JPH09162893A - Device and method for abolishing packet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set all the packets of retransmission objects to be restriction objects by providing a means for abolishing packets containing abolished cells and packers on the same virtual channel, which follow the mentioned packets, with the prescribed number of the packets. SOLUTION: A buffer 3 which temporarily accumulates the cells and a cell abolishing device 2 as the means for abolishing the cells overflowed from the buffer 3 are provided. The cell abolishing device 2 is provided with a packet number counter 7 as the means for abolishing the packets containing the abolished cells and the same packets following the packets with the previously decided number of the packets. The packet number counter 7 starts counting the number of the buffers when the notice of cell abolishment is given from a cell abolishment detection device 6, and counts up the packets by one when the last cell detection of the packet is noticed from a cell abolishment judgment device 5.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an asynchronous transfer mode (A
TM: Asynchronous Transfer Mode) Used for communication networks. The present invention is suitable for use in switching nodes. In particular, it relates to cell disposal technology.

[0002]

2. Description of the Related Art In a communication network based on cell transfer such as an ATM communication network, a packet is divided into several cells and transferred. The switching node that transfers each cell can detect that it is the last cell forming each packet by reading the information in the cell, and know the break between the packets of the transferred cell stream.

When the switching nodes constituting the communication network are congested, the buffer overflows and the cells are discarded. When notification of cell discard is received from the receiving terminal or when the transmitting terminal itself detects the cell, the transmitting terminal retransmits not only the discarded cell but also the packet including the discarded cell and all packets transmitted after the packet. Realize the transfer. This retransmission will be described with reference to FIG. FIG. 18 is a diagram showing the relationship between cell discard and retransmission.

As shown in FIG. 18, when one cell is discarded, the packet containing the cell cannot be reconstructed at the receiving terminal and the packet must be retransmitted. Furthermore, since one packet has been retransmitted, a plurality of subsequent packets may be subject to retransmission.

A method of discarding other cells forming the packet by paying attention to only the packet including the discarded cells, not the continuous packets, has already been proposed. This method will be described. By reading the information written in the cell, the group of cells forming one packet can be identified. For example, in AAL3 / 4 in the ATM communication network, ST (segment type) is written in each cell for each packet, so that the switching node can identify the cell group forming one packet. Further, in the AAL5 in the ATM communication network, the cell group forming one packet can be identified by reading the payload type indication written in the last cell of the cell group forming one packet. Thus, when packet configuration information is written in these cells, other cells that compose a packet including the cell can be discarded together with respect to the cell discard at the time of congestion. .

In the method called Partial Packet Discard, when a cell is discarded due to the overflow of the buffer in the switching node, all subsequent cells forming the same packet are discarded. Discarding is realized by reading the information in the cell at the switching node.

In the method called Early Packet Discard, when the cell located at the head of the packet arrives when the number of cells in the buffer of the exchange node exceeds a certain threshold value, all cells constituting the packet are discarded.

In these methods, when cell discard due to buffer overflow or cell discard is expected, other packets are constructed by positively discarding cells that form a single packet including the cell concerned. It is possible to prevent the disposal of cells. However, the fact that subsequent packets of the discarded packet are to be retransmitted is not considered.

[0009]

When the packet configuration information is written in the cell as in the prior art described above, by reading the information written in the cell,
Other cells that make up the packet containing the discarded cell can be discarded. However, when the notification from the receiving terminal or the transmitting terminal itself detects the discard of the cell,
When it is necessary for the sending terminal to retransmit not only the discarded cells but also the packets containing the discarded cells and all packets transmitted after the packet concerned, consider only a single packet containing the discarded cells. But it doesn't make sense.
That is, not only the packet containing the first discarded cell, but also the subsequent packets are retransmitted. As a result, the communication network performs useless data transfer, resulting in a decrease in throughput.

The present invention has been made against such a background, and restricts all the packets to be retransmitted to a communication network that retransmits a packet including a discarded cell and all the packets transmitted after the packet. An object of the present invention is to provide a packet discard device and method that can be targeted. An object of the present invention is to provide a packet discard device and method capable of improving the throughput of a communication network.

[0011]

Discarding one cell forming a certain packet leads to retransmission of the entire packet, and as a result, the cell transferred without being discarded is also transmitted again. According to the present invention, in order to reduce the number of times the same packet is transferred more than once, the effective packet throughput of the communication network is improved by discarding the cells constituting the packet that is estimated or confirmed to be retransmitted. Can be large.

That is, a first aspect of the present invention is a packet discarding device provided with a buffer for temporarily storing cells and means for discarding cells overflowing from this buffer.
A feature of the present invention is that the discarding means includes means for discarding a packet including a discarded cell and a predetermined number N of packets on the same virtual channel following the packet. It is in.

As a result, it is possible to discard all of a plurality of packets that need to be retransmitted due to the discarding of one cell.
It is possible to avoid useless cell transfer that hinders effective use of the communication network, such as transfer once.

Further, the discarding means includes means for continuously discarding a packet including a discarded cell and a packet subsequent to this packet on the same virtual channel for a predetermined time T from the discard occurrence time. The same effect can be expected with the configuration.

Further, the discarding means includes a packet including a discarded cell and a packet following the packet on the same virtual channel until reaching a predetermined number N or a predetermined time T from the discard occurrence time. The same effect can be expected even if a configuration is provided with a means for continuously discarding until any of the above elapses in time.

The predetermined number N or the predetermined time T is set in the setting information of the number N that is transmitted from the cell source at a predetermined number of cells or periodically transferred. Therefore, it may be variably set.

As a result, the number of packets to be discarded can be adaptively changed according to the change in the communication content, so that the cell discard control that matches the actual communication situation can be further performed.

A second aspect of the present invention is a packet discarding method in a switching node of a communication network which divides a packet into a plurality of cells and transfers the cells. The features of the present invention include:
When a cell overflowing the buffer provided in the switching node is discarded, a predetermined number N of packets on the same virtual channel following the packet including the cell are continuously discarded.

When a cell overflowing from a buffer provided in the switching node is discarded, a packet including the cell is continuously discarded for a predetermined time T from the time when the discard occurs for the packet on the same virtual channel. It may be discarded.

Further, when a cell overflowing a buffer provided in the switching node is discarded, a predetermined number N of packets on the same virtual channel following a packet including the cell or a time when the discard occurs is predetermined. It may be continuously discarded over a period of time T.

The predetermined number N or the predetermined time T can be variably changed by transmitting a predetermined number of cells from the transmitting terminal to the switching node or periodically. It may be set.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

[0023]

【Example】

(First Embodiment) The configuration of the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of the first embodiment of the present invention.

The present invention uses a buffer 3 for temporarily storing cells.
And a cell discarding device 2 as a means for discarding cells overflowing from this buffer 3.

Here, a feature of the present invention is that the cell discarding device 2 discards a packet including a discarded cell and a predetermined number N of packets on the same virtual channel following the packet. It is provided with a packet number counter 7 as a means for doing so.

In the ATM communication network, a virtual channel (hereinafter referred to as VC: Virt) is used for data communication between transmitting and receiving terminals.
The communication is carried out by allocating the (referred to as the ual channel), and the cell flow of each VC is measured at the switching node.

The cell input device 1 is a device for transferring cells from each terminal to the cell discard device 2. Cell discard device 2
Is a device that discards the cells transferred from the cell input device 1 or transfers the cells to the buffer 3 according to the notification from the cell discard determination device 5. The buffer 3 waits until the cells are transferred to the cell transmission device 4, and transfers the cells to the cell transmission device 4 one cell at a time. The cell transmission device 4 transfers the cell to the outside of the node. The cell discard determination device 5 determines whether to discard the cell transferred to the cell discard device 2 or transfer it to the buffer 3. Further, the cell discard determination device 5 determines for each VC whether or not it is the last cell of the packet. The cell discard detection device 6 detects cell discard due to buffer overflow of cells in the buffer 3, and notifies the packet number counter 7 of the occurrence of cell discard and the VC number at which cell discard occurred. The packet number counter 7 starts counting the number of packets when the cell discard detection device 6 notifies the cell discard, and increments the packet count by 1 when the cell discard determination device 6 notifies the cell detection at the end of the packet. Let

FIG. 2 is a flow chart showing the discard algorithm of the first embodiment of the present invention. The cell discard detector 6 detects cell discard due to buffer overflow (S1). The cell discard detector 6 notifies the packet number counter 7 of the cell discard occurrence and the VC number at which the cell discard occurred (S2). The packet number counter 7 starts measuring the number of packets in the VC (S3). The packet number counter 7 detects the last cell arriving at the relevant VC and instructs the cell discard determining device 5 to totally restrict the arriving cell of the relevant VC (S4). Cell discard determination device 5
Then, when the instruction arrives, the cell discarding device 2 is instructed to completely regulate the arrival cell of the VC. Further, the cell discard determination device 5 detects the arrival of the last cell of the packet in the VC and notifies the packet number counter 7 of each arrival (S5). When the instruction arrives, the cell discard device 2 completely controls the arrival cell of the VC (S
6). In the packet number counter 7, the cell discard determination device 5
The measurement is continued until the number of packets which is started to be measured based on the information from (1) reaches the number N as a threshold (S7). When the number of packets reaches the number N as a threshold value, the packet number counter 7 instructs the cell discard determination device 5 to release the restriction on the VC (S8). Cell discard determination device 5
Instructs the cell discard device 2 to release the regulation of the arrival cell of the VC when the instruction arrives (S9). When the instruction arrives, the cell discard device 2 releases the regulation of the arriving cell of the VC (S10).

(Second Embodiment) In the same discarding algorithm as in the first embodiment of the present invention, the number N is not set to a predetermined value, and a predetermined number of R cells are set from the transmission terminal to the switching node. Is transmitted or transmitted at regular intervals of a predetermined fixed time S, thereby making a change. FIG. 3 is a diagram showing a signal sequence between the transmitting terminal and the switching node. Notification is performed between the transmitting terminal and the switching node according to the signal sequence of FIG. A VC is set between the sending terminal and the receiving terminal (S1
1). Data is made into cells and transmitted from the transmitting terminal to the receiving terminal (S12). The control-dedicated cell is transmitted from the transmitting terminal to the exchange node every R number of cells transmitted or at predetermined time intervals S. The number N is written in the control dedicated cell (S13). Upon receiving the control-dedicated cell, the switching node updates and executes the number N as the threshold value of the discard algorithm of the first embodiment of the present invention (S1).
4). When the data transfer is completed, the VC between the transmitting terminal and the receiving terminal is released (S15).

(Third Embodiment) The configuration of the third embodiment of the present invention will be described with reference to FIG. FIG. 4 is a block diagram of the apparatus of the third embodiment of the present invention.

The present invention uses a buffer 3 for temporarily storing cells.
And a cell discarding device 2 as a means for discarding cells overflowing from this buffer 3.

Here, a feature of the present invention is that the cell discarding device 2 operates for a predetermined time T from the discard occurrence time for a packet containing a discarded cell and a packet on the same VC following this packet. It is provided with a timer 8 as a means for continuously discarding.

The structural difference from the first embodiment of the present invention is that a timer 8 is provided instead of the packet number counter 7. When the timer 8 receives a notification of cell discard occurrence from the cell discard detection device 6, it starts counting time.

The discard algorithm of the third embodiment of the present invention will be described with reference to FIG. FIG. 5 is a flowchart showing the discard algorithm of the third embodiment of the present invention. The cell discard detector 6 detects cell discard due to buffer overflow (S
21). The cell discard detection device 6 notifies the timer 8 of the cell discard occurrence and the VC number at which the cell discard occurred (S22).
The timer 8 starts clocking for the VC (S2
3). The timer 8 sends the V
Instruct to completely control the arrival cell of C (S
24). When the instruction arrives, the cell discarding apparatus 5 instructs the cell discarding apparatus 2 to completely restrict the arrival cells of the VC (S25). When the instruction arrives, the cell discard device 2 completely controls the arrival cell of the VC (S26). The timer 8 waits until the measured time reaches the time T as a threshold value (S27). When the value of the measured time reaches the time T as a threshold value, the timer 8 instructs the cell discard determination device 5 to release the restriction on the VC (S28). When the instruction arrives, the cell discard determining device 5 controls the arriving cell of the VC up to the last cell of the next packet, and instructs the cell discarding device to cancel the subsequent cell discard processing (S29). The cell discard device 2 is
When the cell discard processing cancellation instruction arrives, the regulation of the arriving cell of the VC is canceled (S30).

(Fourth Embodiment) In the fourth embodiment of the present invention, in the same discarding algorithm as the third embodiment of the present invention, the time T as the threshold value of the clock time is not set to a predetermined value, The change is made by periodically notifying the switching node every time a predetermined number of R cells are transmitted or at a predetermined constant time S. Between the transmitting terminal and the switching node, the notification of the time T as the threshold value of the clock time is performed according to the signal sequence of FIG. 3 shown in the second embodiment of the present invention. The VC is set between the transmitting terminal and the receiving terminal (S11). Data is made into cells and transmitted from the transmitting terminal to the receiving terminal (S1).
2). The control-dedicated cell is transmitted from the transmitting terminal to the exchange node every R number of cells transmitted or at predetermined time intervals S (S13). The time T is written in the control-only cell. When the exchange node receives the control-dedicated cell, it updates the time T as the threshold value of the time count in the discard algorithm of the third embodiment of the present invention and executes the discard algorithm (S14). When the data transfer is completed, the VC between the sending terminal and the receiving terminal is released (S1
5).

(Fifth Embodiment) The configuration of a fifth embodiment of the present invention will be described with reference to FIG. FIG. 6 is a block diagram of the device of the fifth embodiment of the present invention.

The present invention uses a buffer 3 for temporarily storing cells.
And a cell discarding device 2 as a means for discarding cells overflowing from this buffer 3.

Here, a feature of the present invention is that the cell discard device 2 discards a packet including a discarded cell and a packet on the same VC subsequent to this packet until a predetermined number N is reached or is discarded. It is provided with a packet number counter 7 and a timer 8 as means for continuously discarding any of them from the occurrence time until a predetermined time T elapses, whichever comes earlier in time. The fifth embodiment of the present invention includes both the packet number counter 7 in the first embodiment of the present invention and the timer 8 in the third embodiment of the present invention.

The discarding algorithm of the fifth embodiment of the present invention will be described with reference to FIG. FIG. 7 is a flow chart showing the discard algorithm of the fifth embodiment of the present invention. The cell discard detector 6 detects cell discard due to buffer overflow (S
31). The cell discard detection device 6 uses the packet number counter 7 and the timer 8 for the VC in which the cell discard occurs and the cell discard occurs.
The number is notified (S32). The packet number counter 7 starts measuring the number of packets in the VC. Timer 8
Starts timing for the VC (S33). The packet number counter 7 sends the V
The last cell arriving at C is detected and the VC
To control the arrival cells of the
4). When the instruction arrives, the cell discard determining device 5 instructs the cell discarding device 2 to completely regulate the arrival cells of the VC. Further, in the cell discard determination device 5, the V
The arrival of the last cell of the packet in C is detected, and the packet number counter 7 is notified each time it arrives (S35).
When the instruction arrives, the cell discard device 2 completely controls the arrival cell of the VC (S36). The packet number counter 7 starts the measurement based on the information from the cell discard determination device 5 and continues the measurement until the number of packets reaches the number N as a threshold value. The timer 8 waits until the measured time reaches the time T as a threshold value (S37). In the packet number counter 7, when the number of packets reaches the number N as a threshold value, the V
The cell discard determination device 5 is instructed to release the restriction in C. Further, when the value of the measured time reaches the time T as a threshold value, the timer 8 instructs the cell discard determination device 5 to release the restriction on the VC (S38). When the instruction from the packet number counter 7 arrives, the cell discard determination device 5 instructs the cell discard device 2 to release the regulation of the arrival cell of the VC. Alternatively, when the instruction from the timer 8 arrives, the cell discard determination device 5 instructs the cell discard device 2 to regulate the arrival cell of the VC up to the last cell of the next packet and cancel the subsequent cell discard processing. Yes (S39). The instruction of the packet number counter 7 or the timer 8 is valid, whichever is earlier, and is accepted by the cell discard determination device 5. When the cell discarding processing cancellation instruction arrives, the cell discarding apparatus 2 cancels the regulation of the arriving cell of the VC (S40).

(Sixth Embodiment) In the sixth embodiment of the present invention, in the discard algorithm shown in the fifth embodiment of the present invention, the number N as a threshold of the number of packets is not set to a predetermined value, The change is made by periodically notifying the switching node every time a predetermined number of R cells are transmitted or at a predetermined constant time S. Notification is performed between the transmitting terminal and the switching node according to the signal sequence of FIG. 3 shown in the second embodiment of the present invention. The VC is set between the transmitting terminal and the receiving terminal (S11). Data is made into cells and transmitted from the transmitting terminal to the receiving terminal (S12). A control-dedicated cell is transmitted from the transmitting terminal to the switching node every R number of cells transmitted or at predetermined time intervals S (S1).
3). The number N is written in the control dedicated cell. Upon receiving the control-dedicated cell, the switching node updates the number N as the threshold value of the discard algorithm of the fifth embodiment of the present invention and executes the discard algorithm (S14). When the data transfer is completed, the VC between the sending terminal and the receiving terminal is released (S1
5).

(Seventh Embodiment) In the seventh embodiment of the present invention, in the discard algorithm shown in the fifth embodiment of the present invention, the time T as the threshold value of the clock time is not set to a predetermined value, The change is made by periodically notifying the switching node every time a predetermined number of R cells are transmitted or at a predetermined constant time S. Notification is performed between the transmitting terminal and the node according to the signal sequence of FIG. 3 shown in the second embodiment of the present invention. A VC is set between the sending terminal and the receiving terminal (S1
1). Data is made into cells and transmitted from the transmitting terminal to the receiving terminal (S12). The control-dedicated cell is transmitted from the transmitting terminal to the exchange node every R number of cells transmitted or at predetermined time intervals S (S13).
The time T is written in the control-only cell. Upon receiving the control-dedicated cell, the switching node updates the time T as the threshold value of the time counting time of the algorithm of the fifth embodiment of the present invention and executes the discard algorithm (S14). When the data transfer is completed, the VC between the transmitting terminal and the receiving terminal is released (S15).

(Eighth Embodiment) In the eighth embodiment of the present invention, in the discard algorithm shown in the fifth embodiment of the present invention, the number N as the threshold value of the number of packets and the time T as the threshold value of the clock time are predetermined. Instead of using the predetermined value, the transmitting terminal periodically notifies the switching node every predetermined number of R cells to be transmitted or every predetermined constant time S. Notification is performed between the transmitting terminal and the switching node according to the signal sequence of FIG. 3 shown in the second embodiment of the present invention. The VC is set between the transmitting terminal and the receiving terminal (S11). Data is made into cells and transmitted from the transmitting terminal to the receiving terminal (S12). The control-dedicated cell is transmitted from the transmitting terminal to the exchange node every R number of cells transmitted or at predetermined time intervals S (S13). The number N and the time T are written in the control dedicated cell. When the switching node receives the control-only cell,
The number N as the threshold value of the number of packets of the discard algorithm of the fifth embodiment of the present invention and the time T as the threshold value of the clock time are updated and the discard algorithm is executed (S14). When the data transfer is completed, the VC between the transmitting terminal and the receiving terminal is released (S15).

A simulation model of the first to eighth embodiments of the present invention is shown in FIG. In the simulation model, it is assumed that cell discard at the switching node occurs only in the buffer and not in the switch. The buffer is shared by all VCs, and priority processing in the buffer is not assumed. The input traffic is the same for each VC. Each packet is composed of 35 cells, the arrival time interval of each packet at the node is Poisson arrival, and the arrival time interval of each cell in the same packet is a unit cell time.

The number of packets to be retransmitted in cell discard depends on the parameters of the transport layer protocol used in each terminal. For example, depending on the window size of flow control and the estimation method of the round trip time, here, the number M of packets to be retransmitted for each packet is
Is given, and subsequent M packets on the same VC following the packet at the time of packet loss are to be retransmitted. Further, even if any cell of the packet to be retransmitted is not discarded and is processed by the node, the packet is retransmitted and is not considered to be a valid packet. Retransmission of packets is generally performed at a low transmission rate, but here, it is assumed that the transmission rate does not decrease and the packet transmission rate does not change.

The number of subsequent packets M to be retransmitted when the cell of packet i is lost is determined by the attribute value Mi of packet i.
And Ti are added. Mi follows the hypergeometric distribution (mean μ1, parameters characterizing the hypergeometric distribution a1, a2, a3), and Ti follows the Erlang distribution of order k (mean μ2). If the cell of packet i is discarded due to buffer overflow, the packet number counter 7 and timer 8 for the VC that is sending the packet are started immediately. The packet number counter 7 counts up when a new packet starts to be transmitted. Packets sent until the counter value is set to Mi or the timer value is set to Ti are regarded as retransmission target packets. In the method of determining the number of packets to be retransmitted as described above, it is assumed that the window size of flow control is Mi and the round trip time of flow control is Ti. The simulation was performed under three different traffic conditions. The parameter values that give the traffic conditions are shown in [Table 1].

[0046]

[Table 1] The results of this simulation are shown in FIGS. FIG.
11 is a diagram showing a simulation result under the condition 1 of [Table 1], and FIG. 9 shows cell throughput on the horizontal axis and the vertical axis, respectively. In FIG. 10, the horizontal axis and the vertical axis represent the packet throughput. In FIG. 11, the horizontal axis and the vertical axis represent the throughput of valid packets. 12 to 14 are diagrams showing simulation results under the condition 2 in [Table 1], and FIG. 12 shows cell throughputs on the horizontal axis and the vertical axis, respectively. In FIG. 13, the horizontal axis and the vertical axis represent the packet throughput. In FIG. 14, the horizontal axis and the vertical axis show the throughput of valid packets. 15 to 17 are diagrams showing simulation results under the condition 3 of [Table 1], and FIG. 15 shows cell throughputs on the horizontal axis and the vertical axis, respectively. In FIG. 16, the horizontal axis and the vertical axis represent the packet throughput. In FIG. 17, the horizontal axis and the vertical axis represent the throughput of valid packets.

Uncontrolled, Early Packet D for comparison
iscard (EPD), Partial Packet Discard (PPD)
The results in the case of are also shown. However, Early Packet Dis
The buffer threshold for a card (EPD) is 3/4 of the buffer size. The evaluation items were the cell throughput, the packet throughput including the retransmission target packet, and the effective packet throughput not including the retransmission target packet. Here, the number of VCs is 100 and the buffer size is 100. The peak transmission rate of the cells of each VC is 6.3 Mbps, and the cells forming one packet are transmitted at the peak rate. The time interval of output from the buffer is 150 Mbps. Further, the threshold value of each embodiment is given in advance, and the value is the number N as the threshold value in the case of the first embodiment of the present invention is 6, and the time T as the threshold value is 45 s in the third embodiment of the present invention. In the fifth embodiment of the present invention, the number N as a threshold value is 6, and the time T as a threshold value is
Was 45 s.

9, FIG. 10, FIG. 12, FIG. 13, FIG.
The cell or packet throughput shown in FIG.
The values of the first embodiment of the present invention, the third embodiment of the present invention, and the fifth embodiment of the present invention are lower than those in the case of no control or EPD or PPD. This is because cell discarding is performed more positively than in the case of no control or EPD or PPD in the first embodiment of the present invention, the third embodiment of the present invention, and the fifth embodiment of the present invention.

The throughput of the effective packet shown in FIGS. 11, 14 and 17 is higher than that in the case of no control or EPD or PPD, the first embodiment of the present invention, the third embodiment of the present invention and the fifth embodiment of the present invention. The examples show good results.

As described above, regarding the effective packet throughput, the method of the present invention can obtain a higher throughput than the conventional method.

The result of this simulation is the time until each threshold is updated when the time interval for updating each threshold is sufficiently long in the second, fourth, sixth, seventh and eighth embodiments of the present invention. The performance in the company was evaluated, and its effectiveness was confirmed.

[0052]

As described above, according to the present invention,
For a communication network that retransmits a packet including a discarded cell and all packets transmitted after the packet, all retransmission target packets can be subject to restriction. Thereby, the throughput of the communication network can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a device according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing a discard algorithm of the first embodiment of the present invention.

FIG. 3 is a diagram showing a signal sequence between a transmitting terminal and a switching node.

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

FIG. 5 is a flowchart showing a discard algorithm of the third embodiment of the present invention.

FIG. 6 is a block configuration diagram of a fifth embodiment device of the present invention.

FIG. 7 is a flowchart showing a discard algorithm of the fifth embodiment of the present invention.

FIG. 8 is a diagram showing a simulation model according to an embodiment of the present invention.

FIG. 9 is a diagram showing a simulation result of Condition 1.

FIG. 10 is a diagram showing a simulation result of Condition 1.

FIG. 11 is a diagram showing a simulation result for Condition 1.

FIG. 12 is a diagram showing a simulation result of Condition 2.

FIG. 13 is a diagram showing a simulation result of Condition 2.

FIG. 14 is a diagram showing a simulation result of Condition 2.

FIG. 15 is a diagram showing a simulation result of Condition 3.

FIG. 16 is a diagram showing a simulation result of Condition 3.

FIG. 17 is a diagram showing a simulation result of Condition 3.

FIG. 18 is a diagram showing the relationship between cell discard and retransmission.

[Explanation of symbols]

 1 Cell Input Device 2 Cell Discarding Device 3 Buffer 4 Cell Sending Device 5 Cell Discarding Judgment Device 6 Cell Discarding Detection Device 7 Packet Number Counter 8 Timer

Claims (10)

[Claims] 1. A packet discarding device comprising a buffer for temporarily storing cells and means for discarding cells overflowing from this buffer, wherein the discarding means follows a packet including the discarded cells and this packet. A packet discarding device comprising means for collectively discarding a predetermined number N of packets on the same virtual channel. 2. A packet discarding device comprising a buffer for temporarily storing cells and means for discarding cells overflowing from this buffer, wherein the discarding means follows a packet containing the discarded cells and the packet. A packet discarding device comprising means for continuously discarding packets on the same virtual channel for a predetermined time T from the discarding occurrence time. 3. A packet discarding device comprising a buffer for temporarily storing cells and means for discarding cells overflowing from the buffer, wherein the discarding means follows a packet containing the discarded cells and this packet. A means for continuously discarding packets on the same virtual channel until a predetermined number N is reached or a predetermined time T elapses from the discard occurrence time arrives earlier in time. A packet discarding device characterized by being provided. 4. The predetermined number N is variably set according to the setting information of the number N that is transferred from a cell source at a predetermined number of cells or periodically. 1. The packet discard device according to 1 or 3. 5. The predetermined time T is variably set according to setting information of the time T that is transferred from a cell source at a predetermined number of cells or periodically. 2. The packet discard device according to either 2 or 3. 6. A method of discarding a packet in a switching node of a communication network, which divides a packet into a plurality of cells and transfers the cells. When a cell overflowing from a buffer provided in the switching node is discarded, the packet including the cell is the same. A packet discarding method characterized by continuously discarding a predetermined number N of packets on the virtual channel. 7. A method of discarding a packet in a switching node of a communication network, which divides a packet into a plurality of cells and transfers the cells. When a cell overflowing from a buffer provided in the switching node is discarded, the packet including the cell is the same. The packet discarding method characterized in that the packet on the virtual channel is continuously discarded for a predetermined time T from the discarding occurrence time. 8. A method of discarding a packet in a switching node of a communication network, which divides a packet into a plurality of cells and transfers the same. When a cell overflowing from a buffer provided in the switching node is discarded, the packet including the cell is the same. The packet discarding method characterized by continuously discarding a predetermined number N of packets on the virtual channel or a predetermined time T from the discarding occurrence time. 9. The predetermined number N is set variably by transmitting a predetermined number of cells from a transmitting terminal to a switching node each time or periodically. Packet discard method. 10. The predetermined time T is
9. The packet discarding method according to claim 7, wherein the packet is set variably by transmitting a predetermined number of cells from the transmitting terminal to the switching node at every transmission or periodically.