JP2778552B2 - Buffer management method and buffer management system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a buffer management method for an ATM node device having a buffer memory for temporarily storing ATM cells, and to improve the effective throughput at the upper layer packet level with as little buffer memory as possible. The present invention relates to a buffer management method and a buffer management system capable of performing the above.

[0002]

2. Description of the Related Art In an ATM node device, for example, an ATM exchange, a buffer memory is provided for avoiding collision of ATM cells going to the same output line. The capacity of this buffer memory is finite, and if there is an input exceeding the allowable amount, the overflow occurs and the ATM cells corresponding to the overflow are discarded. Since the upper layer packet lacking even one cell cannot be used by the upper protocol layer, even if it arrives at the destination terminal, it is immediately discarded and retransmitted.

[0003] It is difficult to uselessly store such a useless packet including a cell loss in a cell buffer in an ATM exchange and transfer it to a network after knowing that the packet is unusable from the viewpoint of effective use of network resources. This is undesirable and causes congestion.

[0004] In order to prevent such useless cells from wasting network resources, if the buffer occupancy at the time when the head cell of the ATL packet arrives at the cell buffer exceeds a predetermined threshold value. , The first cell to the last cell (EOM (End of Message) cell) constituting the AAL packet
The selective packet discarding method of discarding all the data before buffering is effective. This selective packet discarding method requires a cell discarding management table for managing whether a packet is being received or discarded for each logical channel (VC). In the cell discard management table used, the states prepared for one logical channel (VC) are as follows:
"Packet not received", "Packet reception permitted", and "Packet discarding". In this selective packet discarding method, when an EOM cell arrives via the logical channel (VC), the state in the table is changed to "packet not received".
Is controlled to be set to When a cell that is not an EOM cell arrives from the logical channel (VC) in the “packet not received” state, the occupancy of the entire buffer at that time is measured, and if the occupancy exceeds the threshold, A cell arriving via the logical channel (VC) is set to a “packet discarding” state in order to forcibly discard the cell until the next EOM cell arrives. If the occupancy is equal to or less than the threshold value, the state is set to "packet reception permitted" and the packet is continuously received until the next EOM cell arrives. FIG. 12 is a flowchart showing conventional selective packet discarding.

Next, the operation of the conventional method will be described with reference to the flowchart of FIG. First, A is input to the cell input control unit 24.
When a TM cell is input (G1), the cell discarding management table 30 is referred to based on the logical channel identifier (VCI) (G2), and the state registered in the management table 30 is checked (G3). If the attribute is "10" (packet reception permitted), the data is stored in the cell buffer as it is (G4). Finally, it is checked whether the arriving cell is an EOM cell (G5), and if it is an EOM cell, the state of the corresponding logical channel (VC) is changed to "01" (packet not received) (G6). .

On the other hand, in step G3, the attribute is "1".
If "1" (packet discarding), the ATM cell is forcibly discarded by the cell input control unit 24 (G7). In step G3, if the state of the logical channel (VC) is “01” (packet not received), the ATM cell may be regarded as the head cell of the upper layer packet. Therefore, the occupancy of the entire cell buffer at that time is measured (G8). If the occupation amount Q_total of the entire buffer is equal to or less than a predetermined threshold value Qth_total, (G
9) It is determined that all ATM cells for the packet can be accommodated, and the state of the logical channel (VC) is set to "10" (packet reception permitted) (G10). The occupation amount Q_total of the entire buffer is equal to a predetermined threshold value Qth_tota.
If it is not less than 1 (G9), "11" (packet discarding) is set (G11), and the ATM cell is discarded.

[0007]

In the conventional method described above, selective packet discarding is performed uniformly for all logical channels (VCs). Some logical channels (VCs) may include some cell loss, so some have requests to send as many cells as possible,
It is not desirable to perform selective packet discard on such a logical channel (VC). Further, in the conventional method, whether to receive or discard an arriving packet is determined from the occupation amount of the entire buffer and the threshold value. Therefore, the packet by which the logical channel (VC) is not considered at all is strongly controlled by the packet and the traffic is strong. In an environment where logical channels (VCs) having different characteristics coexist, the frequency of forced packet discarding may be biased for each logical channel (VC).

An object of the present invention is to select whether or not to apply selective packet discarding for each logical channel (VC). In an environment where logical channels (VC) having different traffic characteristics coexist, the logical channel It is an object of the present invention to provide a selective packet discarding method capable of improving biased discarding for each (VC).

[0009]

According to the present invention, there is provided a buffer occupancy counting section for measuring a buffer occupancy for each logical channel (VC) of a buffer memory, and a buffer occupancy counting section. A packet admission control unit for dynamically generating a threshold value for each logical channel (VC) based on the calculated buffer occupancy and determining whether or not reception is possible based on the calculated threshold value. If the user does not wish to perform selective packet discarding at the time of establishment, the corresponding logical channel (VC) in the cell discarding management table is set to the “not applicable” state.

That is, the buffer management method of the present invention comprises:
A buffer memory for temporarily storing ATM cells and a cell discarding management table holding an attribute indicating whether or not reception is possible for each logical channel (VC) are prepared.
When the attribute of the logical channel of the M cell indicates not received, the total buffer occupancy of the buffer memory is measured,
An ATM cell that arrives when the measured total buffer occupancy is equal to or less than the first threshold is received, and an ATM cell that reaches when the measured total buffer occupancy exceeds the first threshold is received. In the buffer management method for performing selective packet discarding processing so as to discard the packet, when the measured total buffer occupancy is equal to or greater than the first threshold value, the second ATM cell in the logical channel of the reached ATM cell can be used. The method is characterized in that a threshold is calculated, and a selective packet discarding process is performed by deciding to discard or receive an reached ATM cell based on the second threshold.

In the buffer management method of the present invention, when the attribute of the arriving ATM cell indicates that the selective packet discarding process is not to be performed, the buffer management method receives the ATM cell without performing the selective packet discarding process. It is characterized by doing.

Further, in the buffer management method according to the present invention, the second threshold value is calculated based on an average buffer occupancy for each logical channel, and the buffer occupancy of the logical channel of the arriving ATM cell is determined by the second threshold. The ATM cell is discarded when the threshold value exceeds the second threshold value, and is received when the ATM cell value is equal to or less than the second threshold value.

In the buffer management method of the present invention, the second threshold value is obtained by dividing the total buffer occupancy by the number of logical channels whose attribute in the cell discard management table indicates that packet reception is permitted. The calculation is performed by multiplying the average buffer occupancy for each logical channel by a predetermined count.

Further, the buffer management system of the present invention comprises:
In a buffer management system in an ATM node device having a buffer memory for temporarily storing ATM cells, a buffer occupancy amount counting unit for counting an occupancy amount of ATM cells for each logical channel (VC) in the buffer memory; A threshold value is calculated from a status storage unit storing a cell discarding management table holding an attribute indicating whether or not an ATM cell arrives for each logical channel can be received, and a buffer occupancy measured by the buffer occupancy counting unit. A packet admission control unit that determines whether to receive or discard the ATM cell and updates the cell discard management table;
If the attribute of the logical channel of the arrived ATM cell is the first attribute indicating that selective packet discard processing is not performed or the second attribute indicating that packet reception is permitted, the ATM cell of the logical channel is received and the packet is discarded. A cell input control unit for forcibly discarding the ATM cell of the logical channel (VC) in the case of the third attribute indicating the inside is provided.

Further, the buffer management system of the present invention comprises:
When the logical channel is established by the signaling process, the first attribute is set in the cell discard management table for the logical channel for which the selective packet discarding process is not applied, and the selective packet discarding is set. Is set for the logical channel for which the request has been made.

Further, the buffer management system of the present invention comprises:
When an ATM cell arrives from the logical channel having the fourth attribute, the packet reception control unit compares the total buffer occupancy provided from the buffer occupancy counting unit with a first threshold value, If the total buffer occupancy does not exceed the first threshold, the second attribute is set for the logical channel. If the total buffer occupancy exceeds the first threshold, the second attribute is set. Generating a second threshold value for a logical channel corresponding to an ATM cell reached from a buffer occupancy, the number of logical channels having the second attribute in the cell discarding management table, and a predetermined coefficient; If the buffer occupancy of the logical channel given from the occupancy counter exceeds the second threshold, the third attribute is set. If the buffer occupancy is equal to or less than the second threshold, the second attribute is set. Attribute And setting for the logical channel.

Further, the buffer management system of the present invention comprises:
A numerical value obtained by multiplying an average buffer occupancy for each logical channel obtained by dividing the total buffer occupancy by the number of logical channels having the second attribute in the cell discard management table by a predetermined coefficient as the second threshold value Is used.

[0018]

According to the first aspect of the present invention, before storing ATM cells in the buffer, the ATM cells are referred to by referring to the management table.
Since the cell processing is determined, the unnecessary ATM cells for the logical channel (VC) for which selective packet discarding is desired are discarded in advance, and are not stored in the buffer nor flowed to the network thereafter.

In the second invention, when a logical channel (VC) is established by signaling processing, "not applicable" is set for a logical channel (VC) that has been declared not to apply selective packet discarding. By setting "packet not received" for the logical channel (VC) for which selective packet discarding is desired, a request for sending as many cells as possible is acceptable because some cell loss may be included. In an environment in which logical channels (VCs) are mixed, the application / exclusion of selective packet discarding can be easily selected for each logical channel (VC), and a flexible network design can be realized.

In the third invention, when an ATM cell arrives from a logical channel (VC) in a "packet not received" state, first, the occupancy of the entire buffer given from the buffer occupancy counter and a predetermined amount are determined. If the occupation amount of the entire buffer does not exceed the predetermined value, the “packet reception permission” is set to the logical channel (V
Set for C).

On the other hand, if the occupancy of the entire buffer exceeds a predetermined value, the occupancy of the entire buffer and the number of logical channels (VCs) in the "packet reception permitted" state in the management table are determined by a predetermined value. A threshold for the logical channel (VC) is generated from the coefficient, and the threshold for the logical channel (VC), from which the buffer occupancy of the logical channel (VC) given by the buffer occupancy counter is calculated. If the value exceeds the threshold value, "packet discarding" is set for the logical channel (VC). As a specific threshold, the average buffer occupancy for each logical channel (VC) obtained by dividing the occupancy of the entire buffer by the number of logical channels (VC) in the “packet reception permitted” state in the management table is a predetermined value. Use the value multiplied by the coefficient.

In the conventional method, since control can be performed only on a packet basis ignoring each logical channel (VC), there is a problem that packets are excessively discarded depending on the logical channel (VC). According to the invention, the threshold value for each logical channel (VC) can be dynamically set,
It is possible to suppress a phenomenon that packet discarding is biased for each logical channel (VC).

[0023]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a buffer management system according to the present invention. The present invention is applicable to all ATM-related devices including the cell buffer 10. Regarding the configuration of the cell buffer, a type in which the FIFO is completely shared by all logical channels (VCs) was selected from among several existing buffering architectures, but a type in which queuing is performed for each logical channel (VC) is also applicable. It is. A portion 20 surrounded by a broken line in FIG.
Is a buffer management device according to the present invention.

The buffer management unit 20 includes a packet reception control unit 21, a status storage unit 22 in which a cell discard management table 30 (hereinafter, abbreviated as “management table”) to be described later is stored, and a buffer occupancy of the cell buffer 10. A buffer occupancy counter 23 for monitoring the amount, and a cell input controller 24
It is composed of

The cell input control unit 24 checks the cell header of the arriving ATM cell and checks for a VCI (VC identifier).
And the ATM cell detects AAL (ATM A
It identifies whether the cell is an EOM (End of Message) cell indicating the end of a Daption Layer (packet) packet, and notifies the packet admission control unit 21 of this. Further, the cell input control unit 24 refers to the management table 30 stored in the status storage unit 22 and forcibly discards the ATM cell based on the attribute corresponding to the VCI of the input ATM cell.
Processing such as reception accumulation is performed.

FIG. 2 shows an example of the configuration of the cell discarding management table 30 stored in the status storage unit 22. The cell discarding management table 30 is provided with a column for registering a VCI and a column (two bits) indicating an attribute corresponding to the column. The ATM column of the logical channel (VC) is "not applicable" (bit value) in the attribute column. “00”), “packet not received” (bit value “01”), “packet reception permitted” (bit value “10”), “packet discarding” (bit value “11”). )).

When a new logical channel (VC) is established by signaling processing, it is declared whether or not a selective packet discarding processing is desired. If it is desired to perform the selective packet discarding process, “packet not received” (bit value “01”) is displayed in the corresponding logical channel (VC) column of the management table 30. If you do not wish,
“Not applicable” (bit value “00”) is displayed in the corresponding logical channel (VC) column of the management table 30.

The buffer occupancy counting unit 23 counts the buffer occupancy of the cell buffer 10 for each logical channel (VC), and calculates the buffer occupancy of the logical channel corresponding to the VCI notified from the packet admission control unit 21; The occupancy of the entire buffer is output to the packet reception control unit.

The packet admission control unit 21 uses VCI as cell information of the ATM cell arriving from the cell input control unit 24.
And the occupancy of the entire buffer notified from the buffer occupancy counter 23 and the logical channel (V
C), a threshold value is generated from the number and a predetermined constant, and the calculated threshold value is compared with the buffer occupancy of the logical channel (VC) corresponding to the notified VCI, and the status storage unit 22 is generated.
Is updated in the management table 30.

Further, the cell input control unit 24 controls the management table 30 for all ATM cells arriving at the cell buffer 10 based on the logical channel identifier (VCI).
And attribute is "00" (not applicable) or "10"
If it is (packet reception permitted), the packet is stored in the cell buffer 10 as it is, and if it is "11" (packet is being discarded), the ATM cell is forcibly discarded.

When the EOM cell indicating the end of the AAL packet arrives, the cell input control unit 24 notifies the packet reception control unit 21 that the state of the corresponding logical channel (VC) is " Unless it is "00" (not applicable), the management table is changed to "01" (packet not received).

When an ATM cell arrives from a logical channel (VC) in which the state is "01" (packet not received), the cell input control unit 24 sets the VCI of the ATM cell.
To the packet reception control unit 21. The packet reception control unit 21 first compares the occupation amount Q_total of the entire buffer provided from the buffer occupancy counting unit 23 with a predetermined threshold value Qth_total. If the amount does not exceed the predetermined value (Q_total
≦ Qth_total), and “10” (packet reception permitted) is set for the logical channel (VC). On the other hand, if the occupation amount Q_total of the entire buffer exceeds the predetermined value Qth_total (Q_tota
l> Qth_total), the occupation amount Q_ of the entire buffer
Using the total T and the number T of the logical channels (VCs) in the management table in the “10” (packet reception permitted) state and a predetermined coefficient k, the logical logic of Qth_vc = (Q_total / T) × k (1) Threshold Q for channel (VC)
Generate th_vc. If the buffer occupancy Q_vc of the logical channel (VC) provided from the buffer occupancy counter 23 is calculated as a threshold value Qth_vc
If the value exceeds the threshold, "11" (packet discarding) is set for the logical channel (VC) if the value is equal to or less than the threshold, and "10" (packet reception permitted).

Next, the operation of the embodiment will be described with reference to the flowchart of FIG. First, an ATM is input to the cell input control unit 24.
When a cell is input (F1), the cell input control unit 24
The cell discard management table 30 is referred to based on the logical channel identifier (VCI) (F2), and the management table 30
Check the state registered in (3). If the attribute is “00” (not applicable) or “10” (packet reception permitted), it is stored in the cell buffer as it is (F
4). Finally, it is checked whether or not the arriving cell is an EOM cell (F5). If it is an EOM cell, the EOM and VCI are notified to the packet admission control unit 21, and the packet admission control unit 21 ) Is "01" unless the status is "00" (not applicable)
(No packet received) (F7).

On the other hand, in step F3, the attribute is "1".
If "1" (packet discarding), the ATM cell is forcibly discarded by the cell input control unit 24 (F8).

In step F3, if the state of the logical channel (VC) is "01" (packet not received), the ATM cell may be regarded as the head cell of the upper layer packet. Then, the cell input control unit 24 notifies the packet reception control unit 21 of the VCI, and the packet reception control unit 21 causes the buffer occupancy counting unit 23 to measure the occupancy of the entire cell buffer at that time (F9). The occupation amount Q_total of the entire buffer is equal to a predetermined threshold value Qth
If not greater than _total (F10), it is determined that all ATM cells for the packet can be accommodated, and the state of the logical channel (VC) is set to "10" (packet reception permitted) (F11). Q_tota of the occupancy of the entire buffer
If l is equal to or greater than a predetermined threshold value Qth_total (F10), the occupation amount Q_total of the entire buffer and the number T of logical channels (VCs) in the management table in a "10" (packet reception permitted) state are determined by a predetermined value. Coefficient k
, The threshold Qth_vc for the logical channel (VC) corresponding to the VCI notified by equation (1)
Is generated (F12). If the occupancy Q_vc of the logical channel (VC) given from the buffer occupancy counter 23 exceeds the calculated threshold value Qth_vc for the logical channel (VC), “11” (during packet discarding) ) Is set (F16), and if it is below the threshold value, "10" (packet reception permitted) is set for the logical channel (VC) (F15).

As described above, according to the above embodiment, the cell discarding management table 30 for setting whether or not to receive for each logical channel (VC) based on the buffer occupancy and the threshold value for each logical channel (VC). Is set, and for the logical channel (VC) whose attribute in the management table is “11” (packet is being discarded), the cell is forcibly discarded by the cell input control unit 24 before inputting to the buffer. As a result, the possibility that packets of a specific logical channel (VC) are forcibly discarded excessively is reduced, and the effective throughput of the upper layer packet level of all the logical channels (VC) can be evenly improved.

Next, specific cases are shown in FIGS.

FIG. 4A shows a state in which an ATM cell of VCI having an attribute of “00” (not applicable) arrives at the cell input control unit 24. Because the attribute is not applicable,
It is determined that the selective packet discarding process is not applied to the VCI logical channel, and is subjected to the receiving process by the cell input control unit 24 and then stored in the cell buffer 10 (FIG. 4B).
FIG. 5A shows a state in which an ATM cell of VC2 having an attribute of “10” (packet reception permission) arrives at the cell input control unit 24. Since the attribute is packet reception permission, the reception processing is performed by the cell input control unit 24, and the packet is stored in the cell buffer 10 (FIG. 5B).

FIG. 6A shows a state in which the ATM cell of VC3 in the state of "11" (packet is being discarded) arrives at the cell input control unit 24. The reason why the attribute is packet discarding is that the buffer occupancy when the head cell arrived was equal to or larger than the threshold value.
3 is completely invalid, the cell input control unit 2
Discard at step 4 (FIG. 6 (b)).

FIGS. 7 to 9 show a state when the ATM cell of the logical channel (VC) having the “01” (packet not received) attribute arrives at the cell input control unit 24. In this embodiment, the threshold value for the entire buffer is Qth_
total = 30 is set. Also, k = 0.5 is used as a predetermined coefficient. This coefficient can be dynamically set by an administrator.

FIG. 7A shows that the occupation amount Q_total (= 24) of the entire cell buffer is equal to a predetermined threshold value Qth_t.
When it is less than or equal to total, "01" (packet not received)
The ATM cell of VC4 in the state of
Has arrived. Since the state registered in the management table 30 is that the packet has not been received, it is determined that this cell is the first cell of the upper layer packet, and since the cell buffer 10 has a sufficient free space (Q_to
tal ≦ Qth_total), all ATs for packets
Assuming that M cells could be accommodated, the state (Fig. 7
In (b)), the bit value “10” is stored in the management table 30.
(Permission of packet reception) is displayed, and the first cell is stored in the cell buffer 10.

FIG. 8A shows that the occupation amount Q_total (= 63) of the entire cell buffer is equal to a predetermined threshold value Qth_t.
When it is more than total, "01" (packet not received)
The ATM cell of VC5 in the state of
Has arrived. The management table 30 as in FIG.
Is determined to be the first cell of the upper-layer packet because the packet is not yet received. However, since the occupation amount of the entire cell buffer 10 is equal to or larger than a predetermined threshold value (Q_total> Qth_
total), the occupation amount Q_total of the entire buffer, the number T of the logical channels (VC) in the “10” (packet reception permitted) state in the management table 30, and the predetermined coefficient k
Is used to calculate a threshold Qth_vc for the logical channel (VC). The occupancy of the entire buffer is Q_
Total = 63, the number of logical channels (VCs) in the “10” (packet reception permitted) state in the management table 30 is T = 3, and the predetermined coefficient is k = 0.5. Threshold value is Qth_vc = 1
0.5. In cell buffer 10! ATM of VC5
The cell occupancy Q_vc = 5 is calculated by the calculated threshold Qt.
Since h_vc is smaller than 10.5, it is assumed that all ATM cells for the packet will be accommodated, and in the next state (FIG. 8B), the bit value “1” is stored in the management table 30.
0 ”(packet reception permission) is displayed, and the first cell is stored in the cell buffer 10.

FIG. 9A shows that the occupation amount Q_total (= 63) of the entire cell buffer is equal to a predetermined threshold value Qth_t.
When it is more than total, "01" (packet not received)
The ATM cell of VC6 in the state of
Has arrived. The management table 30 as in FIG.
Is determined to be the first cell of the upper-layer packet because the packet is not yet received. However, since the occupation amount of the entire cell buffer 10 is equal to or larger than a predetermined threshold value (Q_total> Qth_
total), the occupation amount Q_total of the entire buffer, the number T of the logical channels (VC) in the “10” (packet reception permitted) state in the management table 30, and the predetermined coefficient k
Is used to calculate a threshold Qth_vc for the logical channel (VC). The occupancy of the entire buffer is Q_
Since total = 63, the number of logical channels (VCs) in the “10” (packet reception permitted) state in the management table 30 is T = 3, and the predetermined coefficient is k = 0.5, VC6 of VC6 is obtained from Expression (1). Threshold value is Qth_vc = 1
0.5. In cell buffer 10! ATM of VC6
The cell occupancy Q_vc = 16 is determined by the calculated threshold Q
Since th_vc exceeds 10.5, it is determined that the upper layer packet constituted by the head cell will contain a cell loss due to buffer overflow, and the bit value “11” is stored in the management table 30 (packet is being discarded). Is displayed, and the first cell is discarded by the cell input control unit 24. Thereafter, all of the ATM cells of VC6 arriving afterwards are inputted to the cell input control unit 2.
Discard at 4

FIG. 10 shows a state where the EOM cell of the VC 7 in the state of “11” (packet is being discarded) arrives at the cell input control unit 24. Since the attribute indicates that the packet is being discarded, it is understood that all the ATM cells of this VC have been discarded by the cell input control unit 24 so far. EO
The arrival of the M cell indicates that all the cells for the packet have arrived for this VC, and that the ATM cell of the next VC 7 is the head cell of another upper layer packet, and the state is set to "01". (No packet received) and then accumulates in the cell buffer 10, and the next VC7 A
It prepares for cell discard control based on the buffer occupancy executed for the TM cell (head cell).

FIG. 11 shows a state where the EOM cell of VC8 having the attribute of “00” (not applicable) arrives at the cell input control unit 24. Since the attribute is not applicable, VC
It is determined that the selective packet discarding process is not applied to the logical channel No. 8, and the state is left as “00” (not applicable).

[0047]

According to the present invention as described above,
In a buffer memory for temporarily storing ATM cells, in an environment where logical channels (VC) having different communication requirements coexist, it is easy to select application / exclusion of selective packet discarding for each logical channel (VC). And flexible network design becomes possible. Also, in an environment where logical channels (VCs) having different traffic characteristics coexist, it is possible to improve biased forced discarding for each logical channel (VC).

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of a buffer management system according to the present invention.

FIG. 2 is a configuration diagram of a cell discarding management table provided in a status storage unit in the embodiment of FIG. 1;

FIG. 3 is a flowchart showing a processing procedure for an ATM cell in the embodiment of FIG. 1;

FIG. 4 is a state diagram illustrating a processing procedure when a VC ATM cell in a state of “00” not applicable in the embodiment of FIG. 1 arrives at a cell buffer;

FIG. 5 is a state diagram illustrating a processing procedure when the ATM cell of the VC in the state of reception permission “10” arrives at the cell buffer in the embodiment of FIG. 1;

FIG. 6 is a state diagram illustrating a processing procedure when an ATM cell of a VC in the state of “11” being discarded arrives at the cell buffer in the embodiment of FIG. 1;

FIG. 7 is a flowchart showing a process when an ATM cell of a VC in a packet unreceived state “01” arrives at a cell buffer when the occupation amount of the entire cell buffer is equal to or less than a predetermined threshold value in the embodiment of FIG. 1; It is a state diagram explaining a procedure.

FIG. 8 is a flowchart showing a process performed when an ATM cell of a VC in a packet unreceived state “01” arrives at a cell buffer when the occupation amount of the entire cell buffer is equal to or more than a predetermined threshold value in the embodiment of FIG. 1; It is a state diagram explaining a procedure.

FIG. 9 is a flowchart showing a process performed when an ATM cell of a VC in a packet unreceived state “01” arrives at a cell buffer when the occupation amount of the entire cell buffer is equal to or larger than a predetermined threshold value in the embodiment of FIG. 1; It is a state diagram explaining a procedure.

10 is a state diagram illustrating a processing procedure when an EOM cell of a VC in the state of “11” is being discarded in the embodiment of FIG. 1;

11 is a state diagram illustrating a processing procedure when an EOM cell of a VC which is in a state of “00” not applicable in the embodiment of FIG. 1 arrives;

FIG. 12 is a flowchart showing a conventional procedure for processing an ATM cell by selective packet discarding.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Cell buffer memory 11 Input line 12 Output line 20 Buffer management device 21 Packet reception control part 22 Status storage part 23 Buffer occupancy amount counting part 24 Cell input control part 30 Cell discarding management table

Claims (7)

(57) [Claims] 1. A buffer memory for temporarily storing ATM cells and a cell discarding management table for holding an attribute indicating whether or not reception is possible for each logical channel (VC) are prepared, and a logical channel of the reached ATM cell is prepared. Measuring the total buffer occupancy of the buffer memory when the attribute indicates non-reception, and receiving an ATM cell that has reached when the measured total buffer occupancy is equal to or less than a first threshold value; A buffer management method for performing a selective packet discarding process so as to discard an reached ATM cell when the measured total buffer occupancy exceeds a first threshold value, wherein the measured total buffer occupancy is the Calculating a second threshold value in the logical channel of the reached ATM cell if it is equal to or greater than 1, and arriving at the ATM cell based on the second threshold value; A buffer management method, wherein a selective packet discarding process is performed by deciding to discard or receive a cell. 2. The method as claimed in claim 2, wherein when the attribute of the arrived ATM cell indicates that the selective packet discarding process is not performed, the ATM cell is received without performing the selective packet discarding process. 2. The buffer management method according to 1. 3. The method according to claim 1, wherein said second threshold value is calculated based on an average buffer occupancy for each logical channel, and
If the buffer occupancy of the logical channel of the M cell exceeds the second threshold, the ATM cell is discarded,
2. The buffer management method according to claim 1, wherein the reception is performed when the value is equal to or less than a second threshold value. 4. The average buffer occupancy for each logical channel, wherein the second threshold value is obtained by dividing the total buffer occupancy by the number of logical channels whose attribute in the cell discard management table indicates that packet reception is permitted. 4. The buffer management method according to claim 3, wherein the calculation is performed by multiplying a predetermined count by a predetermined count. 5. A buffer management system for an ATM node device having a buffer memory for temporarily storing ATM cells, wherein a buffer occupancy for counting an occupancy of an ATM cell for each logical channel (VC) in said buffer memory. An amount counting unit; a status storage unit storing a cell discarding management table holding an attribute indicating whether or not an ATM cell arrives for each logical channel can be received; and a buffer occupancy measured by the buffer occupancy counting unit. A packet admission control unit that calculates a threshold to determine whether to receive or discard an ATM cell, updates the cell discard management table, and performs selective packet discard processing based on the attribute of the logical channel of the reached ATM cell. If the first attribute indicates that there is no packet or the second attribute indicates that packet reception is permitted, the logical channel Receiving the ATM cell, only set the cell input control unit for forcibly discarding ATM cells of the logical channel if the third attribute indicating that the packet discard (VC), when establishing a logical channel by signaling processing
In the cell discard management table, selective packet discard
For logical channels that declare that processing is not applied
Sets the first attribute and wishes to selectively drop packets
Packets have not been received for the specified logical channel
A fourth attribute indicating the following . 6. When the ATM cell arrives from the logical channel having the fourth attribute, the packet admission control unit determines the total buffer occupancy provided by the buffer occupancy counting unit and a first threshold. Comparing the values, if the total buffer occupancy does not exceed the first threshold, the second attribute is set for the logical channel; and the total buffer occupancy exceeds the first threshold. If
Generating a second threshold value for a logical channel corresponding to an ATM cell reached from the total buffer occupancy, the number of logical channels having the second attribute in the cell discard management table, and a predetermined coefficient; If the buffer occupancy of the logical channel given by the buffer occupancy counter exceeds the second threshold, the third attribute is set. If the buffer occupancy is equal to or less than the second threshold, the third attribute is set. 2. The attribute of item 2 is set for the logical channel.
6. The buffer management system according to 5 . 7. An average buffer occupancy for each logical channel obtained by dividing the total buffer occupancy by the number of logical channels having the second attribute in the cell discard management table as the second threshold value. 7. The buffer management system according to claim 6 , wherein a numerical value multiplied by a coefficient is used.