JP3785635B2 - Communication apparatus, priority control method thereof, and priority control program - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to communication packet relaying, and more particularly, to a communication device that prioritizes and forwards packets transmitted through a plurality of channels, a priority control method thereof, and a priority control program.
[0002]
[Prior art]
Some communication devices that relay communication packets relay communication using a plurality of channels, and different service qualities (such as throughput) may be set for each channel.
[0003]
As the throughput set for each channel, for example, a bandwidth guarantee type that always guarantees a constant throughput or a best effort type that makes efforts to maintain good service without guaranteeing a throughput value (Best Effort) Type) etc.
[0004]
[Problems to be solved by the invention]
As described above, in the conventional technology, when the scheduler logic on the receiving side is simplified and bandwidth reservation (scheduling) is performed based only on the maximum guaranteed bandwidth speed (contract rate) of the corresponding channel, multiple packets of different channels are placed in the same time slot. There is a problem that the bandwidth of the transmission interface is concentrated and the maximum guaranteed bandwidth speed traffic is guaranteed on the transmission side, and the best effort traffic control becomes difficult when an unused bandwidth occurs.
[0005]
The object of the present invention is to solve the above-mentioned drawbacks of the prior art, simplify the logic in bandwidth reservation (scheduling) than the conventional device, and further guarantee the traffic with the maximum guaranteed bandwidth rate by the scheduler, and more Provided are a communication apparatus, a priority control method, and a priority control program for realizing efficient priority control with a class transmitted with low priority and best effort according to an unused band.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a communication device according to the present invention is a communication device that preferentially controls a packet transmitted through a plurality of channels and sets the packet length of the received packet and the channel of the packet. Means for scheduling the transfer of packets of a class that guarantees transmission of the maximum guaranteed bandwidth rate, and the order in which packets scheduled by the time slot are transmitted is controlled by the time slot calculated based on the maximum guaranteed bandwidth rate A bandwidth management unit that determines a packet to be transmitted based on the quality of service set in the channel of the packet, a reception-side counter that indicates a timing for executing the scheduling, and a packet to be transmitted in the bandwidth management unit. Sender count that indicates when to decide The reception side counter and the transmission side counter count up at the same fixed cycle, and the update timing of the transmission side counter is shorter than the count-up cycle from the update point of the reception side counter. After a predetermined fixed time, the bandwidth management unit guarantees transmission of the maximum guaranteed bandwidth rate in the period from the update timing of the transmission side counter to the update timing of the reception side counter in the time slot. A packet other than the class that guarantees transmission of the maximum guaranteed bandwidth rate when there is no packet scheduled by the scheduling means in the time slot in the remaining period of the time slot. It is characterized by transmitting.
[0007]
Thus, the communication device of the present invention schedules each packet based on the maximum guaranteed bandwidth speed when the reception side counter is counted up, and then the bandwidth management unit is predetermined in advance, which is shorter than the count-up cycle. By determining a packet to be transmitted based on the service quality set for each channel after a certain time, priority control can be performed efficiently based on the service quality of each channel.
[0008]
The communication apparatus according to claim 2, wherein the bandwidth management unit is configured to perform the maximum guaranteed bandwidth rate scheduled in the time slot based on a packet length of the packet and a quality of service set in a channel of the packet. The amount of used bandwidth set for packet transmission other than the class for guaranteeing transmission at the maximum guaranteed bandwidth rate is updated .
[0009]
The communication apparatus of the present invention according to claim 3 includes a service quality setting of either a bandwidth guarantee type or a best effort type for each channel, and each channel is set based on the set service quality and the amount of bandwidth used. The packet is transferred with priority control.
[0010]
According to a fourth aspect of the present invention, there is provided a priority control method for a communication device for performing priority control and transferring packets transmitted via a plurality of channels, wherein the communication device counts up at the same constant period. A reception side counter and a transmission side counter, and the update timing of the transmission side counter is set to a predetermined time shorter than the count-up cycle from the update point of the reception side counter, and the reception side counter Transfer of a packet of a class that guarantees transmission of the maximum guaranteed bandwidth rate by a time slot calculated based on the packet length of the received packet and the maximum guaranteed bandwidth rate set in the channel of the packet at each update time of performing a scheduling for each time of updating of the transmitting-side counter, the scan by said time slot Together comprising the step of determining the packet to be transmitted based on the service quality set by controlling the turn channel of the packet to be transmitted in the scheduling packets, in determining a packet to be the transmission, the time slot, the update timing of the transmitter-side counter, for a period of up to update timing of the receiver-side counter, and transmits the packet of the class that guarantees the transmission of the maximum guaranteed bandwidth rate at the remainder of the time slot When there is no packet scheduled by the scheduling means in the corresponding time slot, a packet other than a class that guarantees transmission of the maximum guaranteed bandwidth rate is transmitted.
[0011]
The priority control method of the present invention according to claim 5 guarantees transmission of the maximum guaranteed bandwidth rate scheduled in the time slot based on the packet length of the packet and the quality of service set in the channel of the packet. The use band set for packet transmission of the class and the amount of use band set for packet transmission other than the class for guaranteeing transmission of the maximum guaranteed bandwidth rate are updated .
[0012]
The priority control method of the present invention according to claim 6 includes setting of a service quality of either a bandwidth guarantee type or a best effort type in each of the channels, and each based on the set service quality and the amount of bandwidth used. It is characterized by preferentially transferring channel packets.
[0013]
According to a seventh aspect of the present invention, there is provided a priority control program for controlling a computer to perform priority control and transfer of packets transmitted via a plurality of channels. A process of counting up the transmission side counter, and updating the transmission side counter after a predetermined time period shorter than the count-up cycle from the update point of the reception side counter; Each time the counter is updated, a packet of a class that guarantees transmission of the maximum guaranteed bandwidth rate based on the packet length of the received packet and the time slot calculated based on the maximum guaranteed bandwidth rate set in the channel of the packet a process of performing scheduling for transmission of, for each time of updating of the transmitting-side counter, the data Together to execute a process of determining a packet to be transmitted based on quality of service set in the channel of the control the order in which the transmission of the scheduled packets packets by timeslot, in the processing for determining a packet to be the transmission, the time slot, the update timing of the transmitter-side counter, for a period of up to update timing of the receiver-side counter, and transmits the packet of the class that guarantees the transmission of the maximum guaranteed bandwidth speed, the remainder of the time slot Then, when there is no packet scheduled by the scheduling means in the corresponding time slot, a process of transmitting a packet other than the class that guarantees transmission of the maximum guaranteed bandwidth rate is executed.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0015]
FIG. 1 is a block diagram showing a configuration of an example of a communication apparatus 100 according to an embodiment of the present invention.
[0016]
The communication apparatus 100 according to the present embodiment performs packet transfer by guaranteeing the bandwidth of a multiplexed traffic using a plurality of channels set with various service qualities (throughput, etc.) by a scheduler. This packet is not limited to a fixed-length packet, and may be a variable-length packet.
[0017]
The receiving-side scheduler in the communication device 100 has a simplified device configuration as compared with a conventional device, as bandwidth reservation (scheduling) is performed only based on the maximum guaranteed bandwidth speed (contract rate) of the corresponding channel.
[0018]
In addition, due to this simplification, there is a possibility that a plurality of packets of different channels are concentrated in the same time slot and scheduled beyond the bandwidth of the transmission interface. It is assumed that packets scheduled over a certain bandwidth are controlled.
[0019]
As will be described below, the bandwidth management unit 30 determines and transmits a packet to be transmitted with reference to a time slot that is delayed from a time slot that is referred to by the scheduler on the receiving side. As a result, the traffic class having the maximum guaranteed bandwidth rate by the scheduler can be guaranteed, and priority control with a class that is lower priority than that and transmitted to the best effort according to the unused bandwidth is realized.
[0020]
In the following description, the class that is scheduled and guarantees the traffic with the maximum guaranteed bandwidth rate is called A class, and is transmitted to the best effort according to the unused bandwidth of A class with lower priority than this A class. The class will be called B class.
[0021]
Next, referring to FIG. 1 for explaining the function of each unit of the communication device 100 of the present embodiment, the communication device 100 of the present embodiment includes a packet receiving unit 10, a traffic classifying unit 20, a bandwidth management unit 30, An A class scheduler 50, a B class buffer 60, a packet buffer 70, and a packet transmission unit 80 are provided, and a packet input through the packet input line L1 is output from the packet output line L2.
[0022]
In the packet input line L1 and the packet output line L2, a plurality of channels of variable length packet traffic are multiplexed.
[0023]
The packet receiving unit 10 extracts the channel number, the packet priority class, and the packet length of the received packet from the packet received from the packet input line L1, and generates a control cell in the apparatus. The generated control cell uniquely corresponds to the received packet, and is transferred from the packet receiving unit 10 to the traffic classifying unit 20.
[0024]
Further, the packet receiver 10 transfers the packet entity to the packet buffer 70. The control cell generated here includes a channel number, a priority class, a packet length, and a pointer to the packet entity.
[0025]
The packet buffer 70 is a buffer for storing the substance of the received packet. The packet receiving unit 10 writes the received packet to the packet buffer 70, and the packet transmitting unit 80 reads the buffer from the packet buffer 70 and transmits it to the outside.
[0026]
The timer unit 40 divides the internal clock to generate a time slot counter (Ti, reception side counter) used on the reception side and a time slot counter (To, transmission side counter) used on the transmission side. The time slot counter (Ti) is referred to by the A class scheduler 50 on the receiving side, and the time slot counter (To) is referred to by the bandwidth management unit 30 on the transmitting side. Both of the time slot counters (Ti) (To) are counters having the same period, the update timings of which are shifted by (predetermined) α clocks.
[0027]
Further, the timer unit 40 generates a flag (Bm) for designating whether or not to transmit a packet from the B class buffer. This flag (Bm) indicates “0” when packet transmission from the B class buffer is prohibited in the time slot, and indicates “1” when packet transmission is permitted. This flag (Bm) is referred to and used by the bandwidth management unit 30.
[0028]
Further, the timer unit 40 periodically resets a flag (Pf) for designating a class (A, B) referred to by the bandwidth management unit 30. For the flag (Pf), the bandwidth management unit 30 refers to the A class when Pf = 0, and the bandwidth management unit 30 refers to the B class when Pf = 1. The flag (Pf) indicates that there is no untransmitted packet scheduled in the time slot (Rc = 0), and transmission of all the packets scheduled in the time slot in the most recent time slot is completed within one time slot time. “1” is set when (To = Tk) and packet transmission from the B class buffer is permitted (Bm = 1), and the bandwidth management unit 30 periodically resets it to “0”. .
[0029]
The traffic classification unit 20 classifies the control cell into an A class scheduler and a B class buffer according to the priority class in the control cell. For traffic that is permitted to be changed in class priority, the priority class may be changed according to the bandwidth used from the bandwidth management unit.
[0030]
The A class scheduler 50 sets a control cell in response to a request from the traffic classification unit 20 and sets a time slot (TS) to be scheduled from the maximum guaranteed bandwidth rate (PR) set for each channel and the received packet length PL. = TS + PL / PR is calculated and bandwidth reservation is performed (scheduler writing to the corresponding time slot). At this time, the number of packets (Rc) managed for each time slot is incremented. The time slot to be referred to when writing to the scheduler is Ti that is a counter on the receiving side of the timer unit.
[0031]
Further, when reading from the scheduler is performed in response to a request from the bandwidth management unit 30, the number of packets (Rc) is decremented. The time slot referred to when the scheduler is read is Tk of the bandwidth management unit. Here, a plurality of packets of different channels may be concentrated in the same time slot for one time slot and scheduled beyond the bandwidth of the transmission interface.
[0032]
The B class buffer 60 is buffered for each channel. At the time of buffer writing from the traffic classification unit 20, the buffer length (Qc) is incremented. When reading the buffer from the bandwidth management unit 30, the buffer length (Qc) is decremented. In the B class buffer, the buffer may be further divided into relative classes.
[0033]
Based on the received packet length PL obtained from the A class scheduler 50 or the B class buffer 60, the bandwidth management unit 30 updates the A class used bandwidth (AR) and the B class used bandwidth (BR) of the used bandwidth in the time slot. I do. Further, the unused band WR-AR-BR is updated from the transmission interface physical speed (WR).
[0034]
Further, the bandwidth management unit 30 generates Tk that is a counter indicating the read time slot of the A class scheduler. Tk is updated when Pf = 0, Rc = 0, and To ≠ Tk.
[0035]
When “Bm = 0”, the bandwidth management unit 30 reads the control cell scheduled in the corresponding time slot of the A class and transmits it to the packet transmission unit 80. The Rc of the corresponding time slot is decremented at the time of transmission, and the interval in which Bm = 0 is updated within the time slot use band (AR) according to the packet length for each transmission from the A class, even if Rc = 0, B Class control cell reading is not performed.
[0036]
When “Bm = 1”, the bandwidth management unit 30 reads the control cell from the A class and transmits it to the packet transmission unit 80. Here, when “Rc = 0” and “unused bandwidth> received packet length PL”, the control cell is read from the B class buffer and transmitted to the packet transmitter 80. When receiving the packet transferred from the bandwidth management unit 30, the packet transmission unit 80 extracts a pointer to the packet, reads the packet from the packet buffer 70 in accordance with the pointer, and sends the packet to the packet output line L2.
[0037]
Next, the operation of the communication apparatus according to this embodiment will be described.
[0038]
FIG. 2 is a flowchart for explaining the processing of the timer unit 40 of the present embodiment. Here, t: m-bit counter (clock), Ti, To: n-bit counter, s, α constant (where s> α), and the timer unit 40 of the present embodiment operates according to FIG. Note that the symbol “++” shown to the right of a variable (clock or counter) shown in the flowchart indicates that 1 is added to the value of the variable.
[0039]
Ti and To are generated by dividing t by s (ie, having a period s times the counter t). Since Ti is updated when the counter t is “s−α” and To is updated when the counter t is “s”, the Ti and To counters are offset by α clocks.
[0040]
Further, when t = s, which is the update time of To, Bm and Pf are reset to “0”. When t = s−α, which is the Ti update time, “1” is set to Bm.
[0041]
FIG. 4 is a time chart for explaining the operation of the example when the packet according to the present embodiment is distributed and scheduled in the time slots, and FIG. 5 shows the used bandwidth of each class in this example. It is a graph to show.
[0042]
FIG. 6 is a time chart for explaining the operation of the embodiment when the packets of the present embodiment are concentrated and scheduled in the same time slot and exceed the bandwidth of the transmission interface. FIG. It is a graph which shows the use band of each class in an example.
[0043]
In communication apparatus 100 of the present embodiment, packet receiving unit 10 receives a packet from packet input line L1, and extracts a channel number, a packet priority class, a packet length, and a pointer to a packet buffer extracted from the received packet. Then, a control cell in the apparatus is generated and transferred from the packet receiving unit 10 to the traffic classifying unit 20.
[0044]
The traffic classification unit 20 classifies the control cell into A class and B class according to the priority class in the control cell. The control cell classified into the A class uses the A class scheduler 50 to determine the time slot (TS) to be scheduled from the maximum guaranteed bandwidth rate (PR) set for each channel and the received packet length PL by TS = TS + PL / The bandwidth is calculated by PR and the bandwidth is reserved (scheduler writing to the corresponding TS). At this time, the number of packets (Rc) managed for each TS is incremented. TS to be referred to when writing to the scheduler is Ti of the timer unit. The control cell classified into the B class is written to the B class buffer 60 for each channel.
[0045]
FIG. 3 is a flowchart for explaining the processing of the bandwidth management unit 30 according to the present embodiment, and performs selection of a priority class to be transmitted and bandwidth management according to FIG.
[0046]
The bandwidth management unit 30 first refers to the flag Pf, and refers to the A class if “Pf = 0”. When there is a packet scheduled in the corresponding time slot indicated by the counter Tk, that is, when “Rc ≠ 0”, the bandwidth management unit 30 reads the packet scheduled at the head, decrements Rc, and uses the bandwidth AR is added for the packet length. The symbol “-” shown to the right of the variable shown in the flowchart indicates that 1 is subtracted from the value of the variable.
[0047]
If “Rc = 0”, the relationship between the values of To and Tk is determined. If “To> Tk” (this is a packet scheduled in a time slot in a neighboring time slot). (In this case, transmission is not completed within one time slot) Tk is incremented by 1, and BR and AR are reset to “0”.
[0048]
In the case of “To = Tk”, this refers to the value of Bm (in the most recent time slot, indicates that transmission of all packets scheduled in the time slot is completed within one time slot time).
[0049]
In Bm reference, if “Bm = 0”, the B class is prohibited, so the B class packet is not read. If “Bm = 1”, Pf = 1 is set, and the B class buffer length Qc and packet length PL are referred to.
[0050]
If “Qc ≠ 0” and “WR-AR-BR> PL”, the buffer length Qc is decremented, and the use band BR is added for the packet length. The packet read out from the bandwidth management unit in this way is transferred to the packet transmission unit 80. The packet transmission unit extracts a pointer to the packet from the packet, reads the packet from the packet buffer 70 according to the pointer, and sends it to the packet output line L2.
[0051]
Note that the communication device 100 according to the present embodiment realizes the functions of the bandwidth management unit 30, the timer unit 40, and the like as well as other functions in hardware, as well as priority control that is a computer program having each function. The program can be realized by being loaded into a memory of a computer processing apparatus. This priority control program is stored in a magnetic disk, semiconductor memory or other recording medium 90. Then, each function described above is realized by being loaded from the recording medium 90 to the computer processing apparatus and controlling the operation of the computer processing apparatus.
[0052]
Although the present invention has been described with reference to the preferred embodiments and examples, the present invention is not necessarily limited to the above-described embodiments and examples, and various modifications can be made within the scope of the technical idea. Can be implemented.
[0053]
【The invention's effect】
As described above, according to the present invention, the maximum guaranteed bandwidth by the scheduler is selected by selecting the packet to be transmitted based on the time slot (To) delayed from the time slot (Ti) referred to by the scheduler on the receiving side. Efficient priority control between the class that guarantees the traffic of the speed and the class that is lower priority than that and is transmitted to the best effort according to the unused bandwidth, and in the bandwidth reservation (scheduling) than the conventional device Simplification of logic can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an example of a communication apparatus according to an embodiment of the present invention.
FIG. 2 is a flowchart for explaining processing of a timer unit according to an embodiment of the present invention.
FIG. 3 is a flowchart for explaining processing of a bandwidth management unit according to the embodiment of this invention.
FIG. 4 is a time chart for explaining the operation of an example when packets according to an embodiment of the present invention are distributed and scheduled in time slots;
FIG. 5 is a graph showing the bandwidth used in each class of an example when packets according to an embodiment of the present invention are distributed and scheduled in time slots.
FIG. 6 is a time chart for explaining the operation of the embodiment when packets according to an embodiment of the present invention are scheduled in a concentrated manner in the same time slot and exceed the bandwidth of the transmission interface;
FIG. 7 is a graph showing the bandwidth used for each class in the embodiment when packets according to an embodiment of the present invention are scheduled in a concentrated manner in the same time slot and exceed the bandwidth of the transmission interface.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 100 Communication apparatus 10 Packet receiving part 20 Traffic classification part 30 Band management part 40 Timer part 50 Class scheduler 60 Class buffer 70 Packet buffer 80 Packet transmission part 90 Recording medium

Claims (9)

In a communication device that transfers packets that are transmitted via a plurality of channels with priority control,
Means for scheduling transfer of packets of a class that guarantees transmission of the maximum guaranteed bandwidth rate based on the packet length of the received packet and the time slot calculated based on the maximum guaranteed bandwidth rate set in the channel of the packet When,
The time slot to control the order of transmitting the scheduled packets by the band management unit for determining a packet to be transmitted based on quality of service set in the channel of the packet,
A receiver counter that indicates when to perform the scheduling;
A transmission counter for instructing the timing for determining a packet to be transmitted in the bandwidth management unit;
The reception-side counter and the transmission-side counter are counted up at the same fixed cycle, and the update timing of the transmission-side counter is determined in advance from the update time of the reception-side counter, which is shorter than the count-up cycle. After a certain time,
The bandwidth management unit transmits a packet of a class that guarantees transmission of the maximum guaranteed bandwidth rate in a period from the update timing of the transmission side counter to the update timing of the reception side counter of the time slot ,
In the remaining period of the time slot, if there is no packet scheduled by the scheduling means in the time slot, a packet other than a class that guarantees transmission of the maximum guaranteed bandwidth rate is transmitted. apparatus. The bandwidth management unit is configured to transmit a packet of a class that guarantees transmission of the maximum guaranteed bandwidth rate scheduled in the time slot based on the packet length of the packet and the quality of service set in the channel of the packet. 2. The communication apparatus according to claim 1, wherein the amount of used bandwidth set for packet transmission other than the class for guaranteeing transmission of the used bandwidth to be set and the maximum guaranteed bandwidth rate is updated . Each of the channels has a service quality setting of either a bandwidth guarantee type or a best effort type, and forwards the packets of each channel with priority control based on the set service quality and the amount of bandwidth used. The communication device according to claim 2. In a priority control method of a communication device that performs priority control and transfers packets transmitted via a plurality of channels,
The communication device includes a reception side counter and a transmission side counter that count up at the same fixed period, and the update timing of the transmission side counter is set in advance from the update point of the reception side counter shorter than the count up period. After a fixed time,
Each time the receiving side counter is updated , transmission of the maximum guaranteed bandwidth is guaranteed by the time slot calculated based on the packet length of the received packet and the maximum guaranteed bandwidth set in the channel of the packet. Scheduling the transfer of packets of the class ;
A step of controlling a transmission order of packets scheduled by the time slot and determining a packet to be transmitted based on a quality of service set in a channel of the packet every time the transmission side counter is updated;
In the step of determining the packet to be transmitted,
In the time slot, in a period from the update timing of the transmission side counter to the update timing of the reception side counter, a packet of a class that guarantees transmission of the maximum guaranteed bandwidth rate is transmitted,
In the remaining period of the time slot, if there is no packet scheduled by the scheduling means in the corresponding time slot, a packet other than a class that guarantees transmission of the maximum guaranteed bandwidth rate is transmitted. Priority control method. Based on the packet length of the packet and the quality of service set for the channel of the packet, the bandwidth used for transmission of a packet of a class that guarantees transmission of the maximum guaranteed bandwidth rate scheduled in the time slot, and 5. The priority control method according to claim 4, wherein the amount of used bandwidth set for packet transmission other than the class for guaranteeing transmission at the maximum guaranteed bandwidth rate is updated . Each of the channels has a service quality setting of either a bandwidth guarantee type or a best effort type, and forwards the packets of each channel with priority control based on the set service quality and the amount of bandwidth used. The priority control method according to claim 5, wherein: In a priority control program for controlling and transferring a packet transmitted through a plurality of channels by controlling the computer,
The reception side counter and the transmission side counter are counted up at the same fixed period, and the update timing of the transmission side counter is set to a predetermined fixed period shorter than the count-up period from the update point of the reception side counter. After processing,
Each time the receiving side counter is updated , transmission of the maximum guaranteed bandwidth is guaranteed by the time slot calculated based on the packet length of the received packet and the maximum guaranteed bandwidth set in the channel of the packet. A process for scheduling the transfer of packets of a class ;
Each time the transmission side counter is updated, the process of determining the packet to be transmitted is controlled based on the quality of service set in the channel of the packet by controlling the transmission order of the packet scheduled by the time slot. ,
In the process of determining the packet to be transmitted,
In the time slot, in a period from the update timing of the transmission side counter to the update timing of the reception side counter, a packet of a class that guarantees transmission of the maximum guaranteed bandwidth rate is transmitted,
If there is no packet scheduled by the scheduling means in the corresponding time slot in the remaining period of the time slot, a process of transmitting a packet other than the class that guarantees transmission of the maximum guaranteed bandwidth rate is executed. A priority control program. Based on the packet length of the packet and the quality of service set for the channel of the packet, the bandwidth used for transmission of a packet of a class that guarantees transmission of the maximum guaranteed bandwidth rate scheduled in the time slot, and 8. The priority control program according to claim 7, wherein the priority control program executes a process of updating an amount of used bandwidth set for packet transmission other than a class for guaranteeing transmission at a maximum guaranteed bandwidth speed . Each of the channels is provided with a service quality setting of either a bandwidth guarantee type or a best effort type, and a process of preferentially controlling the packet of each channel based on the set service quality and the amount of bandwidth used. The priority control program according to claim 8, wherein the priority control program is executed.

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