JPH11308229A - Cell scheduling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to guarantee a virtual; channel which requires transmission for a specific period by taking out a virtual channel identifier from the head of a scheduling queue of shaping non-correspondence and transmitting its cells when the virtual channel identifier is empty, or the queue length is zero even through the identifier is valid. SOLUTION: When a value 19 of a virtual channel identifier taken out of a shaping correspondence scheduling queue 15 is empty or the queue length is equal to zero even if it is valid, a scheduling part 17 takes out the identifier of the virtual channel from a head of a shaping non-correspondence scheduling queue 16 after inserting the identifier into a final part of the shaping correspondence scheduling queue 15. Then, the scheduling part 17 transmits the value of the virtual channel identifier to a cell transmission part 12. The transmission part 12 transmits a leading cell of a cell queue corresponding to the virtual channel identifier to a communication network.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for scheduling fixed-length packets (cells) in an ATM switch, and more particularly, to a method for reliably transmitting a virtual channel that requires cell transmission (shaping) at a fixed period. The present invention relates to a cell scheduling method that performs shaping and enables cell transmission at a constant period.

[0002]

2. Description of the Related Art Conventionally, as this kind of cell scheduling method, there is a method using a queue length. Hereinafter, FIG.
The operation of this method will be described with reference to FIG.

In FIG. 5, reference numeral 51 denotes a cell receiving section; 52, a cell transmitting section; 53a, 53b, 53c, cell queues provided for each virtual channel; and 54, a weight comparing section for comparing the queue length and weight of the virtual channel. , 55 is a scheduling queue for managing the order of cell transmission between virtual channels, 56 is a scheduling unit for extracting a virtual channel identifier from the head of the scheduling queue 55 and transmitting the value to the cell transmission unit 52, and 57 is a weight for each virtual channel. 9 is a weight comparison table for managing queue lengths.

When receiving a cell from the communication network, the cell receiving section 51 inputs the cell to a cell queue (for example, 53a) corresponding to the virtual channel identifier of the cell. afterwards,
The cell receiving unit 51 transmits the virtual channel identifier to the weight comparing unit 54. After receiving the virtual channel identifier, the weight comparing unit 54 increases the queue length value in the weight comparison table 57 by 1, compares the queue length with the weight value, and if (queue length) ≦ (weight value). For example, the virtual channel identifier is input to the scheduling queue 55.

To output a cell, the scheduling unit 56 extracts one virtual channel identifier from the head of the scheduling queue 55 and outputs the value to the cell transmitting unit 52.
Tell The cell transmission unit 52 sends the head cell of the cell queue (for example, 53a) corresponding to the virtual channel identifier to the communication network. At this time, the scheduling unit 56
In parallel with the cell transmission processing, the value of the virtual channel identifier is transmitted to the weight comparing unit 54, and the weight comparing unit 54, which has received the virtual channel identifier, reduces the value of the queue length in the weight comparing table 57 by one. Thereafter, the weight comparing unit 54 compares the queue length with the value of the weight, and if (queue length) ≧ (value of the weight), inputs the virtual channel identifier to the scheduling queue 55 again.

In such a conventional cell scheduling method using a queue length, when there is a virtual channel that requires cell transmission (shaping) at a constant period, such a virtual channel is not necessarily allocated at a constant period. Is not guaranteed. An example will be described with reference to FIG.

In FIG. 6, weight 1 and shaping 1
Virtual channel # 1 and virtual channel # 2 of weight 2 and shaping 0, the cell transmission rate is 3, and it is desired that cells are transmitted at a constant period in virtual channel # 1. . (a) Time, (b) Cell arrival state of virtual channel # 1, (c)
Shows the state of cell arrival of virtual channel # 2, and (d) shows the state of cell transmission. In the state of cell transmission (d),
It is shown that the cells of the virtual channel # 1 are not transmitted at a fixed period due to the influence of the cells of the virtual channel # 2 arriving in a burst.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a cell scheduling method capable of guaranteeing a virtual channel that requires cell transmission at a constant period.

[0009]

In order to achieve the above object, the cell scheduling method of the present invention stores, for a virtual channel requiring shaping, the value of the identifier of the virtual channel in a shaping-compatible scheduling queue in advance. Step: upon receiving a cell, increasing the value of the queue length in the weight comparison table by 1, and then determining whether the received cell belongs to a virtual channel to be shaped, and determining whether the received cell belongs to a virtual channel to be shaped. If it belongs, the step ends the processing at that point.If the received cell does not belong to the virtual channel to be shaped, the queue length of the cell queue is compared with the weight value of the virtual channel, and the queue length is the weight value. Virtual channel if Inserting the value of the discriminator into the non-shaping-capable scheduling queue; extracting a virtual channel identifier from the head of the shaping-compatible scheduling queue at the time of sending out the cell; Transmitting one or more cells of the virtual channel if one or more are accumulated, and queuing even if the virtual channel identifier extracted from the shaping-capable scheduling queue is empty or the virtual channel identifier is valid; If the length is zero, extracting a virtual channel identifier from the head of the non-shaping-capable scheduling queue and transmitting a cell of the virtual channel identifier. That.

In the cell scheduling method according to the present invention, the step of storing in advance the identifier value of the virtual channel for the virtual channel requiring shaping in the shaping-compatible scheduling queue comprises the step of: Calculating the virtual channel identifier insertion interval based on the calculated insertion interval, storing the virtual channel identifier in the shaping corresponding scheduling queue at the calculated insertion interval, and, if there is no virtual channel identifier to be stored, the shaping corresponding scheduling queue Inserting information indicating "empty" into the information.

In the cell scheduling method of the present invention, at the time of transmitting the cell, a virtual channel identifier is taken out of a shaping-compatible scheduling queue, and one or more cells are stored in a cell queue in which the virtual channel identifier is valid and corresponds to the virtual channel identifier. When the cell is stored, the step of transmitting the cell of the virtual channel includes, after transmitting the head cell of the cell queue corresponding to the extracted virtual channel identifier to the communication network, the queue length in the weight comparison table for managing the cell queue length. And inserting the extracted virtual channel identifier into the end of the shaping-capable scheduling queue again,
At the time of transmitting the cell, the virtual channel identifier taken out of the scheduling queue corresponding to shaping is “empty”.
Or if the queue length is zero even though the virtual channel identifier is valid, the step of taking out the virtual channel identifier from the head of the shaping non-corresponding scheduling queue and transmitting the cell of that virtual channel identifier takes place After transmitting the head cell of the cell queue corresponding to the virtual channel identifier to the communication network, reducing the value of the queue length in the weight comparison table for managing the cell queue length by 1; And, if the queue length is greater than or equal to the weight value, inserting the virtual channel identifier into the non-shaping-capable scheduling queue again.

According to such a cell scheduling method of the present invention, by using the scheduling queue corresponding to shaping, it is possible to reliably perform shaping on a virtual channel that requires cell transmission at a fixed period, and to use other virtual channels. Cells can always be sent out at a fixed period without being affected by cells arriving at the cell. The state of cell transmission according to the method of the present invention is as shown in FIG. A transmission cell shaped according to the present invention can arrive at a communication device such as an adjacent switch or terminal in a traffic shape according to a declared value. As a result, it is possible to reduce the probability of cell discard in an adjacent communication device, and to suppress quality deterioration due to cell fluctuation, cell discard, and the like for applications that require periodic cell arrival. Can be.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining an embodiment of the present invention, in which 11 is a cell receiving unit, 12 is a cell transmitting unit, 13a, 13b, 13
c is a cell queue provided for each virtual channel, 14
Is a weight comparison unit that compares the queue length and weight of the virtual channel, 15 is a shaping-capable scheduling queue that manages the order of cell transmission of virtual channels that require shaping, and 16 is cell transmission of virtual channels that do not require shaping. Scheduling non-corresponding scheduling queue for managing the order, 17 is a scheduling unit that extracts a virtual channel identifier from the head of the scheduling queue 15 or 16 and transmits the value to the cell transmitting unit 12, and 18 is a weight and queue length of each virtual channel. It is a weight comparison table to be managed.

The operation of the cell scheduling method according to the present invention in consideration of the shaping in such a configuration will be described with reference to the flowcharts of FIGS. First, before executing the operation, for a virtual channel requiring shaping, an insertion interval of a virtual channel identifier is calculated based on the weight of the virtual channel (step 21). Next, based on the calculated insertion interval, the value of the virtual channel identifier 19 is stored in the shaping corresponding scheduling queue 15 (step 22).

When the cell receiving section 11 receives a cell from the communication network, the cell is stored in a cell queue (for example, 13a) corresponding to the virtual channel identifier of the cell (step 3).
1). After that, the cell receiving unit 11 notifies the weight comparing unit 14 of the virtual channel identifier. Upon receiving the virtual channel identifier, the weight comparison unit 14
After the value of the queue length is increased by 1 (step 32), the shaping column in the weight comparison table 18 is referred to (step 33). If the shaping column is “1”, the processing ends at that point because the shaping-capable scheduling queue 15 already has the virtual channel identifier. On the other hand, if the shaping field is “0”, the queue length is compared with the weight value, and if (queue length) ≦ (weight value), the virtual channel identifier is input to the non-shaping scheduling queue 16. (Step 34), and the process ends.

When outputting a cell, first, the scheduling unit 17 outputs a scheduling-capable scheduling queue 15.
One virtual channel identifier is taken out from the beginning of step (step 41). If the identifier is valid (not “empty”) and there is a cell in the cell queue corresponding to the identifier (queue length> 0) (step 42), the value of the extracted virtual channel identifier is transmitted to the cell transmitting unit 12. The cell transmitting unit 12 transmits the first cell of the cell queue (for example, 13a) corresponding to the virtual channel identifier to the communication network (step 43). In parallel with this, the scheduling unit 17 inserts the extracted virtual channel identifier again into the tail of the shaping-compatible scheduling queue 15 and reduces the value of the queue length in the weight comparison table 18 by 1 (step 43). To end.

On the other hand, the value 19 of the virtual channel identifier extracted from the scheduling queue 15 for shaping
Is empty (not valid) or if valid but the queue length is equal to 0 (step 42), the scheduling unit 17 inserts the identifier into the end of the shaping-compatible scheduling queue 15 Then, the virtual channel identifier is extracted from the head of the non-shaping scheduling queue 16 (step 44). The scheduling unit 17 transmits the value of the virtual channel identifier to the cell transmitting unit 12, and the cell transmitting unit 12 sends the first cell of the cell queue (for example, 13b) corresponding to the virtual channel identifier to the communication network. At this time, the scheduling unit 17 transmits the value of the virtual channel identifier to the weight comparison unit 14 in parallel with the cell transmission process, and the weight comparison unit 14 that has received the identifier sets the value of the queue length in the weight comparison table 18 to 1 cut back. afterwards,
The weight comparing unit 14 compares the queue length with the value of the weight,
If (queue length) ≧ (weight value), the virtual channel identifier is input to the non-shaping scheduling queue 16 again (step 45), and the process ends.

[0018]

As described above, a transmission cell shaped by the cell scheduling method of the present invention can arrive at an adjacent communication device such as a switch or a terminal in a traffic shape according to a declared value. it can. As a result, the probability of occurrence of cell discard in an adjacent communication device can be reduced, and quality degradation due to cell fluctuation, cell discard, and the like can be suppressed for applications that require periodic cell arrival. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an embodiment of the present invention.

FIG. 2 is a flowchart of a pre-processing.

FIG. 3 is a flowchart of a process when receiving a cell.

FIG. 4 is a flowchart of a process when transmitting a cell.

FIG. 5 is a diagram for explaining a conventional method.

FIG. 6 is a diagram showing a state of cell transmission.

[Explanation of symbols]

 Reference Signs List 11 cell receiving unit 12 cell transmitting unit 13 cell queue 14 weight comparing unit 15 shaping-capable scheduling queue 16 shaping non-corresponding scheduling queue 17 scheduling unit 18 weight comparing table 51 cell receiving unit 52 cell transmitting unit 53 cell queue 54 weight comparing unit 55 scheduling queue 56 Scheduling unit 57 Weight comparison table

Claims (3)

[Claims] 1. A method for separating received cells by virtual channel identifiers and storing the cells in a corresponding cell queue when receiving a cell, and a weight comparison for managing a queue length of a cell queue in which a cell is stored when transmitting a cell. Based on the queue length in the table, determine a cell transmission timing between a plurality of virtual channels, in the cell scheduling method comprising a step of taking out the first cell from the transmission cell queue and performing cell transmission, for a virtual channel requiring shaping, Storing a value of the identifier of the virtual channel in a scheduling queue corresponding to the shaping in advance. At the time of cell reception, after increasing the value of the queue length in the weight comparison table by 1, the received cell belongs to the virtual channel to be shaped. Whether or not Disconnecting, if the received cell belongs to a virtual channel to be shaped, ending the process at that time;
If the received cell does not belong to the virtual channel to be shaped, the queue length of the cell queue is compared with the weight value of the virtual channel, and if the queue length is equal to or less than the weight value, the value of the virtual channel identifier is shaped. A step of inserting the cell into a non-corresponding scheduling queue; at the time of transmitting a cell, extracting a virtual channel identifier from the head of the shaping-compatible scheduling queue; Transmitting the cell of the virtual channel, if the virtual channel identifier extracted from the shaping-capable scheduling queue is "empty" or the virtual channel identifier. If the queue length be effective is zero, it extracts the virtual channel identifier from the beginning of the shaping incompatible scheduling queue, cell scheduling method characterized by comprising the step of transmitting the cells of the virtual channel identifier. 2. A method of storing a virtual channel identifier value of a virtual channel requiring shaping in a shaping-compatible scheduling queue in advance, based on a weight value of the virtual channel. Calculating a virtual channel identifier in the shaping-capable scheduling queue at the calculated insertion interval; and inserting information indicating “empty” in the shaping-compatible scheduling queue when there is no virtual channel identifier to be stored. The method of claim 1, comprising steps. 3. At the time of transmitting the cell, a virtual channel identifier is taken from a head of a shaping-compatible scheduling queue, and when one or more cells are stored in the cell queue corresponding to the virtual channel identifier that is valid and corresponding to the virtual channel identifier. Transmitting the cell of the virtual channel, transmitting the head cell of the cell queue corresponding to the extracted virtual channel identifier to the communication network, and then reducing the value of the queue length in the weight comparison table for managing the cell queue length by one. And inserting the extracted virtual channel identifier again into the end of the shaping-capable scheduling queue, wherein the virtual channel identifier retrieved from the shaping-capable scheduling queue is “empty” when the cell is transmitted.
Or if the virtual channel identifier is valid but the queue length is zero, the step of taking the virtual channel identifier from the head of the non-shaping-capable scheduling queue and transmitting the cell with the virtual channel identifier comprises: After transmitting the head cell of the cell queue corresponding to the virtual channel identifier to the communication network, reducing the value of the queue length in the weight comparison table for managing the cell queue length by one, and determining the queue length and weight value of the cell queue. 2. The cell scheduling method according to claim 1, further comprising, if the queue length is equal to or greater than the weight value, inserting the virtual channel identifier into the non-shaping scheduling queue again.