JPH08125690A - Flow control system for repeater - Google Patents

Abstract

PURPOSE: To enable data transmission, preventing an overflow of reception buffer so as to prevent the buffer from being congested with data. CONSTITUTION: Upon the receipt of broadcast data in the step S1, a residual capacity R of a reception buffer is referenced in the step S2. Then whether or not the total residual amount R of the reception buffers is in a relation of R>=(1/2)N is discriminated, where N is number of the reception buffers in the step S3. When the result of discrimination indicates YES, the received broadcast data are transferred transparently in the step S4. When the result of discrimination indicates NO, the received broadcast data are aborted and the recovery of the capacity of the reception buffers are awaited in the step S5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow control system for a relay device connecting a LAN and a public network.

[0002]

2. Description of the Related Art A relay device placed between a LAN and two networks having different data transfer rates, such as a public network, has a buffer in the device and temporarily stores data from the high-speed LAN side. The speed difference between the two networks is adjusted by sequentially transmitting according to the traffic volume on the low speed public network side.

[0003]

Although it is possible to adjust the speed between two networks having different speeds by the above-mentioned method, since the buffer is a finite resource, the high-speed public network side cannot exceed the allowable amount. When this data is received, the buffer becomes full and further reception becomes impossible. At this time, if the low-speed public network side is congested, the buffer will never become empty, and congestion will occur, and the received data will be discarded more and more. For this reason, the transmitting side tries to recover by retransmitting the discarded data, but if the congestion state is not resolved, it becomes a vicious circle, and there is a problem that communication is no longer established.

The present invention has been made in view of the above circumstances, and provides a flow control system of a relay device capable of preventing overflow of a receiving buffer, preventing data from being in a congestion state, and enabling data transmission. The purpose is to provide.

[0005]

Means and Actions for Solving the Problems
In order to achieve the above object, a first invention is a flow control system of a relay device connecting a LAN and a public network,
When the reception buffer of the relay device receives the broadcast data, the remaining amount R of the reception buffer is referred to. When R ≧ (1/2) N with respect to the total number N of the reception buffers, the broadcast data is transferred transparently, When R <(1/2) N, the broadcast data is discarded and the recovery of the reception buffer is waited for.

A second aspect of the invention is a flow control system for a relay device connecting a LAN and a public network, and when the reception buffer of the relay device receives the first broadcast data A of a plurality of broadcast data, the timer is set to N seconds. After the data A is set and transmitted and registered, when the broadcast data A again arrives while the timer is operating, the data A is discarded, and then the broadcast data or the data designated by the other party arrives. When it does, the timer is released, data is transmitted, and when the received data is broadcast data,
A new timer is set to change the broadcast data A to the broadcast data B, the registration of the data A is deleted when the timer operation is stopped, and the data A is specified when the timer is released when the data is designated by the other party.
It is characterized by deleting the registration of.

A third aspect of the present invention is a flow control system for a relay device that connects a LAN and a public network, and when broadcast data is transmitted from the LAN side to the public network side, depending on the type in the frame in the broadcast data. It is characterized in that the data is selected by judging whether the data is necessary data or unnecessary data, and unnecessary data is discarded from the reception buffer.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. In describing the first embodiment with reference to FIG. 1, first, the transmission speed difference between the LAN and the public network is absolute.
Moreover, since the buffer is finite, the transmission data is limited and unnecessary data is not transmitted.
Therefore, attention is paid to broadcast data, which is the main factor that occupies the buffer of the relay device. This broadcast data is data that is reported to all nodes at once, and its importance is lower than that of data transmitted to individual nodes. Therefore, the transfer of broadcast data is restricted by the following method.

In FIG. 1, when the broadcast data is received in step S1, the remaining amount R of the receiving buffer is referred to in step S2. Next, in step S3, the remaining amount R of the receiving buffer is R ≧ (1 /
2) Determine if N. If the result of the determination is YES, the received broadcast data is transparently transferred in step S4. If the result of the determination in step S3 is NO, the received broadcast data is discarded, and the recovery of the reception buffer is awaited in step S5.

FIG. 2A is an operation explanatory diagram when the judgment result of step S3 is performed. In FIG. 2A, when the number of buffers in use out of the total number N of reception buffers is the number shown by the hatched lines in the drawing, the broadcast data is transferred. It shows the situation.

Similarly, FIG. 2B shows a state in which broadcast data is discarded when the number of buffers in use out of the total number N of reception buffers is large as indicated by the shaded area in the figure.

When the flow control of the broadcast data is performed as in the first embodiment, it is possible to avoid the full state (overflow) of the reception buffer and prevent the congestion state. Further, it is possible to ensure the reliability of the normal data transmission to the individual nodes at the relay device level.

Next, a second embodiment will be described with reference to FIG. First, 31 is a receiving unit for the broadcast data A, 32 is a receiving unit for the broadcast data B, and 33 is a normal data receiving unit designated by the other party, and these receiving units 31, 32, 33 are provided.
It is assumed that the receiving unit 31 has now received the broadcast data A. The reception signal of the reception unit 31 is input to the reception buffer 34. Then, the timer provided in the reception buffer 34 is set to N seconds, the broadcast data A is transmitted, and the broadcast data A is registered. When the broadcast data A is received again while the timer is operating, the broadcast data A is discarded.

Next, the broadcast data B is received by the receiving unit 3
2 receives and the received signal is input to the reception buffer 34, the timer is released, the broadcast data B is transmitted, a new timer is set, the broadcast data A is changed, and the broadcast data B is registered. . After that, when the timer times out, the registration of the broadcast data B is deleted.

A feature of the second embodiment is that among the various broadcast data, when the same broadcast data is continuously received, some of the data are thinned out. When the broadcast data B is received, the monitoring target of continuous reception has moved from the broadcast data A to the broadcast data B, and the registration of the broadcast data A has already been deleted. Even if the time-out occurs, the registration of the broadcast data A will not be deleted again. Therefore, the registration of the broadcast data B is deleted as described above. Broadcast data A is deleted due to a time-out, after registering broadcast data A, without receiving any data other than broadcast data A,
Only when it times out as it is.

Further, not the broadcast data B but the normal data which is the data designated by the destination is received by the receiving unit 33.
Is received and the received signal is input to the reception buffer 34, the timer set for the broadcast data A is released and normal data is transmitted. After that, the registration of the broadcast data A is deleted.

As described above, it is possible to prevent the receiving buffer from overflowing by limiting the time by applying a timer to the broadcast data, and at the same time, the reliability of data transmission to each node can be obtained. .

Next, a third embodiment will be described. In the third embodiment, as shown in FIG. 4, in order to avoid the overflow of the receiving buffer on the LAN side between the two networks on the LAN side and the public network side, in order to select necessary data and unnecessary data, Pa of the frame format shown in FIG.
It is made to judge whether it is necessary data or unnecessary data for each ccketTYPE. Here, the above-mentioned TYPE is a Packet TYPE having a 16-bit field on the frame shown in FIG. 5, and if TYPE is registered in advance, it can be determined whether it is necessary data or unnecessary data.

Referring now to FIG. In FIG. 4, when the broadcast data transmitted from one of the nodes PC1 to PC6 is transmitted from the LAN side to the public network side through the terminal server TMS, is the data necessary for each TYPE on the frame in the broadcast data as described above? It is determined whether it is unnecessary data, and unnecessary data is discarded to avoid overflow of the receiving buffer on the LAN side. With this configuration, data can be transmitted without congestion even between two networks such as a LAN and a public network.

[0020]

As described above, according to the present invention,
It is possible to prevent overflow of the reception buffer and to ensure the reliability of the data transmission to each node at the level of the relay device without filling the buffer with a full state, and between the two networks such as the LAN and the public network. Also enables data transmission without congestion.

[Brief description of drawings]

FIG. 1 is a flowchart showing a first embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of a reception buffer.

FIG. 3 is a structural explanatory view showing a second embodiment of the present invention.

FIG. 4 is a configuration diagram of a terminal server to which the third embodiment of the present invention is applied.

FIG. 5 is a format of a broadcast data frame showing a third embodiment.

[Explanation of symbols]

S1 ... Broadcast data receiving step S2 ... Receiving buffer remaining amount reference step S3 ... Comparison judgment step of receiving buffer remaining amount with respect to total number of receiving buffers S4 ... Transparent data transfer step S5 ... Data discarding step

Claims (3)

[Claims] 1. In a flow control method of a relay device connecting a LAN and a public network, when a reception buffer of the relay device receives broadcast data, the remaining amount R of the reception buffer is referred to and the total number of reception buffers N R ≧ (1
/ 2) N, the broadcast data is transparently transferred, and when R <(1/2) N, the broadcast data is discarded and the recovery of the reception buffer is awaited. Flow control method. 2. In a flow control method of a relay device connecting a LAN and a public network, when a reception buffer of the relay device receives the first broadcast data A of a plurality of broadcast data, a timer is set to N seconds. At the same time, after transmitting and registering the data A, when the broadcast data A again arrives while the timer is operating, the data A is discarded, and when the broadcast data or the data designated by the other party arrives next, When the timer is released, data is transmitted, and the received data is broadcast data, a new timer is set to change to broadcast data A and broadcast data B is registered, and when the timer operation is stopped, data A Delete the registration, and if the data specified by the A flow control method for a relay device, characterized in that the registration of data A is deleted when the communication is canceled. 3. In a flow control system of a relay device for connecting a LAN and a public network, broadcast data is set to L
When transmitting from the AN side to the public network side, the type in the frame in the broadcast data determines whether the data is necessary data or unnecessary data and selects the data, and the unnecessary data is received. A flow control method for a relay device, which is characterized in that it is discarded from a buffer.