JPH1132048A - Cell buffer controller - Google Patents

Abstract

(57) [Summary] The present invention relates to a cell buffer control device, and an object of the present invention is to provide a cell buffer control device in which cell discard does not occur. SOLUTION: A buffer for a user cell and a buffer for an alarm cell are separately provided, a state of the buffer for the user cell is monitored, and when an overflow occurs, the buffer for the alarm 3 cell is used as a buffer for the user cell. A capacity monitoring control unit is provided and configured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cell buffer controller, and more particularly, to an asynchronous transfer mode network (ATM).
The present invention relates to the control of the output of the ATM cell buffer and the alarm / monitoring cell of the transmission device of the network.

[0002]

2. Description of the Related Art FIG. 12 is a block diagram showing the configuration of a conventional apparatus. In the figure, reference numeral 1 denotes a cell buffer for receiving and temporarily storing user cells from the ATM network, 2 denotes an alarm cell buffer for temporarily storing alarm / monitoring cells, 7 denotes an alarm cell buffer for receiving alarm cells and generating alarm cells. 2 is an alarm cell generator to be given to the second alarm cell. The cell buffer 1 is composed of, for example, a two-port memory capable of simultaneously writing and reading. Reference numeral 3 denotes a selector which receives the outputs of the cell buffer 1 and the alarm cell buffer 2 and selects one of them.

Reference numeral 5 denotes a capacity monitoring control unit for monitoring the capacity so that the cell buffer 1 does not overflow, 6 a free cell detection unit for detecting a free slot (free area) on the transmission line, and 4 an output of the free cell detection unit 6. This is an output control unit that outputs a select signal of the selector 3 in response to the signal.

In the device configured as described above, cells transmitted from the ATM network are accumulated in the cell buffer 1. On the other hand, alarm cells are accumulated in the alarm cell buffer 2. During this time, the capacity monitoring control unit 5 monitors the number of write cells and the number of read cells of the cell buffer 1 to monitor whether the cell buffer 1 overflows. On the other hand, the output control unit 4 normally selects the cell buffer 1 to obtain a cell output. On the other hand, when the empty cell detecting section 6 detects that there is an empty area, the output control section 4 recognizes this, switches to the alarm cell buffer 2 side, and outputs an alarm cell from the selector 3.

[0005]

SUMMARY OF THE INVENTION Asynchronous transfer networks (ATMs)
The arrival time of the ATM cells input from the network is not always constant, and in some cases, the ATM cells may continuously arrive in a burst and exceed the reading speed of the cell buffer 1 (usually). The number of output cells is equal to or greater than the number of input cells). In the conventional device, the amount of the cell buffer 1 is constant based on the calculation value prediction at the design stage, and if it exceeds the value, there is a problem that cell discard occurs.

The present invention has been made in view of such a problem, and has as its object to provide a cell buffer control device that does not cause cell discard.

[0007]

[Means for Solving the Problems]

(1) FIG. 1 is a principle block diagram of the present invention. The same components as those in FIG. 12 are denoted by the same reference numerals. In the figure,
10 is a buffer for a user cell for storing an arriving user cell, 11 is a buffer for an alarm cell for storing an alarm cell,
Reference numeral 20 denotes a capacity monitoring control unit which monitors the state of the user cell buffer 10 and uses the alarm cell buffer 11 as a user cell buffer when an overflow occurs.
Is a user cell buffer 10 and an alarm cell buffer 11
Is a selector that selects one of them in response to the output of

According to the configuration of the present invention, the capacity monitoring control unit 20 constantly monitors the state of the user cell buffer 10, and when an overflow occurs, the alarm cell buffer 11
Is controlled so as to be stored in the alarm cell buffer 11. Thereby, it is possible to prevent the cell from being discarded.

(2) In this case, the capacity monitoring control unit 20 does not clear the entire alarm cell buffer when clearing the alarm cell buffer 11, but stores the data when the user cell buffer 10 overflows. alarm·
It is characterized in that a monitoring cell is left.

According to the configuration of the present invention, even when the alarm cell buffer is used as a user cell buffer, it is possible to prevent user cells from being discarded and to retain alarm cell information.

(3) When it becomes necessary to output an alarm / monitoring cell, the alarm / monitoring cell is written into the alarm cell buffer 11, and at the same time, the reception information flag of the alarm / monitoring cell is stored in the user cell buffer. It is characterized by writing in.

[0012] According to the configuration of the present invention, even when congestion or the like occurs in the ATM network, the user cells continuously arrive, and even when there are no empty cells, the alarm / monitoring cell can be reliably output. (4) Further, after receiving the alarm / monitoring cell, the type or priority of the alarm / monitoring cell is multiplexed as information to be written in the user cell buffer 10.

According to the configuration of the present invention, the transmission of the user cell and the alarm / monitoring cell can be controlled by reading the buffer 10 for the user cell. (5) Further, the reception information of the user cell received from the ATM network is written in the alarm cell buffer, and when the flag is detected on the reading side of each of the user cell buffer and the alarm cell buffer, the own buffer is temporarily stored. Reading is stopped and the other cell is output.

According to the configuration of the present invention, output control on the read side of the cell buffer can be made unnecessary.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 is a block diagram showing the first embodiment of the present invention. 1 are denoted by the same reference numerals. In the figure, 10 is AT
A user cell buffer for storing user cells received from the M network, and an alarm cell buffer 11 for storing generated alarm / monitoring cells. Reference numeral 25 denotes an alarm cell generation unit that generates an alarm / monitoring cell. The alarm cell buffer 1
Numeral 1 stores cells generated by the alarm cell generation unit 25.

Reference numeral 21 denotes a first capacity monitoring control unit for monitoring the capacity of the user cell buffer 10 and controlling the address of the buffer. Reference numeral 11 denotes a second capacity monitoring unit for monitoring the capacity of the alarm cell buffer 11 and controlling the buffer address. It is a capacity monitoring control unit. When the user cell buffer 10 overflows, the first capacity monitoring control unit 21 notifies the second capacity monitoring control unit 22 of a signal to that effect. When the alarm cell buffer 11 overflows, the first capacity monitoring control unit 21 sends a signal to that effect. The first capacity monitoring control unit 21 is notified.

3 is the output of the user cell buffer 10;
A selector which receives an output from the alarm cell buffer 11 and selects one of them to output as a cell output. 2
Reference numeral 3 denotes an empty cell detector for detecting an empty cell (empty area) on the ATM transmission line. 24 normally selects a user cell, and upon receiving a vacant cell detection signal detected by the vacant cell detection unit 23, sets the selector 3 to the alarm cell buffer 1
An output control unit that controls to select an alarm / monitoring cell from 1. That is, the selector 3 outputs a user cell from the user cell buffer 10 when no empty cell is detected, and outputs an alarm / monitoring cell from the alarm cell buffer 11 when an empty cell is detected. The first capacity monitoring control unit 21, the second capacity monitoring control unit 22, the empty cell detecting unit 23, and the output control unit 24 constitute the capacity monitoring control unit 20 in the principle diagram of FIG.

The operation of the circuit thus constructed will be described as follows. The user cells from the ATM network sequentially accumulate the user cells from the ATM network at the address of the user cell buffer 10 given from the first capacity monitoring control unit 21. The first capacity monitoring control unit 21
When the user cell buffer 10 is being monitored and the user cell write speed is slower than the user cell read speed, the user cell buffer 1 of a normal user cell is monitored.
Continue writing to 0.

On the other hand, the alarm cell generator 25 receives the alarm / monitoring cells and sequentially accumulates the alarm / monitoring cells at the address of the alarm cell buffer 11 given from the second capacity monitoring controller 22. The vacant cell detection unit 23 constantly checks whether there is a vacant cell area, and when it detects that there is a vacant cell area, notifies the output control unit 24 of the fact. A select signal is given, and the alarm / monitoring cell read from the alarm cell buffer 11 is output. That is, the alarm / monitoring cell is placed in the empty area of the user cell to output the cell.

Here, when user cells from the ATM network are input in bursts, the user cell buffer easily overflows. When the first capacity monitoring control unit 21 detects that the writing speed is higher than the reading speed of the user cell buffer 10 and the user cell buffer 10 overflows, the first capacity monitoring control unit 22 Notify that. The second capacity monitoring control unit 22 clears the alarm cell buffer 11 and then uses it for storing user cells. That is, an address is given to the alarm cell buffer 11, and user cells are sequentially accumulated. When the empty cell detector 23 detects an empty cell, the output controller 24 selects the output of the alarm cell buffer 11, reads the user cell stored at the address, and outputs the user cell from the selector 3. .

Incidentally, such a user cell buffer 1
To prevent the overflow of 0, there is a method of increasing the capacity of the user cell buffer. However, the scale of the hardware is increased, and a fixed delay of the transmission line occurs in the normal operation. However, it is preferable to temporarily use the alarm cell buffer described in this embodiment as a user cell buffer.

According to this embodiment, the capacity monitoring control unit constantly monitors the state of the user cell buffer 10 and controls the ATM cell to reach the alarm cell buffer 11 when an overflow occurs. By doing so, it is possible to prevent the cell from being discarded.

FIG. 3 is a block diagram showing a second embodiment of the present invention. The same components as those in FIG. 2 are denoted by the same reference numerals. This embodiment differs from the first embodiment in that the empty cell detector 23 shown in FIG. 2 is not provided. The operation of the circuit thus configured will be described as follows.

When it becomes necessary to output an alarm / monitoring cell, the alarm / monitoring cell is written into the alarm cell buffer 11 and at the same time, an alarm / monitoring cell reception flag is written into the user cell buffer 10.

On the cell reading side, when the first capacity monitoring controller 21 detects the alarm / monitoring cell reception flag, the reading of the user cell is stopped for one cell, and the alarm / monitoring from the alarm cell buffer 11 is performed. Read cell Selector 3
And outputs an alarm / monitoring cell.

With such a configuration, the alarm / monitoring cell can be reliably output even when it becomes necessary to output the alarm / monitoring cell while the user cells are continuously received (especially, an urgent alarm cell). Cells can be output. In other words, even when congestion or the like occurs in the ATM network, the user cells continuously arrive, and even when there are no empty cells, the alarm / monitoring cell can be reliably output.

FIG. 4 is a block diagram showing a third embodiment of the present invention. The same components as those in FIG. 3 are denoted by the same reference numerals. The difference from the configuration of FIG.
There is no point. The operation of the circuit thus configured will be described as follows.

When it becomes necessary to output an alarm / monitoring cell, the alarm / monitoring cell is written into the alarm cell buffer 11 and at the same time, an alarm / monitoring cell reception flag is written into the user cell buffer 10. Conversely, when writing the user cell to the user cell buffer 10 that has received the user cell, the user cell reception flag is written to the alarm cell buffer 11.

On the read side of each of the buffers 10 and 11,
The first and second capacity monitoring controllers 21 and 22 confirm these flags, and if there is a flag on the reading side of the user cell buffer 10, the reading of the user cell is stopped once. During that time, an alarm / monitoring cell is output. Conversely, if there is a flag on the read side of the alarm cell buffer 11, reading of the alarm cell is stopped once. In the meantime, the user cell is output. According to this operation, the selector 3 functions as an OR circuit.

According to this embodiment, the output control of the ATM becomes unnecessary, and the selector 3 can be realized by an OR gate. FIG. 5 is a diagram illustrating a configuration example of the capacity monitoring control unit according to the first embodiment. FIG. 6 is a time chart showing the operation of the circuit shown in FIG. 5, showing a change in the capacity of the cell buffer. In FIG. 5, the capacity monitoring control unit of FIG. 2 will be described by dividing it into a capacity monitoring unit and a buffer address generation unit. 21A is a user cell buffer address generation unit of the first capacity monitoring control unit 21, 21B is a user cell buffer capacity monitoring unit, 22A is an alarm cell buffer address generation unit of the second capacity monitoring control unit 22, and 22B is an alarm cell buffer. It is a capacity monitoring unit.

The user cell buffer capacity monitoring unit 21B counts up the up / down counter 30 by the cell pulse of the received ATM cell and the cell enable indicating whether the received ATM cell is valid or not. The upper limit of the count-up of the counter (capacity counter) 30 is the same as the capacity of the user cell buffer 10, and the user cell buffer 10 overflows at the upper limit of the count-up.

The up / down counter 30 decrements the count value by one each time a cell is read out.
When the output value becomes "0", a buffer underflow occurs.

On the other hand, the write address counter 31 of the buffer address generator 21A operates in synchronization with the count up of the capacity counter 30. On the other hand, the read address counter 32 also operates in synchronization with the countdown of the capacity counter 30.

The alarm cell buffer capacity monitor 22B and the address generator 22A operate in a similar manner. The alarm cell buffer capacity monitoring unit 22B counts up the up / down counter 40 by the cell pulse of the ATM network and the cell enable indicating whether the received alarm cell is valid. The upper limit of the count-up of the counter 40 is the same as the capacity of the alarm cell buffer 11, and the alarm cell buffer 11 overflows at the upper limit of the count-up.

The up / down counter 40 decrements the count value by one each time a cell is read out.
When the output value becomes "0", a buffer underflow occurs.

On the other hand, the write address counter 41 of the buffer address generator 22A operates in synchronization with the count up of the capacity counter 40. On the other hand, the read address counter 42 also operates in synchronization with the countdown of the capacity counter 40.

In FIG. 6, (a) is an ATM network cell pulse, (b) is a received ATM cell, (c) is an alarm cell output enable, (d) is an alarm cell, (e) is an output cell pulse, and (f) is An output cell, (g) is an output of the counter 30 indicating a user cell capacity, (h) is a full output,
(I) is the output of the counter 40 indicating the alarm cell capacity.

Here, the speed of the ATM cell from the ATM network is twice as high as the speed of the cell on the reading side. At time t1, the cell 1 is received, and immediately after the counter 30 is incremented, the cell is read and decremented. At time t2, when transmitting the alarm cell A input at time t1, the capacity counter 40 is decremented by one.

At time t3, the input of the ATM cell exceeds the allowable output (doubled), and the congestion occurs.
This indicates that the user cell buffer 10 is increasing. At t4, when the capacity of the user cell buffer 10 reaches m (maximum value of the buffer), a FULL flag is generated as shown in (h).

When the FULL flag is generated, the capacity counter 40 is set to "0" and the write address counter 4
1. Load of read address counter 42 (Loa
d) The address is set to "0" by the signal, and the alarm cell buffer 11 is cleared. Thereafter, the alarm cell buffer 11
Write the user cell to.

By using the alarm cell buffer 11 by the operation described above, the capacity of the user cell buffer 10 can be virtually increased, and discard of the user cell can be prevented.

FIG. 7 is a diagram showing another example of the configuration of the capacity monitoring control unit according to the first embodiment. The same components as those in FIG. 5 are denoted by the same reference numerals. In this embodiment,
The up / down counter is applied to the address counters 31 and 32 of the capacity monitoring controller 21.

In this system, when an overflow occurs in the buffer 10 of the user cell, the alarm / monitoring cell stored in the alarm cell buffer 11 is left and other areas are cleared. FIG. 8 shows mapping of the user cell buffer 10 and the alarm cell buffer 11.
(A) is a mapping of the user cell buffer 10;
(B) is a mapping of the alarm cell buffer 11, (c).
Shows a mapping when the alarm cell buffer 11 is used as a user cell buffer, and (d) shows another mapping of the alarm cell buffer.

As shown in (a), the user cell buffer 10 writes data from a lower address. The mapping of the alarm cell buffer 11 shown in (b) is also variable depending on the number of stored alarm / monitoring cells and the storage address when the overflow of the user cell buffer 10 occurs. In the case shown in (b), that is, when the alarm / monitoring cells are stored in k cells from the lowest address, the user cell counts down from the highest address and writes.

The writing is advanced by this operation, and is used as a virtual user cell buffer until the address of the user cell reaches the highest address of the area for k cells of the alarm / monitoring cell ((c)). As shown in (d), when j cells are stored in the middle address, the address of the j cells is subtracted from the address value of the buffer 11 for the alarm cell, and this value is calculated as shown in FIG. It is loaded to the initial value of the up / down counter 31 and counts down. For the purpose of such down-counting, an up-down counter is used as the counter 31.

With the above configuration, when the user cell buffer 10 overflows, it is possible to prevent the user cell from being discarded and to leave the alarm cell information without clearing all the alarm / monitoring cells. it can.

FIG. 9 is a diagram showing the mapping of cell buffers in the second embodiment. (A) is a buffer for user cells, and (b) is a buffer for alarm cells. In this embodiment, when it becomes necessary to output an alarm / monitoring cell, the alarm / monitoring cell is set to the alarm cell buffer 1.
1 is provided with an area 10a for writing a flag indicating reception of an alarm / monitoring cell in the user cell buffer 10 at the same time that the alarm / monitoring cell is written to 1.

FIG. 10 is a time chart showing the operation of the second embodiment. It is assumed that the capacity monitoring controllers 21 and 22 of the second embodiment also have the same configuration as that of the first embodiment. (A) is an ATM network cell pulse,
(B) is a received ATM cell, (c) is an alarm cell enable signal, (d) is an alarm cell, (e) is an output cell pulse,
(F) is an output cell, and (g) is an up / down counter output.

In the figure, in the cycle of T1, no user cells are stored in the user cell buffer 10, so that
As soon as a cell from the ATM network is received, reading from the user cell buffer 10 is started and output. The received ATM cell 1 shown in (b) is read by the output cell pulse (e) and output as shown in (f).

On the other hand, when the alarm / monitoring cell A arrives as shown in FIG.
Since there are no cells, it can be sent immediately after reception,
As shown in (f), the alarm / monitoring cell A is read after the user cell 1.

Next, in the cycle of T2, when the alarm cell B arrives, the user cells are already stored in the user cell buffer 10, and the alarm / monitoring cell B is output after outputting the user cell 100. become. As shown in (f), the alarm / monitoring cell B is output after the user cell 100. The user cell and the alarm / monitoring cell at this time are processed in the order of arrival with the same priority.

Next, in the cycle of T3, when the alarm / monitoring cell C arrives while the user cells are continuously output from the ATM network, when the user cell 201 is written into the user cell buffer 10, Then, the alarm / monitoring cell reception flag is written into the area 10a of the user cell buffer 10 (see FIG. 9). In other words, as shown in FIG. 9, the buffer is extended by one bit, and the last area 1 of the user cell is expanded.
A flag "1" indicating the presence of an alarm / monitoring cell is written in 0a. When there is no alarm / monitoring cell, the flag "0" is written in the flag area 10a.

When the reading side of the user cell buffer 10 detects that a flag is set when reading the user cell 201, it recognizes that there is an alarm / monitoring cell. Then, after the output of the user cell 201 from the user cell buffer 10, the alarm / monitoring cell C is output as shown in (f).

By using the above-described configuration, the alarm / monitoring cell can be reliably output even when the user cells are continuously transmitted in a burst manner, and the user cell buffer 10 can be output to the read side. Notification of the presence / absence of an alarm / monitoring cell can be easily realized.

FIG. 11 is a diagram showing the mapping of a cell buffer according to the third embodiment of the present invention. (A) shows the mapping of the user cell buffer 10, and (b) shows the mapping of the alarm cell buffer 11.

When it becomes necessary to output the alarm / monitoring cell, the alarm / monitoring cell is written into the alarm cell buffer 11 and at the same time, the alarm / monitoring cell reception flag (for example, 1 byte) and multiplexes the priorities of alarm / monitoring cells and the like and notifies the reading side of the user cells. If this flag is present, the user cell reading side can determine that reading of the user cell should be temporarily stopped.

According to this embodiment, the read control of the user cell and the alarm / monitoring cell on the read side of the cell buffer becomes unnecessary.

[0058]

As described above in detail, according to the present invention, (1) a buffer for a user cell and a buffer for an alarm cell are separately provided, and the state of the buffer for the user cell is monitored. When an overflow occurs, a capacity monitoring control unit that uses the alarm cell buffer as a user cell buffer is provided, so that the capacity monitoring control unit constantly monitors the state of the user cell buffer. ATM cells arriving at the cell buffer can be controlled so that cell discard does not occur.

(2) In this case, when clearing the alarm cell buffer, the capacity monitoring control unit does not clear the entire alarm cell buffer, but stores the alarm / monitoring data accumulated when the user cell buffer overflows. By leaving cells, even when the alarm cell buffer is used as a buffer for ATM cells, discarding of user cells can be prevented and alarm cell information can be left.

(3) When it is necessary to output an alarm / monitoring cell, the alarm / monitoring cell is written to the alarm cell buffer, and the reception information flag of the alarm cell is written to the user cell buffer. Accordingly, even when congestion or the like occurs in the ATM network, the user cells continuously arrive, and even when there are no empty cells, the alarm / monitoring cell can be output reliably.

(4) After receiving the alarm / monitoring cell,
By multiplexing the type or priority of the alarm / monitoring cell as information to be written in the user cell buffer, transmission of the user cell and the alarm / monitoring cell can be controlled by reading the user cell buffer.

(5) Further, the reception information of the user cell received from the ATM network is written into the alarm cell buffer, and when the reading side of the user cell buffer and the alarm cell buffer respectively detects the flag, the self By stopping the reading of the buffer and outputting the other cell, the output control of the user cell and the alarm / monitoring cell on the reading side of the cell buffer can be eliminated.

As described above, according to the present invention, it is possible to provide a cell buffer control device in which cell discard does not occur.

[Brief description of the drawings]

FIG. 1 is a principle block diagram of the present invention.

FIG. 2 is a block diagram illustrating a first embodiment of the present invention.

FIG. 3 is a block diagram showing a second embodiment of the present invention.

FIG. 4 is a block diagram showing a third embodiment of the present invention.

FIG. 5 is a diagram illustrating a configuration example of a capacity monitoring control unit according to the first embodiment;

FIG. 6 is a time chart showing the operation of the first embodiment.

FIG. 7 is a diagram illustrating another configuration example of the capacity monitoring control unit according to the first embodiment;

FIG. 8 is a diagram showing mapping of a cell buffer;

FIG. 9 is a diagram illustrating mapping of a cell buffer according to the second embodiment;

FIG. 10 is a time chart showing the operation of the second embodiment.

FIG. 11 is a diagram illustrating mapping of a cell buffer according to the third embodiment;

FIG. 12 is a block diagram showing a configuration of a conventional device.

[Explanation of symbols]

 Reference Signs List 3 selector 10 user cell buffer 11 alarm cell buffer 20 capacity monitoring control unit

Claims (5)

[Claims] 1. A buffer for a user cell and a buffer for an alarm cell are separately provided, the state of the buffer for the user cell is monitored, and when an overflow occurs, the buffer for the alarm cell is used as a buffer for the user cell. A cell buffer control device provided with a capacity monitoring control unit. 2. The capacity monitoring control unit according to claim 1, wherein when the alarm cell buffer is cleared, the alarm cell buffer is not completely cleared, but the alarm / monitoring cell accumulated when the user cell buffer overflows is left. 2. The cell buffer control device according to claim 1, wherein: 3. When it becomes necessary to output an alarm / monitoring cell, write the alarm / monitoring cell into the alarm cell buffer and write the reception information flag of the alarm / monitoring cell into the user cell buffer. Claim 2
The cell buffer control device according to claim 1. 4. The cell buffer control device according to claim 3, wherein after receiving the alarm / monitoring cell, the type or priority of the alarm / monitoring cell is multiplexed as information to be written in the user cell buffer. 5. The reception information of a user cell received from the ATM network is written into the alarm cell buffer, and when the flag is detected on the reading side of each of the user cell buffer and the alarm cell buffer, the buffer of the own buffer is temporarily stored. 4. The cell buffer control device according to claim 3, wherein reading is stopped and the other cell is output.