JP3028985B2 - Cell flow control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cell flow control device in an ATM switching system.

[0002]

2. Description of the Related Art In recent years, ATM (Asynch) as a network architecture for realizing a high-speed and wideband B-ISDN network or the like has been developed.
ronous Transfer Mode) The switching method has attracted attention. In the ATM switching method, a cell to which a header indicating routing information or the like is attached for each piece of information divided by a fixed length is label-multiplexed on a transmission line as a unit of information, and a switching node is used. Then, the switching operation is performed on a cell-by-cell basis only by referring to the information of this header. In the ATM switching system, unlike the conventional circuit switching system, a fixed communication band is not allocated to each communication, and a plurality of communications share a single communication band.

[0003] When communication is started using this ATM exchange, necessary traffic characteristics and communication quality are negotiated between the calling terminal and the ATM exchange network, and the declared traffic characteristics are used in the ATM exchange network. It is determined whether or not the requested communication quality can be provided when the cell flow having the inflow has occurred, and if it is determined that the requested communication quality can be provided, a virtual channel VC (Virtual Chane
l) is set, and cell transfer is performed between the calling terminal and the called terminal. As described above, since a fixed communication band is not allocated to the virtual channel VC, a predetermined communication quality cannot be provided when a cell flow exceeding a predetermined amount is generated. Therefore, in the ATM switching network, a policing function for monitoring whether the traffic characteristics of each virtual channel VC satisfies the declared characteristics is required, and the traffic generated in the terminal is output with the declared characteristics. Is required.

As a method for monitoring and controlling such a cell flow, a method using a leaky packet is known (J.
S.Turner, "New Directions in Communications", pp8-1
5, IEEE Communications Magazine, vol.24, No.10, Octobe
r 1986). FIG. 11 shows a configuration example of a conventional leaky bucket.

[0005] In FIG. 16, upon detecting arrival of a cell, the arrival monitoring unit 101 increments a counter 105 via an AND circuit 103. At this time, the output from the comparator 115 is input to the other side of the AND circuit 103. Also, the counter 109 is incremented by a clock signal output from a clock 107 that generates a clock of a unit time period, and a value A of the counter 109 and an output of a register 111 storing a constant value T and a threshold value B are compared with a comparator 113. And if they match (A = B), decrement the counter 105 by 1 and
09 is reset. When the value of the counter 105 is 0, the value of the counter 105 is not further decremented even when A = B in the comparator 113.

At the same time, the value of the counter 105 is output to the comparator 115, and the value A of the counter 105 is compared with the output B from the register 117.
= B) is determined to be a violation, and the arrival monitoring unit 10
Discard at 1.

As described above, in an ATM switching network, a plurality of virtual channels VC may be multiplexed on one line, and the cell flow must be independently monitored for each virtual channel VC. . However, each virtual channel V
Since the parameter of C does not always have the same value, it is necessary to independently measure the time period and the like. In order to monitor such a plurality of virtual channels VC, the leaky buckets shown in FIG. 16 can be realized by preparing the number of virtual channels for monitoring the cell flow and operating them in parallel. However, since the amount of hardware increases in proportion to the number of virtual channels VC, a large number of virtual channels V
When C is multiplexed, the flow control device becomes very large. Therefore, in order to reduce the amount of hardware, the values of counters and the like are stored in a memory, and one arithmetic unit is shared by a plurality of virtual channels VC, and the value stored in the memory is updated to obtain a leaky bucket. However, the number of virtual channels VC that can be monitored is limited due to restrictions such as the access speed of the memory and the processing capacity of the arithmetic unit, and a large number of virtual channels VC cannot be monitored. Therefore, even if such a configuration is used, when the number of virtual channels VC is large, a plurality of devices must be operated in parallel, and the amount of hardware also increases in this case.

There is also a control in which, when it is determined that a violation has occurred, the cells determined to be in violation are not discarded, but are accumulated in a buffer until a time when the cell is output does not cause a violation, and then output. For example, as described in Japanese Patent Application No. 2-217216 previously filed by the present applicant, conventionally, each time a cell is output from a buffer, it is determined whether each of the stored cells violates. In this case, a configuration is employed in which a search is made for a cell that can be output, and the cell is output. But,
In such a configuration, in addition to the need for large hardware for realizing the leaky bucket, the amount of processing required to search for an outputable cell increases.

[0009]

As described above, conventionally, a cell flow control device for monitoring a cell flow of a multiplexed virtual channel VC increases the amount of hardware when the number of virtual channels VC is large. It is difficult to realize. Further, when the data is accumulated in the buffer and output until the violation is no longer caused, the amount of processing for determining the cell to be output becomes large, resulting in an increase in processing time.

The present invention has been made in view of the above situation, and does not require a hardware amount proportional to the number of virtual channels VC even when the number of target virtual channels VC is large. This realizes a cell flow control device.

[0011]

In order to achieve the above object, a first feature of the present invention is a cell flow control device for controlling a cell flow on a transmission line in which a plurality of virtual channels are multiplexed. Elapsed time measuring means for measuring an elapsed time from a starting point arbitrarily set for each of the channels, storage means for holding a value relating to the flow rate of the arriving cell for each of the virtual channels, and a new cell Calculating means for, upon arrival, updating the value of the storing means for the virtual channel to which the cell belongs based on the elapsed time up to the current time obtained by the elapsed time measuring means; and the value of the storing means updated by the calculating means Control means for performing cell transfer control on the basis of, the elapsed time measuring means,
When a cell arrives via a virtual channel, having a first counter provided for each virtual channel and increasing by N every N cell periods, and a second counter increasing by 1 every one cell period Another object of the present invention is to provide a cell flow control device that measures an elapsed time using a first counter value corresponding to a virtual channel and a second counter value.

A second feature of the present invention is that in a cell flow control device for controlling a cell flow on a transmission line in which a plurality of virtual channels are multiplexed, each cell arrives at a certain point in time for each virtual channel. Means for storing the remaining service time, which is the time it would take to finish outputting one or more cells currently held in the buffer from the buffer, and when a new cell arrives, Means for determining the elapsed time from the time at which the cell immediately before the virtual channel to which the virtual channel belongs to the current time to the current time; And a means for controlling cell transfer.

[0013]

According to the first aspect of the present invention, at an arbitrary point in time, an elapsed time measuring means for knowing an elapsed time from the start point arbitrarily set, for example, from the arrival of the immediately preceding cell or from the time of reading from the memory. , It becomes possible to update the value of the storage means at the same time when a cell arrives. Therefore, it is not necessary to access information of a plurality of virtual channels VC at the same time, and virtual Values required for each channel VC are stored in a memory, and monitoring can be performed using a single arithmetic unit. As a result, even when the virtual channel VC becomes large, it is possible to greatly reduce the amount of hardware necessary for configuring the cell flow control device.

According to the second aspect of the present invention, a time at which a cell can be output at the time of cell input is obtained, and a cell output is reserved at a time after this time which is not reserved first,
By outputting the cell at the reserved time, it becomes possible to output the cell with a predetermined characteristic without determining whether the cell in the buffer can be output at the time of output.

[0015]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a cell flow control device 1 according to a first embodiment of the present invention.

First, the configuration of the cell flow control device 1 of the present embodiment will be described with reference to FIG. This cell flow control device 1
Is used to monitor the flow rate of the cell flow rate of the virtual channels of N channels multiplexed on the incoming line. The transfer control unit 11 as control means, the operation unit 13 as operation means, the memory 15, the clock 17, and the It is constituted by a counter 7 as time measuring means. It is assumed that virtual channel numbers from 0 to (N-1) are assigned to the N virtual channels in advance.

The transfer control unit 11 identifies a virtual channel number from header information of a cell input from an incoming line, and notifies the arithmetic unit 13 connected to the transfer control unit 11 of the virtual channel number.

The operation unit 13 reads information corresponding to the virtual channel stored in the memory 15 based on the virtual channel number notified from the transfer control unit 11,
The transfer control unit 11 is notified of the determination result based on this information. When the result of the determination in the operation unit 13 is a violation cell, the transfer control unit 11 discards the input cell. When it is determined that the cell is not a violating cell, the input cell is output to an outgoing line.

The clock 17 generates a cell cycle signal,
The counter 19 is an N-ary counter operated by a signal generated by the clock 17. That is, the counter 19
Is (N-1), the value of the counter 19 becomes 0 when the next clock is input. However, the cell cycle indicates the time required for transferring one cell on the incoming line or the outgoing line.

Next, the operation of the cell flow control device 1 will be described. The original leaky bucket has a counter which is incremented by 1 when a cell arrives and decremented by 1 at every fixed time T as described in the section of the prior art. The cell arriving at the time is determined to be a violating cell.

The value of the counter 19 can be regarded as indicating the queue length of the queuing system in which the service time of one cell is T. Therefore, the determination in the leaky bucket is performed by the cell in the system of the queuing system. When the number is equal to or less than (B-1), it is equivalent to determining that the number is not a violation. In this queuing system, when the total of the remaining time until the serving cell is output and the service time required by the cells in the queue is the remaining service time CTR1, the number of cells in the system is (B-1)

CTR1 ≦ TH (1) However, the threshold TH = T × (B−1) can be written.

As shown in FIG. 2, the remaining service time CTR1 _new when a _new cell arrives is the remaining service time CTR1 _old when the previous cell arrives.
And the arrival time interval ΔT

## EQU2 ## Since CTR1 _mew = max (CTR1 _old + T−ΔT, 0) (2), if the remaining service time CTR1 _old and the arrival time interval ΔT are known, the remaining service time CTR1 obtained using the above equation is obtained. The violation of the input cell can be determined by comparing _new with the threshold value TH.

The calculation of the arrival time interval ΔT will be described below. Here, in order to obtain the arrival time interval ΔT using the counter 19, the cell arrival time PHS and the elapsed time counter CTR2 are used for each virtual channel VC.

When a new cell arrives via the incoming line, the value of the counter 19 at that time is set in the cell arrival time PHS. The elapsed time counter CTR2 is reset to 0 when a cell arrives, and a value N equal to the number of virtual channels is added each time the counter 19 indicates a value set in the virtual channel VC. Here, the elapsed time counter CTR2 of the channel J indicates that the value of the counter 19 is J.
Shall be increased when By updating the value of the elapsed time counter CTR2 in this way,
In each cell cycle, only the elapsed time counter CTR2 of one virtual channel needs to be increased.

Since the elapsed time counter CTR2 is incremented only every N cell periods, it does not indicate an accurate cell arrival interval.
Using the cell arrival time PHS storing the value of C.9 and the current value CLK of the counter 19, an accurate arrival time interval ΔT
Can be requested.

Arrival time interval ΔT and elapsed time counter CT
R2, cell arrival time PHS, and value CL of counter 19
The relationship between K and the cell arrival time PHS is different from the relationship between the value J of the counter 19 when the elapsed time counter CTR2 is increased by N and the relationship between the current value CLK of the counter 19 and J, and the following equation is used. (3-1), (3-2),
In (3-3), the arrival time interval ΔT is given. FIG. 3 shows this state.

That is, in the case of FIGS. 3 (3) and (1), the arrival time interval ΔT when PHS (J) ≧ J, CLK ≧ J or PHS (J) <J, CLK <J
But,

ΔT = CTR2 (J) + CLK−PHS (J) (3-1) In the case of FIG. 3 (2), the arrival time interval when PHS (J) <J, CLK ≧ J ΔT
But,

ΔT = CTR2 (J) + CLK−PHS (J) −N (3-2) In the case of FIG. 3 (4), arrival when PHS (J) ≧ J, CLK <J Time interval ΔT
But,

５T = CTR2 (J) + CLK-PHS (J) + N (3-3).

Since the cycle of the counter 19 is equal to the number N of monitored channels, the elapsed time counter CTR2 of one virtual channel VC may be increased in each cell cycle.

In order to realize the above-described algorithm, the memory 15 has information having the configuration shown in FIG.
That is, the remaining service time CTR1 is assigned to each of the N virtual channels from channel 0 to channel (N-1).
(0), ~, (J), ~, (N-1), threshold value TH
(0), ~, (J), ~, (N-1), service time of one cell T (0), ~, (J), ~, (N-1), cell arrival time PHS (0), ~, (J), ~, (N-1), elapsed time counter CTR2 (0), ~, (J), ~, (N
-1) as a table. Here, J indicates the corresponding virtual channel number.

The cell arrival time PHS (J) and the elapsed time counter CTR2 (J) are used to determine the elapsed time since the last cell was input in this virtual channel, and the remaining value constitutes a leaky bucket. .

Next, the operation of the cell flow control device 1 in each cell cycle will be described with reference to the flowchart shown in FIG. Thereafter, the cell of the virtual channel number J is input via the incoming line, and the virtual channel number of this cell is
A case will be described as an example in which the cell is identified from the header information of the cell in FIG.

First, in step S11 at the beginning of the cell cycle, in order to enable calculation of ΔT in a subsequent step, the virtual channel number is previously set to the value of the elapsed time counter CTR2 having the virtual channel number equal to the value CLK of the counter 19. A value N equal to the number of channels is added.

When .DELTA.T is larger than (CTR1 + T), the operation described later is not affected by the value of .DELTA.T. Therefore, when CTR2 is equal to or more than an appropriate threshold value, N is not added so that CTR2 overflows. Does not occur. Furthermore, CTR2
May be configured to store only the number of times the value of the counter 19 becomes equal to the virtual channel number, and to multiply this by N when necessary.

Next, in step S13, if there is no cell input (NO), the operation in this cell cycle ends. On the other hand, when a cell is input via the incoming line (YE
In S), the process proceeds to step S15, and the cell arrival time P corresponding to the virtual channel number J of the input and arrived cell
The value of HS (J) is compared with the virtual channel number. If PHS (J) ≧ J, the process proceeds to step S17.
At this time, (3) and (4) shown in FIG. 3 are selected. If PHS (J) <J, the process proceeds to step S19. At this time, (1) and (2) shown in FIG. 3 are selected.

Next, in steps S17 and S19, a comparison is made between the virtual channel number J and the value CLK of the counter 19. In step S17, if CLK ≧ J, the process proceeds to step S23, and if CLK <J, the process proceeds to step S21. At this time, in step S23, equation (3-1) corresponding to FIG. 3 (3) is selected, and in step S21, equation (3-3) corresponding to (4) is selected.

On the other hand, if CLK ≧ J in step S19, the process proceeds to step S25, and if CLK <J, the process proceeds to step S23. At this time, step S25 is performed as shown in FIG.
Equation (3-2) corresponding to (1) is selected in step S23.

Using the result of this comparison, the elapsed time, that is, the arrival time interval ΔT is calculated according to the equations (3-1), (3-2),
It is determined based on (3-3).

At this time, the elapsed time counter CTR2 (J) of the virtual channel J does not necessarily need to be increased when the value CLK of the counter 19 is J, and may be updated at a constant time period. In that case, step S1
In 5, S17 and S19, the value of the counter 19 when the elapsed time counter CTR2 (J) is updated instead of J is used.

Next, in step S27, using the elapsed time ΔT, the next remaining service time CTR1 is calculated according to the following equation (4).
Find a.

[0040]

CTR1a = max {CTR1 (J) + T (J) -ΔT, 0} (4) Further, in step S29, the remaining service time CTR1a obtained by equation (4) is compared with a threshold TH (J). Then, the flow rate violation is determined.

If the remaining service time CTR1a is less than or equal to the threshold value TH (J), the flow advances to step S31 to output the input cell to the outgoing line.
At 33, the remaining service time CTR1a is substituted for the remaining service time CTR1 (J). Next, in step S35, the value of the elapsed time counter CTR2 (J) is set to 0, and the current value CLK of the counter 19 is substituted for the cell arrival time PHS (J).

If the remaining service time CTR1 (J) is longer than the service time T (J) in step S29, the input cell is a violating cell, and the transfer controller 11 discards the input cell in step S37. I do.

As described above, the cell flow control device of the present embodiment provides the cell arrival time PHS for each virtual channel.
(J) and the elapsed time counter CTR2 (J), it is possible to obtain the cell arrival time interval at the time of cell arrival using a single counter 19, and to measure the time interval for each virtual channel It becomes unnecessary to have. Furthermore, by being able to obtain the elapsed time from the time when the previous cell arrived when the cell arrived,
The leaky bucket counter can be updated collectively when the cell arrives. It is not necessary to decrement the counter of each virtual channel in a fixed time period as in the conventional case, and it is guaranteed that only one leaky bucket counter must be updated in one cell period at all times. Therefore, it is possible to accumulate these values on the memory, update the counter of the leaky bucket by an arithmetic unit commonly used for all virtual channels, and determine a violation. Since the memory element can be realized with higher integration than the logic element, even when the number of virtual channels to be monitored is large, the cell flow control device can be realized with a smaller hardware scale than the conventional one.

Next, a description will be given of a cell flow control device 3 according to a second embodiment. This cell flow control device 3
If the input cell violates the specified characteristics of the cell flow, it is stored in a buffer and then output until the cell is not violated.

Hereinafter, the configuration of the cell flow control device 3 in the second embodiment will be described with reference to FIG. The cell flow control device 3 manages the input and output to the header analysis unit 31, the buffer 37 capable of storing the M cells, the slot calculation unit 33 for calculating the time until the input cells can be output, and the buffer 37. And a slot management unit 35.

The slot calculator 33 calculates each virtual channel VC
Manages the parameters of the traffic characteristic, the cell is inputted, it calculates the time X _o to the time when the output from the current time becomes possible, and notifies the slot management unit 35.

The buffer 37 has a storage area for M cells and is sequentially output from the head, but has a function of inputting to an arbitrary position. The occupancy of each area of the buffer 37 is managed by the slot management unit 35. The slot management unit 35 searches for a vacant area X closest to the head after _Xo notified from the slot calculation unit 33 at the time of cell input, and searches for an Xth area from the top. The input cell is stored and X is notified to the slot calculation unit 33. The slot calculation unit 33 updates the parameter with the notified value of X.

FIG. 7 shows an example of the configuration of the slot calculator 33. The slot calculator 33 includes a memory 335 for storing information of each virtual channel, a calculator 333, and a clock 337.
And an N-ary counter 339 incremented by 1. Here, N represents the number of virtual channels to be monitored. The information stored in the memory 335 is equal to the information content of the memory 15 shown in FIG.
Then, a time _Xo until a cell can be output is obtained from the information stored in the cell according to the flowchart shown in FIG.

In the flowchart shown in FIG. 8, the operations in steps S111 to S127 are the same as those in steps S11 to S27 in the flowchart shown in FIG.

Hereinafter, a description will be given of step S127 and subsequent steps.

As Equation 7] _{X o = CTR1a-TH (J} ) (5), we obtain the X _o, and transmits to the slot management unit 35.

Here, a configuration example of the slot management unit 35 will be described with reference to FIG. M-bit shift register 3
Reference numeral 55 denotes a state in which each area of the buffer 37 is occupied. When a cell is stored in the i-th buffer 37, 1 is set in the i-th register of the shift register 355.

When X _o is input from the slot calculation unit 33, the encoder 357 outputs to the control unit 351 the position X of a register which is 0 and is closest to the head after the X _o -th position. Since a plurality of virtual channels are multiplexed and input from the incoming line, there is a possibility that cells of other virtual channels may already be stored at the _Xoth position. Indicates the earliest time that can be output.

The control unit 351 stores the cell in the X-th area of the buffer 37 and outputs X to the decoder 353. The decoder 353 outputs a signal to the X-th register from the head, and sets the value of this register to 1. set. X is notified to the slot calculation unit 33 at the same time.

When it is determined that a cell is to be output after the X cell period, the slot management unit 35 calculates the time at which the next cell can be output when the next cell is input to this virtual channel. FIG. 1 shows the values of the memory 335.
0 is updated according to the flowchart of FIG. That is, in step S211, the value of the remaining service time CTR1 (J) is

CTR1 (J) = max (CTR1a−X, 0) (6) Next, in step S213, -X is set to the elapsed time counter CTR2 (J), and the cell arrival time PHS
The current value CLK of the counter 339 is substituted for (J).

Cell output is performed sequentially from the head of the buffer, and at the same time, the shift register 355 is shifted by one bit. However, at the time of shifting, 0 is set in the last register.
Set. When the first area of the buffer is empty, no cell is output.

With the above configuration, the cells of each virtual channel are output from the cell flow controller 3 according to the determined characteristics.

When a cell having a different priority is input, if _Xo obtained by the equation (5) is equal to or larger than a predetermined threshold, the cell is discarded. By setting the threshold to a different value for each priority, priority control can be performed.

Also in the second embodiment described above, the time interval between the time at which the immediately preceding cell was output and the current time can be obtained when a new cell arrives. Is updated, and it is possible to determine the time until output is possible when the determined traffic characteristics are satisfied. Further, since the time at which output is possible at the time of cell input is specified, it is not necessary to determine the output at the time of output, and it is possible to output at the earliest possible time while satisfying the traffic characteristics with a small amount of processing. .

Next, a third embodiment of the present invention will be described. The cell flow control device 5 according to the third embodiment monitors the cell flow of a virtual channel multiplexed on an incoming line based on a sliding window, and discards cells violating predetermined parameters. That is, when a cell is input, (X0-
1) If the elapsed time TM (hereinafter referred to as monitoring time) from the arrival time of the cell that arrived immediately before to the current time is less than the monitoring period T0, the input cell is determined to be a violating cell and discarded.

In order to realize such a function, the cell flow control device 5 includes a transfer control unit 51, as shown in FIG.
Arithmetic unit 53, memory 55, clock 57, counter 59
Consists of

The operations of the transfer controller 51, clock 57 and counter 59 are the same as those of the transfer controller 11, clock 17 and counter 19 in the first embodiment. Further, the memory 55 has information of the configuration shown in FIG.

That is, from channel 0 to channel (N-
The monitoring times TM (0) to TM (N-1) and the cell arrival interval DT (0,
0) to DT (0, L-1) to (J, 0) to DT (J, L
-1) to (N-1, 0) to DT (N-1, L-1), cell arrival interval pointers n (0) to (J), to (N-
1), monitoring period T0 (0) ~, (J), ~ (N-1),
Maximum cell number X0 (0) ~, (J), ~ (N-1), cell arrival time PHS (0) ~, (J), ~ (N-1), elapsed time counter CTR2 (0) ~, ( J), ~ (N-1)
As a table.

The monitoring time TM (J) is (X0−
1) The elapsed time from the arrival time of the cell that arrived immediately before to the arrival time of the cell that arrived last is stored. The cell arrival intervals DT (J, 0) to DT (J, L-1) store the arrival intervals of the past L cells, and the cell arrival interval pointer n (J)
Indicates the cell arrival interval that stores the newest arrival interval.
That is, DT (J, n (J)) is the newest cell arrival interval.

By using these values, the arithmetic unit 53
The calculation is performed according to the flowchart shown in FIG.
Make a violation decision. Since the operations from steps S211 to S225 are equal to the steps from steps S11 to S25 in the flowchart shown in FIG. 5, step S227 is performed.
The following will be described. In step S227, the TM
Is obtained by the following equation.

[0065]

TM ′ = TM (J) −DT (J, n (J) −X0 (J) +1) + ΔT (7) where (n (J) −X0 (J) +1) is negative in the above equation. In this case, a value obtained by modulo L is used. TM '
Is the elapsed time from the arrival time of the cell arriving (X0 (J) -1) times earlier to the present, and TM ′ is compared with T0 (J) in step S229. TM 'is T0 (J)
In this case, the input cell is not a violating cell and is output to the outgoing line (step S231), and n is determined in step S233 to determine the next cell to arrive.
The value of (J) is increased by 1, and in step S235, the cell arrival interval DT (J, n (J)) determined by this n (J)
ΔT, and TM ′ in TM (J).

Next, at step S237, the cell arrival time PH
The current value of the counter 59 is set in S (J), and the elapsed time counter CTR2 (J) is reset to 0. If TM 'is smaller than T0 (J) in step S229, the input cell is discarded in step S239.

Further, even when a sliding window is used, cells are stored in a buffer until a time when outputting to an outgoing line does not cause a violation as in the cell flow control device 3 of the second embodiment, and then cells to be output are output. It is also possible to configure a flow control device. When the sliding window is used, the time interval required before the time when the output becomes possible is determined by the difference (T0−TM) between the monitoring periods T0 and TM ′.
'), The output of cells from the buffer may be controlled so as to output at the first time after (T0-TM') from the current time and at which output is possible.

In the cell flow control device according to the third embodiment, as in the cell flow control devices according to the first and second embodiments, the cell flow control is performed using only the information regarding the virtual channel to which the arriving cell belongs. Can be controlled.

In addition to a leaky bucket and a sliding window, a jumping window, a triggered jumping window and the like are known as methods for monitoring and controlling a cell flow. As shown in FIG. 14, the jumping window measures the number of input cells in each T1 time period in the T1 time period, and regards a cell input exceeding a predetermined maximum cell number X1 as a violation.

In the triggered jumping window, the time when the cell first arrives after the time T1 has elapsed, the time T1
The one-hour window is reset, and when a cell exceeding the cell X1 is input within the time T1 from this time, this cell is regarded as a violation.

A cell flow control device based on such a jumping window or a triggered jumping window can be realized with the same configuration as the cell flow control devices in the above-described first and third embodiments. .

If the jumping window is used, the cell number counter N is stored in the memory for each virtual channel.
(0) to N (J) to N (N-1), monitoring period T1 (0)
To T1 (J) to T1 (N-1), maximum cell number X1 (0)
To X1 (J) to X1 (N-1), cell arrival phase PHS
(0) to PHS (J) to PHS (N-1), elapsed time counters CTR2 (0) to CTR2 (J) to CTR2 (N
-1).

FIG. 15 is a flowchart showing the operation of the cell flow control device. The operations in steps S311 to S325 are performed in steps S11 to S25 in FIG.
Equivalent to the operation up to. Next, in step S327, Δ
T is compared with T1 (J). If ΔT is smaller than T1 (J), N (J) and X1 are determined in step S329.
(J) is compared. If N (J) is smaller than X1 (J), the cell is output to the outgoing line in step S331, and the value of N (J) is increased by 1 in step S333.
If N (J) is equal to or greater than X1 (J) in step S329, the input cell is a violating cell, and is discarded in step S335. If ΔT is equal to or greater than T1 (J) in step S327, the cell has shifted to a new cycle, so that N (J) is output as a cell in step S337, and 1 is set in N (J) in step S339. substitute.

Next, in step S341, ΔT is added to CTR2 (J) by T to measure the elapsed time in a new cycle.
Substitute the value obtained by taking modulo in 1 (J), and PHS (J)
Is substituted for CLK. The cell flow control device that controls the cell flow based on the triggered jumping window has a different operation flowchart. In step S341 in FIG. 16, a value obtained by modulating ΔT into CTR2 (J) by T1 (J) is substituted. Instead of this, 0 may be substituted. Also in this case, the information necessary for one cell time is only information of one virtual channel VC, so that the cell flow control device can be configured with a small amount of hardware.

[0075]

As described above, according to the present invention,
It is possible to realize a cell flow control device that controls a cell flow in a transmission line in which a large number of virtual channels are multiplexed, with a small hardware scale.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of a cell flow control device.

FIG. 2 is a diagram showing how a remaining service time CTR1 is updated.

FIG. 3 is a diagram illustrating a relationship between an arrival time interval ΔT and a cell arrival interval.

FIG. 4 is a diagram illustrating a configuration example of a memory;

FIG. 5 is a flowchart showing the operation of the cell flow control device.

FIG. 6 is a diagram illustrating a configuration example of a cell flow rate control device according to a second embodiment.

FIG. 7 is a diagram illustrating a configuration example of a slot calculation unit.

8 is a flow chart of the operation for obtaining the X _o.

FIG. 9 is a diagram illustrating a configuration example of a slot management unit;

FIG. 10 is a flowchart of updating a memory.

FIG. 11 is a diagram illustrating a configuration example of a cell flow rate control device according to a third embodiment.

FIG. 12 is a diagram illustrating a configuration example of a memory;

FIG. 13 is a flowchart showing the operation of the cell flow control device.

FIG. 14 is a diagram illustrating a state of determination in a jumping window.

FIG. 15 is a flowchart showing an operation of the cell flow control device based on a jumping window.

FIG. 16 is a configuration example according to a conventional technique.

[Explanation of symbols]

 Reference Signs List 1 cell flow control device 11 transfer control unit 13 operation unit 15 memory 17 clock 19 counter 101 arrival monitoring unit 105 counter 107 clock 109 counter 111 register 113 comparator 115 comparator 117 register 3 cell flow control device 31 header analysis unit 33 slot calculation Unit 35 slot management unit 37 buffer 333 operation unit 335 memory 337 clock 339 counter 351 control unit 353 decoder 355 shift register 357 encoder 5 cell flow control device 51 transfer control unit 53 operation unit 55 memory 57 clock 59 counter

Continuation of the front page (56) References JP-A-3-150944 (JP, A) JP-A-5-110585 (JP, A) JP-A-4-329733 (JP, A) European Patent Application Publication 435046 (EP, A 1)

Claims (3)

(57) [Claims] 1. A cell flow control device for controlling a cell flow on a transmission line in which a plurality of virtual channels are multiplexed, wherein a process for measuring an elapsed time from a starting point arbitrarily set for each of the virtual channels. Time measurement means, for each of the virtual channels, storage means for holding a value relating to the flow rate of the arriving cell, when a new cell arrives, the value of the storage means for the virtual channel to which the cell belongs, Computing means for updating based on the elapsed time up to the current time obtained by the elapsed time measuring means, and control means for controlling cell transfer based on the value of the storage means updated by the computing means. The elapsed time measuring means includes: a first counter provided for each virtual channel, which increases by N every N cell periods; and a first counter which increases by 1 every one cell period. When a cell arrives via the virtual channel, the first counter value corresponding to the virtual channel and the elapsed time using the second counter value A cell flow rate control device characterized by measuring. 2. A cell flow control device for controlling a cell flow on a transmission line in which a plurality of virtual channels are multiplexed, wherein each of the virtual channels arrives at a certain point in time and is held in a buffer at that point in time. Means for storing the remaining service time, which is the time it would take to finish outputting one or more cells from the buffer, and one of the virtual channels to which the cell belongs when a new cell arrives. Means for determining the elapsed time from the time at which the previous cell arrived to the current time; anda cell based on a value obtained by adding the service time of the cell of the virtual channel to a value obtained by subtracting the elapsed time from the remaining service time. Means for performing transfer control of the cell flow rate. 3. A calculating means for calculating a time difference from a current time until a time at which an input cell can be output, and an output is reserved at a time when output after the time difference obtained by the calculating means is not reserved. 2. The cell flow control device according to claim 1, further comprising: a reservation unit that performs the cell output at a time reserved by the reservation unit.