timing signal, the delay and fluctuation monitoring function 71 immediately monitors the arrival interval of high quality ATM cells for each VPI / VCI, and outputs the result to the delay and fluctuation value calculation function 72 (step 802).
[0048]
When the delay and fluctuation value calculation function 72 receives the arrival interval result from the delay and fluctuation monitoring function 71, the delay and fluctuation value calculation function 72 calculates the delay value and fluctuation value for each high-quality ATM cell and outputs them to the delay and fluctuation value comparison function 74 ( Step 803). The delay and fluctuation value comparison function 74 compares the input value from the delay and fluctuation value calculation function 72 with the input values from the maximum allowable fluctuation value storage function 44 and the minimum allowable fluctuation value storage function 45, and the measured value is It is determined whether it is within the allowable range (step 804).
If it is out of the range, the delay and fluctuation value comparison function 74 sends a threshold value change request signal 130 to the threshold value control unit 5 (step 806).
[0049]
On the other hand, if it is within the range, the delay value from the delay and fluctuation value calculation function 72 is compared with the input value from the maximum allowable delay value storage function 73 to determine whether or not the condition is met (step). 805). If not matched, a threshold value change request signal 130 is sent to the threshold value controller 4 (step 806). If the condition is met, it is determined that there is no problem in delay and fluctuation of the high-quality ATM cell. The threshold control unit 5 that has received the threshold change request signal 130 changes the threshold according to the procedure shown in the flowchart of FIG.
[0050]
As described above, in the second embodiment, the delay of the low quality ATM cell is ensured while ensuring the quality of the high quality ATM cell by monitoring the fluctuation and the delay and optimizing the threshold value of the output buffer unit 3. Or it becomes possible to reduce disposal processing.
[0051]
【The invention's effect】
The first effect is that it is possible to ensure the quality of high-quality ATM cells while reducing the discard rate of low-quality ATM cells. The reason is that an appropriate back pressure threshold value is calculated and changed when fluctuation of the high quality ATM occurs. The second effect is that a means for discarding low-quality ATM cells is unnecessary. The reason is that cells are discarded when the input buffer is full.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a first exemplary embodiment of the present invention.
FIG. 2 is a block diagram showing an internal configuration of a fluctuation measuring unit 4;
FIG. 3 is a block diagram showing an internal configuration of a threshold control unit 5;
FIG. 4 is a flowchart showing a fluctuation measurement procedure according to the first embodiment.
FIG. 5 is a flowchart showing a threshold value changing procedure according to the first embodiment.
FIG. 6 is a block diagram showing a configuration of a second exemplary embodiment of the present invention.
7 is a block diagram showing an internal configuration of a delay and fluctuation measurement unit 7. FIG.
FIG. 8 is a flowchart showing a delay and fluctuation measurement procedure according to the second embodiment.
FIG. 9 is a flowchart showing a threshold value changing procedure according to the second embodiment.
FIG. 10 is a block diagram showing a configuration of a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Input buffer part 2 ATM switch part 3 Output buffer part 4 Fluctuation measurement part 5 Threshold control part 6 Line output part 7 Delay and fluctuation measurement part 41 Threshold change timer function 42 Fluctuation monitoring function 43 Fluctuation value calculation function 44 Maximum allowable fluctuation value storage Function 45 Minimum allowable fluctuation value storage function 46 Fluctuation value comparison function 51 Threshold determination function 52 Threshold increase value storage function 53 Threshold decrease value storage function 54 Threshold change function 71 Delay and fluctuation monitoring function 72 Delay and fluctuation value calculation function 73 Maximum allowable delay Value storage function 74 Delay and fluctuation value comparison function

Claims (5)

An input buffer unit that temporarily stores input cells, an ATM switch unit that exchanges and connects cells transmitted from the input buffer unit, and cells that are transmitted from the ATM switch unit are temporarily stored, and a cell storage amount When the value exceeds a preset threshold value, the output buffer unit that suppresses cell transmission to the input buffer unit and the fluctuation of the cell input to the input buffer unit are measured, and the measurement result is outside the allowable range. A fluctuation measurement unit that outputs a threshold value change request signal that sometimes requests the change of the threshold value, and a threshold value control unit that determines a threshold value to be changed according to a request from the fluctuation measurement unit and changes the threshold value of the output buffer unit A back pressure threshold automatic change method characterized by comprising. The fluctuation measurement unit is a threshold change timer unit that notifies threshold change timing, and a fluctuation monitoring unit that monitors the arrival interval of high-quality ATM cells that are input to the input buffer unit at the timing notified from the threshold change timer unit A fluctuation value calculation unit that calculates a fluctuation value from the arrival interval, and a fluctuation that outputs a threshold value change request signal when the fluctuation value is out of an allowable range by comparing the fluctuation value with a preset allowable fluctuation value The back pressure threshold automatic change method according to claim 1, further comprising a value comparison unit. The threshold control unit includes a threshold value determination unit that determines a new threshold value by receiving the threshold value change request signal, and a threshold value change function that sets the threshold value determined by the threshold value determination unit in the output buffer unit. The back pressure threshold automatic change method according to claim 1 or 2. An input buffer unit that temporarily stores input cells, an ATM switch unit that exchanges and connects cells transmitted from the input buffer unit, and cells that are transmitted from the ATM switch unit are temporarily stored, and a cell storage amount An output buffer unit that suppresses cell transmission to the input buffer unit when a threshold value set in advance is exceeded, and a fluctuation value and a delay value of a cell input to the input buffer unit are measured, and the fluctuation value or A delay and fluctuation measuring unit that outputs a threshold change request signal for requesting the change of the threshold when the delay value is outside an allowable range; and a threshold to be changed according to a request from the delay and fluctuation measuring unit, and A back pressure threshold automatic change method, comprising: a threshold control unit that changes a threshold of the output buffer unit. The delay and fluctuation measuring unit monitors a threshold change timer unit for notifying a threshold change timing, and a delay for monitoring an arrival interval of high-quality ATM cells input to the input buffer unit at a timing notified from the threshold change timer unit. And a fluctuation monitoring unit, a delay and fluctuation value calculation unit for calculating a fluctuation value and a delay value from the arrival interval, and comparing the fluctuation value and the delay value with a preset allowable fluctuation value and an allowable delay value, respectively. 5. The back pressure threshold automatic change system according to claim 4, further comprising a delay and fluctuation value comparison unit that outputs a threshold change request signal when the fluctuation value or the delay value is outside an allowable range.

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