JP2002271385A - Round-robin control, method, band control method and packet controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the round-robin retrieval at a high speed in a simple constitution which handles a plurality of priority classes fixedly or dynamically in the packet communication. SOLUTION: On the occasion of selecting either one (FIFO#k) of a plurality of buffers 100 FIFO#0 to #n-1 having stored communication packets 102 in the route-robin system to transmit packets stored in the (FIFO#k), the k-th buffer FIFO#k in the round-robin retrieving order about the FIFO#0 to #n-1 is enabled to send packets, a first binary variable WDR (n-1:0) with a k-th bit, as counted from the least significant bit, set to 0 and others set to 1 is generated, and the least significant bit among the bits of 0 in the first binary variable WDR (n-1:0) is specified to specify an FIFO#k to be selected from this bit position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a round robin control method and a band control method applied to multiplexing and band control of a packet communication system, and a packet control device.

[0002]

2. Description of the Related Art In recent years, with the increase in traffic accommodated on the Internet and the diversification of accommodation services, QoS (Quality (QoS))
There is a demand for realizing packet transfer with guaranteed service of service. Generally, Intserv and Diffserv, which are attracting attention as QoS control techniques for IP packets, are techniques for setting a relative quality assurance class internally to differentiate communication quality to be guaranteed.

In a communication control device according to this, PQ (Pr
iority Queuing),
The communication packets are stored in the buffer by classifying them into the classes of the communication quality, and the packets are sequentially transmitted from the quality class having the highest priority. In contrast, buffers are distinguished based on service types, and communication packets requiring real-time characteristics, such as audio and video, are transferred with priority over packets that allow transmission delay, such as e-mail and file transfer. C
BQ (Class-Based Queuing) may be used in some cases. In any case, in order to realize a method of transmitting a packet by selecting one from a plurality of buffers, basically, a round robin control for imparting a packet transmission right fairly to all the buffers is performed, and each buffer is fixed. This is a method of setting a specific priority and giving a certain rule to the round robin search order.

On the other hand, in ATM communication using fixed-length packets, pure round-robin control without priority control may be used as a means for fairly allocating a bandwidth to all connections, and a minimum bandwidth is guaranteed for each connection. The means to do this is weighted round robin (We
ighted round robin) method is known. This weighted round-robin method can realize the guaranteed minimum bandwidth and the allocation of the surplus bandwidth according to the weight ratio set for each connection.

[0005] In addition, as a method of guaranteeing the minimum band and limiting the upper band at a high speed, Japanese Patent Laid-Open No. 11-23 / 1999
No. 9151, associative memory (CA
There is a band control method using M). In this method, a round-robin search is performed in two stages, a search for a connection that does not satisfy the minimum bandwidth and a search for a connection that satisfies the minimum bandwidth. When the bandwidth is satisfied, the upper limit bandwidth is limited by not setting it as a search target thereafter. A series of round robin searches are performed at high speed by a search mechanism of a content addressable memory (CAM), and high-speed bandwidth control is realized even in a large-scale communication system.

[0006]

Here, both the priority control and the band control are based on round robin control. The technical problem of the round robin control is that the processing load increases as the number of buffers to be selected for determining the next transmission packet increases. For example, 2
Even if 56 buffers are provided, and even if only one of the buffers can transmit a packet, it must recognize that 255 buffers cannot be selected each time, and the transmittable buffer must be selected. However, the procedure for skipping the buffer selection requires a lot of processing time.

Further, if it is necessary to provide a buffer corresponding to a connection, for example, when setting a priority for each connection in the ATM communication, the number of buffers to be handled by the round robin control becomes very large. The line usage efficiency is reduced because no packet is output.

Further, if the above-mentioned method using the associative memory is used, a procedure for skipping the buffer selection is not required, and the processing can be completed in a fixed time even when the number of buffers increases. However, if multiple service classes are to be mixed and controlled collectively, or if the number of priority levels assigned to each buffer is to be increased for more precise bandwidth control, the number of consecutive priority levels will increase. It is necessary to access the fast storage memory, and the number of processing steps increases proportionately. In addition, as a function of the associative memory, there is a problem in practical use in that a special function is selected in which entries that match conditions are selected first after the entry at the search start point. Have.

Therefore, when priority control and band control are realized in a communication system that accommodates various services on a larger scale, the overall processing speed should be equal to the number of buffers to be processed and the number of stages of priority classes. It is desirable not to depend.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a round-robin search that can be implemented with high speed and with a simple configuration, whether fixed or dynamic, and that handles a plurality of priority classes. It is an object to provide a control method, a band control method, and a packet control device.

[0011]

In order to achieve the above object, the present invention provides a round robin control method for selecting one of a plurality of selection candidates, wherein each of the plurality of selection candidates is selectable. Is defined, a control variable is generated by combining the state expressions of all the selection candidates according to the search order of round robin control, and an arithmetic operation or a logical operation is performed on the control variable. Thus, a specific state expression included in the control variable is selected, and a selection candidate to be selected is specified from the specified state expression.

According to the above-described method, a batch round-robin search by an arithmetic operation or a logical operation can be performed. Therefore, a fixed or dynamic round-robin search that handles a plurality of priority classes can be performed at high speed. , Can be realized with a simple configuration.

The present invention also provides a round-robin control method for selecting one of a plurality of buffers storing received packets by a round-robin method and transmitting the packets stored in the buffers. A first binary variable in which the k-th bit from the least significant bit is set to 0 when the k-th buffer in the round-robin search order with respect to the , A second control procedure for specifying the least significant bit of the bits of the first binary variable that are 0, and a bit position specified by the second control procedure. And a third control procedure for specifying a buffer to be performed.

According to the above method, a first binary variable in which bit representations indicating the state of each buffer are arranged according to a round-robin search order is generated, and the most significant bit among the 0 bits of the first binary variable is generated. Since a series of controls for specifying the lower bit position and specifying a buffer to be selected from the specified bit position are performed, round robin control for selecting one of a plurality of buffers having the same selection priority is set. Can be realized at high speed by simple arithmetic processing.

According to the present invention, the plurality of buffers may be fixedly ordered in advance, and the first control procedure may be such that the k-th buffer in the fixedly determined order with respect to the plurality of buffers is used. Generates a binary variable with the k-th bit counted from the least significant bit set to 0 and otherwise set to 1 if the packet can be transmitted, and the bit corresponding to the buffer at the start point of the round robin search. Is cyclically shifted until the first digit is at the least significant digit to generate the first binary variable.

According to the above method, the required first binary variable can be generated by a simple method.

According to the present invention, a selection priority is set in advance, and one of a plurality of buffers that can be selected from among a plurality of buffers storing received packets is selected from buffers having the highest selection priority by a round robin method. A round robin control method of selecting and transmitting a packet stored in the buffer, wherein a priority management procedure of managing a selection priority to be a target of a round robin search for the plurality of buffers as a search priority; If the k-th buffer in the round-robin search order for the buffer is capable of transmitting packets and has the same selection priority as the search priority, the k-th bit counting from the least significant bit is set to 0. Otherwise, a first control procedure for generating a first binary variable set to 1, and a search priority in order from the highest priority If the first binary variable includes a bit of 0 when the first control procedure is repeated while decreasing the value of the first binary variable, the first binary variable is located at the lowest position among the 0 bits of the first binary variable. A second control procedure for specifying a bit, and a third control procedure for specifying a buffer to be selected from the bit positions specified by the second control procedure,
To have.

According to the above method, a first binary variable is repeatedly generated while sequentially lowering the search priority from the highest priority, paying attention to a specific priority, and 0 is assigned to the first binary variable. If a certain bit is included, a series of controls are performed to specify the least significant bit position among the 0 bits of the first binary variable and to specify a buffer to be selected from the specified bit position. In addition, priority control type round robin control for selecting any one of a plurality of buffers for which selection priorities are individually set can be realized by simple arithmetic processing.

In the present invention, the plurality of buffers may be fixedly ordered in advance, and the first control procedure may be such that the k-th buffer in the fixedly determined order with respect to the plurality of buffers is used. Is capable of transmitting a packet and has the same selection priority as the search priority, the k-th bit counted from the least significant bit is set to 0.
To generate a binary variable otherwise set to 1.
The first binary variable is generated by cyclically shifting the binary variable until the bit corresponding to the buffer at the start point of the round robin search comes to the least significant digit.

According to the above method, the required first binary variable can be generated by a simple method.

According to the present invention, the first control procedure sets the first binary variable to each priority in advance.

According to the above method, the first priority is assigned to every priority.
By preparing the binary variables in advance, higher-speed round robin control can be realized.

In the present invention, it is preferable that the third control procedure is performed by setting k
Cyclically shifting the fourth binary variable until a fifth bit corresponds to the k-th buffer in the predetermined fixed order to generate a fifth binary variable;
The buffer to be selected is specified from the position of the bit that is 1 of the binary variable of "."

According to the above method, it is possible to easily recognize the buffer to which the packet transmission right is to be assigned from the result of the addition processing.

According to the present invention, a selection priority p is set in advance, and one of the n selectable buffers in which received packets are stored is selected from among the buffers having the highest selection priority in a round robin manner. In a communication control method for transmitting a packet stored in a buffer selected by a method, a k-th buffer in a round-robin search order for the plurality of buffers can transmit a packet and a p-th highest priority A first control procedure for generating a first binary variable with the (p−1) × n + kth bit counting from the least significant bit set to 0 and otherwise set to 1 0 of the first binary variable
A second control procedure for specifying the least significant bit among the bits, and a third control procedure for specifying a buffer to be selected from the bit positions specified in the second control procedure. To have.

According to the above method, the first binary variable is generated by combining the binary variables generated for all priorities so as to be arranged in the order of higher priority to lower priority. 7. A series of controls for specifying the least significant bit position among the 0 bits of the binary variable and specifying a buffer to be selected from the specified bit position, so that a search operation is performed in comparison with the mode of claim 6. Is not required to be repeated a plurality of times, and a higher-speed search process is realized. In addition, the number of times of branch processing that causes deterioration of processing performance is smaller than in the case of the sixth aspect, and the processing time can always be kept constant.

In the present invention, the plurality of buffers may be fixedly ordered in advance, and the first control procedure may be configured such that the fixed order k
Th buffer is capable of sending packets, and
When the priority is the priority p of interest, a binary variable with the k-th bit counted from the least significant bit set to 0 and otherwise set to 1 is generated for every priority, and After all the bits are cyclically shifted until the bit corresponding to the buffer at the start point of the round robin search comes to the least significant digit, the first binary variable is connected by connecting the first binary variable to the lower priority one with a higher priority. Generated.

According to the above method, the required first binary variable can be generated by a simple method.

According to the present invention, the second control procedure may further include adding 1 to the first binary variable to generate a second binary variable, and converting each bit of the first binary variable. Inverting to generate a third binary variable, performing a logical AND operation on the bits at the same bit position of the second binary variable and the third binary variable to generate a fourth binary variable, The least significant bit position among the 0 bits of the first binary variable is specified from the position of the 1 bit of the fourth binary variable.

According to the above method, the least significant bit position among the 0 bits of the first binary variable can be easily specified by adding 1 to the first binary variable. Round robin search can be performed collectively regardless of the number of buffers to be controlled and the rank of priority.

According to the present invention, the third control procedure may include the step of separating the fourth binary variable by n bits to generate p fifth binary variables, and generating all fifth binary variables. AND operation of each bit at the same bit position to generate a sixth binary variable, and until the k-th bit corresponds to the k-th buffer in a predetermined fixed order, A seventh variable is generated by cyclically shifting the binary variable, and a buffer to be selected is specified from the position of the bit that is 1 of the seventh binary variable.

According to the above method, it is possible to easily recognize a buffer to which a packet transmission right is to be assigned from the result of the addition processing.

Further, in the present invention, in the addition processing, a carry bit propagation mechanism is hierarchized in order to speed up the operation.

According to the above method, the addition processing can be sped up, and a higher-speed processing can be realized in which the processing speed of the round-robin search does not depend on the number of buffers to be controlled and the priority level. it can.

The present invention is also the bandwidth control method using round robin control according to any one of claims 8 to 11, wherein the packet is a fixed-length packet, and a control cycle of a predetermined time is set to set the packet. Counting the number of packets sent from each of the plurality of buffers in a control cycle,
At least one or more threshold values individually set for each of the buffers are compared with the count value to dynamically determine the selection priority p of each buffer. Is controlled so that the selection priority p of the is lower.

According to the above method, the number of packets transmitted from each buffer is counted, and the selection priority of each buffer is dynamically changed by comparing a plurality of threshold values provided for each buffer with the previous count value. Since the priority control type round-robin control is performed, it is possible to easily and quickly realize detailed band control including guarantee of the minimum band.

In the present invention, every time a predetermined cycle is newly started, the count value of the packet transmission amount is cleared and counting is started again.

According to the above method, by fixing the processing time cycle of the band control, the recognition of the band to be realized can be replaced with the recognition of the number of packets, thereby simplifying the processing.

According to the present invention, after the count value of the packet transmission amount becomes equal to or more than the maximum threshold value set in the buffer, the packet is not transmitted from the buffer until the control cycle is updated. So that the restriction is made.

According to the above-mentioned method, it is possible to realize the upper limit bandwidth set for each buffer.

The present invention also relates to a packet control apparatus using the round robin control method according to any one of claims 1 to 12, wherein a packet received from a plurality of ports is transmitted to one of the plurality of buffers. One of the buffers is selected, and one of the buffers is selected to transmit the packet.

According to the above configuration, it is possible to realize a packet control device capable of performing high-speed and simple packet transmission control by the round robin control method described above.

The present invention also relates to a packet control apparatus using the bandwidth control method according to any one of claims 13 to 15, wherein a fixed length packet received from a plurality of ports is transmitted to one of the plurality of buffers. And the packet is transmitted by selecting one of the buffers.

According to the above configuration, it is possible to realize a packet control device capable of performing high-speed and simple packet transmission control by the above-described band control method.

According to the present invention, the fixed-length packet may include an AT
M cells, wherein at least one or more thresholds individually set for each of the buffers are equal to A corresponding to the buffers.
It is configured to be derived in relation to the minimum guaranteed band and / or the upper limit band allocated to the TM connection.

According to the above configuration, it is possible to realize an ATM cell switching control apparatus equipped with a cell scheduling mechanism capable of guaranteeing the minimum bandwidth or limiting the upper bandwidth for each connection.

[0047]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS <First Embodiment> An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram showing a first embodiment of a round robin control method and a packet control device according to the present invention. FIG. 2 is a flowchart for explaining processing of an output control unit in FIG.
FIG. 3 is an explanatory diagram for describing the details of each process in FIG. 2 in detail.

Referring to the first embodiment of the present invention, FIGS.
This will be described with reference to FIG. FIG. 1 shows a plurality of communication buffers 101 that store communication packets (to be simply referred to as packets) 102 to be transmitted in order to realize high-speed and easy round-robin control as read control of a plurality of communication buffers 101 provided. 1 illustrates a communication control device including a buffer 101 and an output control unit 100 that controls reading of a packet from any one of a plurality of communication buffers 101. In the present embodiment, the communication buffer 101 is configured by a FIFO (First In First Out) of a first-in first-out method.

The output control unit 100 performs a round robin type transmission control in which a pointer is circulated in a predetermined order and a transmission right is allocated to a buffer capable of transmitting the packet 102. In the round-robin control, when a certain FIFO is selected as a packet transmission source, the next pointer traversal starts from the FIFO located next to the previously selected FIFO. For the sake of simplicity, in the present embodiment, the communication packet 102 is a fixed-length packet, and therefore, a bandwidth is equally allocated to each buffer capable of transmitting the packet 102. Hereinafter, FIFO selection processing based on round robin control is referred to as round robin search or simply search processing.

FIG. 2 is a flowchart showing the operation of the output control unit 100. FIG. 3 is a supplementary diagram for describing the details of each processing in FIG. 2 in detail. Hereinafter, the round robin search method according to the present invention will be described in detail with reference to FIGS. In the communication control device shown in FIG.
At the timing of reading from # n-1 to # n-1, the output control unit 100 counts the packet accumulation status of each of the FIFOs # 0 to # n-1 and generates a processing variable WDR [n-1: 0] (step S110). . The processing variable WDR has the same bit width as the number n of FIFOs to be controlled, and each bit is 0 when there is a packet 102 that can be transmitted in the corresponding FIFO # 0 to # n-1, and otherwise, Set to 1.

Step S120 shown in FIG. 3 is for explaining the method of generating the above-mentioned variables, and includes n FIFOs to be controlled (in FIG. 3, as an example, eight FIFOs # 0 to # 0).
# 7) is numbered from 0 to n-1 according to the search order of the round robin control. Each FIFO # 0
In # 7, the accumulation state of the packet 102 that can be transmitted is sequentially grasped, and the variable WDR generated therefrom is
The bit representation of the states of FO # 0 to # 7 is collected as one variable.

In the following description, it is assumed that the processing variables are all expressed in binary numbers. If the processing variables are n bits, the least significant bit is the 0th digit and the most significant bit is n.
Expressed as the first digit. If the above processing variable WDR,
The k-th digit of the variable represents the state of the k-th FIFO #k. The search start point F shown in step S120 indicates the start point of the round robin search, and FIG. 3 shows an example in which the round robin search is started from FIFO # 4.

Next, a cyclic shift process is performed on the processing variable WDR in the lower direction to newly generate a processing variable WDS (FIG. 2: step S111). The cyclic shift processing in the lower direction moves the k-th digit of the variable WDR to the (k-1) -th digit and moves the 0-th digit to the (n-1) -th digit. Step S11
In the case of 1, the shift processing is repeatedly executed by the number of search start points F (four times when F = 4). At this time, the processing variable W
Values shifted from the least significant digit are sequentially stored in the upper digit of DR. Steps S121 and S122 in FIG.
Indicates the result of the cyclic shift processing.

This control is performed in order to make the bit array of the control variable WDR correspond to the round robin search order. The processing variable WDS after the shift processing is performed is:
FI whose least significant bit is the starting point of the round robin search
The bit arrangement from the lower digit to the upper digit corresponding to the FO corresponds to the round robin search order of the FIFO corresponding to each bit.

Next, a first calculation process of adding 1 to the processing variable WDS as in the following equation is performed, and the calculation result is set as a processing variable WDB (step S112). WDB [n-1: 0] = WDS + 1 Subsequently, the respective bits of the processing variable WDS are inverted (/
A processing variable WDC is generated by a second operation processing of performing a logical AND operation (AND processing) between each bit of the operation result WDB and the respective bits of the operation result WDB as in the following equation (step S).
113). WDC [n-1: 0] = / WDS.and.WDB

Step S122 and step S1 in FIG.
23, in the first arithmetic processing, the bit located at the least significant digit among the bits of the WDS which are 0 is changed from 0 to 1 and lower than that in the first arithmetic processing. Are all changed from 1 to 0, and the processing variable WD
B. In the second arithmetic processing, each digit of WDS and WDB is compared to generate a processing variable WDC that is 0 in WDS and 1 in only the 1 digit in WDB.

A desired round robin search process is realized by the above series of arithmetic processes. That is, the processing variable WDC
Derivation specifies the least significant bit 0 of each bit of the WDS, and selects the nearest bit along the search order from the search start point located at the least significant digit of the WDS. This means specifying a possible position. Therefore, as a result of the round robin search, the FIFO corresponding to the bit that is 1 in the processing variable WDC is
FO.

The processing variables WDB and WDC generated as a result of the above-mentioned arithmetic processing are variables having the same bit width [n-1: 0] as the WDS, and the result of the addition in the first arithmetic processing causes an overflow. If it wakes up, ie W
If all bits of DS are 1, WDB
Becomes all bits 0, and all bits of WDC become 0.

When all bits of the processing variable WDC are 0 (yes in step S114), that is, all bits of the WDR are 1, and therefore, there is no FIFO that can transmit the packet 102. Is determined (step S115), and the process ends.

On the other hand, when the processing variable WDC is not all the bits 0, one of the bits is 1, and at this time, the processing variable WDC is cyclically shifted upward to generate the processing variable WDD ( Step S116). The cyclic shift process in the upper direction moves the k-th digit of the variable WDC to the (k + 1) -th digit and moves the (n-1) -th digit to the 0-th digit. In the process of step S116, the shift process is repeatedly executed by the number of search start points F (four times when F = 4). Step S124 in FIG. 3 shows the result of the cyclic shift process in the upper direction.

Since the processing in step S116 is the reverse of the processing in step S111, each bit of the resulting processing variable WDD and F
It becomes easy to recognize the correspondence with the IFO. That is, if the number of digits of any one of the bits of the processing variable WDD is F ′, the FIFO selected as a result of the round robin search is F ′, and the next round robin search is = F '+ 1 may be set as the search start point (step S117).

When F ′ indicates the end of the search order,
That is, when F ′ = n−1, the next search start point is set to F = 0.

According to the control method shown in this embodiment, a round robin search for selecting one from a plurality of FIFOs can be realized by a simple arithmetic processing.
High-speed control becomes possible. According to the control of the present invention, the state of all FIFOs can be reflected in the processing at the timing of search, instead of sequentially determining whether or not the corresponding FIFO can be selected in the round robin search order. Therefore, especially when the number of FIFOs to be controlled is large,
Even if the number of selection targets in one round robin search increases, the processing can be completed within a substantially fixed time.

Here, in the round robin control of the present invention, when the number n of FIFOs to be controlled increases, the processing speed law condition is the condition of step S112 in FIG.
The addition process shown in FIG. 7 is WDB [n−1: 0] = WDS + 1. Since the bit width of the processing variable WDS serving as the augend becomes large, the carry in the addition processing is performed at most n times. As a method to speed up the addition process, a layering method (carry skip,
By introducing general methods such as an adder circuit and a carry look-ahead mechanism (carry look ahead mechanism), the speed of the round robin search itself can be increased.

It is desirable that the bit representation of each FIFO state, which is the starting point of the control, is always implemented inside the apparatus prior to the round robin search. When the packet 102 is read from the FIFO as a result of the round robin search, the last packet 10 that can be transmitted from the FIFO at that time is read.
If it is 2, the status bit of the FIFO is changed from 0 to 1 and is not subject to the round robin search. Also, when the communication device newly stores the received packet 102 in the FIFO, the status bit of the FIFO is set to 1 to be a target of the round robin search. The processing time of the entire search can be significantly reduced as compared with the method of checking each FIFO state when the processing variable WDR is generated.

The present invention is characterized in that high-speed and easy round-robin search is realized by performing the lower-order shift step S111 and the first operation step S112 shown in FIG. On the other hand, the second calculation step S113
The bit position that has changed from 0 to 1 as a result of the first operation step S112 is specified, and the subsequent upward shift step S116 recognizes the association between the previously specified bit position and the FIFO number. Do it to make it easier. Therefore, the second calculation step S1
13 and the upward shift step S116 can be replaced with another process or can be omitted without departing from the features and objects of the present invention.

The processing variables shown in FIGS. 2 and 3 are:
It is not necessary to generate and process them as independent variables, and it is also possible to store the result of performing a shift process or an arithmetic process on a certain process variable in the same storage area as the original process variable. In this case, there is no need to define many processing variables, and the registers and main memory of the CPU can be saved. In the present embodiment, it is assumed that the packet 102 stored in the FIFO is a fixed-length packet. However, the condition is fixed to facilitate the description of the round-robin control, and the present invention is not limited to this. Absent.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIGS. In the second embodiment, a method for quickly and easily implementing a priority control type round robin control as a read control of a plurality of communication buffers provided will be described. FIG. 4 shows a plurality of communication buffers (simply referred to as buffers) 201 for storing communication packets (simply referred to as packets) 202 to be transmitted and a plurality of buffers 201 for realizing the priority control type round robin control method. Output control unit 20 for controlling reading of packet 202 from any one of them
1 shows a communication control device with 0. Buffer 201 is FI
FOs, and three levels of selection priority are fixedly determined for each FIFO.

The output control unit 200 realizes priority control type round robin control in consideration of the selection priority of each FIFO, and can output any one of the F which can transmit the packet 202.
The packet transmission right is given to the IFO. If the selection priority determined for each FIFO is three levels, the output control unit 20
0 first searches for a packet that can be sent out of the priority 1 FIFO, and if there is no selectable FIFO, performs a similar search for the priority 2 FIFO, and if there is still no selectable FIFO, A search is performed for the FIFO of priority 3. All of the above-described searches performed three times in succession are performed in a predetermined order by round-robin control. The starting point of the search is the FIFO located next to the FIFO selected in the previous search,
Packet transmission opportunities are equally provided between FIFOs having the same priority.

In the priority control type round robin control, for example, communication data that requires real-time properties, such as audio and video,
It is used when transmission is to be performed with a higher priority than communication data such as e-mail or file transfer that allows a certain delay in the device. By storing communication data requiring real-time performance in a priority 1 FIFO and storing delay-allowed communication data in a priority 2 FIFO, the former communication data always has priority over the latter communication data. Will be sent out.

FIG. 5 is a flowchart showing an example of the control procedure of the output control section 200. Hereinafter, a method of implementing the priority control type round robin control will be described in detail with reference to FIG. In the communication control device shown in FIG.
Is read from the FIFO, the output control unit 200 initializes the processing variable p to 1 and sets the priority to 1 (=
The processing variable WDpR [n-1: 0] is generated by totalizing the packet accumulation status of the FIFO that is p) (step S2).
10). Here, the processing variable p indicates the priority to be searched in one round robin search performed by the output control unit 200. By performing the search sequentially while increasing the control variable p, the priority control type Realizes round robin control. Hereinafter, an example of the search processing of the priority p will be described.

The processing variable WDpR [n-1: 0] has the same bit width as the number n of the FIFOs # 0 to # n-1 to be controlled, and each bit corresponds to the corresponding FIFO # 0.
If # n-1 is the priority p and there is a packet 202 that can be transmitted, 0 is set. Otherwise, 1 is set. All FIFOs # 0 to # n-1 to be controlled
Are numbered from No. 0 to No. n-1 in accordance with the search order of the round-robin control regardless of the priority, and the k-th FIFO # k corresponds to the k-th digit of the processing variable WDpR.

Next, a cyclic shift process is performed on the processing variable WDpR [n−1: 0] in the lower direction, and the processing variable WDS
[N-1: 0] is generated (step S211). Subsequently, a first calculation process of adding 1 to the processing variable WDS [n−1: 0] is performed, and a first calculation result = WDS + 1
Is set as a processing variable WDB [n-1: 0] (step S21).
2) Further, each bit of the processing variable WDS is inverted /
A process variable WDC is generated by a second operation process of performing a logical AND operation between the WDS and each bit of the operation result WDB as in the following equation (step S212). WDC [n-1: 0] = / WDS.and.WDB The above steps S211, S212, and S213 are steps S111 and S11 in the first embodiment, respectively.
2, the same processing as in S113, and the FIFO with priority p
Performs a round-robin search for.

The processing variable WDC generated as a result of the above series of processing is the FIF corresponding to the 1 bit.
O corresponds to the FIFO selected as a result of the round robin search with the priority p, but all bits of the processing variable WDC are 0.
Is satisfied (yes in step S214), it is determined that there is no FIFO having the priority p capable of transmitting the packet 202. At this time, if the priority p is not the lowest priority to be searched (no in step S215), the processing variable p
Is incremented by 1 (step S216) and step S210
And the search processing of steps S210 to S213 is repeated.

As described above, a series of search processing starts with the search of the priority 1 and is repeatedly performed up to the lowest priority to be searched. However, if a selectable FIFO is found in the course of the processing, the subsequent priority search processing is not performed, and the search result is determined at that time.

If the result of the second operation in step S213 is that the processing variable WDC is not all bits 0, the WDC at that time is subjected to a cyclic shift process in the upper direction to generate a processing variable WDD (step S214). → S
217). If the number of digits of the 1 bit of the processing variable WDD is F ′, the result of the round robin search is the F′-th FIFO, as in step S116 of the first embodiment, and the next search start point is F ′. = F ′ + 1-th FIFO is set (step S218). Where F ′ = n−1
If so, the next search start point is set to F = 0. On the other hand, F which can be selected even in the search result of the lowest priority to be searched
If no IFO is found (y in step S215)
es), it is determined that all priority FIFOs cannot transmit the packet, and the process is stopped (step S21).
9).

After that, the communication control device returns to packet 2 again.
At the timing of sending 02, the round robin search processing is started again from the priority 1 starting from the previously set search start point. That is, according to the round robin control according to the present embodiment, every time a packet is read from any of the FIFOs, the search process is started from the priority 1 without fail. As a result, if there is a packet 202 that can be sent to the FIFO of priority 1, the FIFO is always selected,
Packet 2 that can be sent to any FIFO of priority 1
02 does not exist, select priority 2 FIFO,
If neither priority 1 nor priority 2 can be selected,
Priority type control such as selecting an IFO can be realized.

According to the control method shown in the present embodiment, a priority control type round robin search for selecting one from a plurality of FIFOs each having a predetermined priority can be realized by a simple arithmetic processing. Therefore, high-speed control becomes possible. According to the control of the present invention, even when the number of FIFOs to be controlled increases, if the number of priorities to be handled is constant, the processing can be completed within a substantially constant time.

This control method is a method of sequentially performing a search process of each priority. If the number of priorities to be handled is p,
Although a maximum of p search processes are required, the overall process can be sped up by previously executing the processes from step S210 to step S213 shown in FIG. 5 for each priority in parallel. When this parallel processing is performed, for example, an FIF to which a transmission right should be assigned with priority 1
If O is not found, the processing variable WDC indicating the search result of priority 2 may be referred to immediately. According to this control method involving parallel processing, the processing time occupied by the first arithmetic processing in the overall control is always one time, so that even if the number of priorities to be handled increases, the processing performance is reduced. Is reduced.

When this control method is realized by hardware or by software processing having a parallel processing function, the processing from step S210 to step S213 may be performed in parallel for each priority. This is possible and is an effective means for speeding up the processing.

In the present embodiment, the second arithmetic processing (step S 213) and the upward shift processing (step S 217) are performed within a range that does not impair the function and purpose.
A change to another processing is also possible. Further, similarly to the first embodiment, there is no limitation on the usage of variables or the types of communication packets.

<Third Embodiment> Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 6 is a flowchart showing another example of the control procedure of the output control unit 200 shown in FIG. 4, and FIG. 7 is a supplementary diagram for explaining the details of each processing in FIG. Hereinafter, a third embodiment which is simpler than the priority control type round robin control shown in the second embodiment will be described.

At the timing when the packet 202 is read from any of the FIFOs, the output control unit 200 tallies up the packet accumulation status of each FIFO and generates the processing variables WD1R, WD2R, and WD3R for each priority (step S1). S220). As a premise, it is assumed that the number of priorities to be handled is three types of priorities 1 to 3, and the processing variable WD1R
To WD3R represent the packet accumulation status of the FIFOs of the priorities 1 to 3, respectively.

Steps S230 and S231 shown in FIG. 7 correspond to the processing variables WD1R, WD2R, WD3.
This is a description of a method of generating R. Output control unit 200
For each FIFO to be controlled, the packet accumulation status and the selection priority are managed in a table format, and the FIFOs are numbered in a preset round robin search order. In FIG. 7, for example, the fifth F
Since the IFO has a packet that can be transmitted with a priority of 3, a 0 is placed in the fifth digit of the processing variable WD3R corresponding to the priority.
Is set, and 1 is set in the fifth digit of the processing variables WD1R and WD2R. Also, since the fourth FIFO has no packets that can be sent, WD1 does not matter regardless of its priority.
1 is set in the fourth digit of each of R to WD3R.

Next, a cyclic shift process is performed F times in the lower direction for each of the processing variables WD1R to WD3R, and new control variables WD1S to WD3S are generated (step S221). This control is performed to make the bit array of the control variable correspond to the search order of the round robin control, as in the previous embodiment. Steps S231 and S23 in FIG.
2 shows the outline of the cyclic shift processing. Control variable WD
1S to WD3S correspond to a FIFO whose least significant bit is a search start point of the round robin process, and the bit arrangement from the lower digit to the upper digit of the control variable is a round robin search of the FIFO corresponding to each bit. Corresponds to the order.

Next, each of the n-bit processing variables WD3S, WD
2S and WD1S bit sequences are sequentially connected to form a new n
The processing variable WDA [3n-1: 0] of 3 bits is generated (step S222). Processing variables WD1S to WD3S
Is a variable having the same bit width as the number n of FIFOs to be controlled, and a processing variable WDA obtained by connecting three of them has a bit width of 3 × n digits. As shown in step S232 of FIG. 7, the connection order of the variables is set to a higher priority FIFO.
The variable indicating the status is placed on the lower side, that is, WD
WD2R is arranged and connected so that WD2R is positioned lower than 3R and WD1R is positioned lower than WD2R.

By comparing the bit information of the processing variable before and after the concatenation processing, the control variable W indicating the FIFO state of the priority p is obtained.
The k-th digit of DpS and (p−
1) The WDA is generated such that the × n + k digits are equal. As a result, the least significant bit of the linked control variable WDA corresponds to the start point of the round robin search, and the bit arrangement from the lower order to the upper order matches the continuous search order of the priority control type round robin control. Will be.

A first operation for adding 1 to the control variable WDA is performed, and the result is stored in the processing variable WDB [3n-
1: 0] = WDA + 1 (step S223). Subsequently, each bit of the processing variable WDA is inverted / WDA
And a second operation step S2 for performing a logical AND operation (AND processing) between each bit of the operation result WDB and the following equation
24, a process variable WDC is generated (step S2).
24). WDC [3n-1: 0] = / WDA.and.WD
B

The bit position of 1 of the control variable WDC is
It corresponds to the bit position of 0 which is present at the lowest position of WDA, and therefore, the further arithmetic processing has the highest priority among the FIFOs that can transmit packets, and the search order of round robin is the highest. This corresponds to control for selecting a young FIFO. Steps S232 and S233 in FIG.
In this example, none of the FIFOs having the priority 1 can transmit a packet, and the FIFO having the priority 2 is selected.

Note that all bits of the processing variable WDC are 0
Is satisfied (yes in step S225), there is no FIFO capable of transmitting packets for all priorities, and the process is stopped at this point (step S226). If the processing variable WDC is not all bits 0, one of the bits is 1, and at this time, the processing variable WDC having a bit width of 3 × n is replaced with the processing variable W having a bit width of n.
The data is compressed to DD (step S227). This compression process is a process of calculating the logical sum of the bits corresponding to the same FIFO among the bits of the processing variable WDC and degenerating it into 1 bit. The k-th digit, the n + k-th digit, and the 2n + k of the processing variable WDC The logical OR of the digit is made to correspond to the k-th digit of the processing variable WDD. This processing is performed in order to make it easy to recognize the round robin search result indicated by the processing variable by making the correspondence between each bit of the processing variable and the FIFO one-to-one.

The processing variable WDD becomes F
The priority information for each IFO is eliminated, and the information that can be held is the first
Variable WD shown in the second embodiment or the second embodiment
Equal to C. Therefore, a cyclic shift process in the upper direction is performed on the process variable WDD (step S228), and the search result and the next search start point can be specified based on the number of digits of the 1 bit of the obtained variable WDE ( Step S2
29).

In the round robin search featured in the present embodiment, processing variables expressing the state of each FIFO are separately generated for each priority, and they are combined in the search order, and then one addition process is performed. Then, a round robin search across all priorities is performed collectively. Similarly to the second embodiment that implements the priority control type round robin control,
It is not necessary to repeat the addition process for realizing the search operation and the process of judging the result a plurality of times, and a higher-speed search process is realized. Further, the number of times of branch processing that causes deterioration of processing performance is smaller than in the second embodiment, and the processing time can always be kept constant. In order to improve the overall processing speed, a mechanism for performing the addition processing at a high speed may be introduced.
Optimization for achieving desired performance is easy.

By improving this embodiment, it is possible to further simplify the processing and perform a high-speed search. In the process of generating the processing variables indicating each FIFO state for each priority in the process of step S220, it is determined whether there is a FIFO that can be selected for each priority, that is, all bits of the control variable to be generated are 1 It is determined whether or not there is, and only one control variable having the highest priority is selected from the priority classes having selectable FIFOs, and the search processing shown in the first embodiment is performed. I do.

In this control method, although it takes time to select a variable to be processed, the search process is completed only by performing variable processing of n bits once. The advantage of this control method is that it is not necessary to repeatedly perform the search processing as in the second embodiment, and it is not necessary to handle data having a large bit width as in the third embodiment. If this control method is realized as hardware processing and a means for easily selecting a processing variable prior to a search operation is provided, it is expected that the overall processing can be speeded up and the arithmetic unit can be simplified.

In implementing the control shown in the second or third embodiment, each FIFO and its priority need not be physically fixed. If round robin control is performed, each FIF recognized by the processor
By changing the priority of O at a certain point in time, the priority of the corresponding FIFO can be changed without any physical change. Therefore, for each priority,
If it is not necessary to prepare O, for example, if FIFOs are assigned to correspond to communication connections, FIFOs may be provided for the number of connections to be controlled.

Note that the order of steps S225 and S227 shown in FIG. 6 can be changed. In the present embodiment, it is determined whether or not all the bits are 0 for the 3 × n-bit process variable after the second operation process in step S224 is performed. The determination process may be performed after step S227. In this case, since the bit width of the variable to be handled is n bits, the determination can be performed more easily.

The compression of the processing variables shown in step S227, the second arithmetic processing step S224, and the upward shift processing step S228 are performed for the purpose of specifying the search result. It is also possible to replace the means. Even if another means is used, it is sufficient that the round robin search result can be specified from the processing variable WDD. As in the previous embodiment, there is no restriction on how to use variables or types of communication packets, and the number of priorities to be handled can be set arbitrarily.

<Fourth Embodiment> Next, an application example of the priority control type round robin control shown in the third embodiment will be described with reference to FIG.
This will be described with reference to FIGS. In the present embodiment, the priority control type round-robin control is applied to the bandwidth control mechanism of the communication control device that handles fixed-length packets. FIG. 8 shows an example of band control to be realized by the communication device. In the process of multiplexing and outputting a plurality of connections input to the device, the communication control device guarantees a minimum bandwidth set for each connection and limits an upper limit bandwidth. Each of the packets 302 belonging to each connection to be controlled is a fixed-length packet having a fixed length, and is individually stored in a FIFO 301 provided for the connection. The output control unit 300 includes an internal timer that runs at a constant speed, and realizes the above-described band control by controlling the amount of packets read from each FIFO within a specific time period τ.

The output control unit 300 determines a control variable MPR (MiR) based on the minimum guaranteed band and the upper limit band for each connection.
nimum Packet Rate) and PPR (Peak Packet Rate)
Is used for bandwidth control processing. The control variables MPR and PPR indicate how much the set bandwidth corresponds to the packet transmission amount in the processing cycle τ.
For example, if one packet is transmitted during the processing cycle τ, 3
If the value of τ is set to correspond to the use of the bandwidth of 2 kbps (bit per second), the connection # in FIG.
3 is guaranteed to send at least 4 packets every time τ and is restricted to not sending more than 8 packets.

The above band control can be realized by applying the priority control type round robin control shown in the third embodiment. The output control unit 300 determines the actual packet transmission amount in the processing cycle τ by using a control variable APR (Acquired Packe).
t Rate) for each FIFO. Control variable A
The PR is reset to 0 when the processing cycle τ is updated, and is incremented by 1 each time a packet is read from the corresponding FIFO. As shown in FIG. 9A, the priority of each FIFO is determined from the comparison between the MPR and the APR or the comparison between the PPR and the APR, and is dynamically controlled so that the priority decreases gradually as the APR increases. .

Hereinafter, a more detailed control procedure will be described with reference to FIGS. 10 and 11. FIG. 10 is a flowchart showing a method of determining the priority. By the priority control type round robin control shown in the third embodiment, the F′-th FIFO #
When F ′ is selected and the packet 302 is transmitted (step S310), first, 1 is added to the total packet transmission amount APR (F ′) of FIFO # F ′ (step S31).
1). Next, a comparison is made between the PPR value corresponding to the upper limit band and the APR value. If the APR value is equal to or greater than the PPR value (yes in step S312), it is determined that the number of packets that can be transmitted within τ time has already been satisfied, and the FIFO The priority of #F 'is set to 0 (step S313), and thereafter, it is treated as an unselectable FIFO.

If the APR has not reached the PPR (NO in step S312), the MPR value corresponding to the minimum guaranteed bandwidth is compared with the APR value, and the APR value is set to the MPR value.
If the value is equal to or more than the value (yes in step S314), it is determined that the minimum packet transmission amount to be guaranteed within the time τ is already satisfied, and the priority is set to 2 (step S315). AP
If the R value has not reached the MPR value and does not correspond to any of steps S312 and 314 (step S31
No at 4), the priority is set to 1 because the minimum packet transmission amount to be guaranteed within the time τ has not yet been satisfied (step S316).

Thus, every time a packet is transmitted from any of the FIFOs, the selection priority of the FIFO is recalculated. In the present embodiment, the number of priorities to be handled in the round robin search may be two levels of priority 1 and priority 2,
Further, the FIFO having the priority 0 is treated as an unselectable FIFO even if it has the packet 302 inside. By performing the priority control type round robin control together with the dynamic priority control described above, the FIFO which does not satisfy the minimum guaranteed bandwidth among the plurality of FIFOs is given priority over the FIFO which has already satisfied the guaranteed bandwidth. Can be selected.
Further, it is possible to limit the FIFO that satisfies the upper limit band so as not to grant the transmission right thereafter in the processing cycle τ.

FIG. 11 shows a procedure of a timer reset process (processing cycle update) performed for each processing cycle τ. The output control unit 300 constantly monitors the self-running internal timer ts (step S320), and performs reset processing of various variables when the internal timer ts reaches the threshold τ (step S321). When ts = τ is detected, first, the timer value ts
Is reset to 0 (step S322), and then all FIs
Reset the control variable APR of the FO to 0 (step S
323). Next, the selection priority of all the FIFOs is reset to 1 (step S324). However, since the FIFO whose minimum guaranteed bandwidth is 0 already satisfies the condition of APR ≧ MPR, the priority is set to 2 (step S325). FIFO
The total transmission amount and priority for each are reset in a period of time τ, and the same band control is repeatedly performed.

As described above, the control variables MPR, PPR, and APR used in FIGS. 10 and 11 are all provided for each FIFO. That is, the bandwidth control method of the present embodiment can guarantee the minimum bandwidth and limit the upper limit bandwidth individually set for each connection. In a connection in which the minimum guaranteed bandwidth is set to 0, so-called best-effort bandwidth control is performed, and in a connection in which the minimum guaranteed bandwidth and the upper limit bandwidth are set equal, so-called guarantee type bandwidth control is performed. According to the control shown in the present embodiment, high-speed and strict band control can be realized by a communication control device that controls fixed-length packets.

As an application, even if the FIFO reaches the upper limit band, it is possible to control to give a transmission right when there is no other selectable FIFO. In this case, FIG.
As shown in (b), after the APR reaches the PPR, the priority is set to 3, and the number of priorities handled in the priority control type round robin search may be set to three levels. In the present embodiment, the number of priorities is not limited, and more precise band control can be realized by providing an intermediate band in addition to the minimum guaranteed band and the upper limit band.

Note that the processing load of step S325 for the priority preset processing shown in FIG. 11 is large because it is necessary to consider the setting of the bandwidth of each FIFO. When the processing speed is prioritized over the band control accuracy, the processing step S325 can be omitted. In addition, in the present embodiment, the number of FIFOs to be controlled and the control variable MP
There is no limitation on the calculation method of R and PPR and the setting of the control period τ, and any selection can be made within a range that does not impair the effects of the present invention.

[0108]

As described above, according to the first aspect of the present invention, it is possible to perform a round-robin search collectively by an arithmetic operation or a logical operation. A round robin search that handles classes can be realized at high speed with a simple configuration.

According to the second aspect of the present invention, a first binary variable in which bit representations indicating the status of each FIFO constituting the buffer are arranged according to a round robin search order is generated, and the first binary variable is generated. A series of controls are performed to specify the least significant bit position of the 0 bits of the above, and to specify a buffer to be selected from the specified bit position. Therefore, any one of a plurality of buffers with the same selection priority set. Round robin control for selecting one can be realized at high speed by simple arithmetic processing.

According to the third aspect of the present invention, the required first binary variable can be generated by a simple method.

According to the fourth aspect of the present invention, the first binary variable is repeatedly generated while paying attention to a specific priority while sequentially lowering the search priority from the highest priority. If the variable includes a bit that is 0, a series of steps that identify the least significant bit position of the 0 bits of the first binary variable and identify a buffer to select from the identified bit position Since control is performed, priority control type round robin control for selecting any one of a plurality of buffers for which selection priorities are individually set can be realized by simple arithmetic processing.

According to the present invention, the required first binary variable can be generated by a simple method.

According to the sixth aspect of the present invention, a higher-speed round robin control can be realized by preparing the first binary variable for every priority in advance.

According to the seventh aspect of the present invention, it is possible to easily recognize a buffer to which a packet transmission right is to be assigned from the result of the addition processing.

According to the eighth aspect of the present invention, the first binary variable is generated by combining the binary variables generated for all priorities so as to be arranged in descending order of priority. A series of controls for specifying the least significant bit position among the 0 bits of the first binary variable and specifying a buffer to be selected from the specified bit position. Thus, it is not necessary to repeat the addition process for realizing the search operation and the process of determining the result associated therewith a plurality of times, so that a higher-speed search process is realized. In addition, the number of times of branch processing that causes deterioration of processing performance is smaller than in the case of the sixth aspect, and the processing time can always be kept constant.

According to the ninth aspect, the required first binary variable can be generated by a simple method.

According to the tenth aspect, by adding 1 to the first binary variable, it is possible to easily specify the least significant bit position among the 0 bits of the first binary variable. Thus, the round robin search for all buffers can be performed collectively regardless of the number of buffers to be controlled and the priority level.

According to the eleventh aspect of the present invention, it is possible to easily recognize the buffer to which the packet transmission right is to be assigned from the result of the addition processing.

According to the twelfth aspect of the present invention, the addition processing can be sped up, and the processing speed of the round-robin search does not depend on the number of buffers to be controlled and the priority rank. Can be realized.

According to the thirteenth aspect of the present invention, the number of packets transmitted from each buffer is counted, and the selection priority of each buffer is dynamically determined based on a comparison between a plurality of threshold values provided for each buffer and the previous count value. , The priority control type round-robin control is performed, so that it is possible to easily and quickly perform detailed bandwidth control including minimum bandwidth guarantee.

According to the fourteenth aspect, by fixing the processing time cycle of the band control, the recognition of the band to be realized can be replaced with the recognition of the number of packets, thereby simplifying the processing.

According to the fifteenth aspect of the present invention, it is possible to realize the upper limit band setting set for each buffer.

According to the sixteenth aspect of the present invention, it is possible to realize a packet control device capable of performing high-speed and simple packet transmission control by the round robin control method described above.

According to the seventeenth aspect of the present invention, it is possible to realize a packet control device capable of performing high-speed and simple packet transmission control by the above-described band control method.

According to the eighteenth aspect of the present invention, it is possible to realize an ATM cell switching control device equipped with a cell scheduling mechanism capable of guaranteeing the minimum bandwidth or limiting the upper bandwidth for each connection.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a first embodiment of a round robin control method and a packet control device according to the present invention;

FIG. 2 is a flowchart showing a round robin control procedure according to the first embodiment;

FIG. 3 is an explanatory diagram for explaining each processing content of FIG. 2 in detail;

FIG. 4 is an explanatory diagram showing a priority control type round robin control method and a packet control device according to a second embodiment;

FIG. 5 is a flowchart showing a priority control type round robin control procedure according to the second embodiment;

FIG. 6 is a flowchart showing a priority control type round robin control procedure according to the third embodiment;

FIG. 7 is an explanatory diagram for describing each processing content of FIG. 6 in detail;

FIG. 8 is an explanatory diagram showing a bandwidth control method and a packet control device according to a fourth embodiment;

FIG. 9 is an explanatory diagram showing a priority determining method of the bandwidth control method according to the fourth embodiment;

FIG. 10 is a flowchart illustrating a priority determination procedure of the bandwidth control method according to the fourth embodiment;

FIG. 11 is a flowchart illustrating a processing cycle update procedure of the bandwidth control method according to the fourth embodiment;

[Explanation of symbols]

 100, 200, 300 Output control unit 101, 201, 301 Buffer (FIFO) 102, 202, 303 Packet

Claims (18)

[Claims] 1. A round-robin control method for selecting any one of a plurality of selection candidates, wherein a state expression indicating whether each of the plurality of selection candidates is selectable is defined, and A control variable is generated by combining the state expressions of the selection candidates according to the search order of round robin control, and a specific state expression included in the control variable is selected by performing an arithmetic operation or a logical operation on the control variable, A round-robin control method for specifying a selection candidate to be selected from the specified state expression. 2. A round-robin control method for selecting one of a plurality of buffers storing received packets by a round-robin method and transmitting the packets stored in the buffers, the round-robin control method comprising: A first control procedure for generating a first binary variable in which the k-th bit from the least significant bit is set to 0 when the k-th buffer in the search order can transmit a packet and otherwise set to 1 A second control procedure for specifying the least significant bit among the bits of the first binary variable that are 0, and a buffer to be selected from the bit positions specified by the second control procedure. And a third control procedure to be specified. 3. The method according to claim 1, wherein the plurality of buffers have a fixed order in advance, and the first control procedure includes a step in which the k-th buffer in the fixed order with respect to the plurality of buffers transfers packets. If transmission is possible, a binary variable with the kth bit counted from the least significant bit set to 0 and otherwise set to 1 is generated, and the bit corresponding to the buffer at the start point of the round robin search is the least significant bit. 3. The method of claim 2, wherein the first binary variable is generated by cyclically shifting the binary variable until it reaches a digit. 4. A method in which a selection priority is set in advance and one of a plurality of buffers which can store a received packet and which can be selected is selected from buffers having the highest selection priority by a round robin method. A round robin control method for transmitting packets stored in the buffer, wherein a priority management procedure of managing a selection priority to be a target of a round robin search for the plurality of buffers as a search priority; and a round for the plurality of buffers. If the k-th buffer in the Robin search order is capable of transmitting a packet and has the same selection priority as the search priority, the k-th bit counting from the least significant bit is set to 0, and otherwise 1
And the first control procedure is repeated while sequentially lowering the search priority from the highest priority, so that the first binary variable becomes 0. A second control procedure for specifying the least significant bit among the bits of the first binary variable that are 0, and a bit specified by the second control procedure. And a third control procedure for specifying a buffer to be selected from the position. 5. The method according to claim 1, wherein the plurality of buffers have a fixed order in advance, and the first control procedure includes a step in which the k-th buffer in the fixed order with respect to the plurality of buffers transfers packets. If it is possible to transmit and has the same selection priority as the search priority, a binary variable is generated in which the k-th bit counted from the least significant bit is set to 0 and the others are set to 1; The round according to claim 4, wherein the first binary variable is generated by cyclically shifting the binary variable until the bit corresponding to the buffer at the start point of the round robin search is at the least significant digit. Robin control method. 6. The round robin control method according to claim 4, wherein the first control procedure sets the first binary variable in advance for each priority. 7. The third control procedure comprises the steps of: cyclically shifting the fourth binary variable until a kth bit corresponds to the kth buffer in the predetermined fixed order; 7. The round robin control method according to claim 6, wherein a binary buffer is generated, and a buffer to be selected is specified from a position of a bit that is 1 of the fifth binary variable. 8. A selection priority p is set in advance, and one of the n selectable buffers in which received packets are stored is selected by a round robin method from a buffer having the highest selection priority. And transmitting a packet stored in said buffer, wherein the k-th buffer in the round-robin search order for said plurality of buffers is capable of transmitting packets and has a p-th highest priority. A first control procedure for generating a first binary variable in which the (p−1) × n + kth bit counted from the least significant bit is set to 0, and otherwise set to 1; A second control procedure for specifying the least significant bit of the 0 bits of the binary variable, and a buffer to be selected from the bit positions specified in the second control procedure. Round robin control method characterized by a third control procedure to locate § has. 9. The method according to claim 1, wherein the plurality of buffers have a fixed order in advance, and the first control procedure is such that the k-th buffer in the predetermined order can transmit packets. And when the priority is the priority p of interest, a binary variable in which the k-th bit counted from the least significant bit is set to 0 and the others are set to 1 is generated for every priority, All the ternary variables are cyclically shifted until the bit corresponding to the buffer at the start point of the round robin search comes to the least significant digit, and then connected such that the higher priority is located lower, the first binary 9. The method according to claim 8, wherein a hexadecimal variable is generated. 10. The second control procedure includes adding 1 to the first binary variable to generate a second binary variable, and inverting each bit of the first binary variable. Generating a third binary variable; performing a logical AND operation on the bits at the same bit position of the second binary variable and the third binary variable to generate a fourth binary variable; 10. The position of the least significant bit among the 0 bits of the first binary variable is specified from the position of the 1 binary bit of the first binary variable. The described round robin control method. 11. The third control procedure may include: separating the fourth binary variable by n bits to generate p fifth binary variables, wherein each of the fifth binary variables has the same value. ANDing the bits at the bit positions to produce a sixth binary variable, the sixth binary variable until the kth bit corresponds to the kth buffer in a predetermined fixed order. 11. A round-robin method according to claim 10, wherein a seventh binary variable is generated by cyclically shifting, and a buffer to be selected is specified from a position of a bit that is 1 of the seventh binary variable. Control method. 12. The round according to claim 7, wherein in the addition processing, a carry bit propagation mechanism is hierarchized in order to speed up the operation. Robin control method. 13. The bandwidth control method using round robin control according to claim 8, wherein the packet is a fixed-length packet, and a control cycle of a predetermined time is set, and The number of packets sent from each of the plurality of buffers is counted, and the count value is compared with at least one or more thresholds individually set for each of the buffers to dynamically select the priority p of each buffer. And controlling the selection priority p of the buffer to decrease as the packet transmission amount increases in a control cycle. 14. Every time a predetermined cycle is newly started,
14. The bandwidth control method according to claim 13, wherein the count value of the packet transmission amount is cleared and counting is started again. 15. After the count value of the packet transmission amount becomes equal to or more than the maximum threshold value set for the buffer, the packet is not transmitted from the buffer until the control cycle is updated. The bandwidth control method according to claim 14, wherein: 16. A packet control device using the round-robin control method according to claim 1, wherein packets received from a plurality of ports are stored in any one of a plurality of buffers. And a packet controller for selecting one of the buffers and transmitting the packet. 17. A packet control device using the bandwidth control method according to claim 13, wherein a fixed-length packet received from a plurality of ports is transferred to one of a plurality of buffers. A packet control device for storing and transmitting a packet by selecting one of the buffers. 18. The fixed-length packet is an ATM cell, and at least one or more thresholds individually set for each of the buffers are a minimum guaranteed bandwidth or an upper limit assigned to an ATM connection corresponding to the buffer. 18. The packet control device according to claim 17, wherein the packet control device is derived in relation to a band or both.