JPH03283940A - Link congestion control system - Google Patents

Abstract

PURPOSE:To constitute a switch without congestion by measuring a utilizing rate of a buffer in the inside of an asynchronous transfer mode switch, comparing a threshold of the buffer with the utilizing rate measured value, discriminating the link congestion, referencing flow control identification information and raising flow control to a specific call. CONSTITUTION:The utilizing rate of an output buffer 41 is measured by a comparator circuit 51 and when the measured value reaches a prescribed threshold, the comparator circuit 51 informs the congestion information to a call connection controller 70. The call connection controller 70 discriminates link congestion state based on the congestion information noticed from the comparator circuit 51, references the flow control identification information displayed in a call processed by a basic switch 10 and raises a flow stop instruction of a cell from a network flow control sending circuit 60 via an output buffer with respect to a specific call allowing the flow control.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an ATM (Async) with a multi-stage link configuration.
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The present invention relates to a link congestion control method used in a switch using a nous transfer mode (asynchronous transfer mode).

[Conventional technology]

In ATM switching, one outgoing line is commonly used by multiple calls, so there is a probability that multiple fixed-length packets called cells tend to arrive at the same outgoing line at the same time. At that time, the links become congested and cell collisions occur, so conventional methods to avoid such collisions include methods that sufficiently increase the transfer speed of the outgoing link, and methods that temporarily store cells that cannot be carried on the outgoing link in a buffer. Accumulating method%
Formula % [Problem to be solved by the invention] Among the conventional link congestion control methods described above, the method of increasing the transfer speed of the outgoing link has a speed of 100 Mbit/
When accommodating boats with speeds ranging from Sec to several Gbit/See or configuring into multi-stage links, the internal calculation speed of the switch becomes too high, making it uneconomical. In addition, various methods for providing buffers have been proposed, such as cross-point buffers, input buffers, output buffers, and shared buffers, but no matter how large the buffer capacity is, it can only absorb traffic fluctuations up to a certain point in time. If the incoming traffic continuously exceeds the outgoing line processing capacity, there is a problem in that the cells that have flown in beyond the processing capacity are discarded.

An object of the present invention is to provide a link congestion control method that can eliminate cell discards caused by link congestion.

[Means to solve the problem]

The link congestion control method of the present invention includes a call connection control device that controls calls handled by an asynchronous transfer mode switch having a multi-stage link configuration having a buffer, and in the link congestion control method that performs flow control, the method measures the usage rate of the buffer and Comparing means for comparing the threshold value and usage rate measurement value of the buffer, and flow control issuing means for issuing flow control for a specific call for which flow control is permitted in the call control device, The call control device is configured to determine link congestion based on the congestion information notified from the means, refer to flow control identification information displayed on the call handled by the asynchronous transfer mode switch, and issue flow control to the specific call. has been done.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
FIG. 2 is a configuration diagram showing an example of a switch having a multi-stage link configuration in which the basic switches shown in the figure are connected in multiple stages. In FIG. 1, the basic switch 10 has an nXn square lattice, and a person! ! 21 to 2n and outgoing lines 31 to 3n are accommodated, and the case is shown in which the application is applied to an output buffer type having buffers 41 to 4n on the output side of the basic switch 10. Usually, ATM
In the exchange, basic switches 10 are connected in multiple stages as shown in FIG. Output buffer 41-4n
The comparison circuits 51 to 5n respectively connected to measure the usage rate of the output buffer and compare the threshold value and the usage rate measurement value of the output buffer. The call connection control device 70 includes a network flow control issuing circuit 60 that is connected to the comparison circuits 51 to 5n, controls calls handled by the asynchronous transfer mode switch, and issues flow control to specific calls for which flow control is permitted. .

The operation will be explained below. If cells arrive from the incoming line 21.2n to the outgoing line 31 at the same time, a collision occurs. If this collision is temporary, it will be absorbed by the output buffer 41, but if the traffic from the incoming line 21 to the outgoing line 31 and the traffic from the incoming line 2n to the outgoing line 31 continue, the output buffer 41 will reduce its storage capacity. Cells will be discarded due to excess. Therefore, the usage rate of the output buffer 41 is measured by the comparison circuit 51, and when the measured value reaches a predetermined threshold, the comparison circuit 51
The call connection control device 70 is notified of the congestion information.

Here, the traffic loaded on ATM switches can be roughly divided into those that are highly instantaneous, such as voice and video, and those that can tolerate a certain degree of data accumulation and delay, such as communication between computers. be done. Audio and video are not suitable for error correction through retransmission or flow control, but flow control is permitted in computer-to-computer communications. In particular, in future computer-to-computer communications, it is common sense to have an open system interface;--In boat fishing, flow control is performed at the transport layer, which is not supported by the net. Therefore, the call connection control device 70 uses the traffic loaded on the basic switch 10 as flow control identification information in advance at the time of call setup, and classifies the traffic into traffic that is permissible for flow control and traffic that is not permissible for flow control.

The call connection control device 70 determines the link congestion state based on the congestion information notified from the comparison circuit 51, refers to the flow control identification information displayed on the handled call of the basic switch 10, and selects a specific call for which flow control is allowed. In response, the network flow control issuing circuit 60 issues a cell inflow stop instruction via the output buffer.

〔Effect of the invention〕

As described above, the present invention provides a comparison means for measuring the usage rate of a buffer inside an asynchronous transfer mode switch, comparing the threshold value of this buffer and the usage rate measurement value, and A flow control issuing means for issuing flow control is provided, and the call control device determines link congestion based on the congestion information notified from the comparison means, and refers to the flow control identification information displayed on the handled call of the asynchronous transfer mode switch. However, since flow control is issued to a specific call, it is possible to configure a switch free of congestion, which eliminates cell discards caused by ATM switch internal link congestion.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
FIG. 2 is a configuration diagram showing an example of a switch having a multi-stage link configuration in which the basic switches shown in the figure are connected in multiple stages. 10...Basic switch, 21-2n, old...Incoming line, 31-3n...Outgoing line, 41-4n...
...Output buffer, 51-5n...Comparison circuit,
60...Network flow control issuing circuit, 70...
...Call connection control device.

Claims (1)

[Claims] In a link congestion control method that includes a call connection control device that controls calls handled by an asynchronous transfer mode switch having a multi-stage link configuration having a buffer and performs flow control, measurement of the usage rate of the buffer and a threshold value and usage rate of the buffer are provided. Comparing means for comparing measured values, and flow control issuing means for issuing flow control for a specific call for which flow control is permitted in the call control device, A link congestion control method, characterized in that a control device determines link congestion, refers to flow control identification information displayed on the call handled by the asynchronous transfer mode switch, and issues flow control to the specific call.