JPH1155276A - Shaping device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shaping device for efficiently using a network even for low priority data in a simple constitution. SOLUTION: When cell data 305 are received by a cell receiving circuit 2, a virtual channel VC is extracted from header information included in the received cell data 305. Then, a minimum cell interval, a priority, and a previous transmission time are managed as management information for the virtual channel VC by a management table circuit 4A. The minimum cell interval is a parameter expressed by B(the maximum bit rate)/X(a band of each virtual channel VC). Information extracted from a management table circuit 4A is applied in the form of the previous transmission time + the minimum cell interval = next transmission time together with a priority through a control line 303 to a cell transmitting circuit 5. Data whose priority is lower than a constant priority are stored in a low priority cell buffer 3An, and when any cell data whose priority is high are absent, the next transmission time for the highest speed transmission is set in a cell transmitting circuit 5 through a control line 302 by the management table circuit 4A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shaping device, for example, an ATM (Asynchronous Transfer Mod).
e: Asynchronous transfer mode) Applicable to control of cell flow rate in a communication system.

[0002]

2. Description of the Related Art Conventionally, there is a traffic shaping technique for handling a plurality of virtual channels in an ATM switching network.

FIG. 2 is a functional block diagram of a dynamic shaper 1 with a priority control function as an example of the prior art. In FIG. 2, when receiving the cell data 105 of the received cell, the cell receiving circuit 2 writes the control information of the received cell data 105 for each virtual channel VC through the control line 101 as a write process of the received cell data 105. Stored in the management table circuit 4 for management. The management table circuit 4 manages the control information of the received cell data 105, the minimum cell interval and the transmission priority. Received cell data 10
5 is stored in the cell buffer circuit 3 from the cell receiving circuit 2.

At this time, the received cell data 105 is stored in n cell buffers 31 to 3n prepared for each virtual channel identifier (VCI). That is, the cell buffer 31
Stores the received cell of the virtual channel VC # 1. The cell buffer 32 stores the received cell of the virtual channel VC # 2. The cell buffer 3n stores received cells of the virtual channel VC # n.

[0005] The received cell data 105 is cell data from the subscriber side or the transit exchange, and the data traffic for each virtual channel VC is not necessarily constant.

The cell buffer circuit 3 stores the received cell data 105 in a cell data storage allowable value m for each virtual channel VC.
Only cell data can be stored. It is assumed that the received cell data 105 stores all cell data including ATM cell header information in the cell buffer circuit 3.

The cell data stored in the cell buffer circuit 3 is stored in the management table circuit 4 at the previous transmission time (T) 43.
The next transmission scheduled time is determined by the addition of the minimum transmission interval and the minimum cell interval 41, and the next transmission time is determined in the cell transmission circuit 5 by the priority in the management table circuit 4 via the control line 102.

The virtual channel identifier VCI has a minimum cell interval of 3 for VC # 1, a previous transmission time of T1, and a priority of 1. Also, the minimum cell interval for VC # 2 is 4
And the priority is 2, and the previous transmission time is T2.

For the reception cell data 105 of the high priority virtual channel identifier VCI, the transmission time is assigned preferentially, and for the reception cell data 105 of the low priority virtual channel identifier VCI, the transmission time is assigned. Perform non-preferentially. Therefore, the user traffic is allocated in the priority and the transmission band based on the contract with the user.

When the next transmission time is determined, the cell transmission circuit 5 sequentially transmits the cell data allocated to each line. The transmission cell data 106 is transmission cell data transmitted based on the scheduling according to the transmission time determined by the next transmission time.

FIG. 3 is a diagram for explaining the allocation of cell data to transmission slots in the conventional dynamic shaper 1 with a priority control function. This figure 3
FIG. 3A shows a state before allocation to transmission slots. FIG. 3B shows the state of the transmission slots after allocation. FIG. 3C is a diagram showing a state of each virtual channel information of the management table circuit 4.

In FIG. 3A, the transmission slots are SLT0 to SLT0.
It consists of SLT Tn. In FIG. 3C, the management table circuit 4 determines that the virtual channel identifier VCI has a minimum cell interval of 3 with respect to VCI # 1, a previous transmission time of 0, a priority of 1, and a next transmission time of 3 And Also VC
For I # 2, the minimum cell interval is 4, the priority is 2,
The previous transmission time is set to 2 and the next transmission time is set to 7.
Further, for VCI # 3, the minimum cell interval is 6, the previous transmission time is T, the next transmission time is 6 + T, and the priority is 2
And

From the information managed in FIG. 3C, FIG.
The transmission slot SLT is allocated as shown in (b).
That is, for transmission slot SLT0, virtual channel VC
Assign # 1, virtual channel for transmission slot SLT2
VC # 2 is allocated, virtual channel VC # 1 is allocated to transmission slot SLT3, and virtual channel VC # 2 is allocated to transmission slot SLT7.

As described above, the cell transmission circuit 5 refers to the information on the transmission cell data 106 read from the cell buffer circuit 3 from the management table 4 and allocates the cell data to the transmission slot SLT corresponding to the next transmission time. . At this time, if cells are allocated to the same slot at the same time, contention arbitration is performed in the management table circuit 4, and high-priority cell data is allocated to the corresponding transmission slot.

In the dynamic shaper 1 with the priority control function shown in FIGS. 2 and 3, there is a clock circuit for periodically managing the entire operation, and the transmission time slots SLT0 to SLT Tn are provided. The values are shown periodically. At the time of cell transmission, if transmission cell data 106 is allocated to a slot corresponding to the current time (for example, slot Tn), the corresponding transmission slot (transmission slot number T
The cell data 106 is read from n) and transmitted.

[0016]

SUMMARY OF THE INVENTION Large-capacity and high-speed AT
In the M-switched network, ABR (Available Bit Rate: Variable Bit Rate, AT
In recent years, standardization of a service (a service in which the bit rate dynamically changes depending on the use state of the communication network) has been advanced.

The variable bit rate method is UBR (Unspecif
Unlike the ied Bit Rate: low-price service that does not guarantee throughput, the lowest transmission is guaranteed even during congestion, and CBR (Constant Bit Rate: constant bit rate, real-time performance is required Audio / video communication service), VBR (Variable Bit Rate: AT)
There are a mixture of service classes, such as a service that implements communication at a variable speed as it occurs while the information changes while changing the time by taking advantage of the characteristics of M, and a variable bit rate system.

Therefore, in the simple priority system that has been implemented in the conventional ATM exchange, the transmission band is consumed by the class having the higher priority at the time of congestion, so that the service class of each connection cannot be guaranteed.

This is because when the bandwidth is greatly consumed by the user traffic of the user who does not adhere to the service contract value or the user who accesses with the traffic far exceeding the service contract value, congestion occurs in the network. This is because transmission of a service class with a low priority may stop because of the inability to avoid the problem.

Therefore, instead of a simple priority control method, the transmission rate is controlled for each connection and the MCR
It is desired to be able to provide a fair transmission band for each traffic based on (Minimum Bit Rate: minimum cell rate).

For this reason, there is a demand for a shaping device having a simple configuration and capable of efficiently using a network even with low-priority cell data.

[0022]

Accordingly, the present invention provides a cell receiving means for receiving an input cell and extracting information contained in the received cell, and a cell for storing the received cell separately for each virtual channel. A buffer means, a cell transmission schedule management means for generating and managing a cell transmission schedule for each virtual channel in consideration of transmission priority from the extracted information, and a cell transmission means based on the transmission priority of the cell transmission schedule. In a shaping device including a cell transmitting unit that reads out and transmits stored cells, the above-described problem is solved by the following characteristic configuration.

That is, according to the present invention, the cell buffer means includes a low-priority cell buffer unit for storing only low-priority reception cells, and identifies the priority of the reception cells stored in the cell buffer means. When there is no high-priority reception cell, the low-priority cell control unit controls the cell transmission unit to read the low-priority reception cell from the low-priority cell buffer unit and transmit the cell at the maximum speed.

With this configuration, even if the flow rate of the cell data having a low priority fluctuates, it does not occur that the cell data is not transmitted. If no high-priority cell data is present, low-priority cell data is transmitted at the maximum speed, so that the network can be used efficiently even if transmission fluctuations occur a little.

Further, the cell transmission schedule management means comprises:
In order to generate a cell transmission schedule, when the maximum bit rate is B and the band for each virtual channel is X, B
By determining the next transmission time based on the minimum cell interval including the parameter represented by / X, the priority, and the previous transmission time, the transmission rate can be controlled for each priority for each virtual channel. Based on this, a fair transmission band can be allocated to each traffic and controlled.

Further, the cell transmitting means controls the low-priority cell buffer unit so as not to transmit the low-priority receiving cells when the high-priority receiving cells are present in the cell buffer means. It is possible to prevent transmission of high priority cells from being delayed while promoting transmission of high priority cells.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment of the present invention will be described with reference to the drawings. Therefore, in this embodiment, (1)
A shaping device having a priority control function and a shaping function for performing dynamic routing is configured to include a low priority cell buffer for storing and managing low priority cell data.

(2) Further, let B be the maximum bit rate,
Assuming that a band for each virtual channel VC is X, the transmission time is determined by having a parameter represented by B / X and managing the minimum cell interval, priority, and previous transmission time,
When there is high-priority cell data, control is performed so that low-priority cell data is not transmitted by a low-priority cell buffer.

(3) Further, when cell data having a high priority does not exist in the cell buffer and cell data exists in a cell buffer having a low priority, a cell is transferred from the cell buffer having a low priority at the highest speed. It is configured to send data. With this configuration, it is possible to efficiently use the cell data with low priority in the network.

FIG. 1 is a functional configuration diagram of a dynamic shaper 1A with a low priority control function according to the present embodiment. This figure 1
, Dynamic shaper with low priority control function
1A receives the cell data 305, provides control information to the management table circuit 4A via the control line 301, and stores the received cell data in the cell buffer circuit 3A;
A control table circuit 4A for storing and managing control information provided from the cell receiving circuit 2 through the virtual line 301 for each virtual channel and exchanging information with the cell transmitting circuit 5 through the control line 302
And a cell buffer circuit 3A for storing the received cell data 305 received by the cell receiving circuit 2 in a cell buffer prepared for each virtual channel and specially managing the low priority received cell data in the cell buffer. .

The cell buffer circuit 3A can be constituted by a memory circuit, and stores the cell data of the virtual channel VC # 1 in the cell buffer 3A1 to store the cell data in the cell buffer for each virtual channel. The cell data of VC # 2 is stored in the cell buffer 3A2, and in particular, the cell buffer for storing the cell data of the virtual channel VC # n is
Low priority cell buffer that stores low priority cell data
3An is set and cell data with low priority is stored.

The management table circuit 4A can be composed of a memory circuit. For example, for the virtual channel VC # 1, the minimum cell interval is 3, the priority is 1, the previous transmission time is T1, and the next transmission time is T1. The transmission time is T5. Further, for the virtual channel VC # 2, the minimum cell interval is 4, the priority is 5, the previous transmission time is T2, and the next transmission time is T6. Further, for the virtual channel VC # 3, the minimum cell interval is set to 0, the priority is set to 1, and the previous transmission time is set to T3,
The next transmission time is T7. Furthermore, for the virtual channel VC # n, the minimum cell interval is 4, the priority is 6, the previous transmission time is T4, and the next transmission time is T8. The high priority virtual channel is VC # 1,3, and the low priority virtual channel is VC # n.

Further, the dynamic shaper 1A with the low priority control function monitors the presence / absence of high priority cell data from the cell data stored in the cell buffer circuit 3A. When the buffer circuit 3A is exhausted, the control to read the cell data from the low-priority cell buffer 3An is performed via the control line 303 to the low-priority cell buffer 3An. A cell transmission circuit 5 for transmitting the output cell data at the next transmission time and a clock circuit 7 for managing the cell transmission time in the cell transmission circuit 5 are provided.

Next, the schematic operation of the dynamic shaper 1A with the low priority control function shown in FIG. 1 will be described. First, when the received cell data 305 is received by the cell receiving circuit 2, a virtual channel VC is extracted from the header information included in the received cell data 305, and the minimum cell interval is used as management information for the extracted virtual channel VC. , Priority, last transmission time, and the like are managed in the management table circuit 4A.

The minimum cell interval is a parameter represented by B / X, where B is the maximum bit rate and X is the band for each virtual channel VC. Information extracted from the management table circuit 4A is given to the cell transmission circuit 5 through the control line 303 as last transmission time + minimum cell interval = next transmission time together with the priority.

At this time, the cell data having a priority lower than a certain priority, for example, the cell data of the virtual channel VC # n having the priority 6 is stored in the low priority cell buffer 3An of the cell buffer circuit 3A. Have been. That is, since the cell data of the virtual channel VC # n has a priority of 6,
It is stored in the low priority cell buffer 3An.

However, the cell data stored in the low-priority cell buffer 3An is transmitted at the highest speed in the management table circuit 4A when there is no high-priority cell data in the cell buffer circuit 3A. The next transmission time is set in the cell transmission circuit 5 by the control line 302.

The transmission time is indicated by a clock circuit 7 indicating the entire time. When the time indicated by the clock circuit 7 reaches the next transmission time indicated by the management table circuit 4A, the corresponding cell transmission circuit 5 transmits the transmission time. Cell data 306
Is sent.

FIG. 4 shows a cell buffer circuit in the dynamic shaper 1A with the low priority control function shown in FIG.
It is a processing flowchart of the write processing of the received cell data to 3A. In FIG. 4, first, the cell receiving circuit 2
When the cell data 305 arrives at (step S10), a virtual channel VC number is extracted from the received cell data 305,
The priority is determined and stored in the management table circuit 4A (step S20).

Next, the management table circuit 4A calculates and determines the next transmission time from the previous transmission time and the minimum cell interval (step S30). Next, the storage state of the control information of the management table circuit 4A is updated based on the obtained next transmission time, priority, minimum cell interval, and the like (step S40).

As a result, the transmission rate can be controlled for each priority for each virtual channel, and a fair transmission band can be allocated to each traffic based on the MCR and controlled.

FIG. 5 shows a cell buffer circuit in the dynamic shaper 1A with the low priority control function shown in FIG.
It is a processing flowchart of a reading process from 3A. In FIG. 5, first, when a high-priority cell is detected by the high-priority cell presence / absence detection circuit 6, the management table circuit 4A is searched (step S100), and the schedule of the high-priority cell is set to the minimum cell interval, The time, the previous transmission time, the next transmission time, and the like are checked (step S100), the cell transmission circuit 5 is caused to transmit a high priority cell, and the previous transmission time is updated to the current transmission time (step S140). Steps S100 and S140 are repeated until all high priority cells are transmitted.

On the other hand, if no high-priority cell is detected in step S100, it is checked whether or not there is a low-priority cell (step S110). The schedule of the cell is checked in the management table circuit 4A, and the minimum cell interval, priority, previous transmission time, next transmission time, and the like are checked. Then, the low-priority cell data is read from the low-priority cell buffer 3An, transmitted from the cell transmission circuit 5 at the maximum speed, and the last transmission time of the management table circuit 4A is updated to the current transmission time (step S120). Step 120 is repeated until all the low-priority cell data are transmitted (step S130).

The cell transmission circuit 5 and the high-priority cell presence / absence detection circuit 6 determine that a high-priority reception cell is a cell buffer circuit 3A.
In the case where the low priority cell buffer circuit 3An does not transmit the low priority reception cells, the transmission of the high priority cells is delayed while promoting the transmission of the low priority cells. You can make it not.

In general, ATMs where congestion may occur
In a communication network, low-priority cell data is worst-case freeze-out (freeze-out).
Therefore, priority management is required. For this reason, as shown in the management table circuit 4A of FIG. 1, by determining the next transmission time from the previous transmission time and the minimum cell interval, the cell data with low priority may freeze even though the fluctuation may increase. Will not cause out.

When there is no cell data having a high priority, cell data having a low priority can be transmitted at the highest speed, so that the ATM network can be used efficiently.

[0047]

As described above, according to the present invention, the cell buffer means includes the low-priority cell buffer section for storing only the low-priority reception cells, and the reception buffer stored in the cell buffer means. By identifying the priority of the cell and, when there is no high-priority receiving cell, by controlling the cell transmitting means to read out the low-priority receiving cell from the low-priority cell buffer unit and transmit it at the maximum speed With a simple device configuration, even if there is a slight fluctuation in transmission fluctuations, transmission will not be stopped in the event of congestion, etc., and network utilization can be efficiently performed even with low priority cell data. Will be able to do it.

[Brief description of the drawings]

FIG. 1 is a functional configuration diagram of a dynamic shaper with a low priority control function according to an embodiment of the present invention.

FIG. 2 is a functional configuration diagram of a dynamic shaper with a priority control function according to an example of the related art.

FIG. 3 is a diagram for explaining allocation of cell data to a transmission slot in a conventional dynamic shaper with a priority control function.

4 is a flowchart of a process of writing received cell data to a cell buffer circuit in the dynamic shaper with a low priority control function of FIG. 1;

5 is a processing flowchart of a reading process from a cell buffer circuit in the dynamic shaper with a low priority control function of FIG. 1;

[Explanation of symbols]

 2 Cell receiving circuit 3A Cell buffer circuit 3An Low priority cell buffer 4A management table circuit 5 Cell transmission circuit 6 High priority cell presence / absence detection circuit 7 Clock circuit

Claims (3)

[Claims] A cell receiving means for receiving an input cell and extracting information contained in the received cell; a cell buffer means for storing the received cell separately for each virtual channel; A cell transmission schedule management means for generating and managing a cell transmission schedule for each channel in consideration of transmission priority; and reading and transmitting cells stored in the cell buffer means based on the transmission priority of the cell transmission schedule. A shaping device including a cell transmitting unit, wherein the cell buffer unit includes a low-priority cell buffer unit that stores only low-priority receiving cells, and the device includes a receiving cell stored in the cell buffer unit. And if there is no received cell with a higher priority, the lower priority cell buffer unit Shaping apparatus which comprises a low priority cell control means for performing control to delivery at a maximum speed reads every received cell to the cell transmission means. 2. The apparatus according to claim 1, wherein the cell transmission schedule management means generates a cell transmission schedule by setting a maximum bit rate to B and a band for each virtual channel to X. A shaping device that determines a next transmission time from a minimum cell interval including a parameter represented by / X, a priority, and a previous transmission time. 3. The apparatus according to claim 1, wherein said cell transmission means, when a reception cell with a high priority exists in said cell buffer means, said cell transmission means having a low priority from said low priority cell buffer unit. A shaping device which controls so as not to transmit a reception cell.