KR100327162B1 - Cell Scheduling Method According To Weighted Priority In ATM Switch - Google Patents

Abstract

The present invention relates to a cell scheduling method according to a weighted priority of an ATM switch (Asynchronous Transfer Mode). In particular, even in a ATM switch processing various types of traffic, even schedule information stored in a queue having a relatively low priority has a weighted priority. The present invention relates to a cell scheduling method according to a weighted priority of an ATM switch to be outputted accordingly.

According to the cell scheduling according to the absolute priority of the conventional ATM switch, the input cell associated with the schedule information stored in the queue of which the priority is relatively low occupy the cell buffer for a long time, thereby overloading the cell buffer The disadvantage is that the input cell is lost.

The present invention performs cell scheduling according to a weighting priority that compares a predetermined threshold weight given to each queue included in a schedule queue in an ATM switch with a corresponding weighting coefficient value, thereby providing a queue having a relatively low absolute priority. In addition to preventing the schedule information stored in the output for a long time, it is possible to prevent the overload of the corresponding cell buffer and the loss of the input cell.

Description

Cell Scheduling Method According To Weighted Priority In ATM Switch

The present invention relates to a cell scheduling method according to the weighted priority of an ATM switch (Asynchronous Transfer Mode). The present invention relates to a cell scheduling method according to a weighted priority of an ATM switch to be outputted accordingly.

In general, ATM is capable of delivering various kinds of traffic in a BISDN (Broadband Integrated Services Digital Network). In an ATM switching system using the same, an ATM switch in which a user cell is selected from an input module to an output module is used for voice, Various types of traffic such as data and video signals must be processed to satisfy respective quality of service (hereinafter, referred to as 'QoS').

In addition, the ATM switch for satisfying the cell delay time of the QoS must have a function of a scheduler that first processes the traffic sensitive to the cell delay time and outputs it to the output port.

In detail, the ATM switch is divided into a shared memory type, a shared medium type, a fully interconnected type, and a partitioned type according to a path selection and buffering method. The structure of the shared memory type ATM switch is illustrated in the accompanying drawings. 1, reception control means 11, connection control means 12, connection control table 13, scheduler 14, schedule queue 15, and transmission control means 16 as shown in FIG. And a cell buffer 17.

The reception control means 11 transfers the header information of the input cell to the connection control means 12, receives the connection control information from the connection control means 12 and stores the input cell in the cell buffer 17. The scheduler 14 transmits schedule information including an address of the cell buffer 17 storing the corresponding input cell and cell header information to be converted, and determines whether to discard the cell included in the connection control information. The information is used to determine whether to discard the input cell and to process it.

The connection control means 12 reads the connection control information from the connection control table 13 using the cell header information and transmits the connection control information to the reception control means 11, and the connection control table 13 corresponds to the cell header information. Connection control information, that is, information for determining whether to discard a cell and cell header information to be converted are stored.

The scheduler 14 receives the schedule information upon cell input and stores it in the schedule queue 15, and schedules the cell according to a scheduling policy (a policy for determining the order in which the input cells are stored in the cell buffer and outputted). The schedule information is read from the queue 15 and transferred to the transmission control means 16. The schedule queue 15 stores schedule information for each cell.

In this case, the scheduler 14 and the schedule queue 15 will be described in more detail with reference to FIG. 2. The schedule queue 15 can store schedule information corresponding to each QoS class of an input cell. A plurality of queues 15-1 to 15-5, and the scheduler 14 includes a QoS analysis block 14-1, a demux 14-2, and a queue control block 14-. 3) and priority analysis block 14-4 and MUX 14-5.

Here, the types of the queues 15-1 to 15-5 included in the schedule queue 15 storing corresponding schedule information include a constant bit rate (CBR) queue 15-1 related to voice traffic and a real time. Real time variable bit rate (RTVV) queues 15-2 associated with data or compressed voice / video traffic, non-real time VBR queues 15-3 associated with non-real-time data or video traffic, and There are available bit rate (ABR) queues 15-4 associated with data or internet traffic and unspecified bit rate (UBR) queues 15-5 associated with specific data traffic such as e-mail or files.

On the other hand, the QoS analysis block 14-1 of the scheduler 14 transmits the schedule information received from the reception control unit 11 when the cell is input, according to the QoS level, and corresponding queues 15-1 to 1-5 of the schedule queue 15. 15-5) to control the queue selection of the demux 14-2, the demux 14-2 receiving control means 11 according to the queue selection control of the QoS analysis block 14-1. Demultiplexing the schedule information received from the) to store in the corresponding queue (15-1 ~ 15-5) of the schedule queue (15).

Then, the queue control block 14-3 stores whether or not the schedule information for each queue 15-1 to 15-5 of the schedule queue 15 is stored when the cell is output, that is, each queue 15-1 to 15-. The status (available / not available) information of 5) is transmitted to the priority analysis block 14-4, and the corresponding priority analysis block 14-4 receives each queue (received from the queue control block 14-3). In order to transfer the schedule information of the queues 15-1 to 15-5 having a higher priority according to the state information of the devices 15-1 to 15-5 and the predetermined priority, the mux ( 14-5), and the mux 14-5 controls the queue selection of the schedule queue 15 according to the queue selection control of the priority analysis block 14-4. The schedule information read from 5) is multiplexed and transmitted to the transmission control means 16.

The transmission control means 16 reads the corresponding cell from the cell buffer 17 using the cell buffer address included in the schedule information, and then reads the header information VPI of the cell read using the cell header information to be converted; A Virtual Path Identifier (VCI) and a Virtual Channel Identifier (VCI) are converted and outputted, and the cell buffer 17 is a memory capable of dual port random access and stores input cells.

In the conventional shared memory ATM switch configured as described above, the cell is input to the reception control means 11, stored in the cell buffer 17, and then output through the transmission control means 16 according to the scheduling policy of the scheduler 14. When the reception control means 11 transmits the header information of the input cell to the connection control means 12, the connection control means 12 transmits the connection control information recorded in the connection control table 13 to the input cell. The header information is read and transmitted to the reception control means 11.

Then, the reception control means 11 analyzes the connection control information to determine whether to discard the input cell, stores the input cell in the cell buffer 17, and then schedule information, that is, the cell buffer 17 in which the input cell is stored. ) And the header information to be converted are transmitted to the scheduler 14.

Therefore, the QoS analysis block 14-1 of the scheduler 14 stores the received schedule information in the corresponding queues 15-1 to 15-5 of the schedule queue 15 according to the QoS level, and then the cell. The input operation of is terminated.

Subsequently, the output operation of the corresponding cell is performed by the priority analysis block 14-4 of the scheduler 14 of each queue 15-1 to 15-5 received from the absolute priority and queue control block 14-3. If the corresponding queue selection is controlled according to the status information so that the schedule information stored in the predetermined queues 15-1 to 15-5 is transmitted to the transmission control means 16, the transmission control means 16 is included in the schedule information. After reading the cell stored in the cell buffer 17 using the cell buffer address, the header information of the read cell, that is, VPI and VCI information is converted and output.

In this case, the cell scheduling operation according to the absolute priority of the scheduler 14 in the corresponding ATM switch will be described in detail with reference to FIG. 3.

First, the priority analysis block 14-4 of the scheduler 14 is a queue having the highest priority among the plurality of queues 15-1 to 15-5 included in the schedule queue 15, that is, a cell. It is checked whether schedule information to be output to the CBR queue 15-1 most sensitive to delay time is stored (step S31).

At this time, when the schedule information to be output to the corresponding CBR queue 15-1 is stored, the priority analysis block 14-4 controls the queue selection of the mux 14-5 to control the CBR queue 15-1. After transmitting the schedule information stored in the transmission control means 16 (step S36), the flow returns to step S31 to check again whether the schedule information to be output to the CBR queue 15-1, which is the highest priority queue, is stored. do.

However, when the schedule information to be output to the corresponding CBR queue 15-1 is not stored in step S31, the priority analysis block 14-4 is next to the RtVBR queue 15-2 which is the next higher priority queue. It is checked whether the schedule information to be output is stored (step S32). In this case, when the schedule information to be output is stored in the corresponding RtVBR queue 15-2, the RtVBR queue 15-2 is performed in the same manner as in step S36. After transmitting the schedule information stored in the control unit to the transmission control means 16 (step S37), the process returns to step S31 to check whether the schedule information to be output to the CBR queue 15-1, which is the highest priority queue, is stored. The repetitive operation will be performed.

However, when the schedule information to be output to the corresponding RtVBR queue 15-2 is not stored in step S32, the NrtVBR queue 15-3, the ABR queue 15-4, and the UBR queue are set according to the preset absolute priority. The cell scheduling is performed according to whether or not the schedule information to be output is stored in the order of (15-5) (steps S33 to S35, and steps S38 to S40).

As described above, in the conventional ATM switch, the schedule information stored in each queue of the schedule queue is output according to a predetermined absolute priority according to the QoS level. Therefore, the schedule information of the CBR queue having a relatively high priority can be quickly output. Although there is an advantage in that the queue having a lower priority, in particular, the schedule information of the UBR queue having the lowest priority can be output only when the schedule information to be outputted in all queues higher than itself is not stored. There was a disadvantage that can not be output for a long time.

Therefore, according to cell scheduling according to the absolute priority of the conventional ATM switch, the input cell associated with the schedule information stored in the queue of which the priority is relatively low occupies the cell buffer for a long time, thereby overloading the cell buffer. There was a disadvantage that the input cell is lost.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide a predetermined threshold weight for each queue included in a schedule queue in an ATM switch according to a weighting priority for comparing with a corresponding weighting coefficient value. By performing the cell scheduling, it is possible to prevent the schedule information stored in the queue whose absolute priority is relatively low from being output for a long time, and to prevent the overload of the corresponding cell buffer and the loss of the input cell.

1 is a diagram showing the structure of a typical shared memory ATM switch.

2 is a detailed block diagram of a conventional scheduler and a schedule queue in FIG.

3 is a flowchart of cell scheduling according to the absolute priority of a scheduler in a conventional ATM switch.

4 is a detailed block diagram of a scheduler and a schedule queue in accordance with the present invention.

5 is a flowchart illustrating a cell scheduling operation according to a virtual priority of a scheduler in an ATM switch according to the present invention.

Explanation of symbols on the main parts of the drawings

40: scheduler 41: QoS analysis block

42: demux 43: queue control block

44: weighted priority analysis block 45: MUX

50: schedule queue 51: CBR queue

52: RtVBR Queue 53: NrtVBR Queue

54: ABR queue 55: UBR queue

A feature of the present invention for solving the above object is an ATM switch that stores a predetermined input cell in a cell buffer and simultaneously stores and outputs corresponding schedule information in a corresponding queue of a schedule queue according to QoS level. A cell scheduling method comprising: assigning different threshold weights to each queue; Comparing the weighting coefficient values for each queue with corresponding threshold weights; Controlling queue selection to transmit schedule information stored in a queue having a weight factor greater than a threshold weight to a transmission control means and initializing a weight factor corresponding thereto; Increasing the weighting coefficient value for each queue except for the currently selected queue by '1'; And after reading a cell stored in the cell buffer by using the transferred schedule information, converting and outputting header information of the read cell.

If there is no queue having a weighting factor greater than a threshold weight, the schedule information stored in the queue storing schedule information according to the queue selection control according to the absolute priority is transmitted to the transmission control means. And further comprising initializing a corresponding weighting coefficient value.

Further, the step of comparing the weighting coefficient values for the respective queues with the corresponding threshold weights is characterized in that the absolute priority is compared in the order of the queue with a relatively high priority.

In addition, the threshold weight has a different value for each queue except for the queue having the highest absolute priority, and the queue having a higher priority has a smaller value.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the ATM switch according to the present invention, cell scheduling according to weighted priority is performed by assigning a weight value to each priority without performing cell scheduling according to absolute priority as in the prior art. Since the schematic structure of the ATM switch is the same as that of the conventional shared memory ATM switch shown in FIG. 1, the same reference numerals will be used and the description thereof will be omitted.

However, in order to describe the cell scheduling method according to the weighted priority of the ATM switch according to the present invention in detail, the scheduler and the schedule queue will use the reference numerals of FIG. 4.

Meanwhile, the scheduler 40 and the schedule queue 50 of the ATM switch according to the present invention are configured as shown in FIG. 4. The scheduler 40 includes a QoS analysis block 41 and a demux. DEMUX, 42, queue control block 43, weighted priority analysis block 44 and mux (MUX, 45), the corresponding schedule queue 50 corresponds to the QoS class of the input cell It includes a plurality of queues (51 to 55) that can store the schedule information.

At this time, as the types of the queues 51 to 55 included in the schedule queue 50 storing corresponding schedule information, the CBR queue 51, the RtVBR queue 52, , NrtVBR queue 53, ABR queue 54 and UBR queue 55.

On the other hand, the QoS analysis block 41 of the scheduler 40 demux 42 to store the schedule information received when the cell input to the corresponding queue (51 ~ 55) of the schedule queue 50 according to the QoS level The demux 42 demultiplexes the schedule information received when the cell is input according to the queue selection control of the QoS analysis block 41 to control the queue selection of the queue. ).

In addition, the queue control block 43 adds state (available / non-available) information indicating whether or not to store schedule information for each queue 51 to 55 of the schedule queue 50 when the cell is output. 44, the weighted priority analysis block 44 controls the transmission of the schedule information stored in each queue 51 to 55 of the schedule queue 50 according to the weighted priority in association with the queue control block 43. Controlling the queue selection of the mux 45 for delivery to the means 16, the mux 45 being the corresponding queue 51 of the schedule queue 50 in accordance with the queue selection control of the weighted priority analysis block 44. The schedule information read from ˜55 is multiplexed and transmitted to the transmission control means 16.

Here, the queue selection control according to the weighted priority of the corresponding weighted priority analysis block 44 centers a predetermined threshold weight on each of the queues 52 to 55 except the CBR queue 51 having the highest absolute priority. In a state given from an external processor such as a processing unit (not shown), the corresponding threshold weights can be compared with the weighting factor values for the corresponding queues 52-55 to control queue selection irrespective of absolute priority. In this case, the schedule information stored in the queues 52 to 55 having weighting coefficient values larger than the corresponding threshold weight is transmitted to the transmission control means 16.

In this case, the weighting coefficient value is incremented by '1' by the weighting priority analysis block 44 when the schedule information to be outputted in the corresponding queues 52 to 55 is stored but is not outputted. When the schedule information stored in 52 to 55 is transmitted to the transmission control means 16, it is initialized to '0'.

However, if there are no queues 52 to 55 having a weighting factor value greater than the corresponding threshold weight, the queue selection is controlled according to an absolute priority to transmit the schedule information stored in the corresponding queues 51 to 55. Will be forwarded to (16).

In the ATM switch according to the present invention configured as described above, the cell is inputted to the reception control means 11, stored in the cell buffer 17, and according to the cell output order determined by cell scheduling according to the weighted priority of the scheduler 40. It is output through the transmission control means 16. If the reception control means 11 transmits the header information of the input cell to the connection control means 12, the connection control means 12 is an external processor when the call is established. By this, the connection control information recorded in the connection control table 13 is read using the header information of the input cell, and transferred to the corresponding reception control means 11.

Then, the reception control means 11 analyzes the connection control information to determine whether to discard the input cell, stores the input cell in the cell buffer 17, and then schedule information, that is, the cell buffer 17 in which the input cell is stored. ) And the header information to be converted are transmitted to the scheduler 40.

Therefore, the QoS analysis block 41 of the scheduler 40 stores the received schedule information in the corresponding queues 51 to 55 of the schedule queue 50 according to the QoS level, and then terminates the cell input operation. do.

Subsequently, the output operation of the corresponding cell weights the schedule information stored in each queue 51 to 55 of the schedule queue 50 by the weighted priority analysis block 44 of the scheduler 40 in association with the queue control block 43. When the queue selection of the mux 45 is controlled to be transmitted to the transmission control means 16 according to the priority, the corresponding mux 45 is subject to the schedule queue 50 according to the queue selection control of the weighted priority analysis block 44. The schedule information read from the corresponding queues 51 to 55 of the multiplexer is multiplexed and transmitted to the transmission control means 16, and the transmission control means 16 uses the cell buffer (C buffer) using the cell buffer address included in the schedule information. After reading the cell stored in 17), the header information of the read cell is converted and output.

In this case, the cell scheduling operation according to the weighted priority of the scheduler 40 in the corresponding ATM switch will be described in detail with reference to FIG. 5.

First, the weighted priority analysis block 44 of the scheduler 40 fails to deliver the schedule information stored in the queue having a relatively low priority to the transmission control means 16 for a long time, so that the corresponding input cell has a cell buffer 17. In order to prevent overload and cell loss caused by long occupancy, a predetermined threshold weight is given to each queue 52 to 55 except the CBR queue 51 having the highest absolute priority. (Step S51) In this case, the corresponding threshold weights are given different threshold weights for each queue 52 to 55, but the threshold weight of the smaller value is higher for the queue having a higher absolute priority for cell scheduling according to more efficient weighting priority. Will be granted.

Then, the weighted priority analysis block 44 compares the weighting coefficient values for each of the queues 52 to 55 except for the CBR queue 51, which is the highest absolute priority queue, with the corresponding threshold weight to determine the absolute priority and the priority. Regardless of whether or not the queues 52 to 55 having the corresponding weighting factor values larger than the threshold weight exist to control the queue selection (step S52).

In this case, when there are queues 52 to 55 having corresponding weighting coefficient values greater than the threshold weights, the weighting priority analysis block 44 controls queue selection of the mux 45 to control the corresponding queues 52 to 55. 55 transmits the schedule information stored in step 55 to the transmission control means 16, initializes the weighting coefficient values for the corresponding queues 52 to 55 to '0' (step S53), and then executes the currently selected controlled queue. It is checked whether or not there are queues 51 to 55 that store schedule information to be output among the excluded queues 51 to 55 (step S54).

If there are queues 51 to 55 storing the schedule information to be output, the weighted priority analysis block 44 increases the weighting factor value for the corresponding queues 51 to 55 by '1'. Subsequently (step S55), the flow returns to step S52 for checking whether there are queues 52 to 55 having a value whose weighting factor value is greater than the threshold weight, and performs a repetitive operation.

However, if there are no queues 51 to 55 storing the schedule information to be output in step S54, the flow returns to step S52 to perform a repetitive operation without increasing the weighting coefficient value.

On the other hand, if there are no queues 52 to 55 whose weighting factor values are greater than the threshold weight in step S52, the weighting priority analysis block 44 stores schedule information to be output according to an absolute priority. It is sequentially checked whether any of the queues 51 to 55 exist (step S56).

Here, the weighted priority analysis block 44 is assigned to the queues 51 to 55 corresponding to the UBR queue 55 which is the lowest priority queue from the CBR queue 51 having the highest absolute priority. Check whether the schedule information to be output is saved.

At this time, as a result of sequentially checking the respective queues 51 to 55 according to the corresponding absolute priority, when the schedule information to be output to the predetermined queues 51 to 55 is stored, the corresponding weighted priority analysis block 44 is mux 45 Control the queue selection to transmit the schedule information stored in the corresponding queues 51 to 55 to the transmission control means 16 and initialize the weighting coefficient values for the corresponding queues 51 to 55 to '0'. Subsequently (step S57), the schedule information is determined by performing the operation of step S54 for checking whether there are queues 51 to 55 that store schedule information to be output among queues 51 to 55 except for the currently selected controlled queue. For queues that have been stored but not delivered to the transmission control means 16, the weighting factor value is increased by '1', and then there are queues 52 to 55 whose weighting factor values are greater than the threshold weight. The operation of checking step S52 is repeated. All.

However, if the queues 51 to 55 storing the schedule information to be output as a result of sequentially checking the respective queues 51 to 55 according to the absolute priority in step S56, the corresponding weighted priority analysis block 44 Returns to step S52 to check whether there exist queues 52 to 55 whose weighting coefficient values are greater than the threshold weight, without increasing the weighting coefficient values for the corresponding queues 51 to 55 to perform the repetitive operation. do.

On the other hand, the operation of checking whether the queues 52 to 55 having the corresponding weighting factor value greater than the threshold weight in step S52 may exist at the same time, so that a plurality of queues 52 to 55 may exist at the same time. Accordingly, the RtVBR queue 52, the NrtVBR queue 53, the ABR queue 54, and the UBR queue 55 are performed in this order.

As described above, in the ATM switch according to the present invention, the schedule information stored in each queue 51 to 55 of the schedule queue 50 is first transmitted to the transmission control means 16 according to the weighted priority according to the QoS level. Then, by being transmitted according to the absolute priority, it is possible to prevent the schedule information stored in the queue (52 to 55) that the absolute priority is relatively low output for a long time, thereby the corresponding input cell is a cell It is possible to prevent overload and loss of an input cell generated by occupying the buffer 17 for a long time.

In addition, the embodiments according to the present invention are not limited to the above-described embodiments, and various alternatives, modifications, and changes can be made within the scope apparent to those skilled in the art.

As described above, the present invention performs an absolute priority by performing cell scheduling according to a weighting priority that compares a predetermined threshold weight given to each queue included in a schedule queue in an ATM switch with a corresponding weighting coefficient value. The schedule information stored in the relatively low queue can be prevented from being output for a long time, and the overload of the corresponding cell buffer and the loss of the input cell can be prevented.

Claims (5)

In the cell scheduling method of an ATM switch which stores a predetermined input cell in a cell buffer and simultaneously stores corresponding schedule information in a corresponding queue of a schedule queue according to QoS level and outputs the same. Assigning different threshold weights to each of the queues; Comparing the weighting coefficient values for each queue with corresponding threshold weights; Controlling queue selection to transmit schedule information stored in a queue having a weight factor greater than a threshold weight to a transmission control means and initializing a weight factor corresponding thereto; Increasing the weighting coefficient value for each queue except for the currently selected queue by '1'; A cell scheduling method according to a weighted priority of an AT switch, after the cell stored in the cell buffer is read using the transferred schedule information, and the header information of the read cell is converted and output. . delete The method of claim 1, If a queue having a weighting factor greater than a threshold weight does not exist, the schedule information stored in the queue storing the schedule information is transmitted to the transmission control means according to the queue selection control according to the absolute priority. Cell scheduling method according to the weighting priority of the AT switch further comprising the step of initializing the weighting coefficient value. The method of claim 1, In the process of comparing the weighting coefficient values for the respective queues with the corresponding threshold weights, cell scheduling according to the weighted priority of the AT switch, characterized in that the absolute priority is compared from the higher queue to the lower queue in order. Way. The method according to any one of claims 1, 3 and 4, The threshold weight has a different value for each queue except for the queue having the highest absolute priority, and the queue having the higher priority has a smaller value according to the weighted priority of the AT switch. Scheduling Method.