JPH08130543A - Virtual channel multiplexing device - Google Patents

Abstract

PURPOSE: To guarantee the communication quality for an upper class and to guarantee also the absolute minimum communication quality for a lower class. CONSTITUTION: When the number of queuing cells of virtual channels 61 to 6n in a certain quality class exceeds a previously determined threshold, control for preferentially outputting the cells in the class is executed. When there are plural butters 11 requesting priority, cells are outputted from a buffer 11 in an upper quality class. When priority is requested, output permission can be continuously outputted to a butter outputting cells plural times. If no output permission can be obtained at the time of continuously outputting a priority request the previously determined number of times, cells corresponding to a previously determined number are successively canceled from the head. Consequently the whole communication quality of an ATM transfer system can be improved and a network resource can be effectively utilized.

Description

Detailed Description of the Invention

[0001]

The present invention is used in an ATM (Asynchronous Transfer Mode) network. INDUSTRIAL APPLICABILITY The present invention is used in a multiplexer that accommodates virtual channels in virtual paths. In particular, it relates to a cell transmission priority control technique.

[0002]

2. Description of the Related Art In the ATM transfer system, fixed length packets called cells are transferred to transfer information having different traffic characteristics such as voice, video and data or different required quality at high speed on the same network. It is possible to In the ATM transfer network, virtual channels corresponding to individual lines are accommodated in virtual paths, which are virtual paths, using a virtual channel multiplexer. This makes it possible to manage and operate the network on a path-by-path basis, improving the operability and economy of the network. In the virtual channel multiplexer, the cells on the virtual channel are temporarily stored in the buffer, and the cells are output at the minimum cell interval on the virtual path. For this reason,
When the traffic load on the virtual channel multiplexer is heavy, a waiting delay occurs in the buffer, which may deteriorate the communication quality.

When the quality required for each virtual channel differs depending on the type of information transferred on the virtual channel, the virtual channel multiplexer preferentially outputs the cells of the virtual channel with severe requirements. Therefore, a method for improving the quality of a virtual channel having a strict quality requirement has been studied.

A conventional virtual channel multiplexer will be described with reference to FIG. FIG. 4 is a block diagram of a conventional virtual channel multiplexer. In FIG. 4, it is assumed that the number of quality classes is set to 2 or more n classes. The virtual channel multiplexer 1 includes a cell distributor 20 and n quality class buffers 30 ₁
˜30 _n and the output control unit 5. Cells of the virtual channel ₆₁ on to 6 _n, upon arrival to the virtual channel multiplexer 1, the cell sorting apparatus 20, each quality class of virtual channel 6 ₁ to 6 _n is specified in advance, the corresponding buffer 30 ₁ It is distributed to ~ 30 _n and accumulated. The output control unit 5 corresponds to the speed of the virtual path 7 on the virtual path 7 in order from the first cell of the buffer 30 ₁ of the highest quality class among the buffers 30 ₁ to 30 _n in which cells are accumulated. Output at the cell interval.

Therefore, the virtual channel assigned to the higher quality class is not affected by the virtual channel of the lower quality class, and high quality communication becomes possible.

[0006]

As described above, in the virtual channel multiplexer to which the priority output means is added, the virtual channel cells of the lower quality class accumulate the virtual channel cells of the higher quality class. As long as it is not output, the quality of the upper class tends to be excessively good, while the quality of the lower class tends to deteriorate significantly.

Problems of the conventional example will be described with reference to FIG. In FIG. 5, the quality class is divided into two classes, an upper quality class and a lower quality class, and the bandwidth ratio between the upper quality class and the lower quality class is set under the condition that the load of the virtual path is constant. It is a figure which shows the result of having calculated | required the delay of each quality class at the time of changing by simulation. The horizontal axis shows the ratio of the upper class band to the entire band, and the vertical axis shows the delay time.

As is clear from FIG. 5, particularly when the ratio of the upper quality class is large, the output of the cell of the upper class is obstructed, the output of the cell of the lower quality class becomes difficult, and the lower quality is remarkably increased. There is a problem of decrease.

The present invention has been made under such circumstances, and provides a virtual channel multiplexer capable of guaranteeing the quality of the upper class and the minimum quality of the lower class. The purpose is to do.
An object of the present invention is to provide a virtual channel multiplexer that can improve the overall communication quality in the ATM transfer system. An object of the present invention is to provide a virtual path multiplexer that can effectively use network resources.

[0010]

According to the present invention, a virtual channel reader for accommodating a virtual path and for identifying a virtual channel included in the virtual path, and a cell arriving according to the identification result of the reader are provided for each virtual channel. N buffers, each of which is stored in
An output control unit for outputting the cells accumulated in the buffer is provided, and the output control unit is a virtual channel multiplexer in which the priority order of the output order is preset for each virtual channel.

Here, a feature of the present invention is that a priority request threshold value (Tr) is set for a buffer having a lower priority among the plurality of n buffers, and the output control unit is configured to store the priority of the buffer. Among them, there is provided a means for changing a preset priority order and setting a new priority order for those whose accumulated amount exceeds the priority request threshold value (Tr).

As a result, the quality of the upper class can be guaranteed and the minimum quality of the lower class can be guaranteed. Furthermore, the overall communication quality in the ATM transfer system can be improved. Also, it becomes possible to accommodate the virtual channels of the lower class in the free area of the bandwidth of the virtual channels of the upper class,
The network resources can be used effectively.

A priority release threshold (Tc) is set for a buffer having a lower priority among the plurality of n buffers,
It is preferable that the output control unit includes means for canceling the setting of the new priority order for the buffers whose accumulated amount is below the priority cancellation threshold value (Tc). In this case, it is desirable that the priority request threshold value (Tr) be larger than the priority cancellation threshold value (Tc).

Thus, even when a burst of cells arrives immediately after the request for the priority right is released, it is possible to prevent the sudden quality deterioration.

The priority request threshold value (Tr) is the plurality n
It is also possible to have a configuration in which each buffer is individually set. In this case, the priority request threshold value (Tr) is
It is desirable to set a small value for a high priority set in advance.

As a result, it is possible to quickly detect and suppress the quality deterioration of the higher quality class.

A discard threshold value (Tg) is set to a value equal to or higher than the priority request threshold value (Tr), and the output control unit is the buffer whose accumulated amount exceeds the discard threshold value (Tg). It is also possible to adopt a configuration in which a means for discarding m cells stored in the buffer from the one having a long storage time is discarded.

This makes it possible to prevent buffer overflow.

It is also possible to provide a means for presetting the number p of cells that can be continuously transmitted for the same cell transmission opportunity of the same buffer. It is desirable that the number p of cells that can be continuously transmitted is individually set for each of the n buffers, and that the number p is set to be large for a preset high priority.

As a result, the quality of the higher quality class can be greatly improved.

[0021]

When the number of waiting cells of the virtual channel of a certain quality class becomes equal to or more than a predetermined threshold value, the control is performed by preferentially outputting the cells of the class,
Even in a virtual channel of a lower quality class, it is possible to prevent significant quality deterioration and guarantee the minimum quality.

Further, when there are a plurality of buffers requesting priority, cells can be output from a buffer of a higher quality class. As a result, the virtual channel of the higher quality class can be prevented from being affected by the quality deterioration of the lower quality class.

Further, the threshold value which is the condition for canceling the request for the priority right can be set smaller than the threshold value which is the condition for requesting the priority right. This makes it possible to prevent rapid quality deterioration even when a burst of cells arrives immediately after the priority request is released.

Further, the threshold value of the priority request of the higher quality class can be set smaller than the threshold value of the priority request of the lower quality class. This makes it possible to quickly detect and suppress quality deterioration in a higher quality class.

Further, the means for selecting the cell to be output, when there is a request for priority,
It is also possible to give output permission several times in succession. As a result, the quality of the corresponding quality class can be greatly improved.

Further, the means for selecting the cells to be output can set the number of times the output permission is continuously given to the buffer of the higher quality class to be larger when the priority is requested. Thereby, the quality of the high quality class can be guaranteed.

Further, even if the priority request is made a predetermined number of times in succession, if the output permission is not obtained during that time, the cells can be discarded from the beginning by a predetermined number. . This can prevent buffer overflow.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of an apparatus according to the present invention.

The present invention accommodates the virtual path 6 and includes the virtual channels 6 ₁ to 6 included in the virtual path 6.
The virtual channel reading unit 2 for identifying 6 _n , a plurality of n buffers 11 for accumulating cells arriving according to the identification result of the reading unit 2 for each virtual channel 6 _{1 to} 6 _n , and the buffer 11 An output control unit 5 for outputting the generated cells, and the output control unit 5 is a virtual channel multiplexer 1 in which the priority order of the output order is preset for each of the virtual channels 6 _{1 to} 6 _n .

Here, the feature of the present invention is that the priority request threshold value Tr is set in the memory 13 for the one of the plurality of n buffers 11 having the lowest priority, and the output control unit 5 is provided with the buffer 11. Among them, there is provided a means for changing a preset priority order and setting a new priority order for those whose accumulated amount counted by the counter 12 exceeds the priority request threshold Tr.

A priority release threshold Tc is set for a buffer having a lower priority among a plurality of n buffers 11, and the output controller 5 stores the stored amount of the buffer 11 below the priority release threshold Tc. Is provided with a means for canceling the setting of the new priority order. This priority request threshold Tr is a value larger than the priority cancellation threshold Tc.
This priority request threshold Tr is individually set for each of a plurality of n buffers. The priority request threshold value Tr is set small for a preset high priority order.

The discard threshold value Tg is set to a value equal to or higher than the priority request threshold value Tr, and the accumulated amount counted by the priority request counter 101 in the buffer 11 exceeds the discard threshold value Tg in the output control unit 5. It is provided with a means for discarding m cells stored in the buffer 11 from the one having a long storage time.

A continuous output number counter 102 is provided as means for presetting the number p of cells that can be continuously transmitted for the same cell transmission opportunity of the same buffer 11. The number p of cells that can be continuously transmitted is individually set for each of the plurality n of buffers 11, and the number p is set large for a preset high priority.

In the embodiment of the present invention, the quality class is 2
It is assumed that there are the above n pieces. That is, the virtual channel multiplexer 1 reads the virtual channel identifier of the arrived cell, the VCI reading unit 2, the quality class management table 3 for registering the quality class when setting the virtual channel, and the cell for each class. It is composed of output requesting units 4 ₁ to 4 _n for storing and issuing an output request, and an output control unit 5 for selecting a class to be output from among classes having an output request and accumulating cells to which output permission is given.

The output request units 4 ₁ to 4 _n include a buffer 11 for accumulating cells and a counter 1 for measuring the number of accumulated cells.
2, a memory 13 that stores a threshold value, and a control unit 14. As an option, a priority request counter 101 for counting the number of requests for priority right in succession can be provided. Further, the output control unit 5 can optionally include a continuous output number counter 102.

When the cells on the virtual channels 6 _{1 to} 6 _n arrive at the virtual channel multiplexer 1, the cells VC
In I reading unit 2 reads the VCI, by referring to the quality class management table 3, in the output request unit 4 ₁ to 4 _n, accumulates cell buffer 11 the quality class that apply. The quality class management table 3, when a virtual channel connection, is registered relationship Virtual Channel 6 ₁ to 6 _n and quality class, the record is removed from the table when a virtual channel disconnection.

Next, the operation of the output request units 4 ₁ to 4 _{n will be described} with reference to FIG.
This will be described with reference to the flowchart in FIG. Figure 2 is a flow chart showing the operation of the output request unit 4 ₁ to 4 _n of the present invention embodiment. When a cell arrives at the buffer 11 (S1),
If the value of the counter 12 is less than the buffer length, 1 is added (S4) and the cells are accumulated in the buffer 11. Counter 1
If the value of 2 exceeds the buffer length, the arriving cell is discarded (S3).

If the value of the counter 12 is equal to or greater than the priority request threshold value stored in the memory 13 (S5), "1" is added to the priority request counter 101 (S9) and the priority request is output. It outputs to 5 (S12).

When the value of the counter 12 is less than the priority request threshold stored in the memory 13 (S5), it is equal to or more than the priority request release threshold stored in the memory 13 (S6), and the value of the priority request counter 101. Is 1 or more (S7),
The priority request is output to the output control unit 5 (S12). If the value of the counter 12 is less than the priority request cancellation threshold value stored in the memory 13 (S6) or the value of the priority request counter 101 is "0" (S7) and the value of the counter 12 is 1 or more, output control An output request is output to the unit 5 (S1
1).

The output request units 4 ₁ to 4 _n that have received the output permission (S13) output the head cell from the buffer 11 (S).
14). When the cell is output, if the value of the priority request counter 101 is not "0" (S16), the priority request counter 101 is reset (S18).

If the priority request threshold value and the priority right discard threshold value are the same, the operation of option 1 within the dotted line in FIG. 2 can be omitted. When discarding the waiting cell, option 2 is activated. In option 2, as shown in FIG. 2, when there is a request for priority, (S
12), "1" is added to the priority request counter 101 (S9), and when the value of the counter 12 is less than the priority request release threshold and there is no priority request (S6), or output permission is obtained. If so (S13), the priority request counter 101 is reset (S8, S18). If there is no output permission (S13), the priority request counter 10
1 is checked, and if the discard threshold is exceeded (S15), m cells from the beginning are discarded (S17). Note that m is an integer equal to or greater than 1 that is predetermined for each quality class.

Next, the operation of the output control section 5 will be described with reference to the flowchart of FIG. FIG. 3 is a flowchart showing the operation of the output control unit 5 according to the embodiment of the present invention. The output control unit 5 operates at every minimum cell interval of the virtual path 7. The priority of the buffer is denoted by i. However, i is an integer of 1 or more and n or less. Based on a predetermined priority order, it is checked from the upper buffer (S22) whether there is a priority request (S23), and when the priority request is found, output permission is given to the corresponding buffer (S3).
1).

If there is no priority request from any buffer (S23, S27, S28), it is checked whether there is an output request from the upper buffer (S29) based on a predetermined priority order (S30). When an output request is found, output permission is given to the corresponding buffer (S31).

If there is no output request from any buffer (S30, S32, S33), an empty cell is output (S34). When a plurality of cells output permission is continuously given from the buffer giving the priority, the option in the dotted line in FIG. 3 is operated. The buffer to which the priority is given has a continuous output number counter 102 as a counter for measuring the number of continuous outputs at that time point, and its value is j. First, the value of the continuous output number counter 102 is checked, and if it is not "0" (S21), the highest-order buffer is selected from the buffers having the priority request, and it is stored in advance in the output control unit 5 for each quality class. The continuous output number is set in the continuous output number counter 102, and thereafter, the output permission is given to the buffer i at the minimum cell interval of VP until the counter value j becomes “0” (S25). Then, "1" is subtracted from the value j of the continuous output number counter 102 (S26).

[0045]

As described above, according to the present invention,
It is possible to guarantee the quality of the upper class and the minimum quality of the lower class. Furthermore, AT
It is possible to improve the overall communication quality in the M transfer method. Further, the virtual channels of the lower class can be accommodated in the vacant area of the band of the virtual channels of the upper class, and the network resources can be effectively used.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing the operation of the output requesting unit according to the embodiment of the present invention.

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

FIG. 4 is a block configuration diagram of a conventional virtual channel multiplexer.

FIG. 5 is a diagram showing a result of simulating the delay of each quality class.

[Explanation of symbols]

1 Virtual Channel Multiplexer 2 VCI Reader 3 Quality Class Management Table 4 ₁ to 4 _n Output Requester 5 Output Controller 6 and 7 Virtual Path 6 _{1 to} 6 _n Virtual Channel 11, 30 ₁ to 30 _n Buffer 12 Counter 13 Memory 14 Control Unit 20 Cell Distributor 101 Priority Request Counter 102 Continuous Output Number Counter Tr Priority Request Threshold Tc Priority Release Threshold Tg Discard Threshold

Claims (8)

[Claims] 1. A virtual channel reader for accommodating a virtual path and identifying a virtual channel included in the virtual path, and a plurality of n number of cells for accumulating incoming cells for each virtual channel according to the identification result of the reader. The virtual channel multiplexer is provided with a buffer and an output control unit for outputting the cells accumulated in the buffer. In the virtual channel multiplexer in which the priority order of the output order is preset for each virtual channel, A priority request threshold value (Tr) is set for the one of the n buffers having a lower priority order, and the output control unit whose accumulated amount exceeds the priority request threshold value (Tr) of the buffers. About the provision of means for changing the preset priority of Characteristic virtual channel multiplexer. 2. A priority release threshold (Tc) is set for a buffer having a lower priority among the plurality of n buffers, and the output control unit stores the stored amount of the buffer in the priority release threshold (Tc). 2. A means for canceling the setting of the new priority order for those below (Tc).
A virtual channel multiplexer as described. 3. The virtual channel multiplexer according to claim 2, wherein the priority request threshold value (Tr) is a value larger than the priority cancellation threshold value (Tc). 4. The virtual channel multiplexer according to claim 1, wherein the priority request threshold value (Tr) is set individually for each of the plurality of n buffers. 5. The virtual channel multiplexer according to claim 4, wherein the priority request threshold value (Tr) is set small for a preset high priority. 6. A discard threshold value (Tg) is set to a value equal to or higher than the priority request threshold value (Tr), and the output control unit has an accumulated amount exceeding the discard threshold value (Tg) in the buffer. For the thing, the cells accumulated in the buffer are stored from the longest accumulated time m
The virtual channel multiplexer according to claim 1, further comprising means for discarding individual pieces. 7. The virtual channel multiplexer according to claim 1, further comprising means for presetting the number p of cells that can be continuously transmitted for the same cell transmission opportunity of the same buffer. 8. The number p of cells that can be continuously transmitted is individually set for each of the plurality n of buffers, and the number p is set to be large for a preset high priority. 7. The virtual channel multiplexer according to 7.