JPH07321796A - Virtual path shaping device - Google Patents

Abstract

PURPOSE:To utilize effectively network resource and to reduce the transfer cost by recovering a cell interval for each virtual path VP and transferring the cell of a VC not tight for the requirement against delay to an idle zone of VPs with high quality accommodating a virtual channel VC tight in the quality requirement against delay. CONSTITUTION:A VC identifier I identification section 21 reads a VCI in the header of a cell, references a table 22 and sends the cell of class A to a class A buffer 31 and sends a class B cell to a class B buffer 32 and counters 44, 45 are incremented by 1. When the measured value of a VP output timer 43 measuring a cell output interval on the VP reaches a minimum cell interval of the VP stored in the memory 42, the content of the class A counter 44 is checked and when the content is not zero, a head cell is outputted from the class A buffer 31 and the content of the class A counter 44 is decremented by 1. When the count of the class A counter 44 is zero, the similar processing to the class A is implemented for the class B.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an ATM (Asynchronous Trunk).
ansfer Mode: Used for transfer method.
INDUSTRIAL APPLICABILITY The present invention is used in a traffic control device for absorbing cell transfer delay fluctuations in a virtual path (hereinafter referred to as VP). The present invention relates to a technique for effectively using communication network resources.

[0002]

2. Description of the Related Art In the ATM transfer system, fixed length packets called cells are transferred. In an ATM network, virtual channels (hereinafter referred to as VCs) are multiplexed into VPs. However, since multiplexing in the ATM transfer system is performed asynchronously, waiting time in the buffer is increased when passing through a multiplexer or a switch. Due to the difference, cell transfer delay fluctuation occurs. When this cell transfer delay fluctuation occurs, the cell interval may become small, which results in burst traffic on the VP. In this case, in order to guarantee the cell loss condition of the VP, it is necessary to allocate a band larger than the total sum of the bands of the VCs, and the use efficiency of the communication network resources is reduced.
In order to solve this problem, a virtual path shaping device (hereinafter referred to as V
P shaping device) has been proposed. An outline of the configuration of this conventional VP shaping device will be described with reference to FIG. FIG. 9 is a configuration diagram of a main part of a conventional device.

In FIG. 9, cells are represented by # 1, # 2 and # 3,
It is assumed that the cell progresses from left to right in the figure. In FIG. 9, the VP shaping devices 1 and 1'include buffers 20 and 20 'for accumulating cells and this buffer 2
Cell output control units 3 and 3'for controlling the cell output timing from 0 and 20 'are provided. The VP multiplexers 6 and 6'multiplex incoming VCs and input them as VPs to the VP shaping devices 1 and 1 '. The VP shaping devices 1 and 1 ′ handle a VC of a service (service quality A) that guarantees a low delay, and a VP shaping device 1 ′ that handles a VC of a service (service quality B) that allows a delay. And are respectively provided and shaped by the respective VP shaping devices 1 and 1 '.

The cells multiplexed by the VP multiplexer 6 or 6'for each service are # 1, # 2,
In the order of # 3, they arrive at the VP shaping device 1 or 1'and are stored in the buffer 20 or 20 '. Here, a service of service quality A is called a class A service, and a service of service quality B is called a class B service. The cell output control unit 3 or 3'reads cells from the buffer 20 or 20 'at a predetermined constant interval to control the cells so that they are at constant intervals on the VP.

[0005]

In the conventional VP shaping device, the VP is divided for each service quality.
Cells of VCs having different qualities of service are multiplexed into different VPs. Therefore, in the conventional VP shaping apparatus, the statistical multiplexing effect is small when the number of VCs of the same quality is small, and in order to guarantee the maximum waiting time of the cell, the VP shaping is performed at a speed higher than the average arrival speed of the cell. The cell must be output from the buffer in the device.
In the conventional VP shaping device, the VC speed is set to 64.
FIG. 10 shows the calculation result of the upper limit value of the band use rate of the VP when the cell is output so that the cell waiting time in the VP shaping device is 1 ms or less with kbps. Figure 10
FIG. 4 is a diagram showing an upper limit value of a band usage rate that satisfies a delay condition. The horizontal axis represents the number of VCs, and the vertical axis represents the maximum band usage rate of VPs. If cells are transferred beyond the usage rate shown in FIG. 10, the delay in the VP shaping device exceeds 1 ms. For example, under the traffic conditions described above, if the number of VCs is 100 or less, the VP bandwidth usage cannot be 0.9 or more, and if it is 20 or less, the VP bandwidth usage is Must be less than half. As described above, the smaller the number of VCs is, the larger the ratio of the VP allocated bandwidth is to the average used bandwidth, and there is a problem that the network resources cannot be effectively used.

The present invention has been made against such a background, and reproduces a cell interval for each VP and accommodates a VC with a severe quality requirement for delay.
It is an object of the present invention to provide a VP shaping device that can transfer cells of VCs that are tolerant of delays to the vacant band and effectively use network resources.

[0007]

According to the present invention, in a VP shaping device, a means for reading a VCI value and a VC for class A service or a VC for class B service for each VC are provided.
By providing a means for registering a class A service, a buffer for a VC of class A service and a buffer for a VC of class B service, a cell of a VC of class A service and a cell of a VC of class B service are output queues separately. Aligned to
It is characterized in that a VC for class A service and a VC for class B service are multiplexed in the same VP.

That is, the present invention is used in an ATM transfer system in which there is a service that guarantees a low delay, that is, a VC of class A service and a service that allows a delay, that is, a VC of class B service, and a cell that arrives and arrives. Is a VP shaping device that controls the output of the VP and reproduces the cell interval of the VP.

Here, a feature of the present invention is that a first buffer that stores cells of the virtual channel of the class A service and a second buffer that stores cells of the virtual channel of the class B service. , Means for identifying the VCI (Virtual channel Identifier: VC identifier) of the arriving cell and distributing it to the buffer for each service, means for measuring the number of cells accumulated in the first and second buffers, and VP Based on the measurement results of the means for measuring the cell output interval above, the means for measuring the number of cells accumulated in the buffer, and the means for measuring the cell output interval on the VP, the VC cell of the class A service And an output control means for controlling the cell of the class B service to output on the VP in preference to the cell of the VC of the class B service so that the cell interval on the VP becomes constant. In the place provided.

The output control means outputs a cell from this buffer when a cell is stored in the first buffer, and outputs a cell stored in the second buffer when no cell is stored in this buffer. It is desirable to include control means for controlling.

With the above-described configuration, in the present invention, the VP shaping device is controlled so that the cell of class A service is preferentially output and the cell of class B service is output between the cells, so that on the same VP. It is possible to multiplex cells of class A service and cells of class B service.

It is desirable to include means for discarding a predetermined number of cells from the head of this buffer when the number of cells accumulated in the second buffer exceeds a threshold value.

Means for measuring the waiting time of the leading cell of the second buffer is preferably provided, and means for discarding the leading cell when the waiting time exceeds a threshold value is preferably included. This makes it possible to prevent cells of class B service from overflowing the buffer.

The first buffer and the second buffer are common memories, and the address for accumulating the cell of the service that guarantees the low delay is different from the address for accumulating the cell of the service that allows the delay. It can also be configured. As a result, the amount of buffer memory can be reduced.

[0015]

A counter for distinguishing between class A service and class B service, arranging cells in different output queues for each quality of service, and measuring the number of cells accumulated in the buffers of VCs of two types of services. If a cell of VC with a delay and cell loss condition is stored in the buffer, it is preferentially output, and if a cell of VC with a delay and cell loss condition is not stored in the buffer, The VC cell that allows the delay is output.

When the number of VC cells that allow delays exceeds a certain value, discarding a certain number of cells from the beginning is effective in preventing buffer overflow.

Alternatively, discarding this cell when the head cell of the buffer accumulating the cell of the service which allows the delay is not output for a predetermined time or more,
This is effective in preventing buffer overflow.

That is, the present invention provides a VC requiring low delay.
By using the free band of the VP for transferring the cells of (1) to transfer the cells of the VC that allows the delay, it is possible to increase the band usage rate of the VP and effectively use the network resources. Thus, by preferentially outputting the cells requesting the low delay, the delay condition of the service requesting the low delay can be kept. Furthermore, buffer overflow can be prevented by limiting the number of waits or the waiting time in the buffer of the cell of the service that allows the delay.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of a first embodiment device of the present invention.

The present invention is used in an ATM transfer system in which a VC for class A service and a VC for class B service exist, and controls the output of arriving cells to reproduce the cell interval of VP. Is.

Here, a feature of the present invention is that a class A buffer 31 for accumulating VC cells of class A service, a class B buffer 32 for accumulating VC cells of class B service, and arrival. The VCI of the cell to be identified and assigned to the buffer for each service, and the VC separation unit 2 and the class A as a means for measuring the number of cells accumulated in the class A buffer 31 and the class B buffer 32. Counter 44 and class B counter 45, a VP output timer 43 as a means for measuring the cell output interval on the VP, and a measurement result of the class A counter 44, class B counter 45 and VP output timer 43 , Class A service VC
Cell of VP with priority to the cell of VC of class B service
It is provided with a control section 41 as an output control means for outputting the above and controlling so that the cell interval on the VP becomes constant.

The control unit 41 controls the output of cells from the buffer for class A when the cells are stored in the buffer 31 for class A, and the output of cells stored in the buffer for class B when there is no storage of cells in this buffer. Including means.

Further, the control unit 41 includes means for discarding a predetermined number of cells from the head of this buffer when the number of accumulated cells in the class B buffer exceeds a threshold value.

The VC separation unit 2 reads the value of VCI VC
It is composed of an I identification unit 21 and a table 22 for registering the service class of each VC. The VP output control unit 4 includes, in addition to the control unit 41, the VP output timer 43, the class A counter 44, and the class B counter 45 described above,
Memory 42 for storing the minimum cell interval of VP when setting VP
Is included. The solid lines in the figure show the cell paths, and the broken lines show the control signal lines.

Next, the operation of the first embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a flowchart showing the operation of the VC separation unit 2 according to the first embodiment of the present invention. Figure 3
3 is a flowchart showing the operation of the VP output control unit 4 of the first embodiment of the present invention. First, the operation of the VC separation unit 2 when a cell arrives at the VP shaping device 1 will be described with reference to FIG. The VCI identification unit 21 reads the VCI value in the cell header (S1), refers to the table 22 (S2), and class A service (hereinafter abbreviated as class A).
If the cell is a cell (S3), it is sent to the class A buffer 31 (S4), and "1" is added to the class A counter 44 (S5). If the cell is a class B service (hereinafter abbreviated as class B) (S3), the class B buffer 32
(S6), and the class B counter 45 is incremented by "1" (S7).

In the VP output control unit 4, the minimum cell interval of the VP is stored in the memory 42 on the basis of the band of the VP which is assigned in advance.
Stored in advance, and the VP output timer 43
The distance from the cell output immediately before from the shaping device 1 is measured.

Next, the operation of the VP output control section 4 will be described with reference to FIG. When the measured value of the VP output timer 43 becomes equal to or larger than the minimum cell interval of the VP stored in the memory 42 (S11), the value of the class A counter 44 is checked, and if the value is not "0" (S12), The head cell is output from the class A buffer 31 (S13), and "1" is subtracted from the class A counter 44 (S14). Next, the value of the class B counter 45 is set in advance in the memory 4
If it is equal to or larger than the maximum value stored in 2 (S15), the predetermined number of cells stored in the memory 42 is discarded from the head of the class B buffer 32 (S21).
The discarded number is subtracted from the class B counter (S2
2). After that, the VP output timer 43 is reset and restarted (S16). If the value of the class A counter 44 is "0" (S12), the value of the class B counter 45 is checked, and if the value is not "0", the head cell is output from the class B buffer 32 (S18). ), "1" is subtracted from the value of the class B counter 45 (S19), and the VP output timer 43 is reset and restarted (S1).
6). At this time, if there is no cell to be sent to the class B counter 45, an empty cell is output (S20).

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a block diagram of the apparatus of the second embodiment of the present invention. The second embodiment of the present invention is the VP of the first embodiment of the present invention.
This is a configuration in which a class B timer 46 for measuring the waiting time of the first cell of the class B buffer 32 is added to the output control unit 4.

Next, the operation of the second embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a flowchart showing the operation of the VC separation unit 2 according to the second embodiment of the present invention. Figure 6
Is a flowchart showing the operation of the VP output control unit 4 of the second embodiment of the present invention. First, the operation of the VC separation unit 2 when a cell arrives at the VP shaping device 1 will be described with reference to FIG. The VCI identification unit 21 reads the VCI value in the header of the cell (S31), refers to the table 22 (S32), and if the cell is a class A cell (S33), sends it to the class A buffer 31 (S3).
4), "1" is added to the class A counter 44 (S)
35). If the cell is a class B cell (S3
3) The data is sent to the class B buffer 32 (S36), "1" is added to the class B counter 45 (S37), and when the value of the class B counter 45 becomes "1" (S3).
8) Start the class B timer 46 (S3)
9). After that, since the class B timer 46 is reset every time a cell is output from the class B buffer 32, the value of the class B timer 46 always represents the waiting time of the first cell of the class B buffer 32. ing. In the VP output control unit 4, the minimum cell interval of the VP is stored in advance in the memory 42 based on the band of the VP allocated in advance, and the VP output timer 43 causes the VP shaping timer 1 to operate.
The distance from the cell output immediately before is measured.

Next, the operation of the VP output control section 4 will be described with reference to FIG. The value of the VP output timer 43 is the memory 4
When it becomes more than the minimum cell interval of VP stored in 2 (S
41), the value of the class B timer 46 is compared with the maximum waiting time stored in advance in the memory 42 (S4
2) If the value of the class B timer 46 is larger, the head of the class B buffer 32 is discarded and "1" is subtracted from the class B counter 45 (S44). If the value of the class B timer 46 is less than or equal to the maximum waiting time (S4
2), check the value of the class A counter 44 (S45),
If the value is not "0", the head cell is output from the class A buffer 31 (S46), and the class A counter 44 is output.
Is subtracted from "1" (S47), the VP output timer 43 is reset and restarted (S48). If the value of the class A counter 44 is "0" (S45), the value of the class B counter 45 is checked (S49). If the value is "0", an empty cell is output (S55). If the value of the class B counter 45 is not “0”, the class B buffer 32
The first cell is output from (S50), and "1" is subtracted from the value of the class B counter 45 (S51). At this time,
If the value of the class B counter 45 is not "0", the class B timer 46 is reset and restarted (S5).
3). If the class B counter 45 is "0" (S5
2) The class B timer 46 is reset and stopped (S54). Then, the VP output timer 43 is reset and restarted (S48).

In the first and second embodiments of the present invention, when the class A buffer 31 and the class B buffer 32 are made common, and the addresses where the cells are accumulated are distinguished by class A or B and accumulated and output. Can also be configured to select a cell address and select and output a class A or B cell. As a result, VP
The memory amount of the shaping device 1 can be reduced.

Next, FIG. 7 shows a result obtained by simulating the maximum number of class B VCs that can be accommodated by the first and second embodiments of the present invention. FIG. 7 is a diagram showing the maximum accommodation number of the class B. The horizontal axis represents the average load of the VC of the class A with respect to the VP, and the vertical axis represents the maximum accommodation number of the VC of the class B. The simulation parameters are shown in [Table 1].

[0033]

[Table 1] As a class A VC, assuming a voice, 64 kbps
CBR (fixed speed service). Class B VC
Assuming data, the peak speed is 1.5 Mbp
s, peak ratio 0.1, burst 100 cells VBR (variable rate service). The delay condition is 500 μs or less because class A requires immediacy, and class B
Since the immediacy is not required, it was set to 10 ms or less.
The speed of the VP is 52 Mbps.

As shown in FIG. 7, even if the average load of the class A VC is as high as 0.9, it is possible to accommodate 10 more class B VCs in the VP. Further, when the average load of the class A VCs decreases, the maximum number of class B VCs that can be accommodated increases linearly.
When the average load of the VCs is 0.5 or less, it becomes possible to accommodate 100 or more class B VCs in the VP.

Next, FIG. 8 shows band gains obtained by dividing the maximum band usage rate of the VP by the first and second embodiments of the present invention by the maximum band usage rate of the VP by the conventional example apparatus. Figure 8
FIG. 3 is a diagram showing band gains according to the first and second embodiments of the present invention. The horizontal axis represents the average load of the class A VC with respect to the VP, and the vertical axis represents the band gain. Class A V
The band gain increases at a place where the average load on the C VP is small, and the device of the present invention is
It is effective even in a region where the average load on P is large, but is particularly effective at a place where the average load on the VP of the class A VC is small.

[0036]

As described above, according to the present invention,
The cell interval of each VP is regenerated, and the cells of VCs that are forgiving of delay are transferred to the free band of the high-quality VP that accommodates VCs that have severe quality requirements for delay,
It is possible to realize a VP shaping device that can effectively use network resources. As a result, the conventional device can effectively utilize network resources by providing a service for transferring a VC of low quality by utilizing the extra allocated band, and thus the cell transfer cost can be reduced.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of an apparatus according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the VC separation unit according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing the operation of the VP output control unit according to the first embodiment of the present invention.

FIG. 4 is a block configuration diagram of a second embodiment device of the present invention.

FIG. 5 is a flowchart showing the operation of the VC separation unit according to the second embodiment of the present invention.

FIG. 6 is a flowchart showing the operation of the VP output control unit according to the second embodiment of the present invention.

FIG. 7 is a diagram showing the maximum accommodation number of class B.

FIG. 8 is a diagram showing band gains according to the first and second embodiments of the present invention.

FIG. 9 is a configuration diagram of a main part of a conventional device.

FIG. 10 is a diagram showing an upper limit value of a band usage rate that satisfies a delay condition.

[Explanation of symbols]

 1, 1'VP shaping device 2 VC separation unit 3, 3'cell output control unit 4 VP output control unit 6, 6'VP multiplexing device 20, 20 'buffer 21 VCI identification unit 22 table 31 class A buffer 32 class B buffer 41 Control unit 42 Memory 43 VP output timer 44 Class A counter 45 Class B counter 46 Class B timer

Claims (5)

[Claims] 1. An ATM transfer method in which a virtual channel of a service that guarantees a low delay and a virtual channel of a service that allows a delay exist and are used to control the output of arriving cells to control the cell intervals of virtual paths. In a virtual path shaping device for reproducing, a first buffer that stores cells of a virtual channel of the service that guarantees the low delay, a second buffer that stores cells of a virtual channel of the service that allows the delay, and Means for identifying the virtual channel identifier of the cell to be allocated to the buffer for each service, means for measuring the number of cells accumulated in the first and second buffers, and measuring the cell output interval on the virtual path Means for measuring the number of cells accumulated in the buffer And the cell of the virtual channel of the service that guarantees the low delay is prioritized over the cell of the virtual channel of the service that allows the delay on the virtual path based on the measurement result of the means for measuring the cell output interval on the virtual path. And an output control unit for controlling so that the cell interval on the virtual path becomes constant, and a virtual path shaping device. 2. The output control means causes a cell to be output from this buffer when the cell is stored in the first buffer, and the cell stored in the second buffer when there is no cell stored in this buffer. The virtual path shaping device according to claim 1, further comprising control means for outputting 3. The virtual path shaping device according to claim 1, further comprising means for discarding a predetermined number of cells from the head of this buffer when the number of cells accumulated in said second buffer exceeds a threshold value. 4. The virtual according to claim 1, further comprising means for measuring a waiting time of a leading cell of the second buffer, and including means for discarding the leading cell when the waiting time exceeds a threshold value. Path shaping device. 5. The first buffer and the second buffer are a common memory, and have an address for accumulating a cell for a service that guarantees the low delay and an address for accumulating a cell for a service that allows the delay. Claim 1 which is different
5. The virtual path shaping device according to any one of 4 to 4.