JPH09162889A - Shaping device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain efficient shaping without causing cell abort for each channel (path) due to overflow of a first-in first-out FIFO circuit or the like. SOLUTION: A received cell flow is smoothed for a transmission capability of each channel and circuits 5, 6 set threshold levels 1, 2 for FIFO length of FIFO A1-An provided to each channel and a write read timing generating section 2A for FIFO and a channel table TB specifying a transmission capability of 2 each channel are provided. The write read timing generating section 2A is operated independently for each channel. When the FIFO length exceeds the threshold level 1 and data of a channel corresponding to the excess of the threshold level 1 reach, the data are written in the FIFO and read from the same FIFO and whether or not the FIFO exceeding the threshold level 1 once is lower than the threshold level 2 is monitored and a channel lower than the threshold level 2 is read according to the transmission capacity upper limit by this monitoring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shaping device, for example, ATM (Asynchronous).
The present invention can be applied to a transfer network (asynchronous transfer mode) switching network, a terminal side of an ATM communication system, and the like.

[0002]

2. Description of the Related Art Generally, a Virtual Channel Handler (VCH) is used.
dler) makes many connections at the same time, but this VCH
The ATM cell input to the ATM cell is a connection acceptance control (CAC: Call Admission Control).
ol), the usage parameter control (UPC: Usage Parameter)
Control) has been checked.

However, in the VCH, cells are collected in each route by the ATM switch, so that A
TM cells are concentrated, and as a result, virtual paths (VP:
It may happen that ATM cells have to be sent out at a high instantaneous rate beyond the capacity of the Virtual Path). For this reason, each ATM cell is temporarily stored in a buffer memory, and the ATM cell is read so that the instantaneous speed of the ATM cell does not exceed a certain value (capacity of VP). Such a function is called "shaping",
A device that performs such shaping is called a "shaping device".

That is, in the shaping device, the terminal data subjected to UPC control by the ATM switch is VC
(Virtual Channel: Virtual Channel
l: As a virtual channel, a VP (Virtual Pa) in a transmission path that is set up to the ground (between the exchange of the communication destination)
(th: virtual path). However, since this VPI also has a limit of transmission capacity,
When a large amount of ATM cells are simultaneously sent from the ATM switch, an overflow temporarily occurs on the VP. As one method to prevent this, a transmission buffer is provided at the entrance of the VP to average the ATM cell flow.
Therefore, the shaping device controls such an ATM cell flow.

FIG. 2 is a functional block diagram of a conventional shaping device. In FIG. 2, the shaping device includes a plurality of FIFO (Fast In Fast Out) circuits A1 to An, and is configured to access the FIFO circuits A1 to An through the selector circuit 7 for both input and output. .

The input ATM cell is selected by the selector circuit 7 and stored in any of the FIFO circuits A1 to An according to the route. When the ATM cells stored in the FIFO circuits A1 to An are read, they are selected by the selector circuit 9 and output.

Here, the input ATM cell is transferred to the FIFO circuit A.
1 to An, the selector circuit 7 receives the control signal from the write / read timing generation circuit 2 and causes the selector circuit 7 to switch the input ATM cell to the FIFO circuit A1 according to the route.
~ An is accumulated. FIFO circuits A1 to A
Also when reading the ATM cells stored in n, the write / read timing generation circuit 2 supplies a read control signal to the selector circuit 9 to read the ATM cells stored in the FIFO circuits A1 to An.

The write / read timing generation circuit 2 has a VC or VCI (Virt) set in each ATM cell from the input ATM cell flow in the channel detection circuit 1.
ual Channel Identificatio
(n: virtual path identifier) is read, and the input ATM cell is determined by which FIFO circuit A from the information obtained by channel detection.
1 to An is determined.

Further, the write / read timing generation circuit 2 has A stored in the FIFO circuits A1 to An.
Information on the number of TM cells is given to the queue length table circuit 4. Then, the queue length table circuit 4 receives the FIFO circuits A1 to A1 from the write / read timing generation circuit 2.
From the information on the number of ATM cells stored in An, queue length information is managed in a table, and this table management information is given to the write / read timing generation circuit 2 again.

Further, the write / read timing generation circuit 2 defines the transmission capacity for each route (VP) and also defines which FIFO circuit A1 to An to store the ATM cell for which route VP. According to the information from the channel table circuit 3, the scheduler circuit 8 plans which of the FIFO circuits A1 to An is to be read and written, and gives a write control signal to the selector circuit 7 according to the plan information. The read control signal is given to the selector circuit 9.

As a management method of the buffering operation in the above-mentioned FIFO circuits A1 to An, for example,
There are techniques proposed in the following documents. Reference: 1994
Of IEICE Autumn Meeting, B-480,
"Buffer management method for Best Effort traffic in ATM network".

FIG. 3 is an operation flowchart of the write / read timing generation circuit 2. The write / read timing generation circuit 2 inputs the input data to a channel (VC) -corresponding FIFO so that each channel (V
It has a function of reading at a transmission rate of CI). In FIG. 3, when the input data (ATM cell) arrives (step S1), the channel (VC) number is detected (step S2), it is judged whether shaping is necessary (step S3), and the shaping is performed. F if not needed
The data is not accumulated in the IFO and is output through (step S4).

If shaping is required, the route (V
It is confirmed whether or not there is a free space in the FIFO circuit corresponding to P) (step S5), and if there is a free space, it is written in the FIFO of the corresponding route (step S6). Applicable F
If there is no space in the IFO circuit, the input data (AT
The M cell) is discarded (step S7).

In the case of a cell output request (step S8),
It is determined whether or not there is through data (ATM cell) (step S9). If there is through data, the through data is output (step S11). If there is no through data, the scheduler circuit specifies it. FI
It is output from the FO circuit (step S10).

By using the write / read timing generation circuit 2 as described above, it becomes possible to reduce the channel (VC) whose transmission rate is instantaneously increased due to traffic fluctuation to the set transmission rate.

In the example of FIG. 3, the channel (VC) for which the shaping process is not performed is transmitted to the selector circuit 9 on the output side without passing through the FIFO circuit, so that the transmission rate is maintained as it is. It is possible.

[0017]

However, in the conventional technique, if data is continuously input at a rate exceeding the contracted (declared) transmission rate, there is a possibility that a buffer overflow will occur in the FIFO circuit. There is a problem that input data is discarded.

Originally, the shaping device is a B-ISDN.
, It has an optional role, and it is highly undesirable to cause cell discard in such a device.

From the above, it is demanded to provide a shaping device capable of performing efficient shaping without causing cell discard for each channel (route) due to overflow of the FIFO circuit as the cell storage means. There is.

[0020]

Therefore, according to the present invention, a route detecting means for detecting a route (for example, VC, VP, etc.) of an input cell and each route according to the route of the input cell. A plurality of cell accumulating means capable of accumulating a plurality of cells for each cell; a cell accumulating remaining amount managing means for monitoring and managing a cell accumulating remaining amount accumulated and left in these cell accumulating means; Read control means for performing control to read out cells stored in the cell storage means according to a predetermined schedule, and reading out the stored cells while storing the input cells in the plurality of cell storage means. In a shaping device for controlling a cell flow according to the present invention, the above-mentioned problems are solved by the following characteristic configurations.

That is, the shaping device of the present invention monitors the remaining amount of accumulated cells accumulated in each cell accumulating means by a predetermined first threshold value as an appropriate remaining amount of accumulated cells for cell discard prevention measures. When the remaining amount of accumulated cells exceeds the predetermined first threshold value, the predetermined schedule is temporarily avoided, and the cells are removed from the cell accumulation means which has exceeded the predetermined first threshold value. A cell read priority control means for preferentially reading is provided.

By adopting such a configuration, the predetermined first
When the cell storage remaining amount of any one of the cell storage means reaches the predetermined first threshold value or more based on the threshold value of,
If the cell storage means continues cell storage as it is, overflow may occur and cell discard may occur.To prevent this, cell reading from each cell storage means according to a predetermined schedule is avoided, and the above predetermined That is, the cell reading from the cell accumulating means that has reached the first threshold value or more is performed preferentially.

Therefore, it is possible to efficiently perform shaping without causing cell discard for each channel (route) due to overflow of the cell storage means.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment of the present invention will be described with reference to the drawings. In the shaping device of the present embodiment, (1) in the device that smoothes the input cell flow into the transmission capacity of each channel (VC or virtual channel identifier VCI), the channel (VC or VC
I) the FIFO length (FI) of the FIFO circuit provided for each
In a circuit that has thresholds 1 and 2 for the number of cells stored in the FO) and has a writing / writing timing in the FIFO circuit and a channel table that holds the transmission capacity of each channel, The read timing generation unit operates independently for each channel, and when the FIFO length exceeds the threshold value 1 and the data of the channel corresponding to the threshold value 1 excess arrives, the read timing generation unit writes the data to the FIFO circuit and the same FIFO. It is provided with a means for reading from the circuit, a means for monitoring that the FIFO once exceeding the threshold 1 falls below the threshold 2, and a means for reading a channel below the threshold 2 by this monitoring means within the upper limit of the transmission capacity. To configure.

[First Embodiment]: FIG. 1 is a functional block diagram of the shaping device of the first embodiment. In FIG. 1, the shaping device includes a channel detection circuit 1, a write / read timing generation circuit 2A,
Channel table circuit 3 and queue length table circuit 4
And threshold 1 table circuit 5 and threshold 2 table circuit 6
, A selector circuit 7, a scheduler circuit 8, a selector circuit 9, and FIFO circuits A1 to An.

In the configuration of such a shaping device, the configuration different from the conventional one is the threshold 1 table circuit 5 in particular.
And a threshold 2 table circuit 6 are provided, and the FIFO circuit A
This is a configuration for controlling the number of ATM cells accumulated in 1 to An.

The relationship between the threshold 1 and the threshold 2 is that the threshold 1 ≧
The threshold value 2 is set. These threshold relationships are set for use in the accumulation processing of the number of ATM cells in all the FIFO circuits A1 to An.

The threshold 1 information output from the threshold 1 table circuit 5 and the threshold 2 table circuit 6 and the threshold 2 information are sent to the write / read timing generation circuit 2A which controls the write / read of the selector circuits 7 and 9. Given. The write / read timing generation circuit 2A has channel information detected by the channel detection circuit 1 from the input ATM cell flow, and queue length information that is the number of ATM cells remaining in the FIFO circuits A1 to An from the queue length table circuit 4. Threshold 1 table circuit 5 and threshold 2 table circuit 6
From the threshold 1 information and the threshold 2 information from and the plan information indicating the order and frequency of writing and reading the FIFO circuits A1 to An from the scheduler circuit 8,
A control signal for controlling writing / reading of the FIFO circuits A1 to An is generated and given to the selector circuits 7 and 9.

As shown in FIG. 1, the channel table circuit 3 is internally provided with a channel table TB, and when transmission capacity information and the like for each channel is given from a host device or the like, the channel table TB shows each channel. (V
Any of the FIFO circuits A1 to An for each C or VCI)
Is used and the transmission capacity of each channel is set.

Specifically, for example, channel 1 is FI
The FO circuit A2 shares the transmission capacity, sets the transmission capacity to 10 Mbit / s, the channel 2 has no used FIFO circuit, the transmission capacity is 1.5 Mbit / s, and the channel n uses the used F circuit.
It is shared by the IFOA 1 and the transmission capacity is set to 3 Mbit / s or the like. Information of this channel table TB is given to the scheduler circuit 8.

From the management information of the channel table TB from the channel table circuit 3, the scheduler circuit 8 determines F
The frequency and order in which the IFO circuits A1 to An are to be written and read are determined, and the result of this determination is given to the write / read timing generation circuit 2A as plan information (schedule).

(Write Operation of ATM Cell of Shaping Device): Next, the write operation of the ATM cell of the shaping device of FIG. 1 will be described. The outline of the write operation will be described below. First, data (ATM cell) arrives and the channel number of the data is detected. The necessity of shaping is judged by referring to the channel table using this channel number. When the shaping is unnecessary, the through is performed, and when necessary, the writing is performed to the FIFO circuits A1 to An of the corresponding route. When written to the FIFO circuits A1 to An, the FIFO corresponding to the FIFO circuits A1 to An
Increment the counter that counts the O length. Then if its corresponding FIFO length exceeds threshold 1,
The flag FLAG is set to 1.

Next, using the operation flow chart of FIG.
The above operation will be described in detail. In FIG. 4, first, when the input data (ATM cell) arrives at the channel detection circuit 1 (step S20), the channel number is detected here and given to the write / read timing generation circuit 2A. Write / read timing generation circuit 2
At A, it is judged from the queue length information from the queue length table circuit 4 whether or not shaping is necessary (step S2).
2). If it is determined in this determination that shaping is not necessary, the arrived ATM cell is not written in the FIFO circuit and is output through (step S23).

On the other hand, when it is judged that shaping is necessary (step S22), the FIFO circuits A1 to A1 according to the route are formed.
The write / read timing generation circuit 2A generates a write control signal for writing to any of An, and supplies it to the selector circuit 7, and writes the arrived ATM cell to any of the FIFO circuits A1 to An (step S2).
4).

When this writing is completed, the F circuit in any of the FIFO circuits A1 to An in which the ATM cell is written next is written.
The queue length table circuit 4 is instructed to increment the IFO length (queue length) by 1 (step S25).
Next, it is confirmed whether or not the incremented FIFO length (queue length) exceeds the threshold 1 of the threshold 1 table circuit 5 (step S26). If the threshold value 1 is exceeded in this confirmation, the flag FLAG is set to 1 (step S27). When the threshold value 1 is not exceeded, writing can be continued, and the processing ends.

In this way, the FIFO length is monitored and the F
By stopping the traffic of the corresponding channel when the IFO length exceeds the set threshold value 1, it is possible to prevent the data from being discarded.

(Reading Operation of ATM Cell of Shaping Device) Next, the reading operation of the ATM cell in the shaping device of FIG. 1 will be described. The outline of this read operation will be described below. First, at the reference timing, it is determined whether or not data is input to the shaping device. When there is no data input or when the flag FLAG = 0, the scheduler reads data from the corresponding FIFO circuit. When there is data input and the flag FLAG = 1, through data, that is, the data of the channel for which traffic control is not performed, is output as it is, and when the traffic control is performed, it is input to the channel of the input data. Applicable FIFO
Read from the circuit. When reading from the FIFO circuit, the corresponding FIFO length is decremented, and when the FIFO length is smaller than the threshold value 2, the flag F
It is assumed that LAG = 0.

Next, using the operation flow chart of FIG.
The above operation will be described in detail. In FIG. 5, first, the write / read timing generation circuit 2A confirms whether or not the flag FLAG is 1 (step S3).
2). If the flag FLAG is 1, then the input AT
It is determined whether there are M cells (step S33). If there is an input ATM cell, it is next determined whether or not it is through data (step S34). If it is not through data in this determination, the ATM cell is next read from the FIFO circuit corresponding to the input data and output from the selector circuit 9 (step S35).

Next, the queue length table circuit 4 is instructed to decrement the FIFO length of the FIFO circuit that has read out the ATM cell by 1, and the table is updated (step S36). Next, it is confirmed whether or not the corresponding FIFO length is smaller than the threshold 2 (step S37). If the FIFO length is smaller than the threshold 2 in this confirmation, the flag F
LAG = 0 is set (step S38). FI confirmed above
When the FO length is larger than the threshold value 2, the flag FLAG =
The read processing is continued without setting to 0.

In addition, when it is confirmed whether the flag FLAG is 1 or not (step S32), if it is not 1, then the FIF designated by the plan information from the scheduler circuit 8 is next.
Output an ATM cell from the O circuit (step S39),
The queue length table circuit 4 is instructed to decrement the FIFO length of the FIFO circuit by 1 to update the table (step S36).

If it is determined that the data is through data in the determination as to whether or not the data is through data (step S34),
The data is output through (step S40),
Continue the reading process.

(Effects of the first embodiment of the present invention):
According to the shaping apparatus of the first embodiment of the present invention described above, data is discarded by monitoring the FIFO length and stopping the traffic control of the corresponding channel when the set threshold value 1 is exceeded. You can avoid it.

Also, when the input data does not arrive,
Since data is read by the normal scheduler circuit, the number of data in the FIFO circuit is surely reduced,
When the O length reaches a certain threshold value 2 or less, it is possible to return to the original traffic control, and it is possible to realize a shaping device that does not discard data while performing traffic control as much as possible.

[Second Embodiment]: In the shaping apparatus of the second embodiment, in addition to the configuration of the first embodiment described above, in order to perform non-instantaneous switching of the shaping targets. A storage unit that holds a request for changing the traffic control target and a switching timing generation unit are provided, and the switching timing generation unit simultaneously sets thresholds 1 and 2.
Is set to 0, and the F of the FIFO circuit targeted by the FIFO circuit is
When the IFO length is detected to be 0, the traffic control target to be held is changed in the channel table, a new threshold value is set, and the subsequent operation is performed by the shaping device of the first embodiment. It is configured to perform an operation.

FIG. 6 is a functional block diagram of the shaping device of the second embodiment. In FIG. 6, the shaping device includes a channel detection circuit 1, a write / read timing generation circuit 2B, and a channel table circuit 3A.
, Queue length table circuit 4, threshold 1 table circuit 5
A threshold value 2 table circuit 6, a selector circuit 7, a scheduler circuit 8, a selector circuit 9, a channel table rewriting circuit 10, and FIFO circuits A1 to An.

In such a structure, a structure particularly different from that of the first embodiment described above is provided with a channel table rewriting circuit 10 to which rewriting information and the like are provided, and the contents of the channel table TB of the channel table circuit 3A are rewritten. The threshold value 1 table circuit 5 and the threshold value 2 table circuit 6 can be changed and the threshold value can be changed and set. When the write / read timing generation circuit 2B judges from the queue length information from the queue length table circuit 4 and detects that the queue length of the traffic control target FIFO circuits A1 to An has become 0, the channel table rewriting circuit The rewriting instruction is notified to 10. Upon receiving this notification, the channel table rewriting circuit 10 gives specific channel rewriting information to the channel table circuit 3A.

The shaping apparatus of the second embodiment performs the same operation as that of the above-described first embodiment in the normal operation, but it does so without interruption when changing the traffic control target channel. That is the purpose.
That is, it realizes no interruption in the shaping device (there is no discarding of data and inversion of the order of data in each channel).

(Operation of Shaping Device): Next, the shaping target switching operation in the shaping device of FIG. 6 will be described. The outline of the shaping target switching operation will be described below. First, when a channel switching command for a traffic control target is input to the channel table rewriting circuit 10, the threshold value 1 table circuit 5 and the threshold value 2 table circuit 6 are controlled to change the setting to the threshold value 0 respectively. When this setting control is performed, all the data of the target FIFO circuit is discharged to the selector circuit 9.

At the timing when the FIFO length of the FIFO circuit becomes 0, the table rewriting contents held in the channel table rewriting circuit 10 are changed to the channel table circuit 3
A is given to A and the channel table TB is rewritten. The normal operation after rewriting is the same as the operation of the above-described first embodiment.

Next, using the operation flow chart of FIG.
The above operation will be described in detail. In FIG. 6, first, it is confirmed whether or not the table rewriting command is input to the channel table rewriting circuit 10 (step S4).
1) If it is confirmed that the table rewriting command is input, the contents of the command are held (step S42),
Next, the threshold value 1 of the threshold value 1 table circuit 5 is set to 0, and the threshold value 2 of the threshold value 2 table circuit 6 is set to 0.
A read operation is performed (step S43).

Next, by setting these threshold values to 0, the write / read timing generation circuit 2B confirms whether the FIFO length of the FIFO circuit has become 0 (step S).
44), if it is confirmed that the FIFO length has become 0, then the channel table TB of the channel table circuit 3A is rewritten according to the contents of the table rewriting command (step S45). Next, the write / read timing generation circuit 2B returns the threshold value of the threshold value 1 table circuit 5 to 1,
Further, the threshold value of the threshold value 2 table circuit 6 is reset so as to return to 2 (step S46). In this way, the write / read operation is continued again.

If it is confirmed that the table rewriting command has not been input by checking whether or not the table rewriting command has been input to the channel table rewriting circuit 10 (step S41), the above-described first embodiment is performed. The normal operation of writing / reading based on FIGS. 4 and 5 described in the above form is performed (step S47), and the input of the table rewriting command is waited (step S41).

The FIFO length of the FIFO circuit is 0.
When it is confirmed whether or not (step S44), the FIFO
If it is confirmed that the length is not 0, then the normal write / read operation based on FIGS. 4 and 5 described in the first embodiment is performed (step S48), and the FIFO is executed.
It waits until the length becomes 0 (step S44).

(Effects of the Second Embodiment): In the conventional shaping device, in order to change the shaping target, if the data (ATM cell) of the channel is not stopped, switching is performed without interruption. I couldn't. However, according to the above-described shaping device of the second embodiment of the present invention, the thresholds 1 and 2 are changed to 0 so that the data written in the FIFO circuits A1 to An are forcibly discharged. By doing FI
By creating a timing when the ATM cell of the FO circuit becomes empty and rewriting the contents in the channel table TB, the channel (route) to be shaped can be switched without interruption even during data input. is there.

(Other Embodiments) (1) In the above embodiment, the algorithm of the scheduler circuit 8 is preferably fixed reading or minimum interval reading.

(2) Further, the above-mentioned shaping device is
It is effective when applied to an ATM exchange system or an ATM terminal device. Specifically, regarding the traffic control used for the B-ISDN transmission line, an ATM equipped with a FIFO buffer for sending the input cell flow for each channel.
It is effective when applied to the buffer access control of the traffic control device. Further, in an ATM network, it is effective to be applied as a device for correcting traffic to an appropriate one so that traffic fluctuations are not caused by a switch buffer, a multiplexing buffer, etc., and a device in the subsequent stage is adversely affected.

(3) Further, the FIFO circuits A1 to An are
It may be configured by individual memory circuits A1 to An, or may be realized by forming a plurality of cell storage regions inside the shared memory circuit. For such a shared memory system, it is also preferable to adopt the configuration disclosed in the specification and drawings of Japanese Patent Application No. 7-83889.

(4) Furthermore, each of the FIFO circuits A1 to A
Different thresholds 1 and 2 may be set for each n.

[0059]

As described above, according to the present invention, a plurality of cells can be accumulated for each route according to the route detecting means for detecting the route of the input cell and the route of the input cell. A plurality of cell accumulating means, a cell accumulating remaining amount managing means for monitoring and managing a cell accumulating remaining amount accumulated and left in these cell accumulating means, and a cell accumulating in the plurality of cell accumulating means In a shaping device that includes a read control unit that performs control to read out according to a predetermined schedule, and stores the input cells in the plurality of cell storage units while reading the stored cells and controlling the cell flow. Remaining cell accumulation amount accumulated in each cell accumulating means,
As a measure for preventing cell discard, monitoring is performed with a predetermined first threshold value as an appropriate remaining cell storage amount, and when the remaining cell storage amount is equal to or greater than the predetermined first threshold value, the predetermined schedule is set. By providing the cell read priority control means for preferentially reading the cells from the cell storage means which has become equal to or higher than the predetermined first threshold value by temporarily avoiding It is possible to realize a shaping device that efficiently performs shaping without causing cell discard for each path.

[Brief description of the drawings]

FIG. 1 is a functional configuration diagram of a shaping device according to a first embodiment of the present invention.

FIG. 2 is a functional configuration diagram of a conventional shaping device.

FIG. 3 is an operation flowchart of a conventional shaping device.

FIG. 4 is a write operation flowchart of the shaping apparatus according to the first embodiment.

FIG. 5 is a flowchart of a read operation of the shaping device according to the first embodiment.

FIG. 6 is a functional configuration diagram of a shaping device according to a second embodiment.

FIG. 7 is a flowchart of a shaping target switching operation of the shaping device according to the second embodiment.

[Explanation of symbols]

1 ... Channel detection circuit, 2A, 2B ... Write / read timing generation circuit, 3 ... Channel table circuit, 4
... queue length table circuit, 5 ... threshold value 1 table circuit, 6
... threshold value 2 table circuit, 7 ... selector circuit, 8 ... scheduler circuit, 9 ... selector circuit.

Claims (5)

[Claims] 1. A route detecting means for detecting a route of an input cell, a plurality of cell storing means capable of storing a plurality of cells for each route according to the route of the input cell, and these. Cell storage remaining amount management means for monitoring and managing the remaining cell storage amount accumulated in the cell storage means, and reading the cells accumulated in the plurality of cell storage means according to a predetermined schedule. In a shaping device having read control means for controlling and storing the input cells in the plurality of cell accumulating means and controlling the cell flow by reading out the accumulated cells, the accumulating means accumulates in each of the cell accumulating means. When the cell storage remaining amount is monitored by a predetermined first threshold value as an appropriate cell storage remaining amount as a cell discard prevention measure, and this cell storage remaining amount becomes equal to or more than the predetermined first threshold value Has Serial temporarily avoided predetermined schedule shaping apparatus characterized by having a cell read priority control means for reading out cells preferentially from the cell storing means becomes equal to or larger than the predetermined first threshold value. 2. The cell read priority control means is configured so that, after one of the plurality of cell storage means becomes equal to or more than the predetermined first threshold value, the cell storage remaining amount smaller than the predetermined first threshold value. Is detected, the cell read priority control is canceled, and the read control means reads cells from the plurality of cell storage means according to the predetermined schedule. The shaping device according to claim 1, which is performed. 3. A route allocation switching means for switching the route of one of the cell storage means of the routes assigned to the plurality of cell storage means to the assignment to another route. The shaping device according to claim 1. 4. The route allocation switching means sets the predetermined first threshold value and the predetermined second threshold value in order to switch the route of one of the cell accumulating means to another route. The setting is temporarily changed to 0, and the cell storage remaining amount management means sets the cell storage remaining amount to 0.
When it is detected, the route allocation switching means switches the cell accumulating means whose cell accumulation remaining amount is 0 to allocation for accumulating cells of a new route. The shaping device according to claim 3. 5. The route assignment switching means manages the relationship between each cell storage means and the assigned route in order to switch the route of one of the cell storage means to the assignment of another route. After the table is rewritten to a new route, the predetermined first threshold value and the second threshold value are reset from 0 to the original values, and cell writing / reading is continued. Item 4. The shaping device according to item 4.