JP2002314562A - Flow controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flow controller in a network that limits use of a communication band for a packet to inform of congestion on the occurrence of the congestion. SOLUTION: A switching hub 10 is provided with buffers Pri- 0, Pri- 1,..., Pri- m to queue congestion information in the order of priority, controls an output of a congestion notice packet on the basis of the priority to minimize outputs thereby effectively utilizing a transmission band of the packet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a flow control device in a network in which switching hubs having input ports and output ports capable of multiplexing a plurality of terminal groups by group identifiers are connected in a hierarchical structure.

[0002]

2. Description of the Related Art FIG. 6 (1) is a diagram for explaining a flow control in a switching hub as a conventional example. A switching hub SW1 and Ethernet (registered trademark) connected to respective ports P1 to P4 of the switching hub SW1 are registered. ) Terminals A to D support IEEE802.3x full-duplex flow control. Now, assuming that the switching hub SW1 transfers a packet addressed to the terminal A from the terminal B, and furthermore, the terminal C transmits a packet addressed to the terminal A as well, and receives a packet from the terminal B and a packet from the terminal C of the switching hub SW1. If the amount exceeds the amount transmitted to the terminal A, the packet is stored in each input buffer inside the switching hub SW1.

When packets are accumulated in the input buffer for a long time in this way, the input buffer overflows, and overflowing packets are discarded. For this reason, when the input buffer is about to overflow, the switching hub SW1 sends a signal to the corresponding input port P3.
The terminal C that has transmitted the pause packet defining the transmission stop time and has received this pauses the packet transmission during the defined transmission stop time. As a result, the switching hub SW1 can avoid overflow of the input buffer.

[0006] However, since the transmission stop by the pause packet is controlled in units of the ports P1 to P4 of the switching hub SW1, the switching hubs SW2 to SW2 in which a plurality of terminal groups are multiplexed as shown in FIG. S
In a network in which W5 is connected in a hierarchical structure,
This also affects other terminals belonging to different groups connected to the same switching hub.

Here, the switching hub SW2 is a backbone switching hub that bundles the switching hubs SW3 to SW5 in which a plurality of groups are multiplexed, and the switching hubs SW3 to SW5 are front-ends that accommodate the terminal devices A to I corresponding to Ethernet. It is a switching hub. Each of the terminals A to I is recognized as a terminal group by the ports of the front-end switching hubs SW3 to SW5, and a backbone switching hub SW in which a plurality of terminal groups are multiplexed by a group identifier.
Connected to 2. Port P2 of switching hub SW2
When the pause packet is output from the switching hub SW5 to the switching hub SW5, transmission of all packets transmitted from the switching hub SW5 to the switching hub SW2 is stopped. Therefore, from the terminal I connected to the switching hub SW5,
The transmission to the terminal F connected to the switching hub SW4 also stops.

To solve such a problem, Japanese Patent Laid-Open No.
Applying the idea of flow control for transmitting back pressure to a specific terminal disclosed in JP-A-149065, when the input buffer exceeds a threshold, the source address of the latest packet input to the input buffer is determined. Then, it is possible to transmit a pause packet for stopping transmission only to the terminal that has transmitted this packet.

[0007]

However, when the individual flow control method that specifies the terminal input to the input buffer is used, the possibility of packet loss and the terminal of a group that does not cause congestion are also reduced. There is a problem that flow control may be performed.

A specific description will be given with reference to FIG. Fig. 7 (1)
FIG. 6 shows an embodiment in which the system shown in Japanese Patent Application Laid-Open No. 9-149065 is applied to the configuration of FIG. Now, in the same group, the port P41 of the switching hub SW4
The terminal D connected to the switching hub SW5 and the terminal G connected to the port P51 of the switching hub SW5 transmit packets to the terminal A connected to the switching hub SW3 via the ports P22 and P23 of the switching hub SW2, respectively. It is assumed that the input buffer of the port P23 of the switching hub SW2 exceeds the threshold value, and the overflow notification packet is transmitted to the terminal G that is the transmission source of the packet at the time of input.

When receiving this packet, the switching hub SW5 transmits a pause packet to the port P51 to which the corresponding terminal G is connected. According to such a method, only the terminal G that has caused the congestion stops transmitting packets. As a result, the switching hub SW5
Allows a terminal I connected to the port P53 to transmit a packet addressed to the terminal F connected to the port P43 of the switching hub SW4 to the switching hub SW2.

However, if the input buffer at port P23 of switching hub SW2 is still above the threshold,
Group # 4 that has transmitted the packet addressed to terminal F
, The overflow notification packet is transmitted to the terminal I that is not directly related to the congestion. When the determination is made on the input buffer of the port in which a plurality of groups are multiplexed as described above, LA that is not directly related to congestion is used.
There is a problem that there is a possibility that flow control is performed to a terminal belonging to N.

FIG. 7B shows the switching hub SW5.
In the figure, a large number (GM in the figure) of terminals belonging to the same group are connected to each port. Also in this case, when the switching hub SW5 transmits packets from the plurality of terminals G to M to the switching hub SW2, if the input buffer of the port P23 of the switching hub SW2 exceeds the threshold, the switching hub SW2 overflows at all times. The notification packet is transmitted to each of the terminals G to M. Thus, the packet received by the switching hub SW2 until all the terminals G to M stop transmitting may cause the input buffer of the port P23 of the switching hub SW2 to overflow despite the flow control being performed. There is a problem.

In order to solve the above-mentioned problems prior to the present invention, the present applicant has made it possible to minimize the influence on other groups during congestion, and to limit the transmission to only the equipment whose communication is to be restricted. For the purpose of providing a device, a flow control device that performs congestion determination for each group and outputs a congestion notification packet only to a group determined to be congested has already been developed and a patent application has been filed (Japanese Patent Application No. 2000-210).
358378). This application was filed in November 2000 and has not been published yet, and therefore does not constitute a prior art with respect to the present invention.

FIG. 8 shows the operation of a congestion notification packet in the switching hub of the flow control device described in Japanese Patent Application No. 2000-358378. When a packet is input from a port of the switching hub, the state of congestion is determined in two stages based on the data buffer usage for each group provided in the output port, and a single destination determined to be congested or a plurality of destinations is determined. To the flow control. At this time, if a data packet is output from the port,
After the data packet is output, the congestion notification packets are transmitted in the order of the congestion information from the data buffer.

However, in the operation of the congestion notification packet in the flow control device according to the prior application of the present applicant, the destination address or the destination group of the congestion notification packet is duplicated, so that the transmission bandwidth of the packet is wasted. There was a problem of using. There is also a problem that the congestion notification packet overflows depending on the capacity of the congestion notification buffer.

The present invention has been made to solve the problem of the flow control device according to the prior application of the present applicant, and
When the destination address or the destination group of the congestion notification packet is duplicated, the transmission bandwidth of the packet is not wasted, and the congestion notification packet overflows depending on the capacity of the congestion notification buffer. It is therefore an object of the present invention to provide a flow control device which does not have any problem and can reduce communication traffic.

[0016]

In order to achieve the above object, the present invention provides a flow control method in a network in which hubs having input ports and output ports capable of multiplexing a plurality of terminal groups by group identifiers are connected in a hierarchical structure. In the apparatus, the hub has a buffer for each priority for storing the congestion information, and outputs a congestion notification packet after queuing the congestion information. With this configuration, it is possible to restrict the output by the priority of the congestion notification packet, and to discard the low priority congestion notification packet in which the destination address overlaps with the high priority congestion packet by outputting from the high priority congestion packet. The probability increases and traffic on the network can be reduced.

The present invention is also characterized in that when the group or the destination address of the congestion notification packet is included in the group of the congestion notification packets having higher priority, the corresponding congestion notification packet is discarded. With this configuration, the traffic on the network is reduced by discarding the congestion notification packet included in the congestion notification packet having the higher priority, and the communication bandwidth corresponding to that can be effectively used.

The present invention is also characterized in that, when a plurality of first-stage congestion notification packets are generated at the same destination address, one packet is discarded except for one. With this configuration, in a state where the first-stage congestion notification packet has already been transmitted to a certain destination, the first-stage congestion notification packet is not transmitted to the same destination, thereby reducing the traffic on the network by that amount. can do.

The present invention is also characterized in that, when a plurality of congestion notification packets having the same priority to the same group are generated, one of them is discarded except for one. With this configuration, in a state where a congestion notification packet has already been transmitted to a certain group, a congestion notification packet having the same priority is not transmitted to the same group, and the traffic on the network is reduced accordingly. be able to.

The present invention also has a function in which the hub having received the first-stage congestion notification packet has a function of searching for a congestion notification packet of the same destination address already queued in the buffer, and transmits the congestion notification packet of the same destination. It is characterized by searching. The present invention is also directed to, when a first-stage congestion notification packet having the same destination as the first-stage congestion notification packet already queued in a buffer occurs, discarding the congestion notification packet already queued in the buffer. It is characterized by. With this configuration, when the first-stage congestion notification packet is received and the congestion notification packet of the same address already queued in the buffer is discarded, the traffic on the network can be reduced by that amount.

According to the present invention, when a first-stage congestion notification packet having the same destination as the first-stage congestion notification packet already queued in the buffer occurs, the later-generated congestion notification packet is discarded. Features.
With this configuration, when the first-stage congestion notification packet is received, the subsequent congestion notification packet of the same destination generated later is discarded, whereby the traffic on the network can be reduced accordingly.

The present invention also has a function of, upon receiving the congestion notification packet in the second stage or more, searching for a congestion notification packet having the same priority to the same group already queued in the buffer. It is characterized by searching for congestion notification packets having the same priority to the same group. The present invention is also directed to a congestion notification packet already queued in the buffer when a congestion notification packet of the second or higher level already queued in the buffer and a congestion notification packet of the same priority addressed to the same group occur. The packet is discarded. With this configuration, at the stage where the congestion notification packet of the second stage or more is received, if the congestion notification packet of the same priority destined for the same group already queued in the buffer is discarded, the traffic on the network is reduced by that much. Can be reduced.

[0023] The present invention also relates to a congestion notification packet of the second or more stages already queued in a buffer,
When congestion notification packets having the same priority are generated for the same group, the congestion notification packets generated later are discarded. With this configuration, at the stage where the congestion notification packet of the second stage or more is received, if the congestion notification packet of the same priority that is generated later and destined for the same group is discarded, the traffic on the network can be reduced accordingly. it can.

The present invention is also characterized in that, when congestion notification packets having different priorities are queued in the buffer, the congestion notification packets having higher priorities are output in order. With this configuration, the frequency of outputting a low-priority congestion notification packet in which a destination address overlaps with a high-priority congestion notification packet is reduced on the network, and traffic on the network can be reduced.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of a flow control device according to the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating a configuration of a switching hub 10 as an embodiment of a flow control device that implements flow control according to the present invention. The switching hub 10 includes a switch processing unit 12 for switching an input packet from each port and transferring the packet to an output port, and port control units 14, 16,... Since the port controllers 14, 16,... 18 have the same structure, only the port controller 14 will be described below. Port control unit 14
Is composed of a data buffer unit 20, a congestion notification packet transmission processing unit 22, and a transmission processing unit 24.

As shown in detail in FIG. 2, the congestion notification packet transmission processing unit 22
Congestion information buffers by priority order Pri_0, Pri_1, ... Pri_
has m. The symbols Pri_0, Pri_1,... Pri_m indicate congestion information buffers as hardware,
Indicates the priority (priority). That is, the congestion information buffer Pri_0 has the highest priority,
The congestion information buffer Pri_m has the lowest priority. The congestion notification packet transmission processing unit 22 also includes a congestion packet output control unit 28 that controls the packet output of the congestion notification buffer unit 26, and a destination search unit 30 that searches for a destination of the congestion notification in the congestion notification buffer unit 26. And a congestion notification packet generation unit 32 that generates a congestion notification packet when a transmission permission instruction is issued from the transmission processing unit 24 in FIG.

FIG. 3 shows the congestion notification packet transmission processing unit 22.
6 is a flowchart showing the processing in the congestion notification buffer unit 26 of FIG. First, when packet header information, reception / transmission destination information, and congestion priority (priority) information are received from the data buffer unit 20 (step S1), the destination search unit 30 removes the packet from the queue of the congestion notification buffer unit 26. Search for congestion information of the same destination (step S
2).

If there is no congestion information of the same destination (NO in step S2), the received information is transferred to the congestion information buffers Pri_0, Pri_1,.
Stored in m (step S3). If there is congestion information of the same destination (YES in step S2), the priority of congestion is compared, and if the priority of the congestion information already in the queue is equal to or higher than the priority of the received congestion information. (YES in step S4), the received information is discarded without being stored in the queue (step S5). If the priority of the congestion information already in the queue is lower than the priority of the received congestion information (NO in step S4), the received information is stored in the congestion information buffers Pri_0, Pri based on the congestion priority.
,... Pri_m (step S6), and deletes the congestion information of the destination contained in the received information from the buffers Pri_0, Pri_1,.

As a result, when there is congestion information of the same destination, the congestion information having a lower priority is deleted, and only the congestion information having a higher priority remains in the buffer. The transmission bandwidth can be effectively used for the congestion notification packet having a low congestion.

FIG. 4 is a flowchart showing the processing of the congestion packet output control unit 28. Congestion notification buffer 2
6 has congestion information data (YE in step S8)
S) If there is a packet being output to the output port of the switching hub (YES in step S9), immediately after the packet is output, but if there is no packet being output, the congestion information in the congestion notification buffer is immediately stored. Are transmitted to the congestion notification packet generator 32 in descending order of priority (step S10).

FIG. 5 shows an operation example of the congestion notification packet transmission processing unit 22. While data is being output to the output port of the switching hub 10, the congestion notification address destinations are addressed to a, c, and b in the congestion information of the priority order Pri_0.
When the destination of the congestion notification address is notified to the a and the b in the congestion information of the priority order Pri_1, the address is notified to the a and the b. Only the second-stage congestion notification information and the first-stage congestion notification information addressed to c remain, and the others are discarded. Then, after the data packet is output, the packet is output in the order of the congestion notification packet of priority Pri_1 addressed to a and b, and the congestion notification packet of priority Pri_0 addressed to c.

[0032]

As described above, according to the present invention, the hub receiving the congestion notification packet has a buffer for each priority for storing the congestion information, so that the hub is included in the congestion notification packet with a high priority. Congestion notification packets and overlapping congestion notification packets can be discarded, and communication traffic can be reduced accordingly.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an outline of a preferred embodiment of a flow control device of the present invention.

FIG. 2 is a block diagram showing a congested packet transmission processing unit of FIG. 1 in detail;

FIG. 3 is a flowchart showing processing of a congestion notification buffer unit in FIG. 2;

FIG. 4 is a flowchart showing processing of a congestion packet output control unit in FIG. 2;

FIG. 5 is a flowchart showing processing of a congestion packet transmission processing unit in FIG. 2;

FIG. 6 (1) Diagram showing flow control in a conventional switching hub. (2) Flow control in a case where switching hubs multiplexing a plurality of terminal groups are connected in a hierarchical structure in the configuration of (1) in FIG. Figure showing

FIG. 7 (1) Japanese Patent Laid-Open Publication No.
FIG. 1 shows a configuration to which the method disclosed in Japanese Patent Application Publication No. 065 is applied. (2) A configuration in which a plurality of terminals belonging to the same group are connected in the configuration of (1) in FIG.

FIG. 8: Applicant's prior application (Japanese Patent Application No. 2000-358378)
Diagram showing the operation of a congestion notification packet in the switching hub of the flow control device described in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Switching hub 12 Switch processing part 14,16 ... 18 Port control part 20 Data buffer part 22 Congestion notification packet transmission processing part 24 Transmission processing part 26 Congestion notification buffer part 28 Congestion packet output control part 30 Destination search part 32 Congestion notification Packet generator Pri_0, Pri_1, ... Pri_m Congestion information buffer (indicating priority)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5K030 GA13 HA08 HB13 HC14 LC01 LC11 LC15 MB02 5K033 AA07 CB06 CB17 CC01 DA15 DB02

Claims (10)

[Claims] 1. A flow control apparatus in a network in which hubs having input ports and output ports capable of multiplexing a plurality of terminal groups by a group identifier are connected in a hierarchical structure, wherein the hub stores congestion information for each priority. A flow control device having a buffer and outputting a congestion notification packet after queuing congestion information. 2. A congestion occurs in the hub, and
When the data of the congestion information already exists in the buffer,
The flow control device according to claim 1, further comprising a function of searching for a priority of congestion information and a destination for notifying congestion, and searching for a priority of congestion information and a destination for notifying congestion. 3. The method according to claim 1, wherein when the group or the destination address of the congestion notification packet is included in the group or the destination address of the congestion notification packet having a higher priority, the included congestion notification packet is discarded. Item 3. A flow control device according to item 2. 4. The flow control device according to claim 3, wherein when a plurality of congestion notification packets having the lowest priority at the same destination address occur, one packet is discarded except for one. 5. The flow control device according to claim 3, wherein, when a plurality of congestion notification packets having the same priority order are generated for the same group, all but one of them are discarded. 6. When a congestion notification packet having the same priority as the congestion notification packet having the lowest priority already queued in the buffer and having the lowest priority occurs, the packet is already queued in the buffer. The flow control device according to claim 4, wherein the congestion notification packet is discarded. 7. When a congestion notification packet having the same priority as the congestion notification packet already queued in the buffer and having the lowest priority and having the lowest priority is generated, a congestion notification generated later is generated. The flow control device according to claim 4, wherein the packet is discarded. 8. When a congestion notification packet having the same priority as the congestion notification packet having the same priority as the congestion notification packet other than the lowest priority already queued in the buffer occurs, the packet is already queued in the buffer. 6. The method according to claim 5, wherein the congestion notification packet is discarded.
3. The flow control device according to claim 1. 9. A congestion notification packet generated later when a congestion notification packet having the same priority as the congestion notification packet having the same priority as the congestion notification packet other than the lowest priority queued in the buffer is generated. The flow control device according to claim 5, wherein is discarded. 10. The flow control device according to claim 1, wherein when congestion notification packets having different priorities are queued in the buffer, the congestion notification packets having higher priorities are sequentially output.