JP3175724B2 - Cell discard control device and cell discard control method - 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 discard control device and a cell discard control method in an asynchronous transfer mode, and more particularly, to a cell in an asynchronous transfer mode when an overflow occurs in a relay node in a communication system in an asynchronous transfer mode. The present invention relates to a cell discard control device and a cell discard control method for discarding.

[0002]

2. Description of the Related Art Conventionally, an asynchronous transfer mode (Asynchronous
Transfer Mode: Hereinafter, abbreviated as ATM. In the communication method of (1), an exchange or a relay node to which a plurality of terminals that make or answer a call are connected, the ATM throughput of the maximum data rate and the average data rate processed per unit time declared by each of these terminals. By allocating the bandwidth within the range, the bandwidth is effectively used. Therefore, when data faster than the ATM throughput declared by each terminal is actually transferred, an overflow occurs in a built-in transmission buffer in the exchange or the relay node. In this case, the AT that caused the overflow
Discarding M cells is allowed. At that time, A
Since the TM cells are unconditionally discarded regardless of the attributes and priorities of the TM cells, there is a problem that, for example, in voice communication in which retransmission cannot be performed, silence or noise occurs. Therefore, when an overflow occurs in an exchange or a relay node in such an ATM communication system, some cell discard control devices and methods for minimizing the problems in voice communication have been proposed.

FIG. 9 shows an outline of the configuration of a cell discard control device in the ATM communication system proposed in the past. In the cell discard control device 10, a transmission terminal 11 is connected to a header conversion unit 13 via a terminal interface 12. This header converter 13 is an ATM switch 14
And the ATM input from the transmission terminal 11
By rewriting the destination indicated in the header of the cell, the ATM switch 14 performs a switching operation to a line to be transferred. Such rewriting of the ATM cell header section is performed under the control of the signal processing section 15, and the exchange operation of the ATM switch 14 is performed by the switch control section 1
6 is performed. The header conversion unit 17 is also connected to the output side of the ATM switch 14, and similarly to the header rewriting operation in the header conversion unit 13, the destination is set to the transfer destination via the transmission path 19 under the control of the signal processing unit 18. The rewritten header portion is rewritten. Signal processing unit 15,
18 and the switch control unit 16 are centrally controlled by a call processing unit (not shown).

[0004] The header conversion unit 13 includes an inbound header conversion unit 20 to which an ATM cell from the transmission terminal 11 is input via the terminal interface 12, and the header unit of the input ATM cell as described above by the signal processing unit 15. Is rewritten. Further, the header conversion unit 13 includes an AT whose header part has been rewritten by the inbound header conversion unit 20.
Maximum cell rate monitoring unit 21 to which M cells are respectively input
, Average cell rate monitoring unit 22 and non-priority identifier assigning unit 2
3 is provided. The maximum cell rate monitoring unit 21 and the average cell rate monitoring unit 22 monitor the ATM cell rate output from the ingress header conversion unit 20, and can measure the maximum cell rate and the average cell rate per unit time, respectively. It has become. Then, according to the measured maximum cell rate and average cell rate, the non-priority identifier assigning section 23 outputs the ATM output from the ingress header converting section 20.
A non-priority identifier indicating the priority at the time of cell discard is assigned to a predetermined position of the cell.

[0005] The header conversion unit 17 includes an ATM switch 14.
A transmission buffer 24 for sequentially storing ATM cells output after the exchange processing by the CPU, an identifier determination unit 25 for determining a non-priority identifier given to the ATM cells stored in the transmission buffer 24, and control of a signal processing unit 18. And an outgoing header conversion unit 26 that rewrites a header portion addressed to the transfer destination via the transmission path 19 by the transmission side.

The cell discard control device 10 in this proposal
When the transmitting terminal 11 makes a call, the maximum data rate and the average data rate transmitted from the transmitting terminal 11 per unit time are declared. The cell discard control device 10 in which the maximum data rate and the average data rate per unit time are declared is converted into a maximum cell rate and an average cell rate to be transmitted per unit time in the ATM communication system by a call processing unit (not shown). , AT
It is held as M throughput. The held ATM throughput is transmitted to a header conversion unit 13 by a call processing unit (not shown).
Maximum cell rate monitoring section 21 and average cell rate monitoring section 2
2. Compared with the maximum cell rate and average cell rate measured in 2 and if the maximum cell rate or average cell rate exceeds the declared value, a non-priority identifier is assigned until the maximum cell rate and average cell rate fall below the declared value. A non-priority identifier is assigned to a predetermined position of the ATM cell output from the ingress header conversion unit 20 by the unit 23.

The ATM switch 14 includes a header conversion unit 13
With reference to the destination rewritten by the inbound header conversion unit 20, the exchange processing for transferring the ATM cell to the corresponding outbound line is performed. The ATM cell output from the corresponding outgoing line in this manner is input to the header conversion unit 17.

The ATM cells input to the header conversion unit 17 are sequentially accumulated in a transmission buffer, and are stored in the outbound header conversion unit 2.
In step 6, the header portion having the transfer destination as the destination is rewritten via the transmission path 19 under the control of the signal processing section 18, and is transmitted to the transmission path 19. Here, the transmission buffer 24 stores the ATM
When cells are stored, the transmission buffer 24 can detect the blockage of the transmission line 19 via a call processing unit (not shown). When the blockage is detected, the ATM stored in the transmission buffer 24 can be detected. The identifier of the cell indicating the discard priority assigned by the non-priority identifier assigning unit 23 is determined. If it is determined that the identifier of the stored ATM cell is non-priority, the cell is discarded.
On the other hand, when it is determined that the identifier assigned to the stored ATM cell is not non-priority, any non-priority cell among the cells stored in the transmission buffer 24 is discarded.

[0009] A technique relating to such a cell discard control device in the ATM communication system is disclosed in, for example, Japanese Patent Laid-Open No. 5-2521.
No. 81, “Asynchronous transfer mode cell discarding method” is disclosed.

Japanese Unexamined Patent Publication No. 5-91123, "Congestion control method in asynchronous transfer mode", describes an AT from a transmitting terminal.
The M throughput is measured, and when the maximum cell rate per unit time and the average cell rate of the ATM cells previously declared by the transmitting terminal are exceeded, the ATM cells from the transmitting terminal are discarded as they are until the reported value falls below the ATM throughput. A technique relating to a cell discarding control device in the ATM communication system is disclosed.

[0011]

SUMMARY OF THE INVENTION However, Japanese Patent Application Laid-Open
According to the technology disclosed in Japanese Patent Application Publication No. 252181, when a blockage of a transmission path as a transmission destination is detected and an ATM cell to be stored is not non-priority, any cell among cells stored in a transmission buffer is deleted. They are to be discarded. Therefore, when the cells stored in the transmission buffer are sequentially transmitted after the blockage of the transmission path is resolved, there is a problem that the continuity of the cells transferred on the receiving terminal side cannot be maintained. For example, in the case of voice communication, continuity will not be maintained, and in some cases noise will occur,
Inconvenience still arises as a voice communication system.

Further, in the technique disclosed in Japanese Patent Application Laid-Open No. 5-91123, since a transmission buffer is not provided, the above-mentioned cell discard frequently occurs, and it is necessary to tolerate the occurrence of silence and noise due to voice communication to some extent. I can't get it. further,
Similarly, even with such frequent cell discards, there remains a problem that the continuity of the cells transferred on the receiving terminal side cannot be maintained. As described above, in the conventionally proposed technology, no technical idea of maintaining the continuity of cells is disclosed or suggested.

It is an object of the present invention to provide a cell discard control device and a cell discard control method which maintain the continuity of transfer cells as much as possible even if cell discard is performed due to congestion of a transmission line.

[0014]

According to the first aspect of the present invention, there are provided (a) a transfer rate monitoring means for monitoring a transfer rate of a cell inputted from a transmitting terminal, and (b) a transfer rate monitoring means for monitoring the transfer rate. Determining means for determining whether or not the transfer rate of the cell being used exceeds the transmission data rate previously declared by the transmitting terminal; and (c) transmitting the cell whose transfer rate monitored by the determination means has been declared. First identifier adding means for adding a first identifier indicating that processing is to be performed in a non-priority manner at a predetermined position of a cell input from the transmitting terminal when it is determined that the data rate is exceeded; )
Cell storage means having a plurality of entries and storing cells sequentially in these entries; (e) overflow detection means for detecting an overflow state of the cell storage means;
(F) When the overflow state is detected by the overflow detecting means, store it in the cell storage means.
Storing the cell is trying to this storage when the first identifier is added to a predetermined position of Utosuru cells
An overflow state is detected by first cell discarding means for discarding without any error and (g) overflow detecting means ;
At a predetermined position of the cell to be stored in the cell storage means,
When the identifier 1 is not added, the cell storage means
The oldest stored cell among the cells added with the first identifier stored in the cell is discarded and stored in the cell storage means.
An overflow state is detected by a second cell discarding unit that stores a cell to be stored in a cell storage unit and (h) an overflow detection unit, and the cell is stored in the cell storage unit.
The first identifier is added to a predetermined position of the cell
And all the cells stored in the cell storage means
No first identifier is added to these predetermined positions
In some cases, the cell discard control device is provided with third cell discarding means for discarding the cells stored in the cell storage means and storing the cells in the cell storage means.

That is, in the first aspect of the present invention, the transfer rate monitoring means monitors the transfer rate of the cell input from the transmitting terminal, and the determination means determines whether or not the transmission data rate exceeds a previously declared transmission data rate. . And the first
If it is determined by the identifier adding means that the transfer rate of the cell being monitored by the determining means exceeds the declared value, the predetermined position is processed without priority.
It is added to the first identifier indicating a. Further, a cell storage means for sequentially storing a plurality of cells is provided so that an overflow state of the cell storage means can be detected by the overflow detection means. The first cell discarding means is overflow
When an overflow condition is detected by the detection means
Is a predetermined position of the cell to be stored in the cell storage means.
When the first identifier is added to the
Discard cells without storing them. like this
If this was not the case, the second cell
If the first identifier stored in the cell storage means is
Discard the oldest accumulated cells among the added cells.
The cell to be stored in the cell storage means is stored in the cell storage means.
Store. It was not the case that such disposal was also performed
In this case, the third cell discarding means stores the oldest data in the cell storage means.
Discard the stacked cells and store the cells in the cell storage means
I have decided.

According to a second aspect of the present invention, in the cell discard control device according to the first aspect, when it is determined that the transfer rate of the cell monitored by the determination means exceeds the declared transmission data rate, And a transmission rate change requesting means for requesting a change in the transmission rate of the transmitting terminal when the overflow state is detected by the overflow detecting means.

That is, according to the second aspect of the present invention, when the transfer rate of the cell is determined to exceed the declared value by the determination means and an overflow state is detected, the transmission rate of the transmitting terminal is reduced. By doing so, the occurrence of overflow can be avoided as much as possible, and even if an overflow should occur and the transfer cells need to be stored in the transmission buffer, the oldest cells should be discarded and the receiving terminal side as much as possible The continuity of the transferred cells can be maintained.

According to the third aspect of the present invention, (a) a declared value storing step of storing the transmission data rate declared by the transmitting terminal, and (b) a transfer rate of monitoring the transfer rate of a cell input from the transmitting terminal. A monitoring step; (c) a determining step of determining whether or not the transfer rate of the cell monitored in the transfer rate monitoring step exceeds a transmission data rate stored in the storage step; When it is determined that the transfer rate of the cell monitored in the step exceeds the declared transmission data rate, the cell is processed at a predetermined position of the cell input from the transmitting terminal without priority.
A first identifier addition step of adding the first identifier indicating that the overflow detection step of detecting an overflow state of the transmission buffer for sequentially storing these entries cells having a plurality of entries (e), the ( ) When the overflow state of the transmission buffer is detected in this overflow detection step, the data is stored in the transmission buffer.
When the first identifier is added to a predetermined position of the cell to be stored, the cell to be stored is discarded.
A first cell discarding step, and (g) overflow
The detection step detects an overflow condition,
At the specified position of the cell to be stored in the transmission buffer,
When the identifier of 1 is not added, the transmission buffer
Of the cells to which the first identifier stored in
Discard the oldest accumulated cells and put the cells in the transmit buffer
A second cell discarding step for storing;
The row detection step detects an overflow condition.
The position of the cell to be stored in the transmit buffer
Does not have the first identifier and the transmission buffer
All the cells stored in the
When the identifier of 1 is not added, the transmission buffer
The oldest accumulated cells are discarded and cells are sent to the buffer.
And a third cell discarding step stored in the cell discarding control method.

That is, according to the third aspect of the present invention, first, the reported data rate reported from the transmitting terminal is stored in the reported value storing step, and the transmission rate of the cell input from the transmitting terminal is monitored in the transfer monitoring step. In the step, it is determined whether or not the transfer rate of the cell monitored in the transfer rate monitoring step exceeds the transmission data rate stored in the storage step, and the cell is monitored in the determination step in the first identifier adding step. When it is determined that the transfer rate of the cell in question exceeds the declared transmission data rate , processing is performed in a predetermined position of the cell input from the transmitting terminal without priority.
It is the addition of a first identifier indicating that. Then, an overflow state is detected in the overflow detecting step, and the overflow state is detected in the first cell discarding step.
Is detected in the transmit buffer when
When the first identifier is added at a predetermined position in the file
Discards the cell to be stored. This
If this was not the case, the second
Stored in the transmission buffer as a
The oldest stored cell among the cells to which the first identifier has been added.
Discard the cell and store the cell in the transmit buffer. This
If there is no such disposal,
As the cell discarding step, the oldest accumulated
Discarding the stored cell and storing the cell in the transmit buffer
I have to.

According to a fourth aspect of the present invention, in the cell discard control method according to the third aspect, when it is determined in the determining step that the transfer rate of the monitored cell exceeds the declared transmission data rate, And a transmission rate change requesting step of requesting a change in the transmission rate of the transmission terminal when the overflow state is detected in the overflow detection step.

That is, according to the fourth aspect of the present invention, it is determined in the determining step that the transfer rate of the cell exceeds the declared value, and when the overflow state is detected, the transmission rate of the transmitting terminal is reduced. By doing so, the occurrence of overflow can be avoided as much as possible, and even if an overflow should occur and the transfer cells need to be stored in the transmission buffer, the oldest cells should be discarded and the receiving terminal side as much as possible The continuity of the transferred cells can be maintained.

According to a fifth aspect of the present invention, in the cell discarding control device according to the second aspect, the transfer rate monitoring means monitors the maximum cell rate and the average cell rate, and the declared transmission data rate is the maximum data transfer rate and the maximum data rate. The average data transfer rate, the maximum data transfer rate and the average data transfer declared when one of the determination means determines that the value exceeds the declared value, and when the overflow detection means detects an overflow condition. A transmission rate change requesting means for requesting a change in the transmission rate of the transmission terminal based on the speed is provided.

According to a sixth aspect of the present invention, in the cell discard control method according to the fourth aspect, the transfer rate monitoring step monitors the maximum cell rate and the average cell rate, and the declared transmission data rate is the maximum data transfer rate and the maximum data rate. The average data transfer rate, the maximum data transfer rate and the average data transfer declared when one of them is determined to exceed the declared value in the determination step and the overflow state is detected in the overflow detection step A transmission rate change requesting step of requesting a change in the transmission rate of the transmission terminal based on the speed is provided.

That is, in the invention according to claim 5 or 6, the maximum cell rate and the average cell rate are used in the declaration and determination, thereby improving the accuracy of predicting the proportion of cells transmitted per unit time from the transmitting terminal. Can be done.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments.

First Embodiment

FIG. 1 shows an AT according to a first embodiment of the present invention.
1 shows an outline of a configuration of a cell discard control device applied to the M communication system. A transmission terminal 31 and a reception terminal 32 are connected to the cell discard control device 30 according to the first embodiment, and the transmission terminal 31 transmits the ATM to the reception terminal 32 via the cell discard control device 30 in a burst manner. It is assumed that a cell is transferred. The cell discarding control device 30 according to the first embodiment functions as a relay node.
The cell discard control device 30 converts the header portion of the ATM cell transmitted from the transmission terminal 31 into a header portion so that the header portion can be processed internally, and converts the header portion from the input header conversion portion 33. A output
A maximum cell rate monitor 34 and an average cell rate monitor 35 that measure and monitor the maximum cell rate and the average cell rate of the TM cells, and are measured and monitored by the maximum cell rate monitor 34 and the average cell rate monitor 35. A comparison unit 36 for comparing the maximum cell rate and the average cell rate with a preset ATM throughput. Further, the cell discard control device 30 uses the input header conversion unit 33 based on the comparison result of the comparison unit 36 to identify that the header is converted to a predetermined position in the cell format of the ATM cell that is not prioritized. A non-priority identifier adding unit 37 for adding a non-priority identifier, and a transmission buffer 3 for sequentially storing ATM cells output from the non-priority identifier adding unit 37
8 is provided. Furthermore, it has an identifier determination unit 39 and an output header conversion unit 40, and when the ATM buffer is stored when the transmission buffer 38 is in the overflow state, the ATM cell is added by the non-priority identifier addition unit 37 by the identifier determination unit 39. A discarded cell is determined with reference to the non-priority identifier, and the output header conversion unit 40 converts the discarded cell into a header addressed to the receiving terminal 32, opposite to the input header conversion unit 33. The cell discard control device 30 having such a configuration is collectively controlled by the call processing unit 41.

The cell discard control device 30 having the above-described configuration includes:
The data rate to be transferred inside the apparatus is monitored based on the maximum data rate and the average data rate transmitted per unit time declared by the transmitting terminal 31 at the time of calling. Then, an identifier corresponding to the comparison result between the monitoring result and the declared value is added to the transfer cell, and the cell to be discarded when the transmission buffer 38 is in the overflow state is determined by referring to the identifier. .

The transmission terminal 31 for reporting the maximum data rate and the average data rate to be transmitted per unit time at the time of making a call to the call processing unit 41 of the cell discard control device 30 is provided by a central processing unit (not shown). (Central Processing
Unit: hereinafter abbreviated as CPU. ), And an external storage device such as a magnetic disk or a read only memory (Read Only Memory: R
Abbreviated as OM. ) Can be executed based on a program stored in a predetermined storage device.

FIG. 2 shows an outline of the processing contents at the time of a call stored in the transmitting terminal 31 as described above. The transmitting terminal 31 makes a call (step S42:
Y), the maximum data rate and average data rate transmitted per unit time are reported to the cell discard control device 30 (step S43). This may be notified by a general ATM cell or by a dedicated control line. Thereafter, the transfer data is transmitted in a burst to the receiving terminal 32 (step S44).
The data transfer as a series of processing by calling is ended (end).

On the other hand, the cell discard control device 30 which has been notified of the maximum data rate and the average data rate to be transmitted per unit time from the transmitting terminal 31 also has a CPU (not shown), Various controls can be executed based on a program stored in an external storage device such as the above or a predetermined storage device such as a ROM provided separately therefrom.

FIG. 3 shows an outline of the processing contents of the call processing unit 41 of the cell discard control device 30 for the program stored in such a storage device. That is, the call processing unit 41 of the cell discard control device 30 in the first embodiment
It waits for a report of the maximum data rate and the average data rate to be transmitted per unit time from the transmitting terminal 31 as shown in FIG. 2 (step S45: N). And the transmitting terminal 31
Is received (step S45: Y), an ATM comprising the maximum cell rate and the average cell rate to be transmitted per unit time in the ATM communication system.
The data is converted into a throughput and stored (step S46).
Subsequently, the ATM cell transmitted from the transmitting terminal 31 is received, converted into a header for internal processing by the input header conversion unit 33, and received by the maximum cell speed monitoring unit 34 and the average cell speed monitoring unit 35. Measurement and monitoring of the transfer rate of the ATM cell are performed. Then, the maximum cell rate monitoring unit 34
Is compared with the maximum cell rate corresponding to the declared value converted in step S46 (step S47), and the maximum cell rate monitored by the maximum cell rate monitoring unit 34 is determined. When the cell rate exceeds the maximum cell rate corresponding to the declared value (step S4)
7: Y), the non-priority identifier adding unit 37 adds the non-priority identifier to a predetermined position in the cell format of the ATM cell (step S48).

FIG. 4 shows an outline of the configuration of the cell format of the ATM cell in the first embodiment.
FIG. 1A shows a cell format configuration of an ATM cell, and FIG. 2B shows a format configuration of a header portion of the ATM cell. As shown in FIG.
The cell 49 uses a fixed-length data of 53 bytes as a transfer unit and includes a 5-byte length header section 50 and a 48-byte length user information 51. In the header section 50, transfer control information for transfer is written, and in the user information 51, the transfer content itself is written. Therefore, for example, when the maximum data rate and the average data rate transmitted per unit time from the transmitting terminal 31 to the cell discard control device 30 are declared, the header section 50 indicates the report value data, and the user information 51 In this case, the report value data itself may be written. Further, as shown in FIG. 3B, the header section 50 includes a general flow control (GFC) field 52 for performing contention control and a virtual path identifier (Virtual Path Identifier: GFC) for performing routing. VPI) field 53
And Virtual Channel Identifi
er: VCI) field 54 and a payload type (Payload Type: P) for specifying the contents of the user information 51.
T) Field 55 and Cell Loss Priority: CL for indicating the priority at the time of cell discard
P) field 56 and a header error control (HE) which is an error detection and correction code of the header.
C) field 57. The non-priority identifier adding unit 37 assigns a non-priority identifier that prioritizes cell discarding when the transmission buffer 38 is in an overflow state as shown in FIG.
Is written in the CLP field 56 of the ATM cell shown in FIG. Therefore, CLP field 56
, When a predetermined non-priority identifier is written therein, priority is given to discarding this cell, and when it is not written, priority is not given to discarding this cell.

Returning to FIG. 3, the description will be continued. Step S4
In 7 comparison result, if the peak cell rate of the ATM cell being monitored by the peak cell rate monitoring unit 34 does not exceed the maximum cell rate that corresponds to the declared value (Step S47:
N) includes A monitored by the average cell rate monitoring unit 35.
The average cell rate of the TM cell is compared with the average cell rate corresponding to the declared value converted in step S46 (step S58). In step S58, the average cell rate monitoring unit 34
When the average cell rate of the ATM cell monitored in step S5 exceeds the average cell rate corresponding to the declared value (step S5).
8: Y), the non-priority identifier adding unit 37 adds the non-priority identifier to a predetermined position in the cell format of the ATM cell (step S48). The ATM cell to which the non-priority identifier has been added based on the comparison result of the comparison unit 36 in step S48 is stored in the transmission buffer 38 (step S5).
9). In step S58, the average cell rate monitoring unit 34
When the average cell rate of the ATM cell monitored in the step (b) does not exceed the average cell rate corresponding to the declared value (step S
59: Y), the ATM cell is stored in the transmission buffer 38 (step S59). Then, when the transfer is not completed (step S60: N), step S47 is performed again.
When the transfer is completed (step S60: Y), a series of processing is ended.

FIG. 5 shows an outline of the transmission buffer storing process in step S59 shown in FIG.
The transmission buffer 38 has a FIFO having a plurality of entries.
It has a (First-In First-Out) memory structure, and when there is no entry to be stored, it can be detected as an overflow state. In the process of storing in the transmission buffer 38, the call processing unit 41 first determines whether or not the transmission buffer 38 is detected to be in an overflow state (step S61). When it is determined that the transmission buffer 38 has detected that the transmission buffer 38 is in the overflow state (step S61: Y), the cell header portion written in a predetermined position of the format of the ATM cell stored in the transmission buffer 38 is read. By referring to the CLP field, it is determined whether or not this is a priority cell (step S62). If the non-priority identifier is added in step S48, it is not a priority cell. If it is determined in step S62 that the cell is a priority cell (step S62: Y), the oldest non-priority cell stored in the transmission buffer 38 among all cells stored in the overflow state is discarded. (Step S6
3) The cell is stored in the transmission buffer 38 (step S64). When all the cells stored in the transmission buffer 38 are priority cells other than non-priority cells, the oldest storage cell is discarded. On the other hand, step S6
If it is determined in step 2 that the cell is not a priority cell but a non-priority cell (step S62: N), this cell is discarded (step S65).

In the cell discard control device 30 according to the first embodiment, the maximum data rate and the average data rate to be transmitted per unit time are declared when a call is transmitted from the transmission terminal 31. Then, this is converted into an ATM throughput and stored as the maximum cell rate per unit time and the average cell rate. The ATM cell transmitted from the transmitting terminal 31 is monitored by an internal maximum cell rate monitoring unit 34 and an average cell rate monitoring unit 35 for the maximum cell rate and the average cell rate, and a comparison unit 36 monitors the maximum cell rate or the average cell rate. Until the rate falls below the maximum cell rate and the average cell rate converted corresponding to the declared maximum data rate and average data rate, the non-priority identifier adding unit 37 uses a predetermined value in the header of the cell format of the ATM cell. Add a non-priority identifier to the location. The ATM cell to which the non-priority identifier is added by the non-priority identifier adding unit 37 according to the comparison result of the comparing unit 36 is transmitted to the transmission buffer 38.
However, if the transmission buffer 38 is in the overflow state, the cell determined by the identifier determination unit 39 is discarded.

FIG. 6 shows an outline of the configuration of the transmission buffer 38 in the first embodiment. Here, the transmission buffer 38 stores the first to ninth entries 66 _{1 to} 66 ₉
Shall be provided. ATM cell non-priority identifier in the non-priority identifier adding unit 37 is added in accordance with the comparison result of the comparison unit 38, 9 entries every cell from the first entry 66 ₁ is sequentially stored. Generally, in this state, when the next new cell cannot be stored, an overflow state is set.

Hereinafter, the storing process of the transmission buffer 38 having such a configuration will be specifically described.

FIG. 7 shows the relationship between the input cell and the cell storage state of the transmission buffer 38 before and after the cell is discarded. Here, a hatched cell is a non-priority cell to which a non-priority identifier is added, and the other cells are priority cells. FIG. 9A shows that the non-priority cell A is stored in the _first entry 66 ₁ before the cell is discarded, and the second and third entries 66 ₂ and 66 ₃ are stored in the _first entry 66 _1.
Priority cells B and C are assigned to the fourth and fifth entries 6
6 _4, 66 ₅ non-prioritized cells in D, E is a non-priority cell F in the entry 66 _{6-66 8} sixth 8, G, H is, non-priority cell I is stored in the entry 66 ₉ 9 The case where the non-priority cell J is stored in the overflow state is shown. In this case, as shown in FIG. 5, since the input cell is a non-priority cell, the cell is discarded (discard 6
7). Then, after the cell is discarded, it indicates that there is no change in the storage cell from before the discard.

Similarly, FIG. 7B shows the state before the cell is discarded.
First entry 66₁The non-priority cell A is
3 entries 66_Two, 66_ThreePriority cells B and C
And fifth entry 66_Four, 66_FiveTo non-priority cells D and E
Is the sixth to eighth entry 66 ₆~ 66₈Non-preferred cell
F, G, H are the ninth entry 66₉Has non-priority cell I
Priority cell if stored and in overflow state
The case where J is stored is shown. In this case, as shown in FIG.
As described above, since the input cell is the priority cell,
First entry 66 which is the oldest cell among the priority cells₁
Are discarded (discard 68). And
The first and second entries 66₁, 6
6_TwoIn the third and fourth entries 6
6_Three, 66_FourNon-priority cells D and E are the fifth to seventh entries.
Re 66_Five~ 66₇Priority cells F, G, and H are assigned to the eighth entry
Re 66₈Has the ninth entry 66₉Takes precedence
Cell J is stored.

[0042] Similarly, FIG. 7 (c), first to ninth entry 66 _{1-66 9} priority cell A as before cell loss, B,
, H, and I are stored, and when the cell is in the overflow state, the priority cell J is stored. In this case, as shown in FIG. 5, since the input cell is the priority cell and the storage cells are not all the non-priority cells, the first entry 66 ₁ which is the oldest cell among the non-priority cells
Are discarded (discard 69). Then, as after the cell discard, comprising first to priority cell B to the ninth entry _{66 1 ~66 9, C, D} , ···, H, I, a state in which J is stored.

As described above, whether or not a non-priority identifier has been added is determined by the identifier determination unit 39, and the transmission buffer 38 from which the cell has been discarded outputs a transfer cell at a predetermined timing. This transfer cell is output header converter 4
In contrast to the input header conversion unit 33, the header is converted to a header addressed to the receiving terminal 32 and transmitted to the receiving terminal 32.

Second Embodiment

Cell discard control device 3 in the first embodiment
In the case of 0, if the ATM throughput of the transmission cell from the transmission terminal 31 exceeds the declared value and the transmission buffer 38 is in the overflow state, a non-priority identifier is added and A
Until the TM throughput becomes equal to or less than the declared value, the cell determined based on the added non-priority identifier is discarded. However, the cell discard control device according to the second embodiment further transmits the cell transmission rate to the transmitting terminal. , It is possible to reduce the occurrence state of the overflow of the transmission buffer in the cell discard control device.

FIG. 8 shows the outline of the configuration of the cell discard control device in the second embodiment. However, FIG.
The same parts as those of the cell discard control device according to the first embodiment shown in FIG. First, the difference from the first embodiment is that the transmission terminal 71 connected to the cell discard control device 70 in the second embodiment responds to the request for lowering the transmission rate from the cell discard control device 70 by transmitting The ATM cell transmission rate can be reduced. Furthermore, the cell discard control device 7 in the second embodiment
0 includes a transmission rate requesting unit 72, based on the maximum data rate and average data rate declared by the transmitting terminal, the overflow state detected by the transmitting buffer 38, and the comparison result of the comparing unit 36. , A transmission rate that does not cause overflow in the transmission buffer 38 can be requested. Such control is performed by the call processing unit 73.

As described above, from the maximum data rate and the average data rate reported from the transmitting terminal, the accuracy of predicting the ratio of cells transmitted per unit time is improved, and by using this, the request for lowering the transmission rate is requested. It is carried out. As a result, the occurrence of overflow can be avoided as much as possible, and even in the event that an overflow should occur and the transfer cells need to be stored in the transmission buffer, the oldest cells are discarded and transferred to the receiving terminal as much as possible. Cell continuity can be maintained.

In the cell discarding control devices according to the first and second embodiments, the input header conversion unit and the output header conversion unit convert the header for internal processing, and
Although the non-priority identifier is added to the CLP field of the header part of the M cell format, in the present modification, a field for the non-priority identifier is added to the head of the cell simply input by the input header conversion unit, and the output is performed. The header conversion unit may simply delete this non-priority identifier field.

[0049]

As described above, according to the first or third aspect of the present invention, a transmission bar in an overflow state is provided.
When storing transfer cells in the
I decided to. That is, as the first method,
The first identifier to be processed is stored in the transmission buffer.
This cell when attached to the cell to be filled
Discards itself, and this cell has the first identifier
If there are no cells, the second method
There is a cell with the first identifier added to the buffer
Sometimes the oldest accumulated cells are discarded and the corresponding cells
Otherwise, the transmission method is used as a third method.
The oldest accumulated cell in the buffer
Decided to store. Thus the priority of cell processing
The order of disposal, taking into account factors such as
And decided to discard lower priority ones,
Achieve reasonable cell loss in overflow condition
And avoid discarding high priority cells as much as possible.
Thus, continuity of cells can be ensured. This
This is convenient , for example, for voice communication that requires continuity of transfer data .

According to the second or fourth aspect of the present invention, the transmission rate of the transmitting terminal is reduced and changed, so that the occurrence of overflow can be avoided as much as possible. Even when the transfer cells need to be stored in the transmission buffer, the oldest cells are discarded, and the continuity of the cells transferred on the receiving terminal side can be maintained as much as possible.

According to the fifth or sixth aspect of the present invention, the maximum cell rate and the average cell rate are used for the declaration and the determination, so that the ratio of cells transmitted per unit time from the transmitting terminal can be estimated. Can be improved, and the transfer efficiency can be maintained without making useless requests to lower the transmission rate.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an outline of a configuration of a cell discard control device of an ATM communication system according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing an outline of processing contents at the time of calling a transmitting terminal in the first embodiment.

FIG. 3 is a flowchart showing an outline of processing contents of a call processing unit of the cell discard control device in the first embodiment.

FIG. 4 is an explanatory diagram showing an outline of a configuration of a cell format of an ATM cell in the first embodiment.

FIG. 5 is a flowchart showing an outline of contents of a transmission buffer storing process.

FIG. 6 is a configuration diagram illustrating an outline of a configuration of a transmission buffer according to the first embodiment.

FIG. 7 is an explanatory diagram illustrating cell discarding of a transmission buffer in the first embodiment.

FIG. 8 is a configuration diagram illustrating an outline of a configuration of a cell discard control device of the ATM communication system according to the first embodiment of the present invention.

FIG. 9 is a configuration diagram showing an outline of a configuration of a cell discard control device in an ATM communication system proposed in the past.

[Explanation of symbols]

 Reference Signs List 30 cell discard control device 31 transmitting terminal 32 receiving terminal 33 input header converting unit 34 maximum cell rate monitoring unit 35 average cell rate monitoring unit 36 comparing unit 37 non-priority identifier adding unit 38 transmission buffer 39 identifier determining unit 40 output header converting unit 41 Call processing unit

Claims (6)

(57) [Claims] 1. A transfer rate monitoring means for monitoring a transfer rate of a cell input from a transmission terminal, and a transfer rate of a cell monitored by the transfer rate monitoring means is set to a transmission data rate previously reported from the transmission terminal. Determining means for determining whether or not the transmission rate of the monitored cell is greater than the declared transmission data rate by the determining means; First identifier adding means for adding a first identifier indicating that processing is to be performed with a lower priority at a predetermined position in a cell; cell storing means having a plurality of entries and sequentially storing the cells in these entries; An overflow detecting means for detecting an overflow state of the cell storage means; and an overflow detecting means for detecting an overflow state by the overflow detecting means. Attempting to store in said cell storage means
When the first identifier is added to a predetermined position of a cell to be stored, the cell to be stored should not be stored.
A first cell discarding means for discarding the cell, and an overflow state detected by the overflow detecting means, and a cell to be stored in the cell storage means.
The first identifier is not added to the predetermined position of the file
Sometimes, the first knowledge stored in the cell storage means is stored.
A second cell discarding unit for discarding the oldest accumulated cell among the cells to which the identifier is added and storing the cell to be stored in the cell storage unit in the cell storage unit; and the overflow detection unit. overflow condition is detected by, an attempt is made to store in said cell storage unit cell
The first identifier is added to the predetermined position of the file.
All cells stored in the cell storage means
Has a first identifier added to these predetermined positions.
If not, the third oldest cell stored in the cell storage means is discarded and the cell is stored in the cell storage means.
And a cell discarding means. 2. When the determining means determines that the transfer rate of the monitored cell exceeds the declared transmission data rate, and when the overflow detecting means detects an overflow state. 2. The cell discard control device according to claim 1, further comprising a transmission rate change request unit that requests a change in the transmission rate of the transmitting terminal. 3. A declared value storing step of storing a transmission data rate declared by a transmitting terminal, a transfer rate monitoring step of monitoring a transfer rate of a cell input from the transmitting terminal, and monitoring by the transfer rate monitoring step. Determining whether or not the transfer rate of the cell being monitored exceeds the transmission data rate stored in the storage step; and in this determination step, the transfer rate of the monitored cell is reported. A first identifier adding step of adding a first identifier indicating that processing is to be performed in a non-priority manner at a predetermined position of the cell input from the transmitting terminal when it is determined that the transmission data rate is exceeded. An overflow detecting step of detecting an overflow state of a transmission buffer having a plurality of entries and sequentially storing the cells in these entries; The transmission buffer when the overflow condition of the transmission buffer is detected by the overflow detection step
When a first identifier is added to a predetermined position of a cell to be stored in the cell, a first cell discarding step of discarding the cell to be stored and the overflow detecting step Overflow by
-A state is detected and an attempt is made to store in the transmit buffer.
Cell has a first identifier added to the predetermined position.
If not, the first stored in the transmission buffer
Oldest stored cell among cells with the identifier of
And storing the cell in the transmission buffer.
Cell discarding step and overflow detection step.
-A state is detected and an attempt is made to store in the transmit buffer.
A first identifier is added to the predetermined position of the
All the cells stored in the transmission buffer
A first identifier is added to these predetermined locations.
If not, the oldest stored buffer in the transmit buffer
Discard the packet and store the cell in the transmission buffer.
3. A cell discard control method, comprising: 4. When the determination step determines that the transfer rate of the monitored cell exceeds the declared transmission data rate, and when the overflow detection step detects an overflow state. 4. The cell discard control method according to claim 3, further comprising a transmission rate change requesting step of requesting a change in the transmission rate of the transmitting terminal. 5. The transfer rate monitoring means monitors a maximum cell rate and an average cell rate, and the declared transmission data rate is a maximum data transfer rate and an average data transfer rate. When it is determined that the value exceeds the declared value, and when the overflow detecting means detects the overflow state, the transmission rate of the transmitting terminal decreases based on the declared maximum data transfer rate and average data transfer rate. 3. The cell discard control device according to claim 2, further comprising a transmission rate change request unit requesting a change. 6. The transfer rate monitoring step monitors a maximum cell rate and an average cell rate, and the declared transmission data rate is a maximum data transfer rate and an average data transfer rate. When it is determined that the value exceeds the declared value, and when the overflow state is detected in the overflow detecting step, the transmission rate of the transmitting terminal is reduced based on the declared maximum data rate and average data rate. The method according to claim 4, further comprising a transmission rate change requesting step for requesting a change.