JP2590760B2 - ATM node equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ATM node device and, more particularly, to a cell buffer for temporarily storing ATM (Asynchronous Transfer Mode) cells, and arriving ATM cells in the cell buffer. The present invention relates to an ATM node device that determines whether to perform or discard, based on a destination described in a header of an ATM cell.

[0002]

2. Description of the Related Art In an ATM node device such as an ATM switch, a cell buffer for temporarily storing ATM cells is provided in order to prevent collision of ATM cells directed to the same output line. Since the capacity of the buffer is finite, ATM cells are discarded due to buffer overflow in the case of overload.

When such discarding is performed, the upper layer packet relating to the cell becomes unusable by the upper protocol layer. Therefore, the cell relating to the upper layer packet which has reached the destination terminal is not used. And re-transfer processing is performed.

[0004] As described above, transferring incomplete packets including cell loss on a network hinders effective use of network resources. Therefore, ATM node equipment having a cell buffer has conventionally been used. In the case of, when a new packet arrives while the queue length of the buffer exceeds a certain threshold, forced discard of the packet (hereinafter, referred to as packet / cell forced discard) has been studied.

A conventional packet / cell forced discard will be described with reference to FIGS. 12 and 13. FIG. FIG. 12 is a diagram showing an outline of a forced discard management table prepared in an ATM node device which performs packet / cell forced discard.
FIG. 13 shows a conventional ATM for forcibly discarding a packet / cell.
9 is a flowchart illustrating an example of a processing procedure performed by a node device every time an ATM cell arrives.

As shown in FIG. 12, in an ATM node device for forcibly discarding a packet / cell, a forcible discard management table 30 capable of storing an attribute for a VCI which is a header of an ATM cell is prepared. As the attribute, for example, 1-bit data indicating whether the packet / cell is permitted to be received or is subject to forced discard is stored.

In the conventional ATM node device, as shown in FIG. 13, every time an ATM cell arrives, the contents of this forced discard management table are referred to (step S201), and the VCI of the arrived cell is stored. It is determined whether or not the entry has been present in the forced discard management table (step S202). If the entry does not exist in the forced discard management table (step S202; N), the ATM node device determines whether or not there is a free space in the forced discard management table (step S2).
03).

If there is a free space in the forced discard management table (step S203; Y), the queue length of the buffer is measured (step S204), and if the measured queue length is smaller than a predetermined threshold value In (Step S205; Y), the VCI of the target cell and the attribute “reception permitted” are registered in the forced discard management table (Step S206), and the cell is stored in the cell buffer (Step S209). .

Conversely, if the measured queue length is equal to or greater than the predetermined threshold (step S205; N), the VCI of the target cell and the attribute "forced discard" are stored in the forced discard management table. Registration (Step S207)
Then, the cell is discarded without being stored in the buffer (step S208).

If an entry relating to an arriving cell exists in the forced discard management table (step S201; Y), it is determined whether the attribute stored in association with the cell is forced discard. It is determined whether the reception is permitted (step S201). Then, when it is determined that the attribute of the cell is “forced discard” (step S21)
0; Y), the cell is discarded (step S214). In addition, it is determined that “reception is permitted” (step S21).
0; N), the queue length of the cell buffer is measured (step S211), and if there is room for storage in the cell buffer (step S212; N), the arriving cell is stored in the cell buffer. (Step S209) and if there is no room for storage in the buffer (Step S2)
12; Y), the attribute of the entry relating to the target cell is changed to “forced discard” (step S213),
The cell is discarded (step S214).

The entry in the forced discard management table is deleted (step S216) when the cell that has arrived is an EOP (End of Packet) cell indicating the end of a packet (step S215; Y). .

[0012]

As described above,
By performing the packet / cell forced discard, it is possible to prevent a cell related to an incomplete packet from being transferred before the ATM node device, and to effectively utilize network resources.

However, in the conventional ATM node equipment for forcibly discarding a packet / cell, both VCI of traffic having a high cell transfer peak rate and VCI of traffic having a low cell transfer peak rate are treated in the same manner. There is a problem that the forced discard management table is occupied only by the VCI of the traffic having the low transfer peak rate, and the packet / cell forced discard does not function sufficiently.

[0014] Therefore, an object of the present invention is to provide a method in which even if a small capacity forced discard management table is used, the forced discard management table is not occupied by VCI of traffic having a low cell transfer peak rate, and efficiency is always improved. ,
An object of the present invention is to provide an ATM node device capable of forcibly discarding a packet / cell.

[0015]

According to the first aspect of the present invention,
(A) An identifier for identifying to which packet an ATM cell, which is an information transmission unit of a predetermined size, belongs, and an alternative for selectively specifying whether to forcibly discard or permit reception of the cell of the identifier. A forced discard management table in which a plurality of attributes are stored, (b) a cell buffer for temporarily storing arriving ATM cells, and (c) the number of ATM cells in the cell buffer waiting for output. Measuring means for measuring a certain queue length; and (d) when an ATM cell arrives, if the queue length measured by the measuring means is less than a first predetermined value, an identifier contained in the ATM cell is forcibly discarded. If the attribute stored in the management table and the attribute corresponding to the identifier is forced discard, the ATM cell is discarded without being stored in the cell buffer, and the ATM cell is discarded. When Murrell identifier is not stored in the forcibly discarding management table includes a first processing means for storing the ATM cell in the cell buffer, (e) AT
When the queue length measured by the measuring means when the M cell arrives is equal to or greater than the first predetermined value, and the identifier included in the arriving ATM cell is stored in the forced discard management table, the identifier corresponds to the identifier. When the attribute to be discarded is forced discard, the ATM cell is discarded without being stored in the cell buffer, and when the attribute corresponding to the identifier is reception permission, the second processing means for storing the ATM cell in the cell buffer; (F) When the queue length measured by the measuring means when the ATM cell arrives is equal to or larger than the first predetermined value, and the identifier included in the arrived ATM cell is not stored in the forced discard management table, the measurement is performed. When the queue length measured by the means is equal to or larger than a second predetermined value set to be larger than the first predetermined value, the identification is stored in the forced discard management table. When the queue length is less than the second predetermined value, the identifier and the receivable attribute are registered in the forced discard management table, and the ATM cell is discarded. Third processing means for accumulating data in a buffer; and (g) erasing means for erasing data relating to an identifier for the packet from the forced discarding management table when the arriving ATM cell indicates the end of the packet. And

That is, according to the first aspect of the present invention, two threshold values (first predetermined value and second predetermined value) are set for the cell buffer, and the queue length is the smaller threshold value. If the value is equal to or less than the first predetermined value, the identifier (VCI) and attribute are not newly registered in the forced discard management table. If the queue length is equal to or more than the first predetermined value, The ATM node device is configured so that the same process as the conventional packet / cell forced discarding procedure is performed using the second predetermined value as a threshold. As a result, the forced discard management table can be occupied only by VCIs of traffic having a low cell transfer peak rate.

According to a second aspect of the present invention, there is provided (a) an identifier for identifying to which packet an ATM cell which is an information transmission unit of a predetermined size belongs, and whether the cell of the identifier is forcibly discarded or received. (B) a cell buffer for temporarily storing the arriving ATM cells, and (c) a cell buffer in the cell buffer. Measuring means for measuring the queue length, which is the number of ATM cells waiting for output existing in the ATM cell;
If the identifier included in the TM cell is stored in the forced discard management table and the attribute corresponding to the identifier is forced discard, the ATM cell is discarded without being stored in the cell buffer, and the attribute is When the reception is permitted, the registration processing means for storing the ATM cells in the cell buffer; and (e) when the ATM cells arrive,
When the identifier included in the ATM cell is not stored in the forced discard management table, and the queue length measured by the measuring means is equal to or more than the second predetermined value, the identifier is stored in the forced discard management table. In addition to registering the forced discard attribute, the ATM cell is discarded. If the queue length is less than the second predetermined value, the identifier and the receivable attribute are registered in the forced discard management table, and the ATM cell buffer is stored. A non-registered processing unit for storing the packet in a packet, and (f) an erasing unit for deleting data relating to the identifier of the packet from the forced discard management table when the arriving ATM cell indicates the end of the packet. And (g) the queue length measured by the measuring means is equal to or less than a third predetermined value set smaller than the second predetermined value. When the comprises a total erasing means for totally erasing the contents of the forced discarding management table.

That is, according to the second aspect of the present invention, two threshold values (second predetermined value and third predetermined value) are set for the cell buffer, and the larger second predetermined value is set as the threshold value. The same processing as the conventional packet / cell forced discarding procedure is performed, and the queue length measured by the measuring means is equal to the second
The ATM node device is configured such that the content of the compulsory discard management table is completely deleted when the value becomes equal to or less than a third predetermined value set smaller than the predetermined value.

According to a third aspect of the present invention, there is provided (a) an identifier capable of identifying to which packet an ATM cell as an information transmission unit of a predetermined size belongs, and whether the cell with the identifier is forcibly discarded or received. (B) a cell buffer for temporarily storing the arriving ATM cells, and (c) a cell buffer in the cell buffer. Measuring means for measuring the queue length, which is the number of ATM cells waiting for output, which is present in (d) when the queue length measured by the measuring means is smaller than a first predetermined value when an ATM cell arrives The identifier contained in the ATM cell is stored in the forced discard management table, and when the attribute corresponding to the identifier is forced discard, the ATM cell is stored in the cell buffer. If the identifier contained in the ATM cell is not stored in the compulsory discard management table, the first processing means for storing the ATM cell in the cell buffer, and (e) when the ATM cell arrives, If the queue length measured by the measuring means is equal to or greater than the first predetermined value and the identifier included in the arriving ATM cell is stored in the forced discard management table, the attribute corresponding to the identifier is forced discard. ATM
Second processing means for discarding the cell without storing it in the cell buffer and storing the ATM cell in the cell buffer when the attribute corresponding to the identifier is reception permission;
When the queue length measured by the measuring unit when the TM cell arrives is equal to or larger than the first predetermined value, and the identifier included in the arriving ATM cell is not stored in the forced discard management table, the measurement is performed by the measuring unit. If the queue length is equal to or greater than a second predetermined value that is set to be larger than the first predetermined value, the identifier and the forced discard attribute are registered in the forced discard management table, and the ATM cell is discarded. When the queue length is less than the second predetermined value, the third processing means for registering the identifier and the receivable attribute in the forced discard management table and storing the ATM cells in the cell buffer; When the ATM cell indicates the end of the packet, the data relating to the identifier for the packet is deleted from the forced discard management table. And (h) when the queue length measured by the measuring means becomes equal to or less than a third predetermined value which is set to be smaller than the first predetermined value, the content of the forced discard management table is entirely deleted. Means.

That is, according to the third aspect of the present invention, when the queue length measured by the measuring means is equal to or less than a third predetermined value set smaller than the first predetermined value. , An all-erasing means for entirely erasing the contents of the forced disposal management table is added.

[0021]

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

FIG. 1 shows a schematic configuration of an ATM node device according to an embodiment of the present invention. As shown, the ATM node device of the embodiment has a cell buffer 10 and a buffer management device 20 as main components, and the cell buffer 10 is schematically shown in FIG. 1 and FIG. As described above, three types of thresholds A to C are set in advance. Note that, among these threshold values, the threshold value A is a threshold value that has been conventionally used, and as is apparent from FIG. 2, both the threshold value B and the threshold value C are set to be smaller than the threshold value A.
Is set smaller than the threshold value C.

As shown in FIG. 1, the buffer management device 20 constituting the ATM node device includes a management control unit 21, a status storage unit 22, and a buffer queue length measurement unit 23.
And an input processing unit 24.
The cell arriving at the ATM node device through is transmitted to the input processing unit 24.

The input processing unit 24 checks the contents of the cell header of the arriving ATM cell, identifies the VCI, and determines whether or not the ATM cell is an EOP cell indicating the end of the packet. In addition, according to an instruction from the management control unit 21, any process such as discarding the received ATM cell or storing it in the cell buffer 10 is executed.

When receiving an instruction from the management control unit 21, the buffer queue length measurement unit 23 measures the number of cells (queue length) stored in the cell buffer 10 in the output standby state, and the measurement result The management control unit 21 is configured to notify the queue length notified from the buffer queue length measurement unit 23 and the status storage unit 22
Based on the contents of the compulsory discard management table stored in the cell buffer 10 and the thresholds A to C set for the cell buffer 10, the ATM cells that have reached are selectively discarded in the following procedure.

FIG. 3 shows a flow of processing performed by the ATM node device (management control unit) of the embodiment every time an ATM cell arrives. Upon receiving the cell arrival notification from the input processing unit 24, the management control unit 21 instructs the buffer queue length measurement unit 23 to measure the queue length (step S101). If the measured queue length is smaller than the threshold C (step S103; Y), the content of the forced discard management table is referred to (step S103), and the input processing unit 2
It is determined whether or not an entry for the VCI given from No. 4 exists in the forced discard management table (step S104).

If the corresponding entry does not exist (step S104; N), the input processing unit 24 is permitted to receive the ATM cell, so that the input processing unit 24 receives the cell of the ATM cell. The storage in the buffer 10 (step S105) is executed. If the entry exists (step S104; Y), and if the attribute stored in the forced discard management table in association with the VCI is “reception permitted”, The input processing unit 24 includes a cell buffer 10 for ATM cells.
Is executed, and if it is “compulsory discard”,
The input processing unit 24 causes the ATM cell to be discarded (step S106).

When the input processing unit 24 notifies that the cell is an EOP cell (step S107; Y), the entry in the compulsory discard management table for the EOP cell is deleted (step S108). Do.

The operation procedure when the queue length is less than the threshold C (step S102; Y) has been described above. When the queue length is greater than the threshold C (step S102;
In N), the normal processing (step S109) already described with reference to FIG. 13 is executed. In the ATM node device of the embodiment, when the flow illustrated in FIG. 13 is executed (step S109), the processing performed on the threshold in FIG. 13 is performed on the threshold A. Will be.

In the ATM node device of the embodiment, after discarding or accumulating the ATM cells in such a procedure (from step S101 to the ATM switch 109),
The buffer queue length is measured again (step S110), and if the measured queue length is smaller than the threshold value B (step S111; Y), the contents of the forced discard management table are cleared (step S112). After that, the state shifts to an ATM cell arrival waiting state.

Hereinafter, the operation of the ATM node device of the embodiment described with reference to FIG. 3 will be described more specifically with reference to FIGS.

First, referring to FIGS. 4 and 5, when the queue length is less than the threshold value C, the VCI registered in the forced discard management table with the “reception permitted” attribute is set to “V
The operation when the cell C1 "arrives will be described.

As shown in FIG. 4, in this case, the management control unit 21 sends the information “VC
1 "and information indicating that the queue length is the threshold value C from the buffer queue length measuring unit 23. Therefore, the management control unit 21 refers to the contents of the forced discard management table 30. Since the “VC1” entry exists in the compulsory discard management table 30, this cell is subjected to step S106 in FIG.
, That is, the process according to the attribute is performed.

In this case, since the attribute is "reception permitted", as shown schematically in FIG.
Outputs information indicating reception permission to the input processing unit 24,
The input processing unit 24 accumulates cells in the cell buffer 10.

Next, referring to FIG. 6 and FIG. 7, when the queue length is less than the threshold value C, the VCI registered with the “forced discard” attribute in the forced discard management table is “V
The operation when the cell C2 "arrives will be described.

As shown in FIG. 6, in this case, the management control unit 21 sends the information “VC
2 "and information indicating that the queue length is the threshold value C from the buffer queue length measuring unit 23. Therefore, the management control unit 21 refers to the contents of the forced discard management table 30. Since there is an entry “VC2” in the forced discard management table 30, this cell is subjected to step S106 in FIG.
, That is, the process according to the attribute is performed.

In this case, since the attribute is “forced discard”, as shown schematically in FIG.
Outputs information for instructing forced discard to the input processing unit 24, and the input processing unit 24 discards the cell.

Next, referring to FIGS. 8 and 9, when the queue length is less than the threshold value C, when a cell not registered in the forced discard management table and having a VCI of “VC3” arrives, The operation will be described.

As shown in FIG. 8, in this case, the management control unit 21 sends the information “VC
3 "and information indicating that the queue length is the threshold value C from the buffer queue length measurement unit 23. Therefore, the management control unit 21 refers to the contents of the forced discard management table 30. Since the "VC3" entry does not exist in the compulsory discard management table 30, the process of step 105 in FIG. 4, that is, the accumulation in the buffer is performed on this cell. .

Accordingly, as schematically shown in FIG. 9, the management control section 21 outputs information for instructing reception permission to the input processing section 24, and the input processing section 24 outputs the information to the cell buffer of the cell. 10 will be stored.

After performing such a series of processes, as shown schematically in FIG.
In the following case, as described with reference to the flowchart, the management control unit 21 is notified of the fact. Therefore, the management control unit 21 performs, as shown in FIG. For the status storage unit 22, the forced discard management table 3
0 is instructed to be completely erased, and the forced discard management table 30
Are cleared by the situation storage unit 22.

As described above, in the ATM node device according to the embodiment, when the queue length is less than the threshold value C, the VCI is not registered in the forced discard management table 30. It is possible to prevent such a phenomenon that the forced discard management table is occupied only by the VCI of the low-rate traffic and the effect of the packet / cell forced discard is suppressed.

In the ATM node device of the embodiment, 3
Although three thresholds are set, only the threshold C and the threshold A are set, and the apparatus is configured not to execute the steps S111 and S112 in FIG. Is set, and the apparatus is configured so that only the conventional packet / cell selection and discarding process (step S109) and steps S111 and S112 are executed. It is possible to obtain an ATM node device in which the effect of (1) is less suppressed.

[0044]

As described in detail above, claim 1 is as follows.
As described in the invention described above, two thresholds (a first predetermined value and a second predetermined value) are set for the cell buffer, and if the queue length is smaller than the smaller threshold, the forced discard is performed. If the ATM node device is configured so that the VCI and the attribute are not newly registered in the management table, the forced discard management table is occupied only by the VCI of the traffic having the low cell transfer peak rate, and the packet / cell forced discard is performed. Therefore, it is possible to prevent the occurrence of a phenomenon that the effect of (1) is suppressed. Further, since the frequency of performing the registration processing on the forced destruction management table is reduced, the load on the hardware can be reduced.

In the conventional packet / cell forced discarding procedure, when the number of queues in the cell buffer falls below a certain threshold value (third predetermined value), the forced discarding management table is used. A such that a packet / cell is forcibly discarded by a procedure to which a process of erasing all the contents of
When the TM node device is configured, the network can be effectively used, though to a lesser extent than in the first aspect of the invention.

Also, as in the invention of claim 3, according to the invention of claim 1, when the number of queues in the cell buffer falls below a certain threshold value (third predetermined value), the contents of the forced discard management table are set. If means for erasing all is added, the capacity of the forced discard management table is used more efficiently, and packet / cell forced discard is performed.
Effective use of the network can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an ATM node device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining three types of thresholds set for a cell buffer provided in the ATM node device of the embodiment.

FIG. 3 is a flowchart showing a flow of processing performed in the ATM node device of the embodiment when an ATM cell arrives;

FIG. 4 is a diagram illustrating a case where a queue length is less than a threshold value C, which is registered with a “reception permitted” attribute in a forced discard management table.
FIG. 11 is a schematic diagram illustrating an outline of processing performed in the ATM node device of the embodiment when a cell with a VCI of “VC1” arrives.

FIG. 5 is a schematic diagram showing an outline of a process performed subsequent to the process shown in FIG. 4;

FIG. 6 is a diagram illustrating a case where a queue length is smaller than a threshold value C and registered with a “forced discard” attribute in a forced discard management table
FIG. 11 is a schematic diagram illustrating an outline of processing performed in the ATM node device of the embodiment when a cell having a VCI of “VC2” arrives.

FIG. 7 is a schematic diagram showing an outline of a process performed subsequent to the process shown in FIG. 4;

FIG. 8 shows that when the queue length is less than the threshold value C, the VCI not registered in the forced discard management table is “VC
FIG. 9 is a schematic diagram showing an outline of processing performed in the ATM node device of the embodiment when a cell of 3 ″ arrives.

FIG. 9 is a schematic diagram showing an outline of a process performed subsequent to the process shown in FIG. 8;

FIG. 10 is a schematic diagram illustrating an outline of a process performed when a queue length becomes equal to or smaller than a threshold B in the ATM node device of the embodiment.

FIG. 11 is a schematic diagram showing an outline of a process performed subsequent to the process shown in FIG. 10;

FIG. 12 is a schematic diagram showing an outline of a forced discard management table prepared in an ATM node device in which packet / cell forced discard is performed.

FIG. 13 is a flowchart showing a flow of processing performed in a conventional ATM node device when an ATM cell arrives.

[Explanation of symbols]

 Reference Signs List 10 cell buffer 11 input line 12 output line 20 buffer management unit 21 management control unit 22 status storage unit 23 buffer queue length measurement unit 24 input processing unit 30 forced discard management table

Claims (3)

(57) [Claims] An ATM which is an information transmission unit of a predetermined size.
A forced discard management table in which an identifier for identifying which packet the cell belongs to and a plurality of attributes for alternately designating whether to forcibly discard or permit reception of the cell with the identifier are stored. A cell buffer for temporarily storing the arriving ATM cells, a measuring means for measuring a queue length which is the number of ATM cells in the cell buffer and waiting for output, If the queue length measured by the measuring means is less than a first predetermined value,
The identifier contained in the TM cell is stored in the compulsory discard management table, and when the attribute corresponding to the identifier is compulsory discard, the ATM cell is discarded without being stored in the cell buffer. A first processing unit for storing the ATM cell in the cell buffer when the identifier contained in the cell is not stored in the forced discard management table; and a queue measured by the measuring unit when the ATM cell arrives. If the length is equal to or greater than the first predetermined value and the identifier included in the arriving ATM cell is stored in the forced discard management table, and the attribute corresponding to the identifier is forced discard, the ATM cell is deleted. The ATM cell is discarded without being stored in the cell buffer. A second processing unit that accumulates in the buffer; a queue length measured by the measuring unit when the ATM cell arrives is equal to or greater than a first predetermined value; and an identifier included in the arriving ATM cell is stored in the forced discard management table. When the queue length measured by the measuring means is equal to or greater than a second predetermined value set to be larger than the first predetermined value, the identifier and the compulsory value are stored in the compulsory discard management table. When the ATM cell is discarded, the ATM cell is discarded, and when the queue length is less than the second predetermined value, the identifier and the receivable attribute are registered in a forced discard management table, and the ATM cell is discarded. Third processing means for storing data in a buffer; and when the arriving ATM cell indicates the end of the packet, ATM node device, characterized in that the data relating Besshi comprises an erasing means for erasing from the forced discarding management table. 2. An ATM which is an information transmission unit of a predetermined size.
A forced discard management table in which an identifier for identifying which packet the cell belongs to and a plurality of attributes for alternately designating whether to forcibly discard or permit reception of the cell with the identifier are stored. A cell buffer for temporarily storing the arriving ATM cells, a measuring means for measuring a queue length which is the number of ATM cells in the cell buffer and waiting for output, If the identifier included in the ATM cell is stored in the forced discard management table and the attribute corresponding to the identifier is forced discard, the ATM cell is discarded without being stored in the cell buffer. When the attribute is reception permission, a registration processing means for accumulating ATM cells in the cell buffer; In the case where the identifier contained in the ATM cell is not stored in the forced discard management table, if the queue length measured by the measuring means is equal to or more than a second predetermined value, the identifier is stored in the forced discard management table. And the forced discard attribute are registered, and the ATM cell is discarded.
If the value is less than the predetermined value, the identifier and the receivable attribute are registered in the forced discard management table, and the AT
Unregistered processing means for accumulating M cells in the cell buffer; and when an arriving ATM cell indicates the end of a packet, data relating to an identifier for the packet is stored in the forced discard management table. An erasing means for erasing, and a queue length measured by the measuring means,
An ATM node device comprising: a total erasing means for entirely erasing the contents of the compulsory discard management table when the content becomes equal to or less than a third predetermined value set smaller than the predetermined value. 3. An ATM which is an information transmission unit having a predetermined size.
A forced discard management table in which an identifier for identifying which packet the cell belongs to and a plurality of attributes for alternately designating whether to forcibly discard or permit reception of the cell with the identifier are stored. A cell buffer for temporarily storing the arriving ATM cells, a measuring means for measuring a queue length which is the number of ATM cells in the cell buffer and waiting for output, If the queue length measured by the measuring means is less than a first predetermined value,
The identifier contained in the TM cell is stored in the compulsory discard management table, and when the attribute corresponding to the identifier is compulsory discard, the ATM cell is discarded without being stored in the cell buffer. A first processing unit for storing the ATM cell in the cell buffer when the identifier contained in the cell is not stored in the forced discard management table; and a queue measured by the measuring unit when the ATM cell arrives. If the length is equal to or greater than the first predetermined value and the identifier included in the arriving ATM cell is stored in the forced discard management table, and the attribute corresponding to the identifier is forced discard, the ATM cell is deleted. The ATM cell is discarded without being stored in the cell buffer. A second processing unit that accumulates in the buffer; a queue length measured by the measuring unit when the ATM cell arrives is equal to or greater than a first predetermined value; and an identifier included in the arriving ATM cell is stored in the forced discard management table. When the queue length measured by the measuring means is equal to or greater than a second predetermined value set to be larger than the first predetermined value, the identifier and the compulsory value are stored in the compulsory discard management table. When the ATM cell is discarded, the ATM cell is discarded, and when the queue length is less than the second predetermined value, the identifier and the receivable attribute are registered in a forced discard management table, and the ATM cell is discarded. Third processing means for storing data in a buffer; and when the arriving ATM cell indicates the end of the packet, Data about Besshi, and erasing means for erasing from the forced discarding management table, queue length measured by said measuring means, said first
An ATM node device comprising: a total erasing means for entirely erasing the contents of the forced discarding management table when the content becomes equal to or less than a third predetermined value set smaller than the predetermined value.