JP2722053B2 - Congestion notification method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a congestion notification method,
Particularly in an information communication network, the congestion state of a relay node called a gateway or a router for executing a communication protocol process is determined by a protocol layer 4 of an end node.
To a congestion notification method for notification to

[0002]

2. Description of the Related Art In an information communication network, a relay node called a gateway or a router for executing a communication protocol process is used to interconnect between individual LANs constituting a network, another network or a wide area network. , More value-added services are provided. This type of relay node performs communication protocol processing using a buffer that temporarily holds data to be relayed, and when the buffer becomes congested due to a sudden increase in data to be relayed, each of the transmission side and destination side The congestion notification requesting the end node to reduce the amount of transmission data is performed.

Conventionally, several methods have been proposed as methods for notifying end nodes of congestion. First, as a first conventional technique, there is a technique of notifying a congestion state using a congestion message (SQ message: Source Quench) as shown in FIG. 10 (for example, TCP / IP).
System Layer Protocol ICMP: Internet Control M
essage Protocol / document number RFC792). 10, (a) shows the congestion notification sequence, (b) shows the configuration of the congestion message, and (c) shows the configuration of the data packet, where 1 is a relay node, 2 is a source node, 3 is a destination node, 5 Is a communication network connecting the nodes.

In this case, a congestion notification message is transmitted to the transmission node 2 in response to the detection of the congestion state in the relay node 1. The ICMP processing unit that monitors the IP processing unit, which is the network layer (hereinafter, referred to as layer 3) of the OSI reference model, of the transmitting node 2 responds to the reception of the congestion message by using the transport layer (hereinafter, referred to as “OSI reference model”). To the TCP processing unit, which is the layer 4), indicating that the relay node 1 is in a congestion state.
The CP processor reduces the window size, that is, the transmission buffer size, to reduce the amount of transmission data.

As a similar method, there is a method using a "waiting box" (for example, a layer protocol ICMP of TCP / IP system / document number RFC1016). This is because a “waiting box” is provided in the IP processing unit of Layer 3 so that the transmission data packet from the TCP processing unit of Layer 4 waits for a certain time before transmission, and the transmission data is adjusted by adjusting the waiting time. The amount is adjusted. In this case, the ICMP processing unit of the source node 2 notifies the IP processing unit of congestion in response to the reception of the congestion message, and based on the notification, the IP processing unit increases the waiting time to reduce the amount of transmission data. Had become.

As a second prior art, as shown in FIG. 11, a congestion indicator is provided in a packet header of Layer 3 to notify a congestion state (for example, Random E).
arly Detection Gateway for Congestion Avoidance, I
EEE / ACM, Trans.Network, Vol.1, No.4, Aug.1993, pp.397
~ Such). 11A shows a congestion notification sequence, and FIG. 11B shows a layer 3 packet configuration.
In this case, when the congestion state is mild, the relay node 1 sets a congestion indication in the packet header and relays the data packet to the destination node 3. The destination node 3 receives this and reduces the amount of data transmitted to the originating node 2. When the congestion state at the relay node 1 is severe, the data packet is discarded.

Further, as a third prior art, as shown in FIG. 12, there is one which targets a protocol having a window type flow control (for example, Japanese Patent Laid-Open No. 5-91).
No. 144). 12A shows a congestion notification sequence, and FIG. 12B shows a packet configuration based on window-based flow control. In this case, as the window size in the packet header of the data packet to be relayed according to the buffer usage status of the relay node 1,
For example, WS = 20 is changed to WS = 10, and the destination node 3 receiving this changes the window size to the transmittable data amount and performs data transmission to the transmission node 2.

[0008]

Therefore, in such a conventional congestion control method, according to the first and second prior arts (see FIG. 10), each end node transmits a congestion notification from Layer 3 to Layer 4. Therefore, even if the layer 4 protocol is the same between both ends, there is a high possibility that the layer 3 protocol differs depending on the section of each relay node. It was difficult to carry over the notification information to the next section for notification. In addition, since notification of congestion from layer 3 to layer 4 is required, when the protocol processing of each layer header of a received data packet is performed in parallel for the purpose of improving the throughput and reducing the processing delay time, the simultaneous parallel processing is performed. There was a problem that control became complicated.

Further, according to the method using the "waiting box" of the first prior art, even if the transmission data stays in the "waiting box" of layer 3 for a long time, it cannot be recognized by the layer 4; Requests the transmission of data packets one after another to layer 3 and starts a timer for response confirmation.
In layer 3, since the transmission data stays in the "waiting box", the response confirmation timer times out, abnormal processing such as retransmission is easily activated, and the throughput is reduced.

According to the second prior art (see FIG. 11), when the congestion state is severe, the data packet responsible for the congestion notification is discarded, so that the relay node 1 notifies the destination node 3 of the congestion state. It becomes impossible to do. As a result, it takes time for the destination node 3 to detect the occurrence of congestion in the relay node 1, and the reduction of the amount of data transmitted from the destination node 3 to the transmission node 2 in the opposite direction is delayed, and the congestion state of the relay node 1 becomes There was a problem that it became worse. Further, due to the discard of the data packet due to the severe congestion state, it becomes impossible to transmit the control information stored in the packet header to the destination node 3,
In the case of a protocol in which the header of the data packet includes the response information for the data transmission in the opposite direction, the response information does not arrive and there is a problem that the release of the buffer at each end node is delayed.

Further, according to the third prior art (see FIG. 12), in order to notify the congestion status of the relay node 1 by the window size which is the protocol information of the layer 4 level, a flow control having a window method is used. In addition, since there is no notification from the relay node 1 to the transmission node 2, there is a problem that the congestion notification to the transmission node 2 is delayed when the number of packets transmitted in the opposite direction is small. The present invention is intended to solve such a problem, and quickly and accurately notifies a congestion state of a relay node to an end node without depending on a layer 4 flow control method or a layer 3 protocol type. It is an object of the present invention to provide a congestion notification method which can perform the congestion notification.

[0012]

In order to achieve the above object, a congestion notification method according to the present invention provides a relay node with a buffer usage and a plurality of predetermined thresholds in accordance with the reception of a packet. A buffer management unit that detects the degree of congestion that has occurred in the buffer by comparison, and a layer 4 packet that stores congestion information indicating the degree of congestion detected by the buffer management unit in the layer 4 protocol header unit When the occurrence of congestion is detected by the buffer management unit, the layer 4 congestion notification control unit sends congestion information indicating the degree of congestion to the layer 4 protocol header unit. The stored layer 4 packet is generated and transmitted to the destination node or the source node of the received packet.

Further, a relay node congestion discard flag indicating the occurrence of severe congestion in which packets are discarded at the relay node is provided as congestion information in the layer 4 protocol header, and the occurrence of severe congestion is detected by the buffer management unit. In this case, the layer 4 congestion notification control unit sets the relay node congestion discard flag of the received data packet, discards the layer 4 data portion of the data packet, and sets the packet type to the status notification packet. Is generated and transmitted to the destination node.

A relay node congestion warning flag is provided in the Layer 4 protocol header as congestion information, which indicates a slight congestion occurrence at which no packet is discarded at the relay node.
When the buffer management unit detects the occurrence of mild congestion, the layer 4 congestion notification control unit generates a layer 4 packet in which the relay node congestion warning flag of the received data packet is set, and transmits it to the destination node. It is like that. Further, when the occurrence of congestion is detected by the buffer management unit, the packet type in which the relay node congestion warning flag or the relay node congestion discard flag corresponding to the detected congestion state is set by the layer 4 congestion notification control unit A layer 4 packet, which is a notification packet, is generated and transmitted to the originating node.

[0015]

Therefore, the buffer management unit of the relay node compares the used amount of the buffer with a plurality of predetermined threshold values in response to the reception of the packet, detects the degree of congestion occurring in the buffer, and detects the congestion. In this case, the layer 4 congestion notification control unit generates a layer 4 packet in which the congestion information indicating the degree of the congestion is stored in the layer 4 protocol header, and transmits the layer 4 packet to the destination node or the source node of the received packet. Is done.

[0016]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a relay node according to a congestion notification method according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a relay node, and reference numeral 6 denotes a DSU (Digital Service Unit) connected to each communication line 7. Unit). In the relay node 1, reference numeral 11 denotes a buffer for temporarily storing received packets, and reference numeral 12 denotes a buffer management unit for detecting a plurality of congestion levels based on the remaining capacity of the buffer 11.

Reference numeral 13 denotes a line controller for controlling the communication line 7 accommodated via the DSU 6, and 14 denotes a data link layer (hereinafter, referred to as a layer 2) and a layer 3 of the OSI reference model.
A relay communication processing unit 15 that relays a received packet based on the above protocol, and a layer 4 congestion notification control unit 15 that generates a layer 4 packet for notifying the level of congestion generated in the buffer 11. FIG. 2 is a configuration diagram illustrating a packet header of a layer 4 packet generated by the layer 4 congestion notification control unit 15. The packet header of a general layer 4 packet includes the congestion level of congestion generated in the relay node 1. A relay node congestion warning flag CA and a relay node congestion discard flag CD set accordingly are added as congestion information.

FIG. 3 is an explanatory diagram showing the relationship between the remaining amount of the buffer 11 and the congestion level. In this case, the received packets are stored in the buffer 11 in order from the lower side to the upper side as shown in the use direction. When the usage amount of the buffer 11 reaches a predetermined threshold capacity, the buffer management unit 12 determines that the congestion level has reached the threshold capacity. Here, when the threshold capacity 31 is reached, it is detected as a congestion level “1” that prompts a warning, and when the threshold capacity 32 is reached, it is detected as a congestion level “2” indicating discard.

Next, the operation of the present invention will be described with reference to FIGS. FIG. 4 is a flowchart showing the operation of the relay communication processing unit 14, and FIG. 5 is a flowchart showing the operation of the layer 4 congestion notification control unit 15.
6 is a flowchart showing the operation of the first embodiment. First, the line control unit 13 detects the start of communication based on the data packet received via the communication line 7 and the DSU 6, makes a buffer reservation request to the buffer management unit 12, and allocates the buffer according to this request. The received packet is stored in a predetermined area of the buffer 11. After the storage, the relay communication processing unit 14 is notified that the packet has been received.

In response, the relay communication processing section 14 starts the processing shown in FIG. First, the type of activation is determined (step 41). As a result of this determination, the line control unit 13
In the case of activation based on a packet reception notification from the buffer management unit 12, the buffer management unit 12 sets the buffer based on the congestion level detected by comparing the used amount of the buffer 11 shown in FIG. The state of No. 11 is checked (step 42). Here, when the buffer 11 is not in the congestion state, it is determined that the congestion control is unnecessary, and the transmission line is determined from the destination information of the layer 3 header (step 44). Request transmission of a received packet.

On the other hand, if the buffer 11 is in a congestion state, it is determined that congestion control is necessary, and a congestion notification instruction including a congestion level is output to the layer 4 congestion notification control unit 15 (step 43), end the process. In response, the layer 4 congestion notification control unit 15 starts the processing shown in FIG. First, the congestion level included in the congestion notification instruction from the relay communication processing unit 14 is checked (step 51).

Here, when the congestion level of the buffer 11 is the congestion level "1", the relay node congestion warning flag CA in the layer 4 header is set to "1" (= valid), and the relay communication processing unit A transmission request "1" is output to the server 14 (step 52). Subsequently, the layer 4 congestion notification control unit 15 outputs the status notification packet addressed to the source node 2 as
A layer 4 state notification packet CT in which the relay node congestion warning flag CA is set to "1" is generated, and a transmission request "2" is output to the relay communication processing unit 14 (step 5).
3), end the process.

On the other hand, in step 51, the buffer 1
If the congestion level of No. 1 is the congestion level "2", the relay node congestion discard flag CD in the layer 4 header is set to "1" (= valid) (step 54), and the packet type of the received packet is confirmed. (Step 55). Here, when the packet type indicates the data “DT”, the packet type is changed to the status notification packet “CT”, the data part is deleted, and the transmission request “1” is sent to the relay communication processing unit 14. Output (Step 56).

After sending transmission request "1", and step 5
If the packet type is other than the data "DT" in step 5, a layer 4 status notification packet CT with the relay node congestion discard flag CD set to "1" is generated as a status notification packet addressed to the source node 2. Then, the transmission request “2” is output to the relay communication processing unit 14 (step 57), and the process ends. As described above, when the congestion state is severe (congestion level “2”), the data packet is discarded because the buffer of the relay node runs short, but if the header information portion is also discarded, the congestion state ends. Therefore, according to the present invention, a status notification packet is generated and notified. Since the length of the status notification packet is shorter than that of the data packet, the amount of buffer used can be reduced.

In this way, various transmission requests are output from the layer 4 according to the congestion level, the relay communication processing unit 14 is activated again, and the processing shown in FIG. 4 is started. In step 41, the activation type is the layer 4 congestion notification control unit 1.
If it is determined that the transmission request is “1” from the transmission request 5,
In step 44, the transmission line is determined from the destination information in the layer 3 header. In step 45, a transmission request is sent to the corresponding line control unit 13. As a result, the state notification packet CT generated by the layer 4 congestion notification control unit 15 is transmitted to the destination node 3.

If it is determined in step 41 that the activation type is the transmission request “2” from the layer 4 congestion notification control unit 15, the transmission source node 2 is stored as the destination information in the layer 3 and the layer 2 Is generated (step 46), the flow proceeds to step 44 described above, the transmission line is determined from the destination information of the layer 3 header, and a transmission request is made to the corresponding line control unit 13 in step 45. As a result, the state notification packet CT generated by the layer 4 congestion notification control unit 15 is transmitted to the transmission node 2.

FIG. 6 is a sequence diagram showing a congestion notification method when the congestion level is "1". When congestion of level "1" occurs in the relay node 1, the relay node congestion of the data packet DT received thereafter. Warning flag CA is "1"
And transmitted to the destination node 3, thereby reducing the amount of data transmitted in the opposite direction, that is, from the destination node 3 to the source node 2.

FIG. 7 is a sequence diagram showing another congestion notification method in the case of the congestion level "1". When congestion of the level "1" occurs in the relay node 1, the data packet DT received thereafter is transmitted. Relay node congestion warning flag CA
Is set to "1" and transmitted to the destination node 3, thereby reducing the amount of transmission data in the opposite direction. Further, a state notification packet CT in which the relay node congestion warning flag CA is set to “1” is generated and transmitted to the transmission node 2, thereby reducing the amount of data transmitted to the destination node 3. .

FIG. 8 is a sequence diagram showing a method of notifying congestion when the congestion level is "2".
When congestion of level "2" occurs in step 2, the relay node congestion discard flag CD of the subsequently received data packet DT is set to "1", the data portion is discarded, and the packet type is changed to "CT". Status notification packet C
T is generated and transmitted to the destination node 3, thereby reducing the amount of data transmitted in the opposite direction.

FIG. 9 is a sequence diagram showing another congestion notification method in the case of the congestion level "2". When congestion of the level "2" occurs in the relay node 1, the data packet DT of the data packet DT received thereafter is displayed. Relay node congestion discard flag CD
Is set to "1", the data portion is discarded, and the packet type is changed to "CT" to generate a state notification packet CT to be transmitted to the destination node 3, thereby transmitting in the opposite direction. Data volume is reduced.
Further, a state notification packet CT in which the relay node congestion discard flag CD is set to “1” is generated and transmitted to the transmission node 2, whereby the destination node 3
The amount of data to be transmitted to is reduced.

As described above, the buffer management unit 12 of the relay node 1 detects the degree of congestion by comparing the amount of use of the buffer 11 with a plurality of threshold values. In the notification control unit 15, the relay node 1
Since a predetermined layer 4 packet storing the congestion information indicating the degree of the congestion state generated in the above in the protocol header of the layer 4 is generated and transmitted to the end node,
The end node does not depend on the type of the layer 3 protocol of the relay node 1 nor the flow control method in the layer 4 of the end node.
Thus, the congestion state of the relay node can be directly grasped, and the end node can be notified of the congestion state of the relay node quickly and accurately. As a result, the transmission data amount is reduced at the end node, the relay node can quickly recover from the congestion state, and it is possible to avoid a decrease in the network throughput. In particular, a B-ISDN or the like that transmits an enormous data amount can be used. This provides a special effect in a high-speed communication network.

Further, a relay node congestion discard flag CD indicating a severe congestion state is provided in the protocol header of the layer 4, and when the buffer management unit 12 detects the occurrence of the severe congestion, the layer 4 congestion notification control is performed. The unit 15 sets the relay node congestion discard flag CD in the received data packet, discards the layer 4 data portion, generates a layer 4 packet in which the packet type is set to the status notification packet, and transmits it to the destination node 3. Therefore, even if a data packet is received in a severely congested state,
By using the header portion, it is possible to reliably notify the destination node of the congestion state. Further, the control information stored in the header part of the received data packet can be relayed to the destination node, and it is possible to avoid a failure caused by discarding the control information.

A relay node congestion warning flag CA indicating a light congestion state is provided in the layer 4 protocol header, and when the buffer management unit 12 detects the occurrence of light congestion, the layer 4 congestion notification control is performed. The unit 15 generates a layer 4 packet in which the relay node congestion warning flag CA is set in the received packet and transmits the generated packet to the destination node 3, so that the data packet is transmitted before severe congestion occurs in which the data packet is discarded. The amount of data can be controlled, and avoidance control for severe congestion can be performed in accordance with the transmission quality required at the end node.

In response to the occurrence of congestion, the layer 4 congestion notification controller 15 generates a layer 4 status notification packet in which the relay node congestion warning flag CA or the relay node congestion discard flag CD according to the congestion level is set. Is transmitted to the originating node 2, so that even if the amount of data transmitted from the destination node to the originating node is small compared to the congestion notification to the originating node via the destination node, The congestion state can be promptly and accurately notified to the transmitting node.

[0035]

As described above, according to the present invention, a buffer management unit for detecting the degree of congestion that has occurred in a buffer in response to a packet reception, and a layer of congestion information indicating the degree of congestion detected. The relay node is provided with a layer-4 congestion notification control unit for generating a layer-4 packet stored in the protocol-4 header part, and in response to the detection of occurrence of congestion by the buffer management unit, the layer-4 congestion notification control unit sets the congestion state to A layer 4 packet in which the congestion information indicating the degree of the packet is stored in the layer 4 protocol header section is generated and transmitted to the destination node or the source node of the received packet. End node does not depend on the flow from Layer 3 at the end node. It is possible to directly grasp a congestion state of the node can be notified of the congestion state of relay nodes for quickly and accurately end node. As a result, the transmission data amount is reduced at the end node, the relay node can quickly recover from the congestion state, and it is possible to avoid a decrease in the network throughput. This provides a special effect in a high-speed communication network.

Further, a relay node congestion discard flag indicating the occurrence of severe congestion in which packets are discarded at the relay node is provided as congestion information in the layer 4 protocol header, and when the occurrence of severe congestion is detected, The relay node congestion discard flag of the received data packet is set, the layer 4 data portion of the data packet is discarded, and the type of the packet is set to the status notification packet to generate a layer 4 packet, which is transmitted to the destination node. Because
Even when a data packet is received in a severe congestion state, it is possible to reliably notify the destination node of the congestion state by using the header portion. Further, the control information stored in the header part of the received data packet can be relayed to the destination node, and it is possible to avoid a failure caused by discarding the control information.

Also, a relay node congestion warning flag is provided in the layer 4 protocol header as congestion information, which indicates the occurrence of mild congestion in which packets are not discarded at the relay node.
When the occurrence of mild congestion is detected, a layer 4 packet in which the relay node congestion warning flag of the received data packet is set is generated and transmitted to the destination node, so that the data packet is discarded. It becomes possible to control the amount of transmission data before severe congestion occurs, and it is possible to perform avoidance control for the occurrence of severe congestion according to the transmission quality required at the end node.

Further, when the occurrence of congestion is detected,
Since a layer-4 packet in which the type of the relay node congestion warning flag or the relay node congestion discard flag corresponding to the detected congestion state is set is a status notification packet and is transmitted to the source node, the destination node Even if the amount of data transmitted from the destination node to the source node is small as compared with the congestion notification to the source node via the relay node, the source node is notified of the congestion status of the relay node quickly and accurately. be able to.

[Brief description of the drawings]

FIG. 1 is a block diagram of a relay node according to an embodiment of the present invention.

FIG. 2 is a configuration diagram illustrating a packet header of a layer 4 packet.

FIG. 3 is an explanatory diagram showing a relationship between a remaining amount of a buffer and a congestion level.

FIG. 4 is a flowchart illustrating an operation of a relay communication processing unit.

FIG. 5 is a flowchart illustrating an operation of a layer 4 congestion notification control unit.

FIG. 6 is a sequence diagram showing a congestion notification method (congestion level “1”).

FIG. 7 is another sequence diagram showing a congestion notification method (congestion level “1”).

FIG. 8 is another sequence diagram showing a congestion notification method (congestion level “2”).

FIG. 9 is another sequence diagram showing a congestion notification method (congestion level “2”).

FIG. 10 is a sequence diagram showing a conventional congestion notification method.

FIG. 11 is a sequence diagram showing another conventional congestion notification method.

FIG. 12 is a sequence diagram showing another conventional congestion notification method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Relay node, 11 ... Buffer, 12 ... Buffer management part, 13 ... Line control part, 14 ... Relay communication processing part, 15 ...
Layer 4 congestion notification control unit, 2 ... source node, 3 ... destination node, 5 ... communication network, 6 ... DSU, 7 ... communication line, CA ...
Relay node congestion warning flag (congestion information), CD ... relay node congestion discard flag (congestion information), 31 ... threshold capacity (congestion level "1"), 32 ... threshold capacity (congestion level "2").

Claims (4)

(57) [Claims] 1. An information communication system comprising a relay node for temporarily storing a packet received from a predetermined transmission path in a buffer and transferring the packet to another transmission path, and performing information communication between end nodes via the relay node. In the network, the relay node compares a buffer usage with a plurality of predetermined thresholds in response to packet reception to detect a degree of congestion that has occurred in the buffer. And a layer 4 congestion notification control unit that generates a layer 4 packet in which the congestion information indicating the degree of the congestion state detected by the buffer management unit is stored, when the buffer management unit detects the occurrence of congestion. Is
The layer 4 congestion notification control unit generates a layer 4 packet in which congestion information indicating the degree of the congestion is stored in the layer 4 protocol header, and transmits the generated packet to the destination node or the source node of the received packet. Characteristic congestion notification method. 2. The congestion notification method according to claim 1, wherein a relay node congestion discard flag is provided in the layer 4 protocol header as the congestion information indicating a severe congestion in which a packet is discarded at the relay node. When the occurrence of severe congestion is detected by the management unit, the relay node congestion discard flag of the received data packet is set by the layer 4 congestion notification control unit, and the layer 4 data unit of the data packet is discarded. Layer 4 with packet type set to status notification packet
A congestion notification method, wherein a packet is generated and transmitted to a destination node. 3. The congestion notification method according to claim 1, wherein a relay node congestion warning flag is provided in the layer 4 protocol header as the congestion information, indicating a slight congestion occurrence in which no packet is discarded at the relay node. When the occurrence of mild congestion is detected by the unit, the layer 4 congestion notification control unit generates a layer 4 packet in which the relay node congestion warning flag of the received data packet is set, and transmits it to the destination node. A congestion notification method. 4. The congestion notification method according to claim 2, wherein, when occurrence of congestion is detected by the buffer management unit,
The layer 4 congestion notification control unit generates a layer 4 packet in which the type of the packet in which the relay node congestion warning flag or the relay node congestion discard flag corresponding to the detected congestion state is set is a state notification packet, and transmits the packet to the source node. And a congestion notification method.